- 1 Anatomy of the Male Reproductive System – Reproductive System Disorders and Treatments
- 1.1 Different Male Reproductive Organs
- 1.2 1. Scrotum
- 1.3 2. Testes
- 1.4 3. Epididymis
- 1.5 4. Spermatic Cords
- 1.6 5. Vas Deferens
- 1.7 6. Seminal Vesicles
- 1.8 7. Ejaculatory Duct
- 1.9 8. Prostate Gland
- 1.10 9. Cowper’s/Bulbourethral Gland
- 1.11 10. Penis
- 1.12 11. Urethra
- 1.13 Functions of the Male Reproductive System
- 1.14 Hormonal and Neural Control of Testicular Activity
- 1.15 Disorders of the Male Reproductive System
The Biology Topics of biotechnology involve using living organisms to develop new products or solve problems.
Anatomy of the Male Reproductive System – Reproductive System Disorders and Treatments
Different sexual organs of males which are involved in the process of production and secretion of sperm are united to form a system called the male reproductive system.
Different Male Reproductive Organs
The scrotum is a pouch of deeply pigmented skin divided into two compartments each of which contains one testis, one epididymis, and the testicular end of a spermatic cord. It lies below the symphysis pubis and behind the thigh. The coat of the scrotum consists of 7 layers, which are (outside to inside): skin, Tunica dartos, External spermatic fascia, Cremasteric fascia, Internal spermatic fascia, Tunica vaginalis, Visceral layer, and Parietal layer. Hydrocoelic fluid remains between the visceral and parietal layers. The layers of the scrotum control temperature inside the scrotal chamber.
The scrotum maintains a temperature lower than the normal (about 37°C) body temperature. The normal temperature of testes in the scrotum is lower than the internal body temperature by about 2 – 2.5°C. This temperature is ideal for sperm development. When exposure to cold occurs the dartos muscle present in the scrotum contracts and puts up a thicker investiture around the testes and also movement towards the pelvic cavity allows the testes to absorb the heat from the rest of the body, thus keeping the sperm warm. The inguinal canal helps the scrotum to remain connected with the pelvic cavity.
The testes are the primary reproductive organs of the male and are the equivalent of the ovaries in the female. During the early foetal stage (embryonic life) it develops in the abdominal cavity exactly just below the kidney. In embryonic life, the testes remain within the pelvic cavity. Then it gradually begins to descend through the inguinal canal and enter the scrotum about 2 months before the birth of a child. Failure of the testes to descend into the scrotum is called cryptorchidism. They are suspended in the scrotum by the spermatic cords. Each testis is approximately 4.5 cm long, 2.5 cm wide, and 3 cm thick. The weight of one testis is about 15 – 25 gm. A fibrous cord that extends from the caudal end of the testis to the scrotal wall is called a gubernaculum.
Structure of the Testis:
The testis is surrounded by three layers:
- The tunica vaginalis is the outer covering of the testis.
- The tunica albuginea is a fibrous covering surrounding the testis and lies under the tunica vaginalis.
- The tunica vasculosa consists of a network of capillaries that line the tunica vaginalis.
These three layers act as a protective covering. Each testis consists of 200 to 300 lobules composed of germinal epithelial cells which are formed into the convoluted seminiferous tubules. Between the tubules, there are groups of secretory cells known as the interstitial cells. The tubules eventually straighten out to become the straight seminiferous tubule. These tubules are closed at the end but on the other side, they join a network the rete testis, from where fine ciliated ductules and the vasa efferentia arise.
It is a convoluted tube, 6 meters in length. It remains coiled up with the intertwining connective tissue surrounding the tunic at the back of the testis. It is continued as vas deferens. The anterior end of the testes is called caput epididymis, in which vasa efferentia open. The middle part is known as corpus epididymis and the posterior part is called cauda epididymis. The secretions of epididymis provide nourishment for spermatozoa and help them to mature as sperm. Near the top of the testis is the head of the epididymis, which stores sperm until it is ready to undergo maturation.
4. Spermatic Cords
There are two spermatic cords, one leading from each testis. The spermatic cord suspends the testis in the scrotum. The spermatic cord passes through the inguinal canal. At the deep inguinal ring, the structures within the cord diverge. Each spermatic cord is composed of a testicular artery, testicular venous plexus, lymph vessels, vas deferens, and nerves. All of these are covered by a thin layer of fibrous tissue and an inner layer of muscle tissue.
