L03: Testicular Function Flashcards Preview

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Flashcards in L03: Testicular Function Deck (41):
1

When does spermatogenesis begin? Where does it occur?

At puberty in seminiferous tubules

2

What forms Sertolli cells?

Mesodermal cord cells

3

Describe testes development until week 7

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

4

Describe testes development from week 7-8

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

5

Describe testes development following week 8

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

6

Where is AMH produced? What is its role?

Sertolli cells - they’re then activated by SOX 9
Prevents formation of female reproductive system

7

What are the functions of Leydig & Sertolli cells?

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

8

When does puberty begin?

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

9

Where is the blood testes barrier found?

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

10

When does the BTB form?

Prior to onset of spermatogenesis

11

FUNCTION of BTB

- separates sperm from immune system to prevent immune response
- selective transport of molecules to create right environment for spermatogenesis

12

How many sperm are made per day?

100,000 x 100 million

13

Describe the proliferation phase of spermatogenesis (16 days)

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)

14

What are As spermatogonia?

Stem cells - hence they can undergo mitosis or self renewal

15

Why can males produce sperm for whole life?

As spermatogonia can self renew hence there will be constant supply

16

Describe the division phase of spermatogenesis

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)

17

Describe the differentiation phase of spermatogenesis

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

18

How does the acrosome form?

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

How does the flagellum form?

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

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

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

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

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

22

What is spermiation?

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

23

How long does spermatogenesis take in humans?

64 days

24

What is the spermatogenic wave?

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

25

What are the main products of the testes?

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

26

What is the role of oestrogen in males?

Modulates libido, erectile function, spermatogenesis

27

Fate of testosterone after production?

- 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

How is testosterone carried out of testes?

In testicular fluid bound to ABP

29

Where does LH & FSH act?

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

30

Why does sperm need further maturation after leaving testes?

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

31

Describe sperm maturation - where & how does it occur?

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

How long does maturation within epididymis take?

10-14 days

33

Function of vas deferens

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

34

What is contained within the ejaculate?

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

35

What is seminal plasma.?

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

Is semen homogenous?

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

37

Role of seminal vesicles

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

38

Role of prostate

Secrets prostate fluid during intercourse
Alkaline to neutralise acidic vagina, enzymes for ejaculate clotting + liquefaction, high in zinc

39

Role of Bulbourethral gland

Produces pre-ejaculate during arousal phase
For lubrication, neutralisation of acidic urethra, flushes it out

40

What is capacitation?

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

How many sperm make it through final maturation + capacitation?

1 in million