Chapter - I
Anatomy (from the Greek word meaning to cut up, cut open) is the branch of biology that deals with the structure and organization of living things. It can be divided into animal anatomy (zootomy) and plant anatomy (phytonomy). Major branches of anatomy include comparative anatomy, histology, and human anatomy.
Anatomy from point of Medicine consists of a knowledge of the exact form, position, size and relationship of the various structures of the healthy human body, and to this study the term descriptive or topographical human anatomy is given, though it is often, less happily, spoken of as anthropotomy.
So intricate is the human body that only a small number of professional human anatomists, after years of patient observation, are complete masters of all its details; most of them specialize on certain parts, such as the brain or viscera, contenting themselves with a good working knowledge of the rest.
Before proceeding to understand anything about human body, it is imperative to know atleast the names of major body systems and organs present in human body that make it so intricate and astonishing.
Major Body Systems:
Some Major Organs:
Colon or large intestine
Bones in the Human Skeleton:
Collar bone (clavicle)
Thigh bone (femur)
Externally visible parts of the human body:
Other anatomic terms (not classified):
Human anatomy or anthropotomy is a special field within anatomy. It studies gross structures and systems of the human body, leaving the study of tissues to histology and cells to cytology. The human body, like the bodies of all animals, is made up of systems that are made up of organs that are made up of tissues that are made up of cells.
Human organ systems
Cardiovascular system: Blood circulations with heart and blood vessels.
Digestive system: Processing food with mouth, stomach and intestines
Endocrine system: Communicating within the body using hormones.
Immune system: Defending against disease-causing agents
Integumentary system: Skin, hair and nails.
Lymphatic system: Structures involved in the transfer of lymph between tissues and the bloodstream.
Muscular system: Moving the body
Nervous system: Collecting, transferring and processing information with brain and nerves
Reproductive system: The sex organs
Respiratory system: The organs used for breathing, the lungs
Skeletal system: Structural support and protection through bones
Urinary system: The kidneys and associated structures involved in the production and excretion of urine
External body features:
Common names of well known parts of the human body, from top to bottom:
Head -- Forehead -- Eye -- Ear -- Nose -- Mouth -- Tongue -- Teeth -- Jaw -- Face -- Cheek -- Chin
Neck -- Throat -- Adam's apple -- Shoulders
Arm -- Elbow -- Wrist -- Hand -- Fingers -- Thumb
Spine -- Chest -- Breast -- Ribcage
Abdomen -- Belly button -- Sex organs (Penis/Scrotum or Clitoris/Vagina) -- Rectum -- Anus
Hip -- Buttocks -- Leg -- Thigh -- Knee -- Calf -- Heel -- Ankle -- Foot -- Toes
Common names of internal organs (in alphabetical order):
Anatomy of the brain
Amygdala -- Brainstem -- Cerebellum -- Cerebral cortex -- Hypothalamus -- Limbic system -- medulla-- midbrain -- Pituitary gland -- pons
Studying human anatomy
Certain professions, especially medicine and physiotherapy, require the study of human anatomy in depth. Textbooks usually split the body into the following regional groups:
Head and Neck - includes everything above the thoracic inlet
Upper limb - includes everything from your hand, forearm, arm, shoulder, axilla, pectoral region and scapular region.
Thorax - contains the region of the chest from the thoracic inlet to the thoracic diaphragm.
Abdomen - everything from the thoracic diaphragm to the pelvic brim or to the pelvic inlet.
The back - about the spine and its components, the intervertebral disks and bodies
Pelvis and Perineum - the pelvis consists of everything from the pelvic inlet to the pelvic diaphragm. The perineum is everything below the pelvic diaphragm.
Lower limb - the lower limb is usually everything below the inguinal ligament, including the thigh, the hip joint, the leg, and the foot.
First let us understand more about the human skeleton as it forms the framework of human body about which all organs and systems function and perform.
The human skeleton is made of bones, some of them joined together, supported and supplemented by a structure of ligaments, tendons, muscles, and cartilage.
The skeleton changes composition over a lifespan. Early in gestation, a fetus has no hard skeleton — bones form gradually during nine months in the womb. When a baby is born it has more bones than it will as an adult. On average, an adult human has 206 bones in their skeleton (the number can vary slightly from individual to individual), but a baby is born with approximately 270. The difference comes from a number of small bones that fuse together during growth. These include the bones in the skull and the spine. The sacrum (the bone at the base of the spine) consists of six bones, which are separated at birth but fuse together into a solid structure in later years.
There are 6 bones (three on each side) in the middle ear that articulate only with themselves, and one bone, the hyoid bone, which does not touch any other bones in the body.
The longest bone in the body is the femur and the smallest is the stapes bone in the middle ear.
The skeleton functions not only as the support for the body but also in hematopoiesis, the manufacture of blood cells that takes place in bone marrow (which is why bone marrow cancer is very often a terminal disease). It is also necessary for protection of vital organs and is needed by the muscles for movement. Not only does the skeleton serve to help manufacture blood cells, but it also serves as a mineral storage deposit in which nutrients can be stored and retrieved.
One way to group the bones of the human skeleton is to divide them into two groups, namely the axial skeleton and the appendicular skeleton. The axial skeleton consists of bones in the midline and includes all the bones of the head and neck, the vertebrae, ribs and sternum. The appendicular skeleton consists of the clavicles, scapulae, bones of the upper limb, bones of the pelvis and bones of the lower limb.
There are many differences between the male and female human skeletons. Men tend to have slightly thicker and longer limbs and digit bones while women tend to have larger pelvic bones in relation to body size. Women also tend to have narrower rib cages, smaller teeth, less angular mandibles, and less pronounced cranial features such as the brow ridges and occipital protuberance (the small bump in the cranium's posterior). Most striking is the difference in hip bones owing to differences related to the process of reproduction, and very likely also to the biological process of sexual selection. There are also a number of smaller differences between human male and female skeletons.
The skeleton can be affected by many diseases that compromise physical mobility and strength. Skeletal diseases range from minor to extremely debilitating. Bone cancer and bone tumors are extremely serious and are sometimes treated by radical surgery such as amputation of the affected limb. Various forms of arthritis attack the skeleton resulting in severe pain and debility. Osteoporosis can increase the likelihood of fractures and broken bones, especially among post-menopausal women and the elderly. Scoliosis is another, when the spine curves from side to side.
Here is a list of all human bones:
A typical adult human skeleton consists of the following 206 bones. (Numbers in bold refer to the diagram at right.)
In the skull (22):
1. Frontal bone
2. Parietal bone (2)
3. Temporal bone (2)
4. Occipital bone
5. Zygomatic bone (2)
6. Superior and inferior maxilla
9. Nasal bone (2)
Palatine bone (2)
Lacrimal bone (2)
inferior nasal conchae (2)
In the middle ears (6):
In the throat (1):
In the shoulder girdle (4):
25. Clavicle or collarbone (2)
29. Scapula or shoulder blade (2)
In the thorax (25):
28. Ribs (2 x 12)
In the vertebral column (24):
8. Cervical vertebrae (7) incl. Atlas & axis
14. Lumbar vertebrae (5)
Thoracic vertebrae (12)
In the arms (6):
11. Humerus (2)
26. Condyles of humerus
12. Ulna (2)
13. Radius (2)
27. Head of radius
In the hands (54):
Wrist (carpal) bones:
Scaphoid bone (2)
Lunate bone (2)
Triquetrum bone (2)
Pisiform bone (2)
Trapezium (bone) (2)
Trapezoid bone (2)
Capitate bone (2)
Hamate bone (2)
Palm or metacarpal bones:
Metacarpal bones (5 × 2)
Finger bones or phalanges:
Proximal phalanges (5 × 2)
Intermediate phalanges (4 × 2)
Distal phalanges (5 × 2)
In the pelvis (4):
15. Ossa coxa (hip bones or innominate bones) (2)
In the legs (8):
17. Femur (2)
22. Greater trochanter of femur
23. Condyles of femur
19. Patella (2)
20. Tibia (2)
21. Fibula (2)
In the feet (52):
Ankle (tarsal) bones:
Calcaneus (heel bone) (2)
Navicular bone (2)
Medial cuneiform bone (2)
Intermediate cuneiform bone (2)
Lateral cuneiform bone (2)
Cuboidal bone (2)
Metatarsal Bone (5 × 2)
Proximal phalanges (5 × 2)
Intermediate phalanges (4 × 2)
Distal phalanges (5 × 2)
The infant skeleton has the following bones in addition to those above:
1. Sacral vertebrae (4 or 5), which fuse in adults to form the sacrum.
2. Coccygeal vertebrae (3 to 5), which fuse in adults to form the coccyx.
3. Ilium, ischium and pubis, which fuse in adults to form the pelvic girdle
The bones of the human skeleton are structurally and in many taxonomies organized as those of the:
Now let us study in detail about each bony organization in detail.
