Chapter IV - Male Reproduction
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.
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)
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.
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
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.
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 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 (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.
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Chapter IV - Male Reproduction