Biological reproduction is the biological process by which new individual organisms are produced. Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction by an antecedent. The known methods of reproduction are broadly grouped into two main types: sexual and asexual reproduction.

In asexual reproduction, an individual can reproduce without involvement with another individual of that species. The division of a bacterial cell into two daughter cells is an example of asexual reproduction. Asexual reproduction is not, however, limited to single-celled organisms. Most plants have the ability to reproduce asexually.

Sexual reproduction requires the involvement of two individuals, typically one of each sex. Normal human reproduction is a common example of sexual reproduction. In general, more-complex organisms reproduce sexually while simpler, usually unicellular, organisms reproduce asexually.

Asexual reproduction

Asexual reproduction is the biological process by which an organism creates a genetically-similar or identical copy of itself without a contribution of genetic material from another individual. Bacteria divide asexually via binary fission; viruses take control of host cells to produce more viruses; Hydras (invertebrates of the order Hydroidea) and yeasts are able to reproduce by budding. These organisms do not have different sexes, and they are capable of "splitting" themselves into two or more individuals. Some 'asexual' species, like hydra and jellyfish, may also reproduce sexually. For instance, most plants are capable of vegetative reproduction—reproduction without seeds or spores—but can as well reproduce sexually. Likewise, bacteria may exchange genetic information by conjugation. Other ways of asexual reproduction include fragmentation and spore formation that involves only mitosis.

Sexual reproduction
Sexual reproduction is a biological process by which organisms create descendants that have a combination of genetic material contributed from two (usually) different members of the species. Each of two parent organisms contributes half of the offspring's genetic makeup by creating haploid gametes. Most organisms form two different types of gametes. In these anisogamous species, the two sexes are referred to as male (producing sperm or microspores) and female (producing ova or megaspores). In isogamous species the gametes are similar or identical in form, but may have separable properties and then may be given other different names.

Humans, most animals, and plants reproduce sexually. Sexually-reproducing organisms have two sets of genes for every trait (called alleles). Offspring inherit one allele for each trait from each parent, thereby ensuring that offspring have a combination of the parents' genes. Having two copies of every gene, only one of which is expressed, allows deleterious alleles to be masked, an advantage believed to have led to the evolutionary development of diploidy (Otto and Goldstein).

Mitosis and Meiosis
Mitosis and meiosis are an integral part of cell division. Mitosis occurs in somatic cells, while meiosis occurs in gametes.

Mitosis
The resultant number of cell in mitosis is twice the number of original cells. The number of chromosomes in the daughter cells is the same as that of the parent cell.

Meiosis
The resultant number of cells is four times the number of original cells. This results in cells with half the number of chromosomes present in the parent cell. A diploid cell forms two haploid cells. This process occurs in two phases, meiosis I and meiosis II.

Asexual vs. sexual reproduction
Organisms that reproduce through asexual reproduction tend to grow in number exponentially. However, because they rely on mutation for variations in their DNA, all members of the species have similar vulnerabilities. Organisms that reproduce sexually yield a smaller amount of offspring, but the large amount of variation in their genes makes them less susceptible to disease.

Many organisms can reproduce sexually as well as asexually. Aphids, slime molds, sea anemones and many plants are examples. When environmental factors are favorable, asexual reproduction is employed to exploit suitable conditions for survival such as an abundant food supply, adequate shelter, favorable climate, disease, optimum pH or a proper mix of other lifestyle requirements. Populations of these organisms increase exponentially via asexual reproductive strategies to take full advantage of the rich supply resources.

When food sources have been depleted, the climate becomes hostile, or individual survival is jeopardized by some other adverse change in living conditions, these organisms switch to sexual forms of reproduction. Sexual reproduction ensures a mixing of the gene pool of the species. The variations found in offspring of sexual reproduction allow some individuals to be better suited for survival and provide a mechanism for selective adaptation to occur. In addition, sexual reproduction usually results in the formation of a life stage that is able to endure the conditions that threaten the offspring of an asexual parent. Thus, seeds, spores, eggs, pupae, cysts or other "over-wintering" stages of sexual reproduction ensure the survival during unfavorable times and the organism can "wait out" adverse situations until a swing back to suitability occurs.

Male Reproductive System

The human male reproductive system is a series of organs located outside of the body and around the pelvic region of a male. They consist of

Bulbourethral glands - Cowper's glands - Ejaculatory duct - Epididymis - Foreskin - Frenulum - Glans penis - Penis - Prostate - Scrotum - Seminal vesicles - Spermatic cord - Testes - Urethra - Vas deferens

The males contribute to reproduction by ejaculating sperms into the female's vagina. The sperms then fertilize the egg in the female body and the fertilized egg gradually develop into a foetus, and later born as a child.