A skull, or cranium, is a bony structure of Craniates, which serves as the general framework for a head. The skull supports the structures of the face and protects the brain against injury.
In humans, the adult skull is normally made up of 28 bones. Except for the mandible, all of the bones of the skull are joined together by sutures, rigid articulations permitting very little movement.
Eight bones form the neurocranium (braincase), a protective vault of bone surrounding the brain and medulla oblongata. Fourteen bones form the splanchnocranium, the bones supporting the face. Encased within the temporal bones are the six ear ossicles of the middle ear. The hyoid bone, supporting the larynx, is usually not considered as part of the skull, as it does not articulate with any other bones.
Development of the skull
The skull is a complex structure; its bones are formed both by intramembranous and endochondral ossification. The bones of the splanchnocranium and the sides and roof of the neurocranium are formed by intramembranous (or dermal) ossification, while the bones supporting the brain (the occipital, sphenoid, temporal, and ethmoid) are largely formed by endochondral ossification.
At birth, the human skull is made up of 45 separate bony elements. As growth occurs, many of these bony elements gradually fuse together into solid bone (for example, the frontal bones). The bones of the roof of the skull are initially separated by regions of dense connective tissue called "sutures". There are five sutures: the frontal suture, sagittal suture, lambdoid suture, coronal suture, and squamosal suture. At birth these regions are fibrous and moveable, necessary for birth and later growth. This growth can put a large amount of tension on the "obstetrical hinge," which is where the squamous and lateral parts of the occipital bone meet. A possible complication of this tension is rupture of the great cerebral vein of Galen. Larger regions of connective tissue where multiple sutures meet are called fontanelles. The six fontanelles are: the anterior fontanelle, the posterior fontanelle, the two sphenoid fontanelles, and the two mastoid fontanelles. As growth and ossification progress, the connective tissue of the fontanelles is invaded and replaced by bone. The posterior fontanelle usually closes by eight weeks, but the anterior fontanelle can remain up to eighteen months. The anterior fontanelle is located at the junction of the frontal and parietal bones; it is a "soft spot" on a baby's forehead. Careful observation will show that you can count a baby's heart rate by observing his or her pulse pulsing softly through the anterior fontanelle.
If the brain is bruised or injured it can be extremely serious. Normally the skull protects the brain from damage through its hard unyieldingness, but in some cases of head injury, there can be raised intracranial pressure through mechanisms such as a subdural hematoma. In these cases the raised intracranial pressure can cause herniation of the brain out of the foramen magnum ('coning') because there is no space for the brain to expand; this can result in significant brain damage or death unless an urgent operation is performed to relieve the pressure. This is why patients with concussion must be watched extremely carefully.
The skull also contains the sinus cavities. The meninges are the membranes that separate the brain from the skull.
Bones of the human skull
Parietal bone (2)
Temporal bone (2)
Palatine bone (2)
Zygomatic bone (2)
Nasal bone (2)
Lacrimal bone (2)
Inferior nasal conchae (2)
In addition to the usual centers of ossification of the cranium, others may occur, giving rise to irregular isolated bones termed sutural or Wormian bones.
Notable sutures in the skull
Most sutures are named for the bones they articulate, but some have special names of their own.
Sagittal suture - along the midline, between parietal bones
Coronal suture - between the frontal and parietal bones
Lambdoidal suture - between the parietals and the occipital bone
Squamosal suture - between the parietal and the temporal bone
Metopic suture - between the two frontal bones, prior to the fusion of the two into a single bone
Foramina of skull base
The following is a list of holes, or foramina, in the base of the skull and what goes through each of them.
One must be only well versed with these names as they often come across during dictations.
Arranged from anterior to posterior:
Foramen caecum - emissary veins to superior sagittal sinus
Foramina of cribriform plate - olfactory nerve bundles
Posterior ethmoidal foramen - posterior ethmoidal artery, vein and nerve
Optic canal - optic nerve (II), ophthalmic artery
Superior orbital fissure
Oculomotor nerve (III)
Trochlear nerve (IV)
Lacrimal, frontal and nasociliary branches of ophthalmic nerve (V1)
Abducens nerve (VI)
Superior ophthalmic vein
Foramen rotundum - maxillary nerve (V2)
Mandibular nerve (V3)
Accessory meningeal artery
Lesser petrosal nerve (occasionally)
Middle meningeal artery and vein
Meningeal branch of mandibular nerve
Internal carotid artery
Internal carotid nerve plexus
Hiatus of canal of lesser petrosal nerve
Hiatus of canal of greater petrosal nerve
Internal acoustic meatus
Facial nerve (vii)
Vestibulocochlear nerve (VIII)
Inferior petrosal sinus
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Posterior meningeal artery
Internal jugular vein
Hypoglossal canal - hypoglossal nerve (XII)
Meningeal branches of vertebral arteries
Spinal roots of accessory nerves
An ear is an organ used by an animal to detect sound waves. The term may refer to the entire system responsible for collection and early processing of sound (the beginning of the auditory system), or merely the externally-visible part.
Mammals, including humans, have two ears, one on each side of the head.
EXTERNAL EAR: The outer ear is the external portion of the ear and includes the eardrum.
The visible part is called the pinna, or auricle, and functions to collect and focus sound waves. Many mammals can move the pinna in order to focus their hearing in a certain direction in much the same way that they can turn their eyes. Humans have generally lost this ability. From the pinna the sound pressure waves move into the ear canal, a simple tube running to the middle ear. This tube amplifies frequencies in the range 3 kHz to 12 kHz.
The human ear has earlobes at the bottom, which are vestigial but are used by many people to provide an attachment point for earrings. The earlobe is usually formed cleft from the side of the face and hangs from the rest of the ear but occasionally will be found looking fused and "lobeless" due to a recessive gene. The helix is the outer edge of the outer ear.
MIDDLE EAR: The middle ear includes the ossicles (three tiny bones), two muscle tendons (of the stapedius and tensor tympani muscles), and two nerve bundles (the horizontal portion of the facial nerve and a branch of the facial nerve called the chorda tympani). The Latin names of the ossicles are the malleus, incus, and stapes, but they are also referred to by their English translations: the hammer, anvil, and stirrup respectively.
Mammals are unique in having three ear bones. The incus and stapes are derived from bones of the jaw, and allow finer detection of sound. These bones form the linkage between the tympanic membrane and the oval window that leads to the inner ear. The tympanum converts vibrations of air in the ear canal into vibrations of the ossicles. The ossicles in turn transmit the vibrations through the membrane of the oval window into the fluid of the inner ear. The ratio in area between the tympanic membrane and the oval window results in an effective amplification of approximately 14 dB, peaking at a frequency of around 1 kHz. The combined transfer function of the outer ear and middle ear gives humans a peak sensitivity to frequencies between 1 kHz and 3 kHz. The tensor tympani muscle and stapedius muscles of the middle ear contract in response to loud sounds, thereby reducing the transmission of sound to the inner ear. This is called the acoustic reflex.
The middle ear is hollow. If the animal moves to a high-altitude environment, or dives into the water, there will be a pressure difference between the middle ear and the outside environment. This pressure will pose a risk of bursting or otherwise damaging the tympanum if it is not relieved. This is one of the functions of the Eustachian tubes, evolutionary descendants of the gills, which connect the middle ear to the nasopharynx. The Eustachian tubes are normally pinched off at the nose end, to prevent being clogged with phlegm, but they may be opened by lowering and protruding the jaw; this is why yawning helps relieve the pressure felt in the ears when on board an aircraft.
INNER EAR: The inner ear comprises both the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule.
The cochlea (Latin for "snail") is a spiralled, hollow, conical chamber of bone filled with perilymph and endolymph (in the scala media), a fluid medium that receives the sound vibrations transmitted from the air to the oval window through the ear drum and ossicles of the middle ear (see above). Running through its centre is the cochlea duct, which contains the spiral Organ of Corti, the receptor organ responsible for hearing. The bony cavity of the cochlea is divided into three separate chambers: the scala vestibuli, which lies superior to the cochlea duct and abuts the oval window; the scala media, which is the membranous cochlea duct containing endolymph and the organ of Corti; and the scala tympani, which lies inferior to the scala media and terminates at the round window. The two bony chambers (scala vestibuli and scala tympani) both contain perilymph and join together at the cochlear apex, a region called the helicotrema. Separating the scala vestibuli from the scala media is the Reissner's membrane. The basilar membrane separates the scala media from the scala tympani. Sitting on top of the basilar membrane is a cellular layer known as the Organ of Corti, which is lined with hair cells — sensory cells topped with hair-like structures called stereocilia.
