Lect 25

Question 1

what is spermatogenesis

Answer 1

production of sperm

• undifferentiated diploid primordial germ cells (spermatogonia) are converted into haploid spermatozoa (sperm)

Question 2

descent of testes is usually complete by what month of gestation

Answer 2

7th month

Question 3

Why do testes descend into the scrotum

Answer 3

• provides cooler environment (1-2 C below body temperature) essential for spermatogenesis

Question 4

testes perform what two functions

Answer 4

1. produce sperm
2. secrete testosterone

Question 5

where is sperm produced

Answer 5

seminferous tubules

Question 6

testosterone is produced in what cells

Answer 6

Leydig (interstitial) cells

• found in connective tissue of testes

Question 7

Seminiferous tubules contain what two cell types

Answer 7

1. germ cells (spermatogonia)
2. sertoli cells
   
   • provides nutrients to germ cells

Question 8

function of sertoli cells

Answer 8

1. form tight junctions: blood-testes barrier
2. protect sperm and provide nourishment for sperm
3. phagocytize bad germ cells
4. secrete seminferous tubule fluid

Question 9

sertoli cells secrete what three hormones? what is each’s function

Answer 9

1. Inhibin: inhibit FSH release
2. Andorgen Binding protein: maintains high level of testosterone in tubular fluid
3. Anti-Mullerian hormone: development

Question 10

Spermatogenesis is mediated by

Answer 10

testosterone

Question 11

List the three major stages of Spermatogenesis

Answer 11

1. Mitosis: daughter cell -> 4 identical primary spermatocytes
2. Meiosis: each primary spermatocytes -> 4 spermatids
3. Spermiogenesis
   
   • packaging process in which spermatids transform into mature spermatozoa

Question 12

When is a cell considered a primary spematocyte

Answer 12

has finished mitotic division: four identical diploid (4N DNA) cells

Question 13

when is cell considered a secondary spermatocyte

Answer 13

after it has undergone meitoic division once

Question 14

secondary spermatocyte enters the second meiotic division, producing two what

Answer 14

spermatids

Question 15

what is the name of mature sperm

Answer 15

spermatozoa

Question 16

full cycle of spermatogenesis takes how long

Answer 16

60-70 days

Question 17

describe the spermatogenic wave

Answer 17

• production of spermatogenesis happens in waves throughout the entire seminiferous tubule
• guarentees a continuous supply of sperm

Question 18

what is spermiogenesis? what is it mediated by?

Answer 18

• process by which spermatids mature into spermatozoa
• testosterone

Question 19

what goes on during spermiogenesis

Answer 19

1. packaging and elongation into mature spermatozoa
2. remodeling of nucleus
3. condensation of chromatin
4. most of cytoplasm is lost
5. formation of acrosome

Question 20

What is Spermiation

Answer 20

process by which mature spermatozoa are extruded from Sertoli cells into the lumen of semineferous tubules

Question 21

contraction of myoepithelial cells propels spermatozoa into

Answer 21

vas deferens

Question 22

Where are sperm under final maturation prior to storage

Answer 22

epididymus

Question 23

where are sperm stored

Answer 23

vas deferens

Question 24

What is the effect of temperature on spermatogenesis

Answer 24

• lysosomal destruction prevented by cooler temperature
• testes kept cooler by
  
  • air around scrotum, contraction/relaxation of muscles, venous blood flow
• interference with ability of scrotum to stay cool -> low sperm counts
  
  • hot tubs, tight clothing, sitting too long

Question 25

What is Criptorchidism

Answer 25

* undescended testes * affected individuals are unable to produce viable sperm

Question 26

Describe hormonal control of spermatogenesis

Answer 26

1. hypothalamus releases gonadotropin-releasing hormones which acts on anterior pituitary to release FSH-secreting cells and LH secreting cells -\> FSH and LH 2. FSH sensitizes sertoli cells to testosterone and promotes secretion of inhibin and ABP from sertoli cells 3. LH stimulates Leydig cells to produce testosterone by increasing activity of cholesterol desmolase

Question 27

LH stimulates Leydig cells to produce testosterone by increasing activity of

Answer 27

cholesterol desmolase

Question 28

function of androgen binding protein (ABP)

Answer 28

keeps high levels of testosterone within gonads

Question 29

Describe negative feedback mechanisms of spermatogenesis

Answer 29

1. testosterone causes negative feedback on anterior pituitary to inhibit FSH and LH 2. Inhibin acts on anterior pituitary to inhibit FSH

Question 30

testosterone can be sequestered within the seminiferous tubules by binding to

Answer 30

androgen binding protein by sertoli cells

Question 31

testosterone can circulate within the peripheral circulation bound to

Answer 31

sex-hormone binding globulin (SHBG)

Question 32

testosterone can be peripherally converted to what two things in target tissues

Answer 32

1. dihydrotestosterone (DHT) 2. estradiol

Question 33

List the actions of testosterone on target tissues

Answer 33

1. differentiation of epididymis, vas deferens, and seminal vesicles 2. increased muscle mass 3. pubertal growth spurt 4. growth of penis seminal vesicles 5. deeping of voice 6. libido

Question 34

List the actions of dihydrotestosterone on target tissues

Answer 34

1. differentiation of penis, scrotum and prostate 2. male hair pattern/pattern baldness 3. sebaceous gland activity 4. growth of prostate

Question 35

which is more potent: dihydrotestosterone or testosterone

Answer 35

dihydrotestosterone

Question 36

What are the primary effects of exogenous testosterone (steroid) use

Answer 36

1. decrease LH and FSH release 2. decrease sperm production 3. increase in free estrogens (will free estrogens from binding proteins)