Prostate
The prostate is an exocrine gland of the male mammalian reproductive system. Its main function is to secrete and store a clear, slightly basic fluid that constitutes up to one-third of the volume of semen. The prostate differs considerably between species anatomically, chemically, and physiologically. A healthy human prostate is slightly larger than a walnut. It surrounds the urethra just below the urinary bladder. It is located in front of the rectum and can be felt during a rectal exam.

The male urethra has two functions: to carry urine from the bladder during urination and to carry semen during ejaculation. Within the prostate, the urethra coming from the bladder is called the prostatic urethra and merges with the two ejaculatory ducts. Semen is composed of sperm and seminal fluid; about 10-30% of the seminal fluid is produced by the prostate gland, the rest is produced by the two seminal vesicles. The prostate also contains some smooth muscle that helps to expel semen during ejaculation.

Prostatic secretions vary between species. They are generally composed of simple sugars, and are often slightly basic. In human prostatic secretions, the protein content is less than 1% and includes proteolytic enzymes, acid phosphatase, and prostate-specific antigen. Its secretions also contain zinc and citric acid.

To work properly, the prostate needs male hormones (androgens). Male hormones are responsible for male sex characteristics. The main male hormone is testosterone, which is produced mainly by the testicles. Some male hormones are produced in small amounts by the adrenal glands.

Prostate glands are found only in males; Skene's glands in females are homologous to the prostate gland in males.

Disorders of the prostate
Inflammation of the prostate gland is known as prostatitis. If the prostate grows too large it may constrict the urethra and impede the flow of urine, making urination difficult and painful and in extreme cases completely impossible. Prostatitis is treated with antibiotics, prostate massage or surgery.

In older men, the prostate often enlarges to the point where urination becomes difficult. This is known as benign prostatic hyperplasia and can be treated with medication or with surgery that removes part of the prostate. The surgery most often used in such cases is called transurethral resection of the prostate (TURP or TUR). In TURP, an instrument is inserted through the urethra to remove prostate tissue that is pressing against the upper part of the urethra and restricting the flow of urine.

Prostate cancer is one of the most common cancers affecting elderly men in developed countries and a major cause of death. Regular rectal exams are recommended for elderly men to detect prostate cancer early. There is also a blood test that measures the concentration of a protein, Prostate Specific Antigen (PSA), which is normally very low. Elevated test results may be an indicator of disorder within the prostate, either prostatitis, benign hyperplasia or prostate cancer. The PSA test cannot distinguish between them, but can lead a doctor to investigate further. Prostate cancer is treated with hormone manipulation (prevention of production of testosterone), radiation and/or surgery. It has recently been found that the drug Docetaxel can be effective in the treatment of prostate cancer.

Benign Prostatic Hyperplasia
Benign prostatic hyperplasia (BPH) also known as benign prostatic hypertrophy or benign enlargement of the prostate (BEP) refers to the increase in size of the prostate in middle-aged and elderly men. To be accurate, the process is one of hyperplasia rather than hypertrophy, but the nomenclature is often interchangeable, even amongst urologists (who should know better!). In BPH, the prostate grows larger and presses against the urethra and bladder, interfering with the normal flow of urine. It leads to symptoms of urinary hesitancy, frequent urination, increased risk of urinary tract infections and urinary retention. There is remarkably little correlation between BPH symptoms and the presence of prostate cancer.

Symptoms
Urinary symptoms of hesitancy, sensation of incomplete voiding and frequently passing small amounts of urine are all suggestive of BPH in middle-aged and elderly men. Due to the incomplete voiding, there is stasis of bacteria in the bladder residue and an increased risk of urinary tract infections.

A small proportion presents with urinary retention, in which inadequate amounts of urine are passed and the bladder distends greatly. Untreated, this leads to a decrease in renal function and hydronephrosis (obstructive uropathy).

Diagnosis
Rectal examination (palpation of the prostate through the rectum) may reveal a markedly enlarged prostate. It is dependent on the skills of the doctor.

Often, blood tests are performed to rule out prostatic malignancy: elevated prostate specific antigen (PSA) levels suggest prostate cancer. It has to be borne in mind that rectal examination can increase PSA levels in patients without malignancy.

Ultrasound examination of the testicles, prostate and kidneys is often performed, again to rule out malignancy and hydronephrosis.

Treatment
Alpha-blockers (α1-adrenergic receptor antagonists) (such as doxazosin, prazosin and tamsulosin) and certain antiandrogens such as the 5α-reductase inhibitors (finasteride) are used, often together, in suppressing the symptoms.