As the stapes oscillates against the oval window in response to sound, the perilymph within the scala vestibuli also oscillates. For very low frequencies (below 20Hz), the pressure waves propagate along the complete route of the cochlea - up scala vestibuli, around helicotrema and down scala tympani to the round window. Frequencies this low do not activate the organ of Corti and are below the threshold for hearing. Higher frequencies do not propagate to the helicotrema but are transmitted through the endolymph in the cochlea duct to the perilymph in the scala tympani. The hair cells in the organ of Corti are tuned to certain sound frequencies, being responsive to high frequencies near the oval window and to low frequencies near the apex of the cochlea.
All excited hair cells send nerve impulses to the brain, which are perceived as a sound of whatever pitch the hair cell is associated with. A very strong movement of the endolymph due to very loud noise may cause hair cells to die. This is a common cause of partial hearing loss and is the reason why anyone using firearms or heavy machinery should wear earmuffs or earplugs.
The vestibular apparatus is filled with the same endolymph as the cochlea, but instead of detecting sound, it detects rotation of the head. If a line is drawn through the middle of each of the three semicircular canals, perpendicular to the plane in which the canal lies, the three lines would be perpendicular. They would represent three axes of rotation. Any rotation could be represented as three simultaneous rotations about the three axes.
Diseases and medical conditions of the ear and auditory system
Problems with the ear or auditory processing system in the brain can lead to deafness. Other disorders related to auditory system are:
Benign Paroxysmal Positional Vertigo
Conductive hearing impairment
Neurofibromatosis Type 1
Neurofibromatosis Type 2
Noise-induced hearing loss
Nonsyndromic hereditary hearing impairment
Sensorineural hearing loss
This is a glossary of medical terms related to communications disorders such as blindness and deafness.
Acoustic neurinoma - tumor, usually benign, which may develop on the hearing and balance nerves and can cause gradual hearing loss, tinnitus, and/or dizziness. (sometimes called vestibular schwannoma). Also see Neurofibromatosis Type 2.
Acquired deafness - loss of hearing that occurs or develops some time during the lifespan but is not present at birth.
Ageusia - loss of the sense of taste.
Albinism - lack of normal pigment in the skin, eyes, and hair.
Alport syndrome - hereditary condition characterized by kidney disease, sensorineural hearing loss, and sometimes eye defects.
American Sign Language (ASL) - manual language with its own syntax and grammar, used primarily by people who are deaf.
Anosmia - absence of the sense of smell.
Aphasia - total or partial loss of the ability to use or understand language; usually caused by stroke, brain disease, or injury.
Aphonia - complete loss of voice.
Apraxia - inability to execute a voluntary movement despite being able to demonstrate normal muscle function.
Articulation disorder - inability to correctly produce speech sounds (phonemes) because of imprecise placement, timing, pressure, speed, or flow of movement of the lips, tongue, or throat.
Assistive devices - technical tools and devices such as alphabet boards, text telephones, or text-to-speech conversion software used to aid individuals who have communication disorders perform actions, tasks, and activities.
Audiologist - health care professional who is trained to evaluate hearing loss and related disorders, including balance (vestibular) disorders and tinnitus, and to rehabilitate individuals with hearing loss and related disorders. An audiologist uses a variety of tests and procedures to assess hearing and balance function and to fit and dispense hearing aids and other assistive devices for hearing.
Auditory Brainstem Response test (ABR test) - a test for brain functioning in comatose, unresponsive, etc., patients, and for hearing in infants and young children; involves attaching electrodes to the head to record electrical activity from the hearing nerve and other parts of the brain.
Auditory nerve - eighth cranial nerve that connects the inner ear to the brainstem and is responsible for hearing and balance.
Auditory perception - ability to identify, interpret, and attach meaning to sound.
Auditory prosthesis - device that substitutes or enhances the ability to hear.
Augmentative devices - tools that help individuals with limited or absent speech to communicate, such as communication boards, pictographs (symbols that look like the things they represent), or ideographs (symbols representing ideas).
Aural rehabilitation - techniques used with people who are hearing impaired to improve their ability to speak and communicate.
Autoimmune deafness - individual's immune system produces abnormal antibodies that react against the body's healthy tissues.
Autism - brain disorder that begins in early childhood and persists throughout adulthood; affects three crucial areas of development: communication, social interaction, and creative or imaginative play.
Balance - biological system that enables individuals to know where their bodies are in the environment and to maintain a desired position. Normal balance depends on information from the labyrinth in the inner ear, from other senses such as sight and touch, and from muscle movement.
Balance disorder - disruption in the labyrinth, the inner ear organ that controls the balance system, which allows individuals to know where their bodies are in the environment. The labyrinth works with other systems in the body, such as the visual and skeletal systems, to maintain posture.
Barotrauma - injury to the middle ear caused by a reduction of air pressure.
Benign Paroxysmal Positional Vertigo (BPPV) - balance disorder that results in sudden onset of dizziness, spinning, or vertigo when moving the head.
Brainstem implant - auditory prosthesis that bypasses the cochlea and auditory nerve. This type of implant helps individuals who cannot benefit from a cochlear implant because the auditory nerves are not working.
Captioning - text display of spoken words, presented on a television or a movie screen, that allows a deaf or hard-of-hearing viewer to follow the dialogue and the action of a program simultaneously.
Central auditory processing disorder - inability to differentiate, recognize, or understand sounds; hearing and intelligence are normal.
Chemosensory disorders - diseases or problems associated with the sense of smell or the sense of taste.
Cholesteatoma - accumulation of dead cells in the middle ear, caused by repeated middle ear infections.
Cochlea - snail-shaped structure in the inner ear that contains the organ of hearing.
Cochlear implant - medical device that bypasses damaged structures in the inner ear and directly stimulates the auditory nerve, allowing some deaf individuals to learn to hear and interpret sounds and speech.
Cognition - thinking skills that include perception, memory, awareness, reasoning, judgment, intellect, and imagination.
Conductive hearing impairment - hearing loss caused by dysfunction of the outer or middle ear.
Cued speech - method of communication that combines speech reading with a system of handshapes placed near the mouth to help deaf or hard-of-hearing individuals differentiate words that look similar on the lips (e.g., bunch vs. punch) or are hidden (e.g., gag).
Cytomegalovirus (Congenital) - one group of herpes viruses that infects humans and can cause a variety of clinical symptoms, including deafness or hearing impairment; infection with the virus may be either before or after birth.
Decibel - unit that measures the intensity or loudness of sound.
Dizziness - physical unsteadiness, imbalance, and lightheadedness associated with balance disorders.
Dysarthria - group of speech disorders caused by disturbances in the strength or coordination of the muscles of the speech mechanism as a result of damage to the brain or nerves.
Dysequilibrium - any disturbance of balance.
Dysfluency - disruption in the smooth flow or expression of speech.
Dysgeusia - distortion or absence of the sense of taste.
Dyslexia - learning disability characterized by reading difficulties. Some individuals may also have difficulty writing, spelling, or working with numbers.
Dysosmia - distortion or absence of the sense of smell.
Dysphagia - difficulty swallowing.
Dysphonia - any impairment of the voice or speaking ability.
Dyspraxia of speech - in individuals with normal muscle tone and speech muscle coordination, partial loss of the ability to consistently pronounce words.
Dystonia - abnormal muscle tone of one or more muscles.
Ear infection - presence and growth of bacteria or viruses in the ear.
Ear wax - yellow secretion from glands in the outer ear (cerumen) that keeps the skin of the ear dry and protected from infection.
Endolymph - fluid in the labyrinth (the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule).
Gustation - act or sensation of tasting.
Hair cells - sensory cells of the inner ear, which are topped with hair-like structures, the stereocilia, and which transform the mechanical energy of sound waves into nerve impulses.
Haptic sense - sense of physical contact or touch.
Haptometer - instrument for measuring sensitivity to touch.
Hearing - series of events in which sound waves in the air are converted to electrical signals, which are sent as nerve impulses to the brain, where they are interpreted.
Hearing aid - electronic device that brings amplified sound to the ear. A hearing aid usually consists of a microphone, amplifier, and receiver.
Hearing disorder - disruption in the normal hearing process that may occur in outer, middle, or inner ear, whereby sound waves are not conducted to the inner ear, converted to electrical signals and/or nerve impulses are not transmitted to the brain to be interpreted.
