Male reproductive system and the T.S. of testis
The testes in the scrotum make sperms in seminiferous tubules and male hormones in Leydig cells. Ducts and glands store, nourish and carry the sperms out.
Parts of the male reproductive system
| Part | Where or what | Role |
|---|---|---|
| Testes (pair) | In the scrotum, a pouch outside the abdominal cavity | Make sperms and androgens |
| Rete testis, vasa efferentia | A network in the testis, then small ducts that leave it | Carry sperms from the seminiferous tubules to the epididymis |
| Epididymis | Along the back (posterior) surface of each testis | Stores sperms; its secretions help them mature |
| Vas deferens | Rises into the abdomen and loops over the urinary bladder | Carries sperms; joins the duct of the seminal vesicle to open into the urethra as the ejaculatory duct |
| Urethra | Runs from the urinary bladder through the penis to the urethral meatus | Carries semen (and urine) out of the body |
| Penis | External genitalia; its tip, the glans penis, is covered by the foreskin | Special tissue allows erection, which makes insemination possible |
Accessory glands and semen
- The male accessory glands are the paired seminal vesicles, one prostate and the paired bulbourethral glands.
- Their secretions form the seminal plasma, which is rich in fructose, calcium and certain enzymes.
- Semen is sperms plus seminal plasma.
- Secretions of the bulbourethral glands also help lubricate the penis.
- The work of the accessory ducts and glands is kept up by androgens from the testis.
Microscopic anatomy: T.S. of testis (spotting)
- Each testis has a dense outer covering and about 250 testicular lobules. Each lobule has 1 to 3 highly coiled seminiferous tubules.
- Each tubule is lined on the inside by spermatogonia (male germ cells) and Sertoli cells (which nourish the germ cells).
- Moving towards the centre, you see the later stages: primary spermatocytes, secondary spermatocytes, spermatids, and sperms with tails in the lumen.
- The interstitial spaces between tubules hold small blood vessels and Leydig cells, which secrete androgens. Some immune cells are also present.
- Spotting comment: identify it as the T.S. of a mammalian testis; name two cell types and the role of each.
How to draw the male reproductive system (side view)
- 1Draw the urinary bladder at the top. Draw the urethra running down from it through the penis to the urethral meatus; label the glans penis and foreskin.
- 2Below the penis, draw an oval testis inside the scrotum. Draw the epididymis as a curved band along its back.
- 3From the epididymis, draw the vas deferens rising up, looping over the bladder and joining the ejaculatory duct.
- 4Draw the seminal vesicle behind the bladder, the prostate below the bladder around the urethra, and the small bulbourethral gland below the prostate.
- 5★Label every part with straight lines that do not cross. Title: Diagrammatic sectional view of the male pelvis showing the reproductive system.
★ key step
How to draw a seminiferous tubule in section
- Draw a circle with a thick wall for the tubule, and a lumen at the centre.
- Along the outer wall, draw small round spermatogonia; draw tall Sertoli cells reaching from the wall towards the lumen.
- Draw inner rows labelled primary spermatocytes, secondary spermatocytes and spermatids.
- In the lumen, draw sperms with tails.
- Outside the circle, draw groups of interstitial (Leydig) cells and a blood vessel. Title: Diagrammatic sectional view of a seminiferous tubule.
Sperm formation needs the testes cooler than the body. So doctors advise men not to keep a hot laptop on the lap for long hours. A semen test in a clinic checks the sperm made in these tubules.
2 marks: “Why are the human testes placed outside the abdominal cavity? Name the cells that secrete androgens.” The scrotum keeps the testes 2 to 2.5 °C below body temperature, which spermatogenesis needs. Leydig (interstitial) cells secrete androgens.
2 marks: “Name the male accessory glands. What does their secretion contain?” Paired seminal vesicles, one prostate, paired bulbourethral glands. Seminal plasma rich in fructose, calcium and certain enzymes.
5 marks: “Draw a labelled diagram of the male reproductive system. Describe the path of sperms from the seminiferous tubules to the outside.” Labelled diagram; seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra → urethral meatus; role of glands.
Path of sperms: Some Red Vans Enter Very Early Uptown: Seminiferous tubules, Rete testis, Vasa efferentia, Epididymis, Vas deferens, Ejaculatory duct, Urethra.