There is also some evidence of the efficacy of Serenoa repens (saw palmetto) preparations in alleviating BPH symptoms. A systematic review of evidence found comparable efficacy to finasteride. (Wilt et al., 2002)

If medical treatment fails, transurethral resection of prostate (TURP) surgery may need to be performed. This involves removing (part of) the prostate through the urethra. There are also a number of new methods for reducing the size of an enlarged prostate, some of which have not been around long enough to fully establish their safety or side effects. These include various methods to destroy or remove part of the excess tissue while trying to avoid damaging what's left. Transurethral electrovaporization of the prostate (TVP), laser TURP, visual laser ablation (VLAP), TransUrethral Microwave ThermoTherapy (TUMT), ethanol injection, and others are studied as alternatives.

Prostate Cancer
Prostate cancer is a disease in which cancer develops in the prostate, a gland in the male reproductive system. Cancer occurs when cells of the prostate mutate and begin to multiply out of control. These cells may spread (metastasize) from the prostate to other parts of the body, especially the bones and lymph nodes. Prostate cancer may cause pain, difficulty in urinating, erectile dysfunction and other symptoms.

It is the second most common type of cancer in men; among men, it is responsible for more deaths than any other cancer except lung cancer. However, many men who develop prostate cancer never have symptoms, undergo no therapy, and eventually die of other causes. Many factors, including genetics and diet, have been implicated in the development of prostate cancer, but as of 2005, it is not a preventable disease.

Prostate cancer is most often discovered by physical examination of the prostate gland by a physician, systematic or prompted by clinical signs and symptoms or by screening blood tests, such as the PSA (prostate specific antigen) test, systematic or prompted by evidence of metastatic disease. However, there is some current concern about the accuracy of the PSA test and its usefulness. Suspected prostate cancer is typically confirmed by removing a piece of the prostate (biopsy) and examining it under a microscope. Further tests, such as X-rays and bone scans, may be performed to determine whether prostate cancer has spread.

Prostate cancer can be treated with surgery, radiation therapy, hormone therapy, occasionally chemotherapy, or some combination of these. The age and underlying health of the man as well as the extent of spread, appearance under the microscope and response of the cancer to initial treatment are important in determining the outcome of the disease. Since prostate cancer is a disease of older men, many will die of other causes before the prostate cancer can spread or cause symptoms. This makes treatment selection difficult.

Surgery
Surgical removal of the prostate, or prostatectomy, is a common treatment either for early stage prostate cancer, or for cancer which has failed to respond to radiation therapy. The most common type is radical retropubic prostatectomy, when the surgeon removes the prostate through an abdominal incision. Another type is radical perineal prostatectomy, when the surgeon removes the prostate through an incision in the perineum, the skin between the scrotum and anus. Prostatectomy can cure about seventy percent of cases of prostate cancer.

Radical prostatectomy is highly effective for tumors, which have not spread beyond the prostate. However, it may cause nerve damage that significantly alters the quality of life of the prostate cancer survivor. The most common serious complications are loss of urinary control and impotence. As many as forty percent of men will be left with some urinary incontinence, usually in the form of leakage when they sneeze, cough or laugh. Impotence is also a common problem. Although penile sensation and the ability to achieve orgasm usually remain intact, erection and ejaculation are often impaired. Medications such as sildenafil (Viagra), Cialis, or Levitra may restore some degree of potency. In some men with smaller cancers, a more limited "nerve-sparing" technique may help avoid urinary incontinence and impotence.
 
Radical prostatectomy has traditionally been used alone when the cancer is small. However, courses of hormone therapy prior to surgery may increase cure rates and are currently being studied.[33] Surgery may also be offered when a cancer is not responding to radiation therapy. However, because radiation therapy causes tissue changes, prostatectomy after radiation has a higher risk of complications.

Transurethral resection of the prostate, commonly called a "TURP," is a surgical procedure performed when the tube from the bladder to the penis (urethra) is blocked by prostate enlargement. TURP is generally for benign disease and is not meant as definitive treatment for prostate cancer. During a TURP, a small tube (cystoscope) is placed into the penis and the blocking prostate is cut away.

In metastatic disease, where cancer has spread beyond the prostate, removal of the testicles (called orchiectomy) may be done to decrease testosterone levels and control cancer growth.

Radiation therapy
Radiation therapy, also known as radiotherapy, uses X-rays to kill prostate cancer cells. X-rays are a type of ionizing radiation that can damage or destroy the DNA crucial to cancer cell growth. Two different kinds of radiation therapy are used in prostate cancer treatment: external beam radiation therapy and brachytherapy.

Brachytherapy involves the placement of about 100 small "seeds" containing radioactive material (such as iodine-125 or palladium-103) with a needle through the skin of the perineum directly into the tumor. These seeds emit lower-energy X-rays, which are only able to travel a short distance. Brachytherapy seeds will stay in the prostate permanently, but men with implanted seeds are not at risk of exposing others to radiation.

Cryosurgery
Cryosurgery is another method of treating prostate cancer. It is less invasive than radical prostatectomy, and general anesthesia is less commonly used.