Hereditary hearing impairment - hearing loss passed down through generations of a family.
Hoarseness - abnormally rough or harsh-sounding voice caused by vocal abuse and other disorders such as gastroesophageal reflux, thyroid problems, or trauma to the larynx (voice box).
Hypogeusia - diminished sensitivity to taste.
Hyposmia - diminished sensitivity to smell.
Inner ear - part of the ear that contains both the organ of hearing (the cochlea) and the organ of balance (the labyrinth).
Kallmann's syndrome - disorder that can include several characteristics such as absence of the sense of smell and decreased functional activity of the gonads (organs that produce sex cells), affecting growth and sexual development.
Labyrinth - organ of balance located in the inner ear. The labyrinth consists of three semicircular canals and the vestibule.
Labyrinthine hydrops - excessive fluid in the organ of balance (labyrinth); can cause pressure or fullness in the ears, hearing loss, dizziness, and loss of balance.
Labyrinthitis - viral or bacterial infection or inflammation of the inner ear that can cause dizziness, loss of balance, and temporary hearing loss.
Landau-Kleffner syndrome - childhood disorder of unknown origin which often extends into adulthood and can be identified by gradual or sudden loss of the ability to understand and use spoken language.
Language - system for communicating ideas and feelings using sounds, gestures, signs, or marks.
Language disorders - any of a number of problems with verbal communication and the ability to use or understand a symbol system for communication.
Laryngeal neoplasms - abnormal growths in the larynx (voice box) that can be cancerous or noncancerous.
Laryngeal nodules - noncancerous, callous-like growths on the inner parts of the vocal folds (vocal cords); usually caused by vocal abuse or misuse.
Laryngeal paralysis - loss of function or feeling of one or both of the vocal folds caused by injury or disease to the nerves of the larynx.
Laryngectomy - surgery to remove part or all of the larynx (voice box).
Laryngitis - hoarse voice or the complete loss of the voice because of irritation to the vocal folds (vocal cords).
Larynx - valve structure between the trachea (windpipe) and the pharynx (the upper throat) that is the primary organ of voice production.
Learning disabilities - childhood disorders characterized by difficulty with certain skills such as reading or writing in individuals with normal intelligence.
Mastoid - back portion of the temporal bone that contains the inner ear.
Mastoid surgery - surgical procedure to remove infection from the mastoid bone.
Meige syndrome - movement disorder that can involve excessive eye blinking (blepharospasm) with involuntary movements of the jaw muscles, lips, and tongue (oromandibular dystonia).
Ménière's disease - inner ear disorder that can affect both hearing and balance. It can cause episodes of vertigo, hearing loss, tinnitus, and the sensation of fullness in the ear.
Meningitis - inflammation of the meninges, the membranes that envelop the brain and the spinal cord; may cause hearing loss or deafness.
Middle ear - part of the ear that includes the eardrum and three tiny bones of the middle ear, ending at the round window that leads to the inner ear.
Misarticulation - inaccurately produced speech sound (phoneme) or sounds.
Motion sickness - dizziness, sweating, nausea, vomiting, and generalized discomfort experienced when an individual is in motion.
Motor speech disorders - group of disorders caused by the inability to accurately produce speech sounds (phonemes) because of muscle weakness or incoordination or difficulty performing voluntary muscle movements.
Neural plasticity - ability of the brain and/or certain parts of the nervous system to adapt to new conditions, such as an injury.
Neural prostheses - devices that substitute for an injured or diseased part of the nervous system, such as the cochlear implant.
Neural stimulation - to activate or energize a nerve through an external source.
Neurofibromatosis Type 1 (NF-1 von Recklinghausen's) - group of inherited disorders in which noncancerous tumors grow on several nerves that may include the hearing nerve. The symptoms of NF-1 include coffee-colored spots on the skin, enlargement, deformation of bones, and neurofibromas.
Neurofibromatosis Type 2 (NF-2) - group of inherited disorders in which noncancerous tumors grow on several nerves that usually include the hearing nerve. The symptoms of NF-2 include tumors on the hearing nerve which can affect hearing and balance. NF-2 may occur in the teenage years with hearing loss. Also see acoustic neurinoma.
Neurogenic communication disorder - inability to exchange information with others because of hearing, speech, and/or language problems caused by impairment of the nervous system (brain or nerves).
Noise-induced hearing loss - hearing loss caused by exposure to harmful sounds, either very loud impulse sound(s) or repeated exposure to sounds over 90-decibel level over an extended period of time that damage the sensitive structures of the inner ear.
Nonsyndromic hereditary hearing impairment - hearing loss or deafness that is inherited and is not associated with other inherited clinical characteristics.
Odorant - substance that stimulates the sense of smell.
Olfaction - the act of smelling.
Olfactometer - device for estimating the intensity of the sense of smell.
Open-set speech recognition - understanding speech without visual clues (speech reading).
Otitis externa - inflammation of the outer part of the ear extending to the auditory canal.
Otitis media - inflammation of the middle ear caused by infection.
Otoacoustic emissions - low-intensity sounds produced by the inner ear that can be quickly measured with a sensitive microphone placed in the ear canal.
Otolaryngologist - physician/surgeon who specializes in diseases of the ears, nose, throat, and head and neck.
Otologist - physician/surgeon who specializes in diseases of the ear.
Otosclerosis - abnormal growth of bone of the inner ear. This bone prevents structures within the ear from working properly and causes hearing loss. For some people with otosclerosis, the hearing loss may become severe.
Ototoxic drugs - drugs such as a special class of antibiotics, aminoglycoside antibiotics, that can damage the hearing and balance organs located in the inner ear for some individuals.
Outer ear - external portion of the ear, consisting of the pinna, or auricle, and the ear canal.
Papillomavirus - group of viruses that can cause noncancerous wart-like tumors to grow on the surface of skin and internal organs such as the respiratory tract; can be life-threatening.
Parosmia - any disease or perversion of the sense of smell, especially the subjective perception of odors that do not exist.
Perception (Hearing) - process of knowing or being aware of information through the ear.
Perilymph fistula - leakage of inner ear fluid to the middle ear that occurs without apparent cause or that is associated with head trauma, physical exertion, or barotrauma.
Pervasive developmental disorders - disorders characterized by delays in several areas of development that may include socialization and communication.
Pheromones - chemical substances secreted by an animal that elicits a specific behavioral or physiological response in another animal of the same species.
Phonology - study of speech sounds.
Postlingually deafened - individual who becomes deaf after having acquired language.
Prelingually deafened - individual who is either born deaf or who lost his or her hearing early in childhood, before acquiring language.
Presbycusis - loss of hearing that gradually occurs because of changes in the inner or middle ear in individuals as they grow older.
Reading disorders - any of a group of problems characterized by difficulty using or understanding the symbol system for written language.
Round window - membrane separating the middle ear and inner ear.
Sensorineural hearing loss - hearing loss caused by damage to the sensory cells and/or nerve fibers of the inner ear.
Sign language - method of communication for people who are deaf or hard of hearing in which hand movements, gestures, and facial expressions convey grammatical structure and meaning.
Smell - to perceive odor or scent through stimuli affecting the olfactory nerves. See olfaction.
Smell disorder - inability to perceive odors. It may be temporary, caused by a head cold or swelling or blockage of the nasal passages. It can be permanent when any part of the olfactory region is damaged by factors such as brain injury, tumor, disease, or chronic rhinitis.
Sound vocalization - ability to produce voice.
Spasmodic dysphonia - momentary disruption of voice caused by involuntary movements of one or more muscles of the larynx or voice box.
Specific language impairment (SLI) - difficulty with language or the organized-symbol system used for communication in the absence of problems such as mental retardation, hearing loss, or emotional disorders.
Speech - spoken communication.
Speech disorder - any defect or abnormality that prevents an individual from communicating by means of spoken words. Speech disorders may develop from nerve injury to the brain, muscular paralysis, structural defects, hysteria, or mental retardation.
Speech processor - part of a cochlear implant that converts speech sounds into electrical impulses to stimulate the auditory nerve, allowing an individual to understand sound and speech.
Speech-Language pathologist - health professional trained to evaluate and treat people who have voice, speech, language, or swallowing disorders (including hearing impairment) that affect their ability to communicate.
Stroke - also known as a cerebrovascular accident (CVA); caused by a lack of blood to the brain, resulting in the sudden loss of speech, language, or the ability to move a body part, and, if severe enough, death.
Stuttering - frequent repetition of words or parts of words that disrupts the smooth flow of speech.
Sudden deafness - loss of hearing that occurs quickly due to such causes as explosion, a viral infection, or the use of some drugs.
