male reproductive system
The male reproductive system is located in the pelvic region. It includes a pair of testes along with accessory ducts, glands and external genitalia.
- The testes are situated outside the abdominal cavity within a pouch called the scrotum helps in maintaining the low temperature of the testes (2-2.50C )lower than the normal internal body temperature), which is necessary for spermatogenesis. The slightly cooler temperature of the scrotum is necessary for the development of normal sperms.
- Testes start their development in the abdominal cavity. During the 7th month of the foetal life, the descend into the scrotal sacs in presence of testosterone. Hence, The testes of human males are extra- abdominal . If they fail to descend, the condition is called cryptorchidism that can lead to infertility or sterility
- Scrotum remains connected with the abdomen or pelvic cavity by the inguinal canal. Blood vessels, nerves and conducting tubes pass through it.
- There are certain mammals in which testes remain permanently in the abdomen and does not cause any defect. Examples are elephant, aquatic mammals like whales, dolphins, seal and prototherians or egg laying mammals like Omithorhynchus.
In mammals which breed seasonally, testes descend into scrotum only during the breeding season, example-bat and otter
In adult man, each testis is oval in shape with a length of about 4 to 5 cm and width of about 2 to 3 cm. Each testis is covered by a dense sheath enclosing it in an outer tough capsule of collagenous connective tissue called tunica albuginea. Each testis has about 250 compartments called testicular lobules and these compartments contain highly coiled tubules called seminiferous tubules.
Each lobule contains one to three seminiferous tubules in which the sperms are produced. Each seminiferous tubule is lined on its inside by two types of cells called male germ cells (spermatogonia) are Sertoli cells. Spermatogonia lining these tubules give rise to spermatozoa which are released into the the lumen of the tubule.
In between spermatogenic cells, Sertoli or sustentacular or nurse cells are present which provide nourishment to developing spermatozoa and regulate spermatogenesis by releasing inhibin to check FSH over-activity.
The other functions of sertoli cells are as follows:-
(i) To absorb the parts being shed by developing spermatozoa.
(ii) To release anti mullerian factor (AMF) to prevent development of mullerian duct/oviduct in male.
(iii) To release Androgen Binding Protein (ABP).
(iv) to form blood-testis barrier.
- Group of polyhedral cells called Interstital cells of leydig, are located in the connective tissue around the seminiferous tubules. They constitute the endocrine part of testis.
- Leydig cells synthesise and secrete testicular hormones called Androgens into the blood.
- Seminiferous tubules unite to form several straight tubules called tubuli recti which open into irregular cavities in the posterior part of the testis which is a highly anastomosing labyrinth of cuboidal epithelium lined channels called rete testis.
- Several tubes called vasa efferentia arise from it and conduct spermatozoa out of the testis.
- Tubuli recti, rete testis and ductuli efferentes form the intra-testicular genital duct system.
- The extratesticular duct system consists of tubes which conduct sperms from the testes to the outside.
- It startswith ducts known as vasa efferentia. From each testis, 10-12 vasa efferentia confluent to form a folded and coiled tube called epididymis behind each testis.
- The epididymis consists of three parts (i) Caput (ii) Corpus (iii) Cauda.
The epididymis stores the sperms temporary. From cauda epididymis, a partially coiled tube called vas deferens ascends into the abdomen through inguinal canal and passes over the urinary bladder. The ductus deferens/vas deferens then dilates to form ampulla which receives the duct from the seminal vesicle behind the urinary bladder and forms an ejaculatory duct. The final portion of ampulla passes through the prostate gland to open into the urethra shortly after its origin from the urinary bladder.
Urethra:- Male urethra provides a common pathway for the flow of urine and semen. It is much longer in male than in female, measuring
about 20 cm.
The urethra receives the ducts of the prostate and Cowper’s glands, passes through the penis and opens the outside.
Penis:- This is the copulatory organ of man. It is a cylindrical, erectile, pendulous organ suspended from pubic region in front of scrotum. It remains small and limp (flaccid) but on sexual arousal it becomes long, hard and erect when it is ready for copulation (coitus or intercourse). Erect human penis is, on an average , about 15 cm long.
- The urethra passes through the penis, an erectile copulatory organ that deposits the semen in the female reproductive tract.
- Penis is the male external genitalia, made up of three cylinders of special spongy tissue.
- Filling of blood in these tissue helps in erection of the penis that facilitates insemination.
