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Reproductive Biology 3 > L8: Male Reproductive Physiology > Flashcards

L8: Male Reproductive Physiology Flashcards

(47 cards)

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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

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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?

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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?

Study These Flashcards
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?

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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?

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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?

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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
What is the evidence of **epididymis** importance?
Sperm taken straight from the testis are unable to fertilise an oocyte in vivo
26
How long is **epidydimis**?
Six meters long
27
How is **epididymal pH** important? What is the evidence?
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
What is the function of **epididymal stereocilia**?
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
Does **epididymis** require **androgens** for normal development?
Knock out: involution - shrinks, cells get really small
30
What is the function of **vas deferens**?
- 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
How can **vas deferens** be manipulated as male contraception?
- 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
What is **congenital bilateral absence of vas deferens**? What causes it?
- 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
Which parts produce **seminal plasma**?
- prostate gland - seminal vesicle
34
What does **seminal plasma** consist of? What's the percentage? What's the function of each component?
- nutrients (fructose, proteins) - alkaline solution (needed for survival) - lubricant (helps sperm swim)
35
What is the function of **seminal vesicles**?
- seminal vesicle fluid makes up 70-85% seminal fluid - composes the second part of the ejaculate - contains fructose: provides sperm with energy
36
What promotes **semen coagulation** at ejaculation?
Promoted by semenogelin I and II, expressed exclusively in the seminal vesicles
37
Why do rodents need **large seminal vesicles**?
Large seminal vesicles needed in species where males leave a **copulatory plug**, to stop another male sperm from getting in
38
What is the function of **prostate**?
Produces prostatic fluid which mixes with sperm to make up the first part of the ejaculate.
39
What's the **pH of prostatic fluid**? How is that important?
Alkaline: helps sperm survive in the acidic female reproductive tract, contains Zn2+
40
What is **benign prostatic hyperplasia**?
- non-cancerous enlargment of the prostate due to cell multiplication - 90% of men around the age of 80 have BPH
41
Where is **prostate-specific antigen** produced?
PSA a.k.a kallikrein 3 (Klk3) is produced by prostate epithelial cells
42
What is the function of **PSA**?
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
When can levels of **PSA** increase?
Levels may increase with prostate cancer/BPH, can be used as a diagnostic test
44
Which structure in penis causes erection?
**Corpus cavernosum** - spongy structure, erection when filled with blood
45
What is the mechanism of **erection**?
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
How does **viagra** work?
cGMP is reduced by PDE-5, viagra acts as PDE-5 inhibitor, causing more erection
47
What is the **mechanism of semen coagulation** and **liquification**?
- 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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