Swallowing disorders - any of a group of problems that interferes with the transfer of food from the mouth to the stomach.
Syndromic hearing impairment - hearing loss or deafness that, along with other characteristics, is inherited or passed down through generations of a family.
Tactile - related to touch or the sense of touch.
Tactile devices - mechanical instruments that make use of touch to help individuals who have certain disabilities, such as deaf-blindness, to communicate.
Taste - sensation produced by a stimulus applied to the gustatory nerve endings in the tongue. The four tastes are salt, sour, sweet, and bitter. Some scientists indicate the existence of a fifth taste, described as savory.
Taste buds - groups of cells located on the tongue that enable one to recognize different tastes.
Taste disorder - inability to perceive different flavors. Taste disorders may result from poor oral hygiene, gum disease, hepatitis, or medicines and chemotherapeutic drugs. Taste disorders may also be neurological.
Throat disorders - disorders or diseases of the larynx (voice box), pharynx, or esophagus.
Thyroplasty - surgical technique to improve voice by altering the cartilages of the larynx, which houses the vocal folds (vocal cords), in order to change the position or length of the vocal folds. Also known as laryngeal framework surgery.
Tinnitus - sensation of a ringing, roaring, or buzzing sound in the ears or head. It is often associated with many forms of hearing impairment and noise exposure.
Tongue - large muscle on the floor of the mouth that manipulates food for chewing and swallowing. It is the main organ of taste, and assists in forming speech sounds.
Touch - tactile sense; the sense by which contact with the skin or mucous membrane is experienced.
Tourette syndrome - neurological disorder characterized by recurring movements and sounds (called tics).
Tracheostomy - surgical opening into the trachea (windpipe) to help someone breathe who has an obstruction or swelling in the larynx (voice box) or upper throat or who has had the larynx surgically removed.
Tuberous Sclerosis - Hereditary disease with multiorgan manifestation. Typical symptoms are epileptic seizures, autism, skin disorders, and renal tumors.
Tympanoplasty - surgical repair of the eardrum (tympanic membrane) or bones of the middle ear.
Umami - Taste of substances such as L-glutamate salts (MSG) that are found in foods like bouillon and other stocks.
Usher syndrome - hereditary disease that affects hearing and vision and sometimes balance.
Velocardiofacial syndrome - inherited disorder characterized by cleft palate (opening in the roof of the mouth), heart defects, characteristic facial appearance, minor learning problems, and speech and feeding problems.
Vertigo - illusion of movement; a sensation as if the external world were revolving around an individual (objective vertigo) or as if the individual were revolving in space (subjective vertigo).
Vestibular Neuronitis - infection at the vestibular nerve.
Vestibular system - system in the body that is responsible for maintaining balance, posture, and the body's orientation in space. This system also regulates locomotion and other movements and keeps objects in visual focus as the body moves.
Vestibule - bony cavity of the inner ear.
Vibrotactile aids - mechanical instruments that help individuals who are deaf to detect and interpret sound through the sense of touch.
Vocal cord paralysis - inability of one or both vocal folds (vocal cords) to move because of damage to the brain or nerves.
Vocal cords (Vocal folds) - muscularized folds of mucous membrane that extend from the larynx (voice box) wall. The folds are enclosed in elastic vocal ligament and muscle that control the tension and rate of vibration of the cords as air passes through them.
Vocal folds - see Vocal cords.
Vocal tremor - trembling or shaking of one or more of the muscles of the larynx, resulting in an unsteady-sounding voice.
Voice - sound produced by air passing out through the larynx and upper respiratory tract.
Voice disorders - group of problems involving abnormal pitch, loudness, or quality of the sound produced by the larynx (voice box).
Waardenburg syndrome - hereditary disorder that is characterized by hearing impairment, a white shock of hair and/or distinctive blue color to one or both eyes, and wide-set inner corners of the eyes. Balance problems are also associated with some types of Waardenburg syndrome.
In anatomy, the throat is the part of the neck anterior to the vertebral column. It consists of the pharynx and larynx.
The throat contains various blood vessels, various pharyngeal muscles, the trachea (windpipe) and the esophagus. The hyoid bone is the only bone located in the throat of mammals.
The pharynx is the part of the digestive system and respiratory system of many animals immediately behind the mouth and in front of the esophagus. In mammals, it is where the digestive tract and the respiratory tract cross, commonly called the "throat" (which term may also include the larynx) The pharynx attaches to the larynx, which is the first element of the airways. The human pharynx is bent at a sharper angle than other mammal pharynges, enabling us to produce a wider variety of sounds, but also putting us in danger of choking.
The human pharynx is conventionally divided into three sections:
Nasopharynx: Lying behind the nasal cavity. Posterosuperiorly this extends from the level of the junction of the hard and soft palates to the base of skull, laterally to include the fossa of Rosenmueller. The inferior wall consists of the superior surface of the soft palate.
Oropharynx: Which lies behind the oral cavity. The anterior wall consists of the base of tongue and vallecula; the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars; the superior wall consists of the inferior surface of the soft palate and the uvula.
Hypopharynx: Which includes the pharyngoesophageal junction (postcricoid area), the piriform sinus, and the posterior pharyngeal wall.
The larynx (plural larynges), or voice-box, is an organ in the neck of mammals involved in protection of the trachea and sound production. The larynx houses the vocal cords, and is situated at the point where the upper tract splits into the trachea and the esophagus.
The structure of the larynx is mainly composed of cartilage bound by ligaments and muscle. At the front is the thyroid cartilage, creating the prominence of the Adam's apple in humans. The inferior horns (protrusions at the bottom rear of the thyroid cartilage) of the thyroid cartilage rest on a ring-shaped cartilage called the cricoid cartilage which connects the larynx to the trachea. The cricoid cartilage resembles a signet ring (narrow in front, broader in back). Above the larynx is the hyoid bone, by which (via various muscles and ligaments) the larynx is connected to the jaw and skull. These muscles move the larynx during swallowing. The hyoid is the only floating bone in the body; it is not 'attached' to any other bones. The epiglottis is another cartilage that extents upwards behind the back of the tongue and projects down through the hyoid bone. It connects to the thyroid cartilage just beneath the thyroid notch (the Adam's apple).
The space defined by these main cartilages can be divided roughly into the supraglottis at the top and the glottis.
The glottis is defined as the space between the vocal folds (more commonly known as vocal cords), which are located at the upper rim of the cricoid cartilage. They attach to the thyroid cartilage at the front, and to the Arytenoid cartilages at the back. These are two roughly tetrahedral cartilages responsible for pulling the vocal folds together and apart (adduction and abduction — see Anatomical terms of location). The glottis is the laryngeal area of most interest to speech researchers, as it is widely believed to be where most of the control of phonation and pitch goes on. The vocal folds are muscular masses coated with a mucous membrane which protects much of the respiratory tract from foreign particles. Their inner edges contain the vocal ligament.
The supraglottis is that part of the larynx above the glottis. It contains the ventricle of the larynx (laryngeal sinus), the ventricular folds (or false vocal folds), the epiglottis, and the aryepiglottal folds — two folds of connective tissue that connect the epiglottis to the arytenoid cartilages. Muscles in the aryepiglottal folds can pull the leaf-shaped epiglottis down, sealing the larynx and protecting the trachea below from foreign objects.
During swallowing the larynx (at the epiglottis and at the glottis) closes to prevent swallowed material entering the lungs, there is also a strong cough reflex to protect the lungs. Sensation is transferred by the superior laryngeal nerve (glottis and supraglottis) and the recurrent laryngeal nerve (subglottis and muscles), both branches of the vagus nerve.
While articulation of the sound (the fine manipulation that creates the many different vowel and consonant sounds of the world's languages) is achieved by the use of the teeth, tongue, palate, and lips, sound is generated in the larynx, and that is where pitch and volume are manipulated.
The vocal folds can be held close together (by adducting the arytenoid cartilages), so that they vibrate (see phonation). The muscles attached to the arytenoid cartilages control the degree of opening.
Vocal fold length and tension can be controlled by rocking the thyroid cartilage forward and backward on the cricoid cartilage, and by manipulating the tension of the muscles within the vocal folds. This causes the pitch produced during phonation to rise or fall.
There are several things that can cause a larynx to not function properly. Some symptoms are hoarseness, loss of voice, pain in the throat, and breathing difficulties. Acute laryngitis is the sudden inflammation and swelling of the larynx. It is caused by the common cold or by excessive yelling. It is not serious. Chronic laryngitis is caused by smoking, dust, frequent yelling, or prolonged exposure to polluted air. It is much more serious then acute laryngitis.