- Erectionof penis is regulated by parasympathetic stimulation while ejaculation is controlled by sympathetic stimulation.
- The anteriorly extended part of penis called corpus spongiosum is enlarged, forming a bulging, conical structure called glans penis. The surface of glans is formed of thin, smooth and shiny, hairless skin. The base line of glans is referred to as the neck of the penis. The loose skin of penis becomes folded here to form a loose, retractile skin covering upon the glans, called foreskin or prepuce.
At the tip of glans penis, is the slit like external urethral orifice or meatus by which urethra opens out and discharges urine or semen
Surgical removal of prepuce is called circumcision.
Accessory Glands of male:–
- Seminal vesicles:- These are paired, tubular, coiled glands situated behind the bladder. They secrete viscous fluid which constitutes the main part of the ejaculate. Seminal fluid contains fructose, inositol and prostaglandins.
- Prostate gland:- The prostate gland is a chestnut shaped unpaired gland and is a collection of 30-40 tubuloalveolar glands which lie at the base of the bladder and surrounded the first part of the urethra. It contributes an alkaline component to the semen. (Although, the alkalinization of semen is primarily accomplished through secretions from the seminal vesicles.)
The main alkaline secretions of prostate gland help the sperms to become active and counteract any adverse effects that the urine may have on the sperms. The prostatic fluid provides a characteristic odour to the seminal fluid. Prostate gland secretes, calcium, phosphate ions, clotting enzyme and fibrinolysin.
Prostatitis:- Inflammation of prostate gland.
- Bulbourethral glands or Cowper’s glands:- The two bulbourethral glands are pea sized structures lying adjacent to the urethra at the base of penis. They secrete a viscous mucus which acts as a lubricant.
The duct system, accessory glands and penis are secondary male sex organs. Their growth, maintenance and functions are promoted by testosterone, secrete by Leydig cells. On the other hand, the growth, maintenance and functions of seminiferous tubules and Leydig cells are regulated respectively by FSH and ICSH of anterior pituitary.
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Semen
Semen is a mixture of sperms and seminal fluid. The latter is the liquid portion of semen that consists of secretions of the semminiferous tubules, seminal vesicles, prostate gland and bulbourethral glands. The average volume of semen in an ejaculation 2.5- 5 ml.
Semen has a slightly alkaline pH of 7.2- 7.7. The prostatic secretion gives semen a milky appearance whereas the fluids from the seminal vesicles and bulboureththral glands gives it a sticky consistency. Semen provides sperms with transportation medium and nutrients. It neutralizes the hostile acidic environment of the male urethra (due to presence of urine) and the female vagina.
Semen is forcefully expelled from the penis by the contractions of smooth muscles that line the urethra. This process is ejaculation.
The male reproductive system consists of both internal and external structures:
- External: Penis, scrotum
- Internal: Testes, epididymis, vas deferens, seminal vesicles, prostate gland, and urethra
The testes have two primary functions:
- Sperm Production: They produce sperm (spermatogenesis).
- Hormone Production: They produce testosterone, which is crucial for the development of male secondary sexual characteristics and reproductive function.
Sperm production begins in the testes and proceeds through the following pathway:
- Testes (production)
- Epididymis (maturation and storage)
- Vas deferens (transport)
- Seminal Vesicles (secretion of seminal fluid)
- Prostate Gland (additional fluid secretion)
- Urethra (ejaculation)
The prostate gland secretes fluid that nourishes and protects sperm. This fluid makes up a significant portion of semen and helps to enhance sperm motility and longevity.
Erectile dysfunction (ED) is the inability to achieve or maintain an erection sufficient for satisfactory sexual performance. It can result from physical, psychological, or a combination of both factors.
Common disorders include:
- Erectile Dysfunction (ED)
- Prostate Diseases: Prostatitis, benign prostatic hyperplasia (BPH), prostate cancer
- Testicular Disorders: Testicular cancer, varicocele, hydrocele
- Sexually Transmitted Infections (STIs)
vasectomy is a surgical procedure for male sterilization or permanent contraception. It involves cutting and sealing the vas deferens, preventing sperm from entering the semen.
Common signs include:
- Difficulty urinating
- Frequent urination, especially at night
- Pain or discomfort during urination
- Blood in urine or semen
- Pain in the lower back, hips, or thighs (prostate cancer-related)