Hormonal therapy
Hormonal therapy uses medications or surgery to block prostate cancer cells from getting dihydrotestosterone (DHT), a hormone produced in the prostate and required for the growth and spread of most prostate cancer cells. Blocking DHT often causes prostate cancer to stop growing and even shrink. However, hormonal therapy rarely cures prostate cancer because cancers, which initially respond to hormonal therapy typically become resistant after one to two years. Hormonal therapy is therefore usually used when cancer has spread from the prostate. It may also be given to certain men undergoing radiation therapy or surgery to help prevent return of their cancer.

Penis
The penis (plural penises or penes) or phallus is an external male sexual organ. The penis is the male reproductive organ and for mammals additionally serves as the external male organ of urination. The human penis differs from those of some other mammals. It has no baculum, or erectile bone; instead it relies entirely on engorgement with blood to reach its erect state. It cannot be withdrawn into the groin, and is larger than average in proportion to body mass.

Structure
The human penis is made up of three columns of erectile tissue:

· The two corpora cavernosa (singular: corpus cavernosum) and
· One corpus spongiosum
The corpus spongiosum lies on the underside (known also as the ventral side) of the penis; the two corpora cavernosa lie next to each other on the upper side (dorsal side).

The end of the corpus spongiosum is enlarged and cone-shaped and forms the glans penis. The glans supports the foreskin or prepuce, a loose fold of skin that in adults can retract to expose the glans. The area on the underside of the penis, where the foreskin is attached, is called the frenum (or frenulum).

The urethra, which is the last part of the urinary tract, traverses the corpus spongiosum and its opening, known as the meatus, lies on the tip of the glans penis. It is both a passage for urine and for the ejaculation of semen. Sperm is produced in the testes and stored in the attached epididymis. During ejaculation, sperm are propelled up the vas deferens, two ducts that pass over and behind the bladder. Fluids are added by the seminal vesicles and the vas deferens turns into the ejaculatory ducts, which join the urethra inside the prostate gland. The prostate as well as the bulbourethral glands add further secretions, and the semen is expelled through the penis.

The raphe is the visible ridge between the lateral halves of the penis, found on the ventral or under side of the penis, running from the meatus (opening of the urethra) across the scrotum to the perineum (area between scrotum and anus).

Erection
Erection is the stiffening and rising of the penis which occurs in the sexually aroused male, though it can also happen in non-sexual situations. The primary physiological mechanism that brings about erection is the autonomic dilation of arteries supplying blood to the penis, which allows more blood to fill the three spongy erectile tissue chambers in the penis, causing it to lengthen and stiffen. The now engorged erectile tissue presses against and constricts the veins that carry blood away from the penis. More blood enters the penis than leaves until an equilibrium is reached (equal volume of blood flowing into the dilated arteries and out of the constricted veins). A constant erectile size is achieved at equilibrium.

Erection facilitates sexual intercourse though it is not essential for some other sexual activities. Although many erect penises point upwards (see illustration), it is common and normal for the erect penis to point nearly vertically upwards or nearly vertically downwards, depending on the tension of the suspensory ligament that holds it in position. Stiffness of erectile angle also varies.

Disorders affecting the penis:
Edema (swelling) of the foreskin can result from sexual activity, including masturbation.

Paraphimosis is an inability to move the foreskin forward over the glans. It can result from fluid trapped in a foreskin which is left retracted, perhaps following a medical procedure, or accumulation of fluid in the foreskin because of friction during vigorous sexual activity.

In Peyronie's disease, anomalous scar tissue grows in the soft tissue of the penis, causing curvature. Severe cases can benefit from surgical correction.

A thrombosis can occur during periods of frequent and prolonged sexual activity, especially fellatio. It is usually harmless and self-corrects within a few weeks.

Pudendal nerve entrapment is a condition characterized by pain on sitting and loss of penile (or clitoral) sensation and orgasm. Occasionally there is a total loss of sensation and orgasm. The pudendal nerve can be damaged by narrow hard cycle seats and accidents.

Penile fracture can occur if the erect penis is bent excessively. A pop or cracking sound and pain is normally associated with this event. Emergency medical assistance should be obtained. Prompt medical attention lowers likelihood of permanent penile curvature.

In diabetes, peripheral neuropathy can cause tingling in the penile skin and possibly reduced or completely absent sensation. The reduced sensations can lead to injuries for either partner and their absence can make it impossible to have sexual pleasure through stimulation of the penis. Since the problems are caused by permanent nerve damage, preventive treatment through good control of the diabetes is the primary treatment. Some limited recovery may be possible through improved diabetes control.

Erectile dysfunction or impotence is the inability to have and maintain an erection sufficiently firm for satisfactory sexual performance. Diabetes is a leading cause, as is normal aging. A variety of treatments exist, including drugs such as sildenafil citrate (marketed as Viagra®) which works by vasodilation.

