Lecture 4: Spermatogenesis

Question 1

What is Spermatogenesis?

Answer 1

The production of spermatozoa from primordial cells in male, starting as undifferentiated spermatogonia into primary spermatocytes

Question 2

Label the structure of a Mature Spermatozoon.

Answer 2

1. Tail
2. Plasma Membrane
3. Middle piece
4. Mitochondrion (spiral shape)
5. Neck
6. Head
7. Nucleus
8. Across me —> bubble containing enzymes; when rxn occurs = helps in fertilization

Question 3

Label the Male Reproductive Tract.

Answer 3

1. Vas Deferens
2. Head of Epididymus
3. Body of Epididymus
4. Tail of Epididymus
   - mature sperm stays in epididymus for fertilization —> giving motility once released
5. Testis
6. Seminiferous tubules —> spermatogenesis occurs
7. Lobule of testis

Question 3

Explain the process from spermatagonium into 4 sperm cells.

Answer 3

Question 4

What are the 4 stages of Spermatogenesis?

Answer 4

1. Spermatocytesogenesis
2. Spermatidogenesis
3. Spermiogenesis
4. Spermiation

Question 5

Explain the process of Spermatocytogenesis.

Answer 5

Spermatogonium —> primary spermatocyte (1st phase) —> secondary spermatocyte (2nd phase)
- formations of spermatocytes containing half of genetic material

1st phase: Spermatogonial phase
1. Create Type A dark (Ad) spermatogonia and Type A pale (Ap) spermatogonia
- From Type Ad —> will replicate to make more spermatogonia
- From Type Ap —> will be differentiated into Type B cells
2. Type B cells will divide to provide 2 primary spermatocytes

2nd phase:
Each primary diploid (2N) spermatocyte duplicates DNA and divides into two aploid (1N) secondary spermatocytes by meiosis I

Question 6

Explain the process of Spermiogenesis.

Answer 6

Spermatid —> mature spermatozoa but not motile
Starts to grow structure:
- growing tail on body by microtubules
- mitochondria organizes itself within midpiece of tail acting as an energy supply
- DNA undergoes tight packaging —> no transcription of genetic material
- Golgi apparatus surrounds condensed nucleus, creating acrosome
- testosterone removes extra residual bodies and organelles which are phagocytoses by Sertoli cells

Question 7

Explain the process of Spermiation.

Answer 7

Becomes mature and motile spermatozoon
- Sertoli cells release mature spermatozoa into lumen of seminiferous tubule gaveling to epididymus for motile rxn to occur

Question 8

What are Sertoli cells and their functions during Spermatogenesis?

Answer 8

• Extends from lumen to seminiferous tubule to provide structural / metabolic support for developing sperm cells
• maintains the right environment for development and maturation (blood-testis barrier) by secreting testicular fluid, ABP (androgen binding protein that concentrates testosterone close to gametes), and hormones (inhibin —> affecting pituitary gland control)

Question 9

What are some Hormonal Controls of Spermatogenesis?

Answer 9

• at puberty FSH stimulates both ABP and formation of the blood-testis barrier
• inhibin acts to decrease FSH levels
• Sertoli mediates spermatogenesis Byron producing estradiol and inhibin

Question 10

Sperm Transport in the Male

Answer 10

• Testis —> head of epididymus (lasts for 4-12 days) —> Chemical rxn for formation of sperm to become motile and can be fertilized —> seminiferous tubules —> creates right environment for sperm

Question 11

What process occurs during Ejaculation?

Answer 11

• on ejaculation, semilunar fluid maintains a buffer environment with a pH between 7 - 8.3 for the sperm to survive in the acidic environment of the female

Question 12

What factors can affect spermatogenesis and male fertility?

Answer 12

Age, stress levels and testosterone levels affect volume, amount and quality of spermatozoa

Question 13

What are some differences and similarities of Spermatogenesis and Oogenesis?

Answer 13