Male Reproductive System
The male reproductive system is located in the pelvis region. It includes a pair of testes along with accessory ducts, glands and the external genitalia.
Testes
The testes are situated outside the abdominal cavity within a pouch called scrotum. The scrotum helps in maintaining the low temperature of the testes (2–2.5°C lower than the normal internal body temperature) necessary for spermatogenesis. In adults, each testis is oval in shape, with a length of about 4 to 5 cm and a width of about 2 to 3 cm. The testis is covered by a dense covering. Each testis has about 250 compartments called testicular lobules.
Each lobule contains one to three highly coiled seminiferous tubules in which sperms are produced. Each seminiferous tubule is lined on its inside by two types of cells called male germ cells (spermatogonia) and Sertoli cells. The male germ cells undergo meiotic divisions finally leading to sperm formation, while Sertoli cells provide nutrition to the germ cells.
The regions outside the seminiferous tubules called interstitial spaces, contain small blood vessels and interstitial cells or Leydig cells. Leydig cells synthesise and secrete testicular hormones called androgens. Other immunologically competent cells are also present.
Feature |
Points to Remember |
|---|---|
| Location | Outside the abdominal cavity |
| Pouch | Scrotum |
| Temperature | 2–2.5°C lower than the normal internal body temperature |
| Importance of low temperature | Necessary for spermatogenesis |
| Shape | Oval |
| Length | About 4 to 5 cm |
| Width | About 2 to 3 cm |
| Covering | Dense covering |
| Compartments | About 250 |
| Compartments called | Testicular lobules |
| Each lobule contains | One to three highly coiled seminiferous tubules |
| Site of sperm production | Seminiferous tubules |
| Cells lining seminiferous tubules | Male germ cells (spermatogonia) and Sertoli cells |
| Male germ cells | Undergo meiotic divisions finally leading to sperm formation |
| Sertoli cells | Provide nutrition to the germ cells |
| Regions outside seminiferous tubules | Interstitial spaces |
| Interstitial spaces contain | Small blood vessels and interstitial cells or Leydig cells |
| Leydig cells | Synthesise and secrete testicular hormones called androgens |
| Other cells | Immunologically competent cells are also present |
Male Sex Accessory Ducts
The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens.
The seminiferous tubules of the testis open into the vasa efferentia through rete testis. The vasa efferentia leave the testis and open into epididymis located along the posterior surface of each testis.
The epididymis leads to vas deferens that ascends to the abdomen and loops over the urinary bladder. It receives a duct from seminal vesicle and opens into urethra as the ejaculatory duct.
These ducts store and transport the sperms from the testis to the outside through urethra. The urethra originates from the urinary bladder and extends through the penis to its external opening called urethral meatus.
Male Accessory Ducts
| Duct/Structure | Points to Remember |
|---|---|
| Rete testis | Seminiferous tubules open into the vasa efferentia through rete testis |
| Vasa efferentia | Leave the testis and open into epididymis |
| Epididymis | Located along the posterior surface of each testis |
| Vas deferens | Leads from epididymis and ascends to the abdomen |
| Vas deferens | Loops over the urinary bladder |
| Seminal vesicle | Its duct is received by vas deferens |
| Ejaculatory duct | Opens into urethra |
| Urethra | Originates from the urinary bladder and extends through the penis |
| Urethral meatus | External opening of urethra |
| Function of ducts | Store and transport the sperms from the testis to the outside |
Penis
The penis is the male external genitalia. It is made up of special tissue that helps in erection of the penis to facilitate insemination.
The enlarged end of penis called the glans penis is covered by a loose fold of skin called foreskin.
| Structure | Points to Remember |
|---|---|
| Penis | Male external genitalia |
| Tissue | Made up of special tissue |
| Erection | Facilitates insemination |
| Enlarged end | Glans penis |
| Covering | Loose fold of skin |
| Fold of skin | Foreskin |
The Mechanism of Penis Erection
The mechanism of penis erection is based on the stimulation of nerves in the penis that direct more blood to the penis. These nerves allow the arteries in the penis to relax and expand, leading to an increase in blood in the erectile tissues. The penis becomes hard and erect, thus contributing to sexual activity.
Once semen is released, the blood supply to the erectile tissues gradually stops, thus leading to softening of the penis.
Male Accessory Glands
The male accessory glands include paired seminal vesicles, a prostate and paired bulbourethral glands. Secretions of these glands constitute the seminal plasma which is rich in fructose, calcium and certain enzymes. The secretions of bulbourethral glands also help in the lubrication of the penis.
| Accessory gland | Number/Type | Points to Remember |
|---|---|---|
| Seminal vesicles | Paired | Secrete fluid forming part of seminal plasma |
| Prostate | A prostate | Secretes fluid forming part of seminal plasma |
| Bulbourethral glands | Paired | Secrete fluid forming part of seminal plasma and help in lubrication of the penis |
| Secretions of accessory glands | — | Constitute the seminal plasma |
| Seminal plasma | — | Rich in fructose, calcium and certain enzymes |
Labelled Structures
| Structure | Points to Remember |
|---|---|
| Ureter | Carries urine towards the urinary bladder |
| Seminal vesicle | Male accessory gland |
| Urinary bladder | Stores urine |
| Vas deferens | Accessory duct for sperm transport |
| Prostate | Male accessory gland |
| Penis | Male external genitalia |
| Urethra | Extends through the penis |
| Glans penis | Enlarged end of penis |
| Foreskin | Loose fold of skin covering glans penis |
| Testis | Male reproductive organ |
| Scrotum | Pouch containing testes |
| Ejaculatory duct | Opens into urethra |
| Rectum | Posterior structure |
| Anus | External opening of alimentary canal |
| Bulbourethral gland | Male accessory gland |
Testis and Associated Ducts
| Structure | Position/Relation |
|---|---|
| Ureter | Associated with urinary system |
| Urinary bladder | Located above the prostate |
| Seminal vesicle | Accessory gland associated with vas deferens |
| Vas deferens | Duct carrying sperm from epididymis |
| Prostate | Accessory gland below urinary bladder |
| Bulbourethral gland | Accessory gland |
| Urethra | Passage through penis |
| Epididymis | Located along the posterior surface of testis |
| Vasa efferentia | Connect testis with epididymis |
| Rete testis | Receives seminiferous tubules and connects to vasa efferentia |
| Testicular lobules | Compartments of testis |
| Testis | Male reproductive organ |
| Glans penis | Enlarged end of penis |
| Foreskin | Loose fold of skin over glans |
Seminiferous Tubule
The diagrammatic sectional view of a seminiferous tubule shows interstitial cells, spermatogonia, spermatozoa and Sertoli cells.
| Cell/Structure | Role |
|---|---|
| Seminiferous tubule | Highly coiled tubule present inside testicular lobule |
| Spermatogonia | Male germ cells |
| Meiotic divisions | Finally lead to sperm formation |
| Spermatozoa | Formed sperm cells |
| Sertoli cells | Provide nutrition to the germ cells |
| Interstitial cells | Also called Leydig cells |
| Leydig cells | Synthesise and secrete testicular hormones called androgens |
| Interstitial spaces | Contain small blood vessels and interstitial cells or Leydig cells |
Read Also
Female Reproductive System | Structure and Functions | Human Reproduction