Priapism is a painful and potentially harmful medical condition in which the erect penis does not return to its flaccid state. The causative mechanisms are poorly understood but involve complex neurological and vascular factors. Potential complications include ischaemia, thrombosis, and impotence. In serious cases the condition may result in gangrene, which may necessitate amputation.

Developmental disorders of the penis
Hypospadias is a developmental disorder where the meatus is positioned wrongly at birth. Hypospadias can also occur iatrogenically by the downward pressure of an indwelling urethral catheter.[2] It is usually corrected by surgery.

A micropenis is a very small penis caused by developmental or congenital problems.

Diphallia, or penile duplication (PD), is the condition of having two penises.

Penis replacement
The first successful penis allotransplant surgery was done on September 2005 in a military hospital in Guangzhou, China (Guangzhou Daily, source.) A man at 44 sustained an injury after an accident and his penis was severed. Urination became difficult as his urethra was partly blocked. A newly brain-dead man, at 23, was tracked down and his penis selected for the transplant. Despite atrophy of blood vessels and nerves, the arteries, veins, nerves and the corpora spongiosa were successfully matched. It remains to be observed if infection or rejection has occurred after the transplant and how much sexual function the man would regain.

Sperm & Seminal Fluid
A mature sperm, or spermatozoan, has 3 distinct parts: a head, a mid-piece, and a tail. The tail is made up of microtubules that form cilia and flagella, and the mid-piece contains energy-producing mitochondria. The head contains 23 chromosomes within a nucleus. The tip of the nucleus is covered by a cap called the acrosome, which is believed to contain enzymes needed to breach the egg for fertilization. A normal human male usually produces several hundred million sperm per day. Sperm are continually produced throughout a male's reproductive life, though production decreases with age.

During ejaculation, sperm leaves the penis in a fluid called seminal fluid. This fluid is produced by 3 types of glands, the seminal vesicles, the prostate gland, and Cowper's glands. Each component of a seminal fluid has a particular function. Sperm are more viable in a basic solution, so seminal fluid has a slightly basic pH. Seminal fluid also acts as an energy source for the sperm, and contains chemicals that cause the uterus to contract.

Ejaculation
As sexual stimulation becomes intense, sperm enter the urethra. Sperm and seminal fluid together are called semen. Once semen is in the urethra, rhythmical muscle contractions cause it to be expelled from the penis in spurts. During ejaculation, the bladder is closed off so that no urine enters the urethra. The contractions that expel semen are also a part of male orgasms. There may be more than 400 million sperm in 3.5 milliliters of semen expelled during ejaculation. However, fertilization may still occur even if the sperm count is lower.

Following ejaculation and/or loss of sexual arousal, the penis returns to its normal flaccid state. After ejaculation a male typically experiences a period of time, called the refractory period, during which stimulation doesn't result in an erection.

Testes
The testicles, known medically as testes (singular testis), are the male generative glands in animals. Male mammals have two testicles, which are often contained within an extension of the abdomen called the scrotum.

In mammals the testes are located outside of the body as they are suspended by the spermatic cord and within the scrotum. This is due to the fact that spermatogenesis is more efficient at a temperature somewhat less than the core body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit). The cremasteric muscle is part of the spermatic cord. When this muscle contracts the cord is shortened and the testicle is moved closer up toward the body, which provides slightly more warmth to maintain optimal testicular temperature. When the temperature needs to be lowered, the cremasteric muscle relaxes and the testicle is lowered away from the warm body and are able to cool. This phenomenon is known as the cremasteric reflex. It also occurs in response to stress (the testicles rise up toward the body in an evolutionary effort to protect them in a fight) and they also contract during orgasm.

It is normal for one testis to hang lower than the other (usually the left). This is primarily due to differences in the vascular anatomical structure on the right and left sides. It is thought that this is another evolutionary development that protects each testis from bouncing off the other.

Function
Like the ovaries (to which they are homologous), testicles are components of both the reproductive system (being gonads) and the endocrine system (being endocrine glands). The respective functions of the testicles are:

· Producing sperm (spermatozoa)
· Producing male sex hormones, of which testosterone is the best-known - Both functions of the testicle, sperm-forming and endocrine, are under control of gonadotropic hormones produced by the anterior pituitary:

· Luteinizing hormone (LH)
· Follicle-stimulating hormone (FSH)

Structure
Under a tough fibrous shell, the tunica albuginea, the testis contains very fine coiled tubes called the seminiferous tubules. The tubes are lined with a layer of cells that, from puberty into old-age, produce sperm cells. The sperm travel from the seminiferous tubules to the rete testis, the efferent ducts, and then to the epididymis where newly created sperm cells mature (see spermatogenesis). The sperm move into the vas deferens (also called the ductus deferens) which opens into the urethra. Upon any sufficient sexual arousal, the sperm cells move through the ejaculatory duct and into the prostatic urethra, where the prostate, through muscular contractions, ejaculates the sperm, mixed with other fluids, out through the penis.

