Lecture 44: Male reproductive system II

Question 1

Describe the structure of the penis:

What are the three cylindrical erectile tissues?

Answer 1

• Cylindrical organ
• root(bulb), body and glans are covered by prepuce/foreskin
• function: urination and copulation
  Erectile tissues
• two corpora cavernosa
  = main erectile tissue and dorsal aspect
• one corpus spongiosm
• contains urethra
• froms bulb and glans
• ventral aspect

Question 2

Describe the structure of the scrotum - what does the scrotum do?

What is its function?

What keeps the temperature of the scrotum constant?

Answer 2

The scrotum housed the testes away from the body to maintain temperature = 34 C

• testes are surrounded by dartos muscle which can contract to keep the testicles warm when it is too cold and relax to keep the testes cool when it is too warm
• the muscle of the inner abdominal wall form the cremaster muscle which helps to raise and lower the scrotum

Question 3

What structures does the spermatic cord contain?

Answer 3

• ductus deferens
• blood vessels - testicular arteries and veins
• nerves
• lymphatics
  Cremaster muscle = abdominal muscle which surrounds the spermatic cord - muscle contracts to lift testes closer to the body to keep them warm

Question 4

What are the accessory organs of the male reproductive system?

what is their function?

Answer 4

Three glands
- Seminal vesicles
- prostate gland
- bulbourethral glands
= contribute to seminal fluid composition and volume

Question 5

What are the components of semen?

Answer 5

60% from seminal vesicles
30% from prostate
5% from bulbourethral gland
5% from spermatogenesis

Question 6

What are seminal vesicles ?
- describe them

Where are they located?

What do they do?

Answer 6

• two seminal vesicles
• behind urinary bladder lateral to ampulla of ductus deferent
• form ejaculatory ducts with ampulla
• produce viscous secretion - 60% of semen
• contains fructose to nourish sperm
• alkaline pH neutralises acidic environment and vagina

Question 7

What is the prostate gland?
- describe it

Where is it located?

What do they do?

Answer 7

• inferior to bladder
• wraps around urethra
• produces secretion - 30% of semen
• Slightly acidic, milky fluid containing enzymes (PSA - prostate-specific antigen)
• contains citrate to nourish sperm
• contributes to sperm activation, viability and motility

Question 8

What are the bulbourethral glands?

Where are they located?

What do they do?

Answer 8

• two glands located in urogenital diaphragm
• open into spongy/penile urethra
• contribute 5% of semen volume
• secretions lubricate and neutralise acidity in urethra prior to ejaculation

Question 9

What is spermatogenesis

Answer 9

The process by which spermatogonia are transformed to mature spermatozoa(sperm)
= Formation of the male gamete

Question 10

Describe the process of spermatogenesis

Answer 10

• spermatogonia divide by mitosis into type A and type B spermatogonia
• Type B spermatogonia differentiates into primary sex cells = primary spermatocytes which undergo meiosis I
• Forms secondary spermatocytes (haploid-23 chromosomes)
• These undergo meiosis II to form spermatids (haploid)
• Spermatids differentiate into spermatozoa with a head, body and tail via spermiogenesis
• spermatozoa released into lumen
• 1 spermatogonium forms 4 sperm

Question 11

How is spermatogenesis controlled?

- hormonal control

Answer 11

• GnRh is released from the hypothalamus and stimulates FSh and LH
• LH stimulates leydig cells to produce testosterone

= testosterone works together with FSH to promote spermatogenesis

• testosterone negative feedback to inhibit LH and GnRh
• inhibin(stroll cells ) inhibits FSH