4.0 Male Gametogenesis

Question 1

Define fecundity

Answer 1

<b>The potential for reproduction</b><br></br>- Gamete production, fertilization and carrying pregnancy to term

Question 2

Define fertility

Answer 2

<b>Measure of reproduction</b><br></br>Number of children born per person, couple or population

Question 3

Define fertility rate

Answer 3

<b>Number of births per time period per person, couple or population</b>

Question 4

What factors affect fertility in women?

Answer 4

1) Age (puberty → menopause)<br></br>2) Choice (abstinence)<br></br>3) Fecundity is episodic (monthly)<br></br>4) Sub-fertility<br></br>5) Social convention<br></br>6) Access to A.R.T

Question 5

What factors affect fertility in men?

Answer 5

1) Age (post-puberty)<br></br>2) Choice (abstinence)<br></br>3) Social convention<br></br>4) Sub fertility<br></br>5) Fecundity is continuous<br></br>6) Access to A.R.T

Question 6

What causes cessation of fecundity in women?

Answer 6

<b>Menopause</b><br></br>Usually ~40yrs (2% early menopause - 20yr+)<br></br>Ovarian decline/failure → <b>secondary amenorrhoea</b>

Question 7

What causes menopause?

Answer 7

<b>Ovarian decline and failure</b><br></br>1) Fewer oocytes of lower quality → ↑ chromosomal anomalies<br></br>2) Follicular decline → hormonal changes → secondary amenorrhoea

Question 8

What causes male cessation of fecundity?

Answer 8

1) Loss of libido<br></br>2) Erectile dysfunction<br></br>3) Vascular pathology

Question 9

On average how many years earlier do girls hit puberty?

Answer 9

2 years earlier

Question 10

What are the cells in the male gonad?

Answer 10

1) Germ cells (primordial germ cells, spermatogonia, spermatocytes)<br></br>2) Spermatozoa<br></br>3) Sertoli cells<br></br>4) Leydig cells

Question 11

What are the cells in the female gonad?

Answer 11

1) Germ cells (oocyte)<br></br>2) Ova<br></br>3) Granulosa cells<br></br>4) Thecal cells

Question 12

Compare the germ cells in the testis and ovary:

Answer 12

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Question 13

At what stage are cells arrested in the <b>dictyate stage</b>?

Answer 13

Meiotic prophase

Question 14

Compare the generation of gametes in testis and ovaries:

Answer 14

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Question 15

How many degrees cooler are the testes compared to body temp?

Answer 15

4-7 degrees

Question 16

What contributes to the testes being cooler than body temp?

Answer 16

1) Position (in scrotum outside body)<br></br>2) Circulation (pampiniform plexus)<br></br>3) Divided into compartments

Question 17

What forms the blood-testis barrier?

Answer 17

<b>Sertoli cells</b><br></br>- Junctional complexes between sertoli cells = main barrier to diffusion

Question 18

What is the purpose of the blood-testis barrier?

Answer 18

Prevents penetration of tubular wall<br></br>Prevents penetration of basal component and adluminal compartment

Question 19

What are the consequences of breakdown of blood/testis barrier?

Answer 19

1) Autoallergic orchitis<br></br>2) Alterations in tubular microenvironment

Question 20

What cells are located within the seminiferous tubules in the male gonads?

Answer 20

1) <b>Spermatogonia</b> (mitotic)<br></br>2) <b>Spermatocyte</b> (meiotic)<br></br>3) <b>Spermatid</b> (haploid)<br></br>4) <b>Sertoli cells</b> (produce inhibin and testicular fluid)

Question 21

What cells are located outside tubules (interstitially) in the male gonads?

Answer 21

1) <b>Leydig cells</b> - 4-10mg androgen daily<br></br>2) <b>Blood vessels and lymphatics</b>

Question 22

What are the stages of spermatogenesis:

Answer 22

<b>1) Mitosis</b><br></br>- 5 to 7 divisions<br></br>- Mitotic activity of spermatogoni<br></br><b>2) Meiosis</b><br></br>- Occurs in spermatocytes<br></br>- They move more luminally as they divide<br></br><br></br><b>3) Maturation (spermiogenesis)</b><br></br>- Post-meotic <b>spermatids</b> change phenotypes<br></br>- round spermatid → elongated spermatid → spermatozoa

Question 23

What is spermiation?

Answer 23

Release of spermatozoa into testicular fluid

Question 24

What cell regulates all stages of spermatogenesis?

Answer 24

Sertoli cells

Question 25

How long does it take from stem cell to spermatozoa?

Answer 25

64 days

Question 26

What is the interval between groups of cells initiating sperm development?

Answer 26

16 days<br></br><br></br>Locally coordinated but different localities are not synced → <b>continuous output of sperm</b>

Question 27

What cells secrete androgens?

Answer 27

Leydig cells

Question 28

Functions of androgens?

Answer 28

1. <b>Masculinise soma</b><br></br>2. <b>Influence brain and behaviour</b><br></br>3. <b>Stimulate accessory sex gland growth and secretion in men</b> (seminal vesicle, prostate, epididymis)<br></br>4. <b>Secondary sex body hair patterns in both men and women</b><br></br>3. Exert anabolic and myotrophic effects to affect body shape

Question 29

What are the three gonadotrophins needed for testicular function?

Answer 29

<b>1) LH</b><br></br><b>2) FSH</b><br></br><b>3) Inhibin</b>

Question 30

Structure of LH:

Answer 30

Glycoprotein with 2 peptide chains<br></br><br></br><b>α chain</b><br></br>Common with FSH - 92 amino acid + 2 carb groups<br></br><b>β chain</b><br></br>Unique - 122 amino acids + 2 carb groups

Question 31

Where is LH secreted from and what cell does it act on?

Answer 31

Secreted from <b>ant. pituitary</b><br></br>Acts on <b>Leydig cells</b>

Question 32

Structure of FSH:

Answer 32

Glycoprotein with 2 peptide chains<br></br><br></br><b>α chain</b><br></br>Common with LH - 92 amino acid + 2 carb groups<br></br><b>β chain</b><br></br>Unique - 111 amino acids + 6 carb groups

Question 33

Where is FSH secreted from and what cell does it act on?

Answer 33

Secreted from <b>ant. pituitary</b><br></br>Acts on <b>Sertoli cells</b>

Question 34

Structure of inhibin:

Answer 34

<b>α chain</b> + <b>β chain</b> joined by <b>disulphide bridge</b>

Question 35

Where is Inhibin secreted from and where is it secreted into?

Answer 35

Secreted by Sertoli cells (under influence of FSH)<br></br><br></br>75% → testicular fluid<br></br>25% → testicular lymph