Health issues
The testicles are well-known to be very sensitive to impact and injury. The most important diseases of testicles are:

· Inflammation of the testicles, called orchitis
· Testicular cancer and other neoplasms
· Accumulation of clear fluid around a testicle, called hydrocele testis
· Inflammation of the epididymis, called epididymitis
· Spermatic cord torsion also called testicular torsion
· Varicocele- swollen vein to the testes, usually affecting the left testicle
· Anorchidism is the absence of one or both testicles.
· The removal of one or both testicles is termed orchidectomy, in medicine (where orchiectomy and orchectomy are synonymous), and Castration in general use, especially when done for the benefit of others than the subject, for example, to produce a high-voiced castrato from the castration of a pre-pubescent boy

Scrotum
The scrotum is an external bag of skin and muscle containing the testicles. It is an extension of the abdomen, and is located between the penis and anus. The function of the scrotum appears to be to keep the testicles at a temperature slightly lower than that of the rest of the body. For the human, a temperature around 34.4 degrees Celsius (94 degrees Fahrenheit) appears to be ideal; 36.7 degrees Celsius (98 degree Fahrenheit) may be damaging to sperm count. The temperature is controlled by making the scrotum tighter or looser, hence moving the testicles closer to the abdomen when it is cold, and conversely away when hot, through the cremasteric reflex, the gradual tightening and loosening of the cremaster muscle in the abdomen and the dartos fascia (muscular tissue under the skin) in the scrotum.

Health issues
A common problem of the scrotum is the development of masses. Common scrotal masses include

· Sebaceous cyst, also called a epidermal cyst
· Hydrocele-A hydrocele testis is the accumulation of fluids around a testicle, and is fairly common, but should be treated surgically. The older method for removing the fluid was to use a needle to suck it out. However, because of the high risk of infection and because the fluid often returns, a more permanent approach is necessary. An incision is made, and the testicle sac is taken out (it's still attached, but removed), and all the fluid is taken out. It's considered an outpatient surgery.
· Hematocele-A hematocele is a collection of blood around the testicle. Hematoceles are often more painful than a hydrocele.
· Spermatocele-Spermatocele is a retention cyst of a tubule of the rete testis or the head of the epididymis distended with a milky fluid that contains spermatozoa. Spermatocele are the most common cystic condition encountered within the scrotum. They vary in size from several millimeters to many centimeters. Spermatocele are generally not painful. 
· Varicocele-Varicocele is a mass of enlarged veins in the scrotum that develops in the spermatic cord, which leads from the testicles (testes) up through a passageway in the lower abdominal wall (inguinal canal) to the circulatory system. The spermatic cord is made up of blood vessels, lymphatic vessels, nerves, and the duct that carries sperm from the body (vas deferens). If the valves that regulate blood flow from these veins become defective, blood does not circulate out of the testicles efficiently, which causes swelling in the veins above and behind the testicles. Varicoceles may be managed with a scrotal support (e.g. Jockstrap, Briefs). However, if pain continues or if infertility or testicular atrophy results, the varicocele may need to be surgically ligated (tied off).
· Varicocelectomy, the surgical correction of a varicocele, is performed on an outpatient basis.

Other conditions include:

· Contact dermatitis: may cause redness, swelling, and itching of the entire scrotum. Can result from soaps, solvents, detergents, and natural irritants such as poison ivy.
· Inguinal hernia
· Yeast infection
· Swelling resulting from conditions external to the scrotum, including:
· Heart failure
· Kidney or liver disease

Inguinal hernia
Inguinal hernias are protrusions of abdominal cavity contents through an area of the abdominal wall, commonly referred to as the groin. They are very common and their repair is one of the most frequently performed surgical operations. They usually arise as a consequence of the descent of the testis from the abdomen into the scrotum during early fetal life, and are therefore far more commonly seen in men than women. They present as painless bulges in the groin area that can become more prominent when coughing, straining, or standing up. The bulge commonly disappears on lying down. The presence of pain, or the inability to "reduce" the bulge back into the abdomen, usually indicates the onset of complications.
As the hernia progresses, contents of the abdominal cavity, such as the intestine, can descend into the hernia and run the risk of being strangulated within the hernia, causing an intestinal obstruction. If the blood supply of the portion of the intestine that is caught in the hernia is compromised, gut ischemia and gangrene can result, with serious consequences.

There are two types of inguinal hernia, direct and indirect. Femoral hernias, while they occur within the myopectineal orifice, are usually classed as separate from the "inguinal" hernias.

