Spermatogenesis

Question 1

What accounts for the majority of the total testis volume? What important event takes place here?

Answer 1

Seminiferous tubules (80% of volume)

• where spermatogenesis takes place
• starts at puberty

Question 2

How does spermatogenesis progress in the seminiferous tubules?

Answer 2

They bud out from the basement membrane to the lumen of the sminiferous tubules
- Spermatogonia –>
Primary Spermatocytes –>
Spermatids

• you can find blood vessels and Leydig cells in between the seminiferous tubules
• sertoli cells are found adjacent to the developing spermatocytes

Question 3

Starting point of spermatogenesis is a _____ and end point is a _____

Answer 3

spermatogonia (stem cell) -->
primary spermatocyte -->
secondary spermatocyte -->
early spermatid -->
Late spermatid -->
spermatozoa

Question 4

Chromosome number of Type A and Type B spermatogonia

Answer 4

diploid (46 ch)
2N (N = ploidy = sets of 23 ch)
2C (C = # chromatids)

Question 5

Number of chromosomes of primary spermatocyte

Answer 5

Diploid (46 sister chromatids)
2N
4C

• But here (2nd step), the DNA material replicate and have double the amt of genetic material.
• Genetic info is exchanged btwn non-sister chromatids

Question 6

Number of chromosomes of secondary spermatocyte

Answer 6

Haploid (2 sets of 23 sister chromatids)
1N
2C

• Is present after the first meiosis and homologous chromosomes are separated, and the chromosome number is reduced by half

Question 7

What happens after the second meiosis

Answer 7

the sister chromatids (of secondary spermatocyte) are separated by the end of meiosis II and become spermatids
- then it enters spermiogenesis and there is no more change in terms of # of genetic materials

Question 8

Phases of spermiogenesis

Answer 8

1. Golgi phase
   - golgi apparatus forms around acrosomal vesicle and spermatid nucleus
2. Cap phase
   - acrosomal vesicles bcome acrosomal cap
3. Acrosomal phase
   - cytoplasm is pulled away from the cap + nucleus and form the tail
4. Maturation phase
   - excess cytoplasm comes off
5. Spermiation
   - mature spermatozoa are released and deposited to the lumen by sertoli cells

• spermiogenesis is a dynamic process
• remember 3 stages of spermatogenesis: proliferative, meiotic, and spermiogenic

Question 9

What is released into the epididymus from the seminiferous tubules?

Answer 9

Spermatozoa (1N, 1C)
- morphologically like sperm, but immotile
- maturation takes place in epididymus
(Post testicular maturation of sperm)

Question 10

Head, body tail of epididymus

- main fxns

Answer 10

Head: most of the concentration of testicular fluid that transport spermatozoa from the seminiferous tubules will be reabsorbed in head (caput)

Body: maturation
(motility + fertil capable)

Tail: major storage space for spermatozoa (70% of all spermatozoa present)

Question 11

The whole process of spermatogenesis from spermatogonia –> spermatozoa takes about ____ days

Answer 11

64 days
- certain stages of sperm cells are seen at diff sections of seminiferous tubules.

• each stage takes ~ 16 daysa:
  ie: from spermatogonia to primary spermatocyte,
  to spermatid, to spermiation

Question 12

Sertoli cell fxn

Answer 12

1. Form blood testis barrier
2. Support and nutrition
3. Movement and release of germ cells
4. secretory fxn
   - tubule fluid
   - androgen binding protein
   - inhibin

Question 13

What are found in between seminiferous tubules?

- what does it produce?

Answer 13

Leydig cells - make T

• 5% of seminiferous tubules
• recieves LH signals and can produce T

Question 14

What are found in and around developing sperm?

- what does it produce?

Answer 14

1. Sertoli cells
   can produce ABP
   - high affinity for T to ensure the high [ ] of testosterone in the seminiferous tubules
   - critical for spermatogenesis
2. Can also produce Inhibin:
   - acts as a neg feedback on pituitary to control release of FSH
   (T from leydig cells have neg feedback to control LH, keeps them in balance)

Question 15

Three stages of spermatogenesis (process by which spermatogonial stem cells give rise to spermatozoon)

Answer 15

1. Proliferative phase
   - spermatogonia proliferate to give rise to spermatocytes, while maintaining their number by self renewal
2. Meiotic phase
   - spermatocytes undergo meiosis that reduce the ch # by half
3. Spermiogenic phase
   - spermatids undergo significantly morphological changes and mature into spermatozoa
   - no change in terms of ch #or DNA amt

Question 16

Diploid or Haploid?
and # N(ploidy) and # C for:
Spermatogonium
Primary spermatocyte
Secondary spermatocyte
Spermatid
Mature spermatozoon

Answer 16

Spermatogonium

• Diploid
• 2N, 2C

Primary spermatocyte

• Diploid
• 2N, 4C

Secondary spermatocyte

• Haploid
• 1N, 2C

Spermatid

• Haploid
• 1N, 1C

Mature spermatozoon

• Haploid
• 1N, 1C

Question 17

____ continues to extend out away from the nucleus to form the flagellum, and in the process it pulls most of the cytoplasmic inclusions away from the nucleus

Answer 17

Centriole

*moves to opp pole from acrosome (nuclear cap)