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Reproductive Biology 3 > L8: Male Reproductive Physiology > Flashcards

L8: Male Reproductive Physiology Flashcards

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1
Q

What are the most important anatomical structures of testis?

A
  • interstitium
  • seminiferous tubules (highly coiled, site of sperm production)
  • tunica albuginea
  • rete testis (all the seminiferous tubules anastomose, join together)
  • ductili efferentes
  • vas deferens
  • epididymis (separate from testis, but closely related)
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2
Q

What’s the function of tunica albuginea?

A

Thick layer of connective tissue, protective function

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3
Q

What are the two main functions of the testis? Where do they take place?

A
  • spermatogenesis (in seminiferous tubules)
  • steroidogenesis (in interstitium, Leydig cells)
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4
Q

Where does spermatogenesis take place?

A

Production of haploid germ cells takes place in seminiferous tubules

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5
Q

Where does steroidogenesis take place?

A

production of hormones takes place in interstitium (between seminiferous tubules), Leydig cells

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6
Q

Which way does germ cell maturation occur in males?

A

From the basal to luminal surface of the seminiferous epithelium

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7
Q

What are Sertoli cells? Where are they located?

A

Sertoli cells are the somatic supporting cells of spermatogenesis in the seminiferous epithelium

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8
Q

What are Sertoli cells? What is their function?

A

inside the epithelium, somatic supporting cells of spermatogenesis, very large cells
- structural
- protective
- secretory
- phagocytic
- stimulatory
- receive and transmit endocrine and paracrine signals

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9
Q

What is the structural function of Sertoli cells?

A

structural: scaffold for germ cells connected with adherens junctions, move germ cells basal –> apical

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10
Q

What is the protective function of Sertoli cells?

A

form blood testis barrier tight junctions between sertoli cells forms an immunologically privileged site – ensures that developing germ cells have undergone meiosis are not attacked by the host immune system

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11
Q

What is the secretory function of Sertoli cells?

A

secrete fluid to form seminiferous tubule lumen, secrete androgen binding protein to transport luminal androgens (fills the lumen)

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12
Q

What is the phagocytic function of Sertoli cells?

A

absorb waste organelles of developing germ cells

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13
Q

What is the stimulatory function of Sertoli cells?

A

gap junctions between SCs and sperm allow transfer of molecules

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14
Q

What is the receive and transmit endocrine and paracrine signals function of Sertoli cells?

A

eg they have receptors for FSH, testosterone whereas germ cells do not – germ cells do not have endocrine hormone receptors, all the receptors are on Sertoli cells

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15
Q

How many germ cells does one Sertoli cell support?

A
  • Each Sertoli cell supports a fixed number of germ cells
  • Number of Sertoli cells per testis is proportional to the daily sperm production
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16
Q

When do Sertoli cells stop dividing?

A

At puberty

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17
Q

What does interstitium consist of?

A
  • Blood vessels,
  • Leydig cells (androgen production)
  • macrophages (phagocytosis)
  • lymphatic cells (produces ECM),
  • capillaries,
  • fibrocytes (produces ECM))
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18
Q

What are the two main functions of interstitium?

A
  • support spermatogenesis
  • testosterone production
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19
Q

Where is testosterone produced? Which cells? Describe the pathway

A

Leydig cells are the site of testicular steroidogenesis
- Enzyme 3BHSD – important in testosterone production, can label Leydig cells
- Leydig cells are stimulated by LH
- Stimulation triggers cascade where from cholesterol testosterone is produced
- This testosterone is then converted to dihydrotestosterone (DHT) by 5alpha- reductase

20
Q

What is the evidence that testosterone is needed for normal spermatogenesis?

A
  • article showed that destruction of Leydig cells using EDS (ethane dimethane sulphonate) causes reduction in interstitial testosterone.
  • 2 weeks after - reduction in testosterone causes gradual degeneration of spermatogenesis
  • However after 2 weeks there is also regeneration of these Leydig cells observed
21
Q

What is the function of Peritubular myoid cells? Where are they located?

A

PTM cells are smooth muscle cells, move sperm out of the testis and they surround seminiferous tubules.

22
Q

What is the mechanism causing the contraction of PTM cells?

A

In sertoli cell: Big ET-1 is covnerted to ET-1 by ECE-1. ET-1 then activates Eta and Etb dimerised receptor on PTM cell, causing contraction.

23
Q

Where does the sperm go after contraction of seminiferous tubules?

A

It brings sperm to the rete testis through the seminiferous tubule lumen and through efferent ducts

24
Q

Where is epididymis found? What is the function of epididymis?