Indirect inguinal hernia
An indirect inguinal hernia protrudes through the inguinal ring and is ultimately the result of the failure of embryonic closure of the internal inguinal ring after passage through it of the testicle and the trailing supply of blood vessels and nerves, which make up the spermatic cord.
An indirect hernia occurs when intra-abdominal contents, commonly including preperitoneal fatty tissues and intestines, traverse the ring to enter the inguinal canal. As time passes, the hernia contents may enlarge, extend the length of the canal, and even exit the canal through the external inguinal ring into the scrotum. During surgical repair, or herniorrhaphy, a surgeon recognizes the "indirect" hernia by noting that the hernia sac begins lateral to the inferior epigastric vessels, indicating that it arose at the top of the inguinal canal. Conversely, the "direct" inguinal hernia enters through a weak point in the fascia of the abdominal wall, and its sac is noted to be medial to these vessels.

Direct inguinal hernias
A direct inguinal hernia protrudes through a weakened area in the transversalis fascia within an anatomic region known as the medial or Hesselbach's triangle, an area defined by the edge of the rectus abdominis muscle, the inguinal ligament and the inferior epigastric artery. While these hernias do not involve the inguinal canal directly, they do compromise the structures of the inguinal region. When a patient suffers a simultaneous direct and indirect hernia on the same side, the result is called a "pantaloon" hernia, and the defects can be repaired separately or together.

Herniorrhaphy
Herniorrhaphy (Hernioplasty, Hernia repair) is a surgical procedure for correcting hernia. A hernia is a bulging of internal organs or tissues, which protrude through an abnormal opening in the muscle wall.

Bulbourethral Glands

The bulbourethral glands (or Cowper's glands) are two small, rounded, and somewhat lobulated bodies, of a yellow color, about the size of peas, placed behind and lateral to the membranous portion of the urethra, between the two layers of the fascia of the urogenital diaphragm. They lie close above the bulb, and are enclosed by the transverse fibers of the Sphincter urethrae membranaceae. Their existence is said to be constant: they gradually diminish in size as age advances.

The excretory duct of each gland, nearly 2.5 cm long, passes obliquely forward beneath the mucous membrane, and opens by a minute orifice on the floor of the cavernous portion of the urethra about 2.5 cm in front of the urogenital diaphragm.

They secrete a clear fluid known as pre-ejaculate or Cowper's fluid (colloquially known as "pre-cum") which is generated upon sexual arousal.

Cowper's glands in males are homologous to Bartholin's glands in females.

Ejaculatory duct
The ejaculatory ducts are part of the human male anatomy, which cause the reflex action of ejaculation. Each male has two of them. They begin at the vas deferens, pass through the prostate, and empty into the urethra at the Colliculus seminalis. During ejaculation, semen passes through the ducts and exits the body via the penis.

Epididymis
The epididymis is part of the human male reproductive system and is present in all male mammals. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens. The epididymis can be divided into three main regions, the head (caput), body (corpus) and tail (cauda). Sperm formed in the testis enter the caput epididymis, progress to the corpus, and finally reach the cauda region, where they are stored. Sperm entering the caput epididymis are incomplete - they lack the ability to swim forward (motility) and to fertilize an egg. During their transit in the epididymis, sperm undergo maturation processes necessary for them to acquire these functions. Sperm maturation is completed in the female reproductive tract (capacitation).

During ejaculation, sperm flow from the lower portion of the epididymis (which functions as a storage reservoir). They are packed so tightly that they are unable to swim, but are transported via the peristaltic action of muscle layers within the vas deferens, and are mixed with the diluting fluids of the seminal vesicles and other accessory glands prior to ejaculation (forming semen).

Inflammation of the epididymis is called epididymitis.

Foreskin
The foreskin or prepuce is a retractable double-layered fold of skin and mucous membrane that covers the glans penis and protects the urinary meatus when the penis is not erect. In humans, the outside of the foreskin is like the skin on the shaft of the penis but the inner foreskin is a mucous membrane like the inside of the eyelid or the mouth. This undersurface of the foreskin contains ectopic glands to produce emollients commonly called smegma, which some believe carry antibacterial proteins, although this can also lead to balanitis among persons with poor hygiene. In children, the foreskin covers the glans completely but in adults this need not be so.

Conditions
Frenulum breve is where the frenulum is insufficiently long to allow the foreskin to fully retract, which may lead to discomfort during intercourse. The frenulum may also tear during intercourse.

Phimosis is a condition when the foreskin of an adult cannot be retracted properly. (Before adulthood, the foreskin may still be separating from the glans [31].) Phimosis can be treated by gently stretching the foreskin, using topical steroid ointments, preputioplasty, or by circumcision. See phimosis for more information.