Ulcers are caused by the epiglottis hitting the trachea due to the making of certain sounds. Polyps and nodules are small bumps on the vocal cords caused by excessive yelling for a long time and prolonged exposure to cigarette smoke. Finally, two types of cancer, squamous cell carcinoma and verrucous carcinoma. These are both caused almost exclusively by repeated exposure to cigarette smoke.
Trachea is a common biological term for an airway through which respiratory gas transport takes place in organisms.
The trachea, or windpipe, is a tube extending from the larynx to the bronchi in mammals, and from the pharynx to the syrinx in birds, carrying air to the lungs. It is lined with ciliated cells which push particles out and cartilage rings which reinforce the trachea and prevent it from collapsing on itself during the breathing process. These numerous cartilaginous half-rings located one above the other along the trachea have open ends adjacent to the oesophagus. The rings are connected by muscular and fibrous tissue, and they are lined inside with a ciliated mucous membrane.
In ill or injured persons, the natural airway formed by the trachea may be damaged or closed off. Intubation is the medical procedure of inserting an artificial tube into the trachea to permit breathing. See also choking.
Diseases of the trachea include:
The esophagus (also spelled oesophagus) or gullet is the muscular tube in vertebrates through which ingested food passes from the mouth area to the stomach. Food is passed through the esophagus by using the process of peristalsis. Specifically, in mammals, it connects the pharynx, which is the body cavity that is common to the digestive system and respiratory system behind the mouth (buccal cavity), with the stomach, where the second stage of digestion is initiated (the first stage of digestion is in the mouth, with teeth and tongue masticating food and mixing it with saliva).
The esophagus is lined with mucous membrane, and is more deeply lined with muscle that acts with peristaltic action to move swallowed food down to the stomach.
The junction between the esophagus and the stomach is not actually considered a valve, although it is sometimes called the cardiac valve, cardia or cardias, but is actually more of a stricture. Many people experience acid reflux, where stomach acid gets pushed up into the esophagus, causing a burning sensation, commonly termed heartburn. Extended exposure to heartburn may erode the lining of the esophagus, leading to a potentially cancerous condition called Barrett's Esophagus.
Some people also experience a sensation known as globus esophagus, where it feels as if a ball is lodged in the lower part of the esophagus.
The word "esophagus" is the result of the "o" being dropped from the typographic œ (oe) in "œsophagus".
Esophageal diseases and conditions
The following are diseases and conditions that affect the esophagus:
Caustic injury to the esophagus
The human upper arm, the shoulder joint is composed of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone). Two joints facilitate shoulder movement. The acromioclavicular (AC) joint is located between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle. The glenohumeral joint, to which the generic term "shoulder joint" usually refers, is a ball-and-socket joint that allows the arm to rotate in a circular fashion or to hinge out and up away from the body. (The "ball" is the top, rounded portion of the upper arm bone or humerus; the "socket," or glenoid, is a dish-shaped part of the outer edge of the scapula into which the ball fits.) Arm movement is further facilitated by the ability of the scapula to slide both laterally and vertically along the rib cage. The capsule is a soft tissue envelope that encircles the glenohumeral joint. It is lined by a thin, smooth synovial membrane.
The bones of the shoulder are held in place by muscles, tendons, and ligaments. Tendons are tough cords of tissue that attach the shoulder muscles to bone and assist the muscles in moving the shoulder. Ligaments attach shoulder bones to each other, providing stability. For example, the front of the joint capsule is anchored by three glenohumeral ligaments.
The rotator cuff is a structure composed of tendons that, with associated muscles, holds the ball at the top of the humerus in the glenoid socket and provides mobility and strength to the shoulder joint.
Two filmy sac-like structures called bursae permit smooth gliding between bone, muscle, and tendon. They cushion and protect the rotator cuff from the bony arch of the acromion.
The human rib cage. In anatomy, ribs (Latin costae) are the long curved bones, which form the rib cage. Ribs surround the chest (Latin thorax) of land vertebrates, and protect the lungs, heart, and other internal organs of the thoracic cavity.
Types of Ribs
The human skeleton has 24 ribs, 12 on each side. (A small proportion have one pair more or fewer.) They are attached behind the vertebral column. The first seven pairs are connected to the sternum in front and are known as true ribs (costae verae, I-VII). The eighth, ninth, and tenth are attached in front to the cartilaginous portion of the next rib above and are known as false ribs (costae spuriae, VIII-X). The lower two, that is the eleventh and twelfth, are not attached in front and are called floating ribs (costae fluitantes, XI-XII). The spaces between the ribs are known as intercostal spaces; they contain the intercostal muscles, nerves, and arteries. The rib cage allows for breathing due to its elasticity. In some humans, the rib remnant of the 7th neck vertebra on one or both sides is replaced by a free extra rib called a cervical rib, which can cause trouble for the nerves going to the arm.
The third through ninth ribs are "typical ribs" since they share the same structure. They each have a head that has two facets separated by a crest. One head articulates with the rib's corresponding vertebra and one head articulates with the vertebra superior (above) to it. They have a neck that connects the head with the shaft. The neck meets the shaft at a tubercle. The shaft is thin, flat, and curved. The curve is most prominent at the costal angle. The concave (inside) surface has a groove to protect the intercostal nerve and vessels.
The atypical ribs are the 1st, 2nd, and 10th to 12th.
The first rib has a shaft that is wide and nearly horizontal, and has the sharpest curve of the seven true ribs. Its head has a single facet to articulate with the first thoracic vertebra (T1). It also has two grooves for the subclavian vessels, which are separated by the scalene tubercle.
The second rib is thinner, less curved, and longer than the first rib. It has two facets to articulate with T2 and T1, and a tubercle for muscles to attach to.
The 10th to 12th ribs have only one facet on their head, and the 11th and 12th ribs are short with no necks or tubercles.
Rib Fractures and Associated Injuries
The first rib is rarely fractured because of its protected position behind the clavicle (collarbone). However, if it is broken serious damage can occur to the brachial plexus of nerves and the subclavian vessels.
The middle ribs are the ones most commonly fractured. Fractures usually occur from direct blows or from indirect crushing injuries. The weakest part of a rib is just anterior to its angle, but a fracture can occur anywhere.
A lower rib fracture has the complication of potentially injuring the diaphragm, which could result in a diaphragmatic hernia.
Rib fractures are painful because the ribs have to move for inspiration and expiration of air. Rib pain may also be associated with metastasis of cancer, especially from the breast or prostate.
Bifid rib, bifurcated rib
A Bifid rib or bifurcated rib is a congenital abnormality occurring in about 1% of the population. The sternal end of the rib is cleaved into two. It is usually unilateral. Effects of this neuroskeletal anomaly can include respiratory difficulties, neurological difficulties, limitations, and limited energy from the stress of needing to compensate for the neurophysiological difficulties.
The vertebral column (backbone or spine) is a column of vertebrae situated in the dorsal aspect of the abdomen. It houses the spinal cord in its spinal canal.
Viewed laterally the vertebral column presents several curves, which correspond to the different regions of the column, and are called cervical, thoracic, lumbar, and pelvic.
Cervical curve: The cervical curve, convex forward, begins at the apex of the odontoid (tooth-like) process, and ends at the middle of the second thoracic vertebra; it is the least marked of all the curves.
Thoracic curve: The thoracic curve, concave forward, begins at the middle of the second and ends at the middle of the twelfth thoracic vertebra. Its most prominent point behind corresponds to the spinous process of the seventh thoracic vertebra.
Lumbar curve: The lumbar curve is more marked in the female than in the male; it begins at the middle of the last thoracic vertebra, and ends at the sacrovertebral angle. It is convex anteriorly, the convexity of the lower three vertebrae being much greater than that of the upper two.
Pelvic curve: The pelvic curve begins at the sacrovertebral articulation, and ends at the point of the coccyx; its concavity is directed downward and forward. The thoracic and pelvic curves are termed primary curves, because they alone are present during fetal life. In the early embryo, the vertebral column is C-shaped, and the cervical and lumbar curvatures are not yet present in a newborn infant.
The cervical and lumbar curves are compensatory or secondary, and are developed after birth, the former when the child is able to hold up its head (at three or four months), and to sit upright (at nine months), the latter at twelve or eighteen months, when the child begins to walk.
The vertebral column also has a slight lateral curvature, the convexity of which is directed toward the right side. This may be produced by muscular action, most persons using the right arm in preference to the left, especially in making long-continued efforts, when the body is curved to the right side. In support of this explanation it has been found that in one or two individuals who were left-handed, the convexity was to the left side. This curvature is regarded by others as being produced by the aortic arch and upper part of the descending thoracic aorta – a view which is supported by the fact that in cases where the viscera are transposed and the aorta is on the right side, the convexity of the curve is directed to the left side.