A
  • Found within the scrotum
  • concentrates sperm
  • provides movement (tail)
  • structural maturation (acrosome)
  • storage
  • Sperm taken straight from the testis are unable to fertilise in vivo
25
Q

What is the evidence of epididymis importance?

A

Sperm taken straight from the testis are unable to fertilise an oocyte in vivo

26
Q

How long is epidydimis?

A

Six meters long

27
Q

How is epididymal pH important? What is the evidence?

A

Changes in epididymal pH can cause sperm tail malformations.

Evidence: Knockout of C-ros gene in mice causes underdevelopment of initial segment of epididymis. This results in a more alkaline epidydimal pH and defects in sperm tails and volume.

28
Q

What is the function of epididymal stereocilia?

A

Help concentrate sperm
epithelial cells are tall columant; stereocilia, thought to increase surface area for absorption of testicular fluid (fluid is absorbed in epididymis)

29
Q

Does epididymis require androgens for normal development?

A

Knock out: involution - shrinks, cells get really small

30
Q

What is the function of vas deferens?

A
  • straight muscular tube
  • in humans, spermatozoa are stored in the vas prior to -ejaculation (in vas and in epididymis)
  • it is thick layer of smooth muscle cells
  • the thick muscular layers contract for peristalsis of sperm along the vas during ejaculation
31
Q

How can vas deferens be manipulated as male contraception?

A
  • vasectomy
  • vasalgel injected in lumen, acts as a blocker for sperm, can be flushed from vas by an injection of sodium bicarbonate - fully reversible
32
Q

What is congenital bilateral absence of vas deferens? What causes it?

A
  • When vasa deferentia (plural) do not develop properly
  • common in men with mutations in the cystic fibrosis transmembrane regulator (CFTR) gene
  • some men with mutations in CFTR have full CF, but in others CBAVD is their only symptom
33
Q

Which parts produce seminal plasma?

A
  • prostate gland
  • seminal vesicle
34
Q

What does seminal plasma consist of? What’s the percentage? What’s the function of each component?

A
  • nutrients (fructose, proteins)
  • alkaline solution (needed for survival)
  • lubricant (helps sperm swim)
35
Q

What is the function of seminal vesicles?

A
  • seminal vesicle fluid makes up 70-85% seminal fluid
  • composes the second part of the ejaculate
  • contains fructose: provides sperm with energy
36
Q

What promotes semen coagulation at ejaculation?

A

Promoted by semenogelin I and II, expressed exclusively in the seminal vesicles

37
Q

Why do rodents need large seminal vesicles?

A

Large seminal vesicles needed in species where males leave a copulatory plug, to stop another male sperm from getting in

38
Q

What is the function of prostate?

A

Produces prostatic fluid which mixes with sperm to make up the first part of the ejaculate.

39
Q

What’s the pH of prostatic fluid? How is that important?

A

Alkaline: helps sperm survive in the acidic female reproductive tract, contains Zn2+

40
Q

What is benign prostatic hyperplasia?

A
  • non-cancerous enlargment of the prostate due to cell multiplication
  • 90% of men around the age of 80 have BPH
41
Q

Where is prostate-specific antigen produced?

A

PSA a.k.a kallikrein 3 (Klk3) is produced by prostate epithelial cells

42
Q

What is the function of PSA?

A

PSA cleaves semenogelins to liquify coagulated semen in the female reproductive tract: allows sperm to swim freely (liquifies in a few minutes in female)

43
Q

When can levels of PSA increase?

A

Levels may increase with prostate cancer/BPH, can be used as a diagnostic test

44
Q

Which structure in penis causes erection?

A

Corpus cavernosum - spongy structure, erection when filled with blood

45
Q

What is the mechanism of erection?

A

Nitric oxide acts on guanylate cyclase, which converts GTP to cGMP, the more cGMP the more relaxation of smooth muscle, the more blood flows to the penis

46
Q

How does viagra work?

A

cGMP is reduced by PDE-5, viagra acts as PDE-5 inhibitor, causing more erection

47
Q

What is the mechanism of semen coagulation and liquification?

A
  • PSA and Zinc (inhibits PSA) released from prostate
  • sperm released from epididymis
  • semenogelin released from seminal vesicles

upon ejaculation all of these mixed up, zinc preferably binds to semenogelins, causes crosslinking (coagulation)

15-60 min after in the cervix, PSA is activated when zinc is bound by semenogelin, causing liquification.

Reproductive Biology 3 (21 decks)

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