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My VETS2008 > Spermatogenesis 1&2 and male hormones > Flashcards

Spermatogenesis 1&2 and male hormones Flashcards

1
Q

What is the structure of the blood testes barrier

A

Sertoli cells, junctions with each other which is what forms the blood testis barrier

there is a basal compartment and an abluminal compartment, and an interstitual compartment to the blood testes barrier.

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2
Q

Why do males need reproductive hormones

A 
general behaviour (find females)
mating behaviour (successful mating)
secondary sex characteristics (attract females)
sperm production (successful fertilisation)
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3
Q

What is a hormone? (general definition)

A

Diverse group of signalling molecules, the messengers of the endocrine system.

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4
Q

Where are the major male reproductive hormones produced (origins - 3 main ones)

A
  • hypothalamic
  • pituitary
  • gonadal
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5
Q

What hormones are produced in the hypothalamic region?

A

GnRH
Oxytocin

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6
Q

What hormones are produced in the pituitary gland

A

LH
FSH

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7
Q

What hormones are produced in gonadal region

A

testosterone
inhibin
estradiol
PGF2a (not focused as much)

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8
Q

What is the HPG axis?*
What does it regulate?

A

Hypothalamic pituitary gonadal axis regulated production of reproductive hormones in BOTH SEXES

  • Production of hormones is controlled by positive and negative feedback*
  • LH and FSH mainly by GNRH -> gonadotroph releasing hormone
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9
Q

Two parts of the pituitary gland

A

anterior pituitary and posterior pituitary

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10
Q

What is the role of GnRH? Where is it produced?

A

GnRH is produced in the hypothalamus and is going to act on the pituitary

  • GnRH super important → acts on anterior pituitary → releases two gonadotropins (LH and FSH)
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11
Q

What are LH and FSH? Where are they produced? **

A

LH and FSH are gonodotropins (action in the testes)

  • GnRH releases these hormones, which comes from the hypothalamus
  • these hormones are released from the pituitary (anterior)
  • LH = luteinizing hormone
  • FSH = follicle stimulating hormone
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12
Q

What is the role of LH hormone? What cell do they bind too? (think L)

A

LH - bind to ILH receptors in leydig cells to produce testosterone (support leydig cell functions - hormone production)

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13
Q

What is the role of FSH? What cells to they bind to? (think S)

A

Binds to receptors on Sertoli cells and role is to support their function which is sperm production*

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14
Q

Gonadal hormones: what hormones do leydig cells and sertoli cells produce (separate)

A

Produce gonadal (sex) hormones

  • Leydig cells: testosterone and estradiol (important hormones*)
    • Sertoli cells convert T to DHT and E2 and produce inhibin
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15
Q

Where are LH and FSH produced?

A

Anterior pituitary

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16
Q

Role of testosterone hormone:

A

Produced by leydig cells

  • localised function - drive sperm production
  • reproduction male characteristics (mating)
  • increase muscle mass
    • behaviour/libido
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17
Q

Role of DHT

A
  • Produced by sertoli mainly
  • development of repro anatomy and sexondary characteristics
    • similar to T
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18
Q

Role of estradiol

A

produced by leydig and sertoli cells

  • drive sperm production
    • assists in fluid resorption in epididymis (become more concentrated in epididymis)
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19
Q

Inhibin = inhibiting*

Role of inhibin

A

produced by sertoli cells

  • negative feedback on AP release of FSH → inhibits release of FSH in pituitary and reduces LH releasing hormone
20
Q

What are the two negative feedback loops involved in the HPG axis feedback?

A
  • inhibin - blocks FSH directly (in pituitary)
  • Gonadal hormones block GnRH (in hypothalamus)
  • Feedback mechanisms regulate hormone production
    • ensures hormone synthesis remains active
21
Q

Why do we need the HPG axis feedback mechanism (why can’t hormones be in high concentrations when they leave the gonad?)

A

High concentrations in gonad, but as soon as they leave they get dilated by about 500 times because if they were in really high concentrations in circulation, they would shut down the HPG access. So the concentration is enough to control GnRH being produced and ensure regulated hormone production along HPG access but not enough to shut down the axis.

22
Q

Why does LH and FSH follow a GnRH release pattern?

A

because GnRH is causing them to be released → GnRH release by hypothalamus → acts on pituitary gland to release LH and FSH

  • GnRH is short acting, and LH is higher peak than FSH due to inhibin dampening down FSH (inhibin inhibits FSH)
23
Q

What hormones in the HPG axis inhibit the release of FSH?

