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RED Lectures > L03: Testicular Function > Flashcards

L03: Testicular Function Flashcards

1
Q

When does spermatogenesis begin? Where does it occur?

A

At puberty in seminiferous tubules

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2
Q

What forms Sertolli cells?

A

Mesodermal cord cells

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3
Q

Describe testes development until week 7

A

Indifferent stage:
Primordial germ cells arise during gastrulation (wk 3/4) in epithelium of yolk sac
They then migrate to genital ridges on dorsal embryo wall in AGM region

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4
Q

Describe testes development from week 7-8

A

Depends on SRY gene on Y chromosome - Produces TDF that activates other genes (architectural TF)
Influx of 3 cell population to gonads:
- columns of coelomic epithelium proliferate + penetrate deep into medullary mesenchyme forming primitive sex cords
- PGCs arrive & cord cells surround forming seminiferous tubules - PGCs become prospermatogonia
- migratory cells from mesonephric primordia form Leydig cells, myoid cells + vasculature

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5
Q

Describe testes development following week 8

A

SRY no longer needed - testes direct further growth

  • Formation of Sertolli cells from mesodermal cord cells
  • Inhibition of meiosis until puberty, prospermatogonia become dormant
  • Clusters of Leydig cells form between tubules + vascularisation occurs
  • Production of androgens & AMH
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6
Q

Where is AMH produced? What is its role?

A

Sertolli cells - they’re then activated by SOX 9

Prevents formation of female reproductive system

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7
Q

What are the functions of Leydig & Sertolli cells?

A

Leydig - produce testosterone

Sertolli - produce AMH, inhibin, ABP, site of spermatogenesis

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8
Q

When does puberty begin?

A

When hypothalamus starts to release GnRH —> LH & FSH release

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9
Q

Where is the blood testes barrier found?

A

Within seminiferous tubules, between basal + adluminal compartments
Formed by adherens, gap + tight junctions between Sertolli cells

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10
Q

When does the BTB form?

A

Prior to onset of spermatogenesis

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11
Q

FUNCTION of BTB

A
  • separates sperm from immune system to prevent immune response
  • selective transport of molecules to create right environment for spermatogenesis
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12
Q

How many sperm are made per day?

A

100,000 x 100 million

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13
Q

Describe the proliferation phase of spermatogenesis (16 days)

A

OCCURS IN BASAL COMPARTMENT

  • prospermatogonia reactivated + undergo mitosis compartment —> As spermatogonia
  • As spermatogonia —> A spermatogonia by mitosis (start of spermatogenesis)
  • A —> B spermatogonia (first mitotic division of spermatogenesis)
  • B —> primary spermatocytes (2nd division)
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14
Q

What are As spermatogonia?

A

Stem cells - hence they can undergo mitosis or self renewal

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15
Q

Why can males produce sperm for whole life?

A

As spermatogonia can self renew hence there will be constant supply

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16
Q

Describe the division phase of spermatogenesis

A

OCCURS IN ADLUMINAL COMPARTMENT - MEOSIS PHASE

  • primary spermatocytes —> 2 secondary spermatocytes (meiosis!)
  • recombination occurs for genetic variation (takes 24 days)
  • secondary —> 2 haploid round spermatids (few hrs)
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17
Q

Describe the differentiation phase of spermatogenesis

A
  • round spermatids elongate to form elongated spermatids + finally mature spermatozoa
  • formation of specialised structures e.g. acrosome, flagellum occurs
18
Q

How does the acrosome form?

A

From Golgi apparatus
Contains hydrolytic enzymes for acrosome reaction
Inner acrosomal membrane contains receptor for egg fusion (hence fertilisation cant occur w/o acrosome reactiom

19
Q

How does the flagellum form?

A

From distal centriole - elongates to from axoneme (microtubules)
Proximal centriole remains to act as spindles for 1st mitotic division of zygote (as egg has to centriole)

20
Q

What changes occur to the nucleus of sperm during differntiation phase?

A

DNA becomes condensed to fit inside head + his tones replaced w protamines for compact coiling
DNA no longer accessible for transcription (dependent on environment for further changes)

21
Q

What changes occur to the cytoplasm of sperm during differentiation phase?

A

Cytoplasm buds off as residual body - phagocytosed by Sertolli cells
Allows cell to be streamlined but translation can no longer occur

22
Q

What is spermiation?

A

Occurs after spermatogenesis
Release of mature spermatozoa from Sertolli cells to lumen of tubule
Washed down into epididymis via rete testes

23
Q

How long does spermatogenesis take in humans?

A

64 days

24
Q

What is the spermatogenic wave?

A

Cells enter spermatogenesis at diff days hence there are always cells at diff stages
Allows constant production

25
Q

What are the main products of the testes?

A

Androgens - for embryonic development, reproductive + sexual function
Oestrogen (small amount)
Cytokines e.g. inhibin, AMH

26
Q

What is the role of oestrogen in males?

A

Modulates libido, erectile function, spermatogenesis

27
Q

Fate of testosterone after production?

A
  • travel in blood to rest of body (can suppress HPG axis)
  • travel in lymph to accessory sex glands
  • bind to ABP for storage + carriage in testicular fluid
  • Stimulate spermatogenesis
28
Q

How is testosterone carried out of testes?

A

In testicular fluid bound to ABP

29
Q

Where does LH & FSH act?

A

LH binds to LHCG on Leydig cells for testosterone production
FSH binds to Sertolli cells & activates many genes

30
Q

Why does sperm need further maturation after leaving testes?

A

At this point they’re on morphological mature - they’re immobile + can’t recognise egg

31
Q

Describe sperm maturation - where & how does it occur?

A

In EPIDIDYMIS

  • oestrogen regulates absorption of fluid for concentration of spermatogenesis within semen
  • cells lining epididymis act on sperm, dependent on androgens
  • sperm acquires motility (in head of epididymis) + fertilising ability (body)
32
Q

How long does maturation within epididymis take?

A

10-14 days

33
Q

Function of vas deferens

A

Storage reservoir of sperm before ejaculation, densely packed
Vasectomy = cut/seal ends of vas deferens

34
Q

What is contained within the ejaculate?

A

Semen = sperm & seminal plasma (approx 3ml in humans w 100 million sperm)

35
Q

What is seminal plasma.?

A

Fluid from prostate + seminal vesicles to facilitate transport, provide nutrition for sperm (fructose), buffer acidic urine, antioxidants to protect DNA
Also contains STI agents
Forms 60-70% of ejaculate volume

36
Q

Is semen homogenous?

A

No - first part from prostate, middle from vas deferens containing spermatogenesis & last from seminal vesicles

37
Q

Role of seminal vesicles

A

Sac like glands that empty seminal plasma into ejaculatory duct upon ejaculation
Secretes fibrinogen like substance to induce clotting of ejaculate

38
Q

Role of prostate

A

Secrets prostate fluid during intercourse

Alkaline to neutralise acidic vagina, enzymes for ejaculate clotting + liquefaction, high in zinc

39
Q

Role of Bulbourethral gland

A

Produces pre-ejaculate during arousal phase

For lubrication, neutralisation of acidic urethra, flushes it out

40
Q

What is capacitation?

A

Final maturation of sperm within female tract
Sperm acted on by uterine flushings - causes sperm hyperactivation (increased motility for getting through ZP) + acrosome reaction

41
Q

How many sperm make it through final maturation + capacitation?

A

1 in million

RED Lectures (6 decks)

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