4.0 Male Gametogenesis Flashcards
Define fecundity
<b>The potential for reproduction</b><br></br>- Gamete production, fertilization and carrying pregnancy to term
Define fertility
<b>Measure of reproduction</b><br></br>Number of children born per person, couple or population
Define fertility rate
<b>Number of births per time period per person, couple or population</b>
What factors affect fertility in women?
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
What factors affect fertility in men?
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
What causes cessation of fecundity in women?
<b>Menopause</b><br></br>Usually ~40yrs (2% early menopause - 20yr+)<br></br>Ovarian decline/failure → <b>secondary amenorrhoea</b>
What causes menopause?
<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
What causes male cessation of fecundity?
1) Loss of libido<br></br>2) Erectile dysfunction<br></br>3) Vascular pathology
On average how many years earlier do girls hit puberty?
2 years earlier
What are the cells in the male gonad?
1) Germ cells (primordial germ cells, spermatogonia, spermatocytes)<br></br>2) Spermatozoa<br></br>3) Sertoli cells<br></br>4) Leydig cells
What are the cells in the female gonad?
1) Germ cells (oocyte)<br></br>2) Ova<br></br>3) Granulosa cells<br></br>4) Thecal cells
Compare the germ cells in the testis and ovary:
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At what stage are cells arrested in the <b>dictyate stage</b>?
Meiotic prophase
Compare the generation of gametes in testis and ovaries:
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How many degrees cooler are the testes compared to body temp?
4-7 degrees
What contributes to the testes being cooler than body temp?
1) Position (in scrotum outside body)<br></br>2) Circulation (pampiniform plexus)<br></br>3) Divided into compartments
What forms the blood-testis barrier?
<b>Sertoli cells</b><br></br>- Junctional complexes between sertoli cells = main barrier to diffusion
What is the purpose of the blood-testis barrier?
Prevents penetration of tubular wall<br></br>Prevents penetration of basal component and adluminal compartment
What are the consequences of breakdown of blood/testis barrier?
1) Autoallergic orchitis<br></br>2) Alterations in tubular microenvironment
What cells are located within the seminiferous tubules in the male gonads?
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)
What cells are located outside tubules (interstitially) in the male gonads?
1) <b>Leydig cells</b> - 4-10mg androgen daily<br></br>2) <b>Blood vessels and lymphatics</b>
What are the stages of spermatogenesis:
<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
What is spermiation?
Release of spermatozoa into testicular fluid
What cell regulates all stages of spermatogenesis?
Sertoli cells
How long does it take from stem cell to spermatozoa?
64 days
What is the interval between groups of cells initiating sperm development?
16 days<br></br><br></br>Locally coordinated but different localities are not synced → <b>continuous output of sperm</b>
What cells secrete androgens?
Leydig cells
Functions of androgens?
- <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
What are the three gonadotrophins needed for testicular function?
<b>1) LH</b><br></br><b>2) FSH</b><br></br><b>3) Inhibin</b>
Structure of LH:
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
Where is LH secreted from and what cell does it act on?
Secreted from <b>ant. pituitary</b><br></br>Acts on <b>Leydig cells</b>
Structure of FSH:
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
Where is FSH secreted from and what cell does it act on?
Secreted from <b>ant. pituitary</b><br></br>Acts on <b>Sertoli cells</b>
Structure of inhibin:
<b>α chain</b> + <b>β chain</b> joined by <b>disulphide bridge</b>
Where is Inhibin secreted from and where is it secreted into?
Secreted by Sertoli cells (under influence of FSH)<br></br><br></br>75% → testicular fluid<br></br>25% → testicular lymph