5. Vas Deferens
It is the finely coiled tubule connected to the end part of the epididymis (the tail of the epididymis). It enters the pelvic cavity through the inguinal canal and forms a loop around the urinary bladder and opens at the base of the ejaculatory duct. Through vas deferens, sperms reach the urethra from the seminal vesicle. The Vas deferens serve as a secondary storehouse for spermatozoa, which will release sperm at the time of ejaculation.
6. Seminal Vesicles
There are two seminal vesicles that lie on each side of the front part at the neck region of the urinary bladder. They are approximately 5 cm long and pyramidal in shape. The seminal vesicle does not store spermatozoa but acts as an activator and secretes a thick alkaline fluid that mixes with the sperm.
7. Ejaculatory Duct
It is a fine duct through which a seminal vesicle opens into the urethra. This duct is formed by the union of the duct of the seminal vesicle and the end part of the vas deferens. Each duct is about 2 cm long. Through this ejaculatory duct, sperms are discharged with semen into the urethra during intercourse.
8. Prostate Gland
This gland lies around the urethra at the base of the neck region of the urinary bladder and is covered by a vascular capsule. It is composed of fibro-elastic tissue, mucosal gland, and plain muscles. The secretion of this gland makes the urethra slippery for the discharge of semen. It acts as a nutritive fluid for male gametes. It also increases the volume of semen. The prostatic fluid contributes 20% of the total volume of semen.
9. Cowper’s/Bulbourethral Gland
There is a pair of pea-shaped glands below the prostate gland. The glands open into the urethra through fine ducts. Cowper’s glands secrete a thin milky fluid that forms 30% volume of the semen. The secretion of these glands makes the urethra slippery.
It is the muscular copulatory organ in males. It contains 3 cylindrical bodies of erectile cavernous tissue, Corpus spongiosum muscle at the centre, Corpus cavernosa muscle surrounding the corpus spongiosum from both sides.
The penis is covered by skin and is made of three parts: Bulb, Body, and Giants. At the anterior part of the glans, the skin is connected by fine folds. This is called a prepuce. The penis becomes hard and enlarged during intercourse.
The male urethra provides a common pathway for the flow of urine and semen. It is much longer than in females, measuring about 19 – 20 cm. It has three parts. The first part is surrounded by the prostate gland and is called the prostatic urethra. The second part is the membranous urethra which is situated in the perineum. The third part is the spongy urethra which is situated in the penis.
Functions of the Male Reproductive System
- Spermatogenesis: The germinal epithelial cells of seminiferous tubules produces sperm.
- Male Sex Hormones: Leydig’s cells (interstitial cells) of the testes produce male sex hormones testosterone.
- Transfer of Sperm: The penis (copulatory organ) transfers sperm into the vagina during copulation.
Hormonal and Neural Control of Testicular Activity
1. Stimulatory Control:
The growth and maturation (spermatogenesis) of male reproductive organs begin at puberty and continue throughout adult life and decline in old age. It is believed that the anterior pituitary releases gonadotrophins:
- Follicle Stimulating Hormone (FSH).
- Luteinising Hormone (LH) or Interstitial Cell Stimulating Hormone (ICSH).
The release of anterior pituitary gonadotrophins is regulated by the two Releasing Factors (RF). FSH-RF and LRF, are liberated from the hypothalamus. Thus GnRH is secreted from the hypothalamus which stimulates the anterior pituitary gland to secrete FSH and LH. LH stimulates interstitial cells or Leydig cells. The mechanism appears that by increased formation of cAMP and increased protein synthesis, LH stimulates Leydig cells of the testis to secrete androgen (Testosterone). Testosterone secreted from the Leydig cells diffuses into the seminiferous tubules. It acts on both the Sertoli cell and the germ cell.
Testosterone is required for the development of accessory sex organs in males as well as in the process of spermatogenesis (formation of mature sperm). FSH also indirectly affects testosterone synthesis by increasing the LH receptors on the Leydig cell. FSH control spermatogenesis by means of stimulating Sertoli cells, which help in the conversion of spermatid to sperm. FSH stimulates Sertoli cells to secrete ABP (Androgen Binding Protein) which stabilizes the (high) supply of testosterone to the developing germ cell in the seminiferous tubules. FSH also promotes inhibin synthesis from the Sertoli cells of the testis.
2. Inhibitory Control (Feedback):
A negative feedback mechanism controls the speed of spermatogenesis. Inhibin, secreted from the Sertoli cells acts directly on the anterior pituitary which in turn inhibits FSH secretion. Testosterone has its feedback effect at the hypothalamic (GnRH) level which in turn inhibits, LH secretion. But it is noticeable that the physiological level of plasma testosterone does not produce significant feedback inhibition of FSH secretion.