A condition called paraphimosis may occur if a tight foreskin becomes trapped behind the glans and swells as a restrictive ring. This can cut off the blood supply ischaemia to the glans penis.

Aposthia is a rare condition in which the foreskin is not present at birth.

Surgical and other modifications of the foreskin
Circumcision is the removal of the foreskin, either partially or completely. It may be done for religious, aesthetic, health, or hygiene reasons, or to treat disease.

Preputioplasty is a procedure to relieve a tight foreskin without resorting to circumcision.

Other practices include genital piercings involving the foreskin and slitting the foreskin

Frenulum
The word frenulum on its own is often used for the frenulum preputii penis, which is an elastic band of tissue under the glans penis that connects to the prepuce, or foreskin, and helps contract the prepuce over the glans. It may be partially or totally removed during the style of hospital circumcision practiced in various countries.

Frenulum breve is the condition in which the frenulum of the penis is short and restricts the movement of the prepuce, and may or may not interfere with normal sexual activity. The condition can be treated by frenuloplasty, frenectomy, or circumcision, but recently, frenulum breve has been treated with the use of corticosteroid creams and manual stretching of the frenulum. The frenulum may be entirely missing in cases of first degree Hypospadias.[

Glans penis
The glans penis is the sensitive erectile tip of the penis. It is wholly or partially covered by the foreskin, except when the foreskin is retracted, such as during sexual intercourse while the penis is erect, or when the foreskin has been removed by circumcision.

Medical considerations
The meatus (opening) of the urethra is at the tip of the glans penis. In young boys who wear nappies (diapers), the meatal area of the glans penis is at risk from meatitis, meatal ulceration, and possibly meatal stenosis.

Inflammation of the glans penis is known as balanitis. It occurs in 3-11% of males, and up to 35% of diabetic males. It has many causes, including irritation, or infection with a wide variety of pathogens.

Spermatic cord
The spermatic cord is the name given to the cord-like structure formed by the vas deferens and surrounding tissue (veins, arteries, nerves, and lymphatic vessels) that run from the abdomen down to each testicle.

The spermatic cord is sensitive to torsion, in which the testicle rotates within its sac and kinks off its own blood supply. Testicular torsion may result in irreversible damage to the testicle within hours.

Urethra
In anatomy, the urethra is a tube, which connects the urinary bladder to the outside of the body. The urethra has an excretory function in both sexes, to pass urine to the outside, and also a reproductive function in the male, as a passage for sperm.

The external urethral sphincter is a striated smooth muscle that allows voluntary control over urination. Men have a longer urethra than women. This means that women tend to be more susceptible to infections of the bladder (cystitis) and the urinary tract. The length of a male's urethra, and the fact it contains a number of bends makes catheterization more difficult.

In the human female, the urethra is about 1-1.5 inches (2.5-4 cm) long and opens in the vulva between the clitoris and the vaginal opening. In the human male, the urethra is about 8 inches (20 cm) long and opens at the end of the penis.

The urethra is divided into three parts in men, named after the location:

The prostatic urethra crosses through the prostate gland. There is a small opening where the vas deferens enters.
The membranous urethra is a small (1 or 2 cm) portion passing through the external urethral sphincter. This is the narrowest part of the urethra.
The spongy (or penile) urethra runs along the length of the penis on its ventral (underneath) surface. It is about 15-16 cm in length, and travels through the corpus spongiosum.

Medical problems of the urethra

Hypospadias and epispadias are forms of abnormal development of the urethra in the male, where the opening is not quite where it should be (it occurs lower than normal with hypospadias, and higher with epispadias). A chordee is when the urethra develops between the penis and the scrotum.
Infection of the urethra is urethritis, said to be more common in females than males. Urethritis is a common cause of dysuria (pain when urinating).
Related to urethritis is so called urethral syndrome
Passage of kidney stones through the urethra can be painful and subsequently it can lead to urethral strictures

Endoscopy of the bladder via the urethra is called cystoscopy.

Vas Deferens
The vas deferens, also called ductus deferens, (Latin: "carrying-away vessel") is part of the human male anatomy. There are two of them; they are muscular tubes (surrounded by smooth muscle) connecting the left and right epididymis to the ejaculatory ducts in order to move sperm. Each tube is about 30 centimeters long. During ejaculation the wall of the vas deferens thickens and thins itself, thus propelling the sperm forward. The sperm are transferred from the vas deferens into the urethra, collecting fluids from the male accessory sex glands en route.

Vasectomy is a method of contraception where the vasa deferentia are permanently cut.

BPH Benign prostatic hypertrophy.
DRE Digital rectal examination.
GU (genitalis) genitourinary.
HSV Herpes simplex virus.
NGU Nongonococcal urethritis.
RPR Rapid plasma reagin.
TRUS Transrectal ultrasonography.
TUR Transurethral resection.

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Male Reproduction System