When viewed from in front, the width of the bodies of the vertebrae is seen to increase from the second cervical to the first thoracic; there is then a slight diminution in the next three vertebrae; below this there is again a gradual and progressive increase in width as low as the sacrovertebral angle. From this point there is a rapid diminution, to the apex of the coccyx.
The posterior surface of the vertebral column presents in the median line the spinous processes. In the cervical region (with the exception of the second and seventh vertebrae) these are short and horizontal, with bifid extremities. In the upper part of the thoracic region they are directed obliquely downward; in the middle they are almost vertical, and in the lower part they are nearly horizontal. In the lumbar region they are nearly horizontal. The spinous processes are separated by considerable intervals in the lumbar region, by narrower intervals in the neck, and are closely approximated in the middle of the thoracic region. Occasionally one of these processes deviates a little from the median line — a fact to be remembered in practice, as irregularities of this sort are attendant also on fractures or displacements of the vertebral column. On either side of the spinous processes is the vertebral groove formed by the laminae in the cervical and lumbar regions, where it is shallow, and by the laminae and transverse processes in the thoracic region, where it is deep and broad; these grooves lodge the deep muscles of the back. Lateral to the vertebral grooves are the articular processes, and still more laterally the transverse processes. In the thoracic region, the transverse processes stand backward, on a plane considerably behind that of the same processes in the cervical and lumbar regions. In the cervical region, the transverse processes are placed in front of the articular processes, lateral to the pedicles and between the intervertebral foramina. In the thoracic region they are posterior to the pedicles, intervertebral foramina, and articular processes. In the lumbar region they are in front of the articular processes, but behind the intervertebral foramina.
The lateral surfaces are separated from the posterior surface by the articular processes in the cervical and lumbar regions, and by the transverse processes in the thoracic region. They present, in front, the sides of the bodies of the vertebrae, marked in the thoracic region by the facets for articulation with the heads of the ribs. More posteriorly are the intervertebral foramina, formed by the juxtaposition of the vertebral notches, oval in shape, smallest in the cervical and upper part of the thoracic regions, and gradually increasing in size to the last lumbar. They transmit the spinal nerves and are situated between the transverse processes in the cervical region, and in front of them in the thoracic and lumbar regions.
The vertebral canal follows the different curves of the column; it is large and triangular in those parts of the column which enjoy the greatest freedom of movement, such as the cervical and lumbar regions; and is small and rounded in the thoracic region, where motion is more limited.
Occasionally the coalescence of the laminae is not completed, and consequently a cleft is left in the arches of the vertebrae, through which a protrusion of the spinal membranes (dura mater and arachnoid), and generally of the spinal cord (medulla spinalis) itself, takes place, constituting the malformation known as spina bifida. This condition is most common in the lumbosacral region, but it may occur in the thoracic or cervical region, or the arches throughout the whole length of the canal may remain incomplete.
The following abnormal curvatures may occur in some people:
Kyphosis is an exaggerated posterior curvature in the thoracic region. This produces the so-called "humpback".
Lordosis is an exaggerated anterior curvature of the lumbar region, "swayback". Temporary lordosis is common among pregnant women.
Scoliosis, lateral curvature, is the most common abnormal curvature, occurring in 0.5% of the population. It is more common among females and may result from unequal growth of the two sides of one or more vertebrae.
In anatomy, the arm is the upper limb of a bipedal mammal, specifically the segment between the shoulder and the elbow. Arm can also refer to any analogous structure, such as one of the paired forelimbs of a quadruped, or any muscular hydrostat similar to a tentacle, as seen on some cephalopods, such as octopuses.
The term arm also refers to the entire upper limb in an organism. Anatomically, the segment between the elbow and wrist is properly called the forearm.
In primates the arms are richly adapted for both climbing and for more skilled, manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the presence of two forearm bones which can rotate around each other allows for additional range of motion at this level.
Anatomy of the human arm
The human arm contains bones, joints, muscles, nerves and blood vessels. Many of these muscles are used for everyday tasks. There are clinical uses for the arm, including venepuncture and peripheral venous cannulation in the cubital fossa.
Bony structure and joints
The humerus is the (upper) arm bone. It articulates with the scapula above at the glenohumeral joint (shoulder) and with the ulna and radius below as the elbow joint.
The shoulder is the ball-and-socket joint between the proximal end of the humerus and the clavicle and scapula.
The elbow joint is the hinge joint between the distal end of the humerus and the proximal ends of the radius and ulna.
The arm is divided by a fascial layer (known as lateral and medical intermuscular septa) separating the muscles into an anterior and posterior osteofascial compartments. The fascia merges with the periosteum (outer bone layer) of the humerus. The compartments contain muscles which are innervated by the same nerve and perform the same action.
The anterior compartment is known as the "flexor compartment" as flexion is its main action. The muscles contained therein are:
They are all supplied by the musculocutaneous nerve, which has nervous origins of C5, C6, C7 (see brachial plexus).
The deltoid muscle is considered to have part of its body in the anterior compartment. This huge muscle is the main adductor of the upper limb and extends over the shoulder.
The brachioradialis muscle originates in the arm but inserts into the forearm. This muscle is responsible for supination.
The posterior compartment contains muscles, which are all supplied by the radial nerve. This compartment is also known as the "extensor compartment", extension being its main action. Muscles of this compartment are:
Triceps brachii, a huge muscle which contains three heads, the lateral, medial and middle.
Anconeus, a tiny muscle, which some embryologists suggest may be the fourth head of the triceps brachii muscle. This muscle stabilizes the elbow joint during movements. As the upper and lower limbs have similar embryological origins and the lower limb contains the quadriceps femoris muscle (the lower limb equivalent of the triceps), which has four heads, this would seem to make sense.
This important area is clinically important for venepuncture and for blood pressure measurement. It is an imaginary triangle with borders being:
Laterally, the medial border of brachioradialis muscle.
Medially, the lateral border of pronator teres muscle.
Superiorly, the intercondylar line, an imaginary line between the two condyles of the humerus
The floor is the brachialis muscle
The roof is the skin and fascia of the arm and forearm
The structures, which pass through the cubital fossa, are vital. The order from which they pass into the forearm are as follows, from medial to lateral:
1. Median nerve, which starts to branch
2. Brachial artery
3. Tendon of the biceps brachii muscle
4. Radial nerve
5. Median cubital vein - this important vein is where venepuncture occurs. It connects the basilic and cephalic veins.
6. Lymph nodes
Important nerves related to arms:
1. Musculocutaneous nerve
2. Radial nerve
3. Median nerve
4. Ulnar nerve
Blood supply and venous drainage
The main artery in the arm is the brachial artery. This artery is a continuation of the axillary artery. The point at which the axillary becomes the brachial is distal to the lower border of teres major. The brachial artery gives off an important brach, the profunda brachii (deep artery of the arm). This branching occurs just below the lower border of teres major.
The profunda brachii travels through the lower triangular space with the radial nerve. From here onwards it has an intimate relationship with the radial nerve.
The veins of the arm carry blood from the extremities of the limb, as well as drain the arm itself. The two main veins are the basilic and the cephalic veins. There is a connecting vein between the two, the median cubital vein, which passes through the cubital fossa and is clinically important for venepuncture (withdrawing blood). The basilic travels on the medial side of the arm and terminates at the level of the 7th rib. The cephalic travels on the lateral side of the arm and terminates as the axillary vein. It passes through the deltopectoral triangle, a space between the deltoid and the pectoralis major muscles.
The hand is the portion of the arm or anterior limb of a human or other primate, where the appendage terminates. This part of the limb is especially used in grasping and holding. Each hand is a mirror image of the other.
What constitutes a hand?
Although many mammals and other animals have grasping appendages similar in form to a hand, these are scientifically not considered to be so, and have other varying names, including paws. Using the term hand is merely a scientific usage of anthropomorphization, to distinguish the terminations of the front paws from the hind ones. The only true hands appear in the mammalian order of primates. Hands must also feature opposable thumbs, as described later in the text.
Human anatomy of the hand
The human hand consists of a broad palm (metacarpus) with five digits, attached to the forearm by a joint called the wrist (carpus).