A

Inhibin → directly limits FSH production

testosterone, DHT and ER → secreted by the gonads, negative feedback of the hypothalamus → so will decrease GnRH secretion and thus lower FSH secretion.

24
Q

Why is cholesterol important for hormones?

A

cholesterol is the precursor to all steroid hormones

25
Q

Role of cholesterol in testosterone (what is it converted into to become testosterone?)

A

Cholesterol → pregnenolone → progesterone → testosterone

  • T can then ne aromatised to E2 (estradiol)
26
Q

Basic steps of testosterone synthesis: (4 main steps)

A
  1. cholesterol important into Leydig cells then into mitochondria of cell
  2. cholesterol → pregnenolone → progesterone
  3. progesterone exported into cytoplasm
    1. progesterone → testosterone
27
Q

What is the action of testosterone?

A

Acts by binding to the androgen receptor in the nucleus

This complex acts as a transcription factor to alter gene expression

28
Q

Other male repro hormones: role of oxytoxin:

A

Produced by para-ventricular nucleus

  • Oxytocin transported by reproductive tract and stimulates smooth muscle contraction and production of PGF2a (prostaglandin → not studied much in males..)
29
Q

Summary: main actions of:

  • GnRH
  • LH
  • FSH
  • Testosterone
  • Estradiol
  • Inhibin
  • Oxytocin
A
  • GnRH → LH and FSH release
  • LH → testosterone prod.
  • FSH → sertoli cell func.
  • Testosterone → spermatogenesis, anabolic growth
  • Estradiol → sexual behaviour
  • Inhibin → inhibits FSH release
  • Oxytocin → pre-ejac sperm transport, PGF2A prod.
30
Q

What occurs during meiosis in spermatogenesis?

A

Haploid cells are produced by dividing the cell

allows constant production of sperm

31
Q

What happens during meiosis to create genetic diversity?

A

Crossing over of dna allowing recombination, get daughter cells that have a different mixture of alleles depending on which chromatid that daughter cell inherited.

32
Q

What is the importance of the blood testis barrier In terms of immunity?

A

Preventing an immune response from occurring - haploid cells are being produced which look very different to diploid cell, so if the barrier wasn’t there then the immune system would attack the haploid cells

33
Q

Third step in spermatogenesis is spermiogenesis. What occurs in this stage

A

Spermatids produced by meiosis 2

  • go from round to elongated

round spermatids undergo spermiogenesis to form elongated spermatids that will eventually mature

34
Q

what is the order of the 3 steps of spermatogenesis?

A

Mitosis (continual supply of cells) - meiosis (genetic diversity of haploid cells)- spermiogenesis (elongated spermatids)

35
Q

In what stage would you see spermatogonia?

A

Mitosis

36
Q

In what stage would you see spermatocytes in spermatogenesis

A

Meiosis

37
Q

structurally, what will mature sperm contain

A
  • a head with nucleus and acrosome
  • tail with mid piece, mitochondria, principal piece and end piece
38
Q

What are the cells that form tight junctions in BTB?

  • leydig cells
  • sertoli cells
  • Extracellular cells
A
  • Sertoli cells form tight junction between one another to form the BTB and protect non self haploid cells during sperm development
39
Q

what are the ‘stages’ of seminiferous epithelium cycle referring to

A

the stages classify what is going on in the epithelium/classifying groups of cells in a section of the seminiferous tubule

40
Q

What is the seminiferous epithelium cycle

A

Time taken for The reappearance of the same stage at a given location

41
Q

What is a spermatogenic cycle

A

Full process from spermagonia to spermatozoa = 4.5 x seminiferous epithelial cycle

42
Q

What are spermatogonia waves

A

Sequential order of stages along the tubule allowing sequential sperm release

43
Q

What alters daily sperm production?

A

Testis size or spermatogenesis efficiency

44
Q

What are factors that impact spermatogenesis

A
  • breakdown of btb- if compromised then immune cells will attack developing sperm
  • diet - vitamin deficiencies
  • irradiation - e.g. cancer treatment, can cause permanent infertility
  • excess heat *
  • ‘drugs and toxic agents
  • endocrine disrupting chemicals (EDCs) - pesticides
45
Q

What causes excess heat of the testes?

A
  • high environmental temperature
  • fever
  • cryptorchidism

My VETS2008 (34 decks)

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