Pathway for Sperm Passage:
Seminiferous tubule → Rete testis → Vasa efferentia → Head of epididymis → Duct of epididymis → Vas deferens → Ampulla → Ejaculatory duct → Urethra
Disorders of the Male Reproductive System
Literally, it means “Hidden Testicle”. A condition in which the descent of the testes may fail to occur or may be incomplete.
- Androgen secretion of the testes is unaffected, so male secondary characters develop normally.
- Spermatogenesis often fails to occur in cryptorchidism resulting in sterility.
- This type of testis is more likely to develop a malignant tumor than a normal one.
This type of disease should be treated as early as possible. If not corrected, usually by surgery, before puberty, can lead to sterility and a high risk of testicular cancer.
The inability of a male to produce or maintain an erection of a penis long enough to complete sexual intercourse.
- Primary impotence (rare occurrence).
- Secondary impotence may have organic causes.
- Psychological factors (stress and depression) are most often stated as causes of impotence.
- Vascular disorders as well as neurological disorders and syphilis can also cause impotence. Certain drugs cure impotency.
3. Prostate Cancer:
The prostate gland in the male repro¬ductive system may develop cancer. It causes 2 to 3% of male death.
- Most prostate cancer is slow-growing, but sometimes, cases of aggressive prostate cancer are also found.
- Early prostate cancer usually causes no symptoms. Sometimes it causes symptoms, often similar to benign prostatic hyperplasia.
- Prostate cancer is associated with urinary dysfunction as the prostate gland surrounds the prostatic urethra.
- Advanced prostate cancer can spread to other parts of the body, possibly causing additional symptoms, the most common is bone pain (vertebrae, pelvis, or ribs).
Malignant prostate cells are usually stimulated by testosterone, so the removal of testes to avoid the production of hormones is often treated as a remedy for this disease.
4. Benign Prostatic Hypertrophy (BPH):
The enlargement of the prostate gland. Usually occur in old age.
- Swelling of the prostate gland which surrounds the base of the male bladder and urethra.
- Compressed urethra causes difficulty in urinating, and dribbling, and nocturia (frequent night urination) happens. Untreated BPH may lead to kidney damage.
Dilated and twisted veins of the testis, sort of “hemorrhoids” of the scrotum.
- Occurs due to incompetence of venous valves resulting in retrograde flow of blood.
- Swelling on the side of the scrotum which may look and feel like a “bag of worms”.
- This cause reduced sperm count and male sterility due to sluggish blood flow elevating testicular temperature.
A heat exchange mechanism is suggested. May be surgically corrected if causing discomfort.
6. Infertility or Sterility:
Male infertility or sterility refers to the inability of sperm to fertilize an ovum.
Caused by Androgen dysfunction with abnormal sperm count:
- hypothalamic-pituitary defects
- androgen resistance
- Leydig cell defects
Failure of deposition of sperm in female genital tract erection during intercourse:
- obstruction of the vas deferens
- failure of ejaculation and erection during intercourse.
7. ADAM (Androgen Deficiency in Ageing Males):
Male menopause is the cause of reducing the production of testosterone. It occurs at the age of 40.
A fluid-filled sac partially surrounds the testes. Swelling on the side of the scrotum.
9. Inguinal Hernia:
Inguinal hernia is a condition in which the tearing of inguinal tissue may result in the protrusion of a part of the intestine into the scrotum.
10. Genetic Disorders:
A few genetic disorders also cause reproductive abnormalities.
- Kallmann Syndrome: Genetic disorder causing decreased functioning of the sex hormone-producing glands causes retarded development of gonads, resulting in deficient development of secondary sex characteristics.
- Androgen Insensitivity Syndrome: A genetic disorder causing people who are genetically male (i.e. XY chromosome pair) to develop sexually as a female due to an inability to utilize androgen.
- Intersexuality: A person who has genitalia and/or other sexual traits which are not clearly male or female.
After the age of 50, the testosterone secretion of males starts declining, it is mainly accompanied by the decreased humor and activity of Leydig cells. The low level of testosterone increases the FSH and LH levels. That leads to changes in males’ physical structures. This type of change is called male climacteric. Though it does not affect most men, still some of them men are developed symptoms like female menopausal syndrome, i.e., hot flashes, illusion, suffocations, mood swings, etc.