The Five Fingers
Five fingers on the hand are located at the outermost edge of the palm. These four digits can be folded over the palm, this allows for the holding of objects, and furthermore the grasping of small objects. Each finger, starting with the one closest to the thumb, has a colloquial name to distinguish it from the others:
Index finger, pointer finger, or forefinger
Little finger or 'pinky'
The thumb (connected to the trapezium) is located on one of the sides, parallel to the arm. The thumb can be easily rotated 90º, on a perpendicular level compared to the palm, unlike the fingers which can only be rotated approximately 45º. A reliable way of identifying true hands is from the presence of opposable thumbs. Opposable thumbs are identified by the ability to be brought opposite to the fingers.
The human hand has at least 27 bones: the carpus or wrist account for 8; the metacarpus or palm contains 5; the remaining 14 are digital bones.
Bones of the wrist
The wrist has eight bones, arranged in two rows of four. These bones fit into a shallow socket formed by the bones of the forearm.
Bones of the palm
The palm has 5 bones, one to each of the 5 digits.
Also called phalanx bones. Human hands contain 14 of them; 2 in the thumb, and 3 in each of the four fingers, called;
Distal phalanx, carrying the nail,
Middle phalanx and
(The thumb has no middle phalanx).
Sesamoid bones are small ossified nodes embedded in the tendons to provide extra leverage and reduce pressure on the underlying tissue. Many exist around the palm at the bases of the digits, but the exact number varies between different people. The patella is the largest example of a sesamoid bone in the human body.
Muscles and tendons
The movements of the human hand are accomplished by two sets of each of these tissues. They can be subdivided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm.
Intrinsic hand muscles
The Intrinsic muscle groups are the thenar and hypothenar muscles (thenar referring to the thumb, hypothenar to the small finger), the interosseus muscles (between the metacarpal bones, four dorsally and three volarly) and the lumbrical muscles. These muscles arise from the deep flexor (and are special because they have no bony origin) and insert on the dorsal extensor hood mechanism.
The extrinsic muscles of the hand
The flexors: The fingers have two long flexors, located on the underside of the forearm. They insert by tendons to the phalanges of the fingers. The deep flexor attaches to the distal phalanx, and the superficial flexor attaches to the middle phalanx. The flexors allow for the actual bending of the fingers. The thumb has one long flexor and a short flexor in the thenar muscle group. The human thumb also has other muscles in the thenar group (opponens- and abductor muscle), moving the thumb in opposition, making grasping possible.
The extensors: Located on the back of the forearm and a connected in a more complex way then the flexors to the dorsum of the fingers. The tendons unite with the interosseous and lumbrical muscles to form the extensor-hood mechanism. The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm; the tendons of these form the anatomical snuffbox. Also, the index finger and the little finger have an extra extensor, used for instance for pointing.
Some people have more than the usual number of fingers or toes, this is normally caused by a genetic condition called Polydactyly.
The name Phalanges is commonly given to the bones that form fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three.
The phalanges do not really have individual names but are named after the digit, and their distance from the body. Distal phalanges are at the tips of the fingers and toes, the proximal phalanges are closest to the hand (or foot) and articulate with the metacarpals or metatarsals. Middle phalanges are between the distal and proximal. The thumb and big toe do not have middle phalanges.
The phalanges of the foot correspond with those of the hand. They differ from them in their size (the bodies being much reduced in length) and being laterally compressed.
First Row: The body of each is compressed from side to side, convex above, concave below. The base is concave; and the head presents a trochlear surface for articulation with the second phalanx.
Second Row: The phalanges of the second row are remarkably small and short, but rather broader than those of the first row.
The ungual phalanges, in form, resemble those of the fingers; but they are smaller and are flattened from above downward; each presents a broad base for articulation with the corresponding bone of the second row, and an expanded distal extremity for the support of the nail and end of the toe.
The phalanges are each ossified from two centers: one for the body, and one for the base. The center for the body appears about the tenth week, that for the base between the fourth and tenth years; it joins the body about the eighteenth year.
The pelvis is the bony structure located at the base of the spine (properly known as the caudal end). The pelvis incorporates the socket portion of the hip joint for each leg (in bipeds) or hind leg (in quadrupeds). It forms the lower limb (or hind-limb) girdle of the skeleton.
The pelvis is symmetrical and each side is actually made up of three separate bones — the upper half (the broad "wings") is the ilium; the middle (the top half of the lower "loops") is the pubis, and the bottom (the lower half of the "loops") is the ischium. These three bones fuse together with age and are collectively known as the hip bone, ossa coxae or the innominate bone. The pelvis is joined to the sacrum bone by ligaments (the sacroiliac joint), and the hip bones nest in specially shaped sockets (the acetabulum) on each side. The upper edge of the ilium is known as the iliac crest. The place at the front of the pelvis where the two sides join together is called the symphysis pubis. This is normally a very inflexible joint, but it softens and becomes more flexible during late pregnancy, allowing it to expand during labour for the baby's head to pass through. A female pelvis is also wider and shallower than a male pelvis.
A well-known way of determining the sex of a pelvis is to compare the angle of the width of the frontal opening to one's hand. If the angle is about the same as between the outstretched thumb and index finger, it is a female pelvis (arcus pubis). If it is closer to the angle between the spread index and middle fingers, it is a male pelvis (arcus subpubis).
The pelvis protects the digestive and reproductive organs in the lower part of the body, and many large nerves and blood vessels pass through it to supply the legs. It is also an important load-bearing part of the skeletal system.
In common language a leg is the entire lower limb, including (at least) the thigh, the knee, and the calf. In the strict sense of human anatomy, the leg is the part of the lower limb that lies between the knee and the foot. This article follows the popular usage that includes the lower limb from hip to ankle, including the buttock and excluding the foot.
Long bones of the lower limb
Femur (thigh bone)
Tibia (shin bone)
Fibula (calf bone)
Muscles of the human lower limb
Muscles of the thigh
Anterior compartment of the thigh
Quadriceps femoris, which is composed of:
Tensor fascia lata
Posterior compartment of the thigh
Muscles of the calf
The anterior compartment
Extensor digitorum longus
Extensor hallucis longus
The posterior compartment
Gastrocnemius (attached to the calcaneus by Achilles' tendon)
The lateral compartment
The deep posterior compartment
Flexor digitorum longus
Flexor hallucis longus
Vasculature of the leg
Common femoral artery
Deep femoral artery
Superficial femoral artery
Anterior tibial artery
Posterior tibial artery
Greater saphenous vein
Lesser saphenous vein
Anterior tibial vein
Posterior tibial vein
The foot is a biological structure found in many animals that is used for locomotion. The plural of foot is feet, and this pair is one of seven mutated English plurals.
The structural quality of a foot varies from animal to animal. Many vertebrates that have legs also have a foot located at the end of each leg. For these animals, the foot is a complex structure of bone, muscle, and other connective tissue. Among animals that have soft or padded feet, the foot is commonly called a paw. In mollusks, on the other hand, the foot is a purely muscular structure.
Human beings use their legs and feet for bipedal locomotion, also known as walking. The structures of the human foot and hand are variations on the same basic five-digit anatomy, in common with many other vertebrates. They are also the most complex, comprising half the bones in the body. The medical specialty related to treatment of the feet is podiatry.
Parts of the foot
Common disorders of the feet
In anatomy, the ankle is the part of the lower limb that is located between the foot and the leg, and is actually comprised of two separate joints: the talocrural joint (or "true" ankle joint) and the subtalar joint.
The talocrural joint, is a synovial joint that connects the distal ends of the tibia and fibula with the proximal end of the talus and is responsible for dorsiflexion and plantar flexion.
The subtalar joint connects the talus with the calcaneus and helps with inversion and eversion of the foot.
The ankle does not allow rotation.
The heel is the prominence at the posterior end of the foot. It is based on the projection of one bone, the calcaneus, behind the articulation of the bones of the lower leg. In the long-footed mammals, both the hoofed species (unguligrade) and the clawed forms which walk on the toes (digitigrade), the heel is well above the ground at the apex of the angular joint known as the hock. In plantigrade species it rests on the ground.
The Sole is the bottom of the foot. Much like the palm of the hand, it has thicker skin than most other parts of the body, and is relatively less pigmented. A set of creases formed in the womb criss-cross the sole. In anatomy, the sole of the foot is referred to as the plantar aspect.
Toes are the digits of the foot of a human or animal.
In humans, the toe includes the phalanges of the foot's skeleton; the bones of each toe continue all the way to the heel, although in from the base of the toes they are united in the body of the foot. The innermost toe (the leftmost one on the right foot, see picture) is by far the thickest (big toe, great toe, or hallux); the one on the other end is short and thin.
The toes, especially the big toe, play an essential role in walking, although a loss of the smallest toe will not affect gait.
The ball of the foot is where the toes join to the rest of the foot. It is quite muscular, as well as getting blistered the easiest.