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Human Reproduction > Male gametogeneis > Flashcards

Male gametogeneis Flashcards

1
Q

What is fertility?

A

A statistical measure of the outcome of reproduction, given in terms of number of children born per reproducing couple.

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2
Q

What is fecundity?

A

The biological potential for reproduction; in terms of gametogenesis, fertilisation and pregnancy.

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3
Q

What is the role of the scrotum?

A

Keeps testes hanging below the body, where temperatures are 2-3o lower and optimum for spermatogenesis.

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4
Q

What are the compartments of the testes?

A
  • Seminiferous tubules:
    1. Basal compartment
    2. Adluminal compartment
  • Intertubular:
    1. Vascular compartment
    2. Interstitial compartment (Leydig cells, lymphatics)
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5
Q

What are the functions of the blood-testes barrier?

A
  1. Prevents spermatozoa from leaking into the blood, lymphatics, triggering immune response.
  2. Maintains microenvironment of the adluminal space optimum for sperm maturation (since intratubular fluid significantly different in composition to intertubular fluid).
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6
Q

What is the structure of the blood-testes barrier?

A

Tight junctions between Sertoli cells

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7
Q

What are the stages of spermatogenesis?

A
  1. Mitosis: Produces large numbers of genetically identical precursor cells (primary spermatocytes).
  2. Meiosis: Generates genetic diversity and produces haploid spermatids.
  3. Cytodifferentiation: Transformation of spermatocytes into elongated cells with motile tail, specialised to deliver chromosomes to the oocyte. This process is called spermiogenesis.
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8
Q

What is the rate of sperm production in testes?

A

~100 million/day

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9
Q

What types of cells undergo mitosis in spermatogenesis and what is their location?

A
  • Spermatogonial stem cells
  • Basal compartment of seminiferous tubules
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10
Q

What are the stages of spermatogenesis?

A

Spermatogonial stem cells

↓

[Mitosis]

↓

Primary spermatocyte

↓

[Meiosis I]

↓

Secondary spermatocyte

↓

[Meiosis II]

↓

Spermatids

↓

[Spermiogenesis (cytodifferentiation)]

↓

Spermatozoons

↓

[Spermiation (release)]

↓

Spermatozoa

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11
Q

When does meiosis occur?

A

When spermatocytes are migrating from basal compartment to adluminal compartment

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12
Q

How do spermatocytes cross the blood-testes barrier?

A

Unzipping tight junctions between Sertoli cells and re-zipping them behind

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13
Q

What is the structure of a spermatozoa?

A
  1. Elongated headpiece containing chromosomes that have condensed (histones replaced with protamines, and transcription is switched off).
  2. Acrosome containing enzymes that aid sperm in breaking through zona pellucida of oocyte.
  3. Midpiece containing mitochondria to generate energy for motility.
  4. Tail that pulsates to facilitate sperm motility.
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14
Q

What are the functions of Sertoli cells?

A
  1. Forms blood-testes barrier
  2. Secretion of testiculat fluid
  3. Secretion of inhibin
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15
Q

Why are spermatocytes dependent on Sertoli cells during their development?

A

Their chromosomes are tightly packed by protamines and all transcription is switched off

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16
Q

What is the association between spermatocytes during meiosis and its functional significance?

A
  • During meiosis, the sperm are connected by a thin cytoplasmic bridge.
  • The purpose of this seems to be to allow for exchange of genetic information so that all sperm haploid (X or Y only) can produce both X and Y coded proteins.
17
Q

What is the length of development cycle for one sperm and how is continuous secretion maintained?

A
  • 64 days.
  • Different parts of the seminiferous tubule are out of sync with each other, allowing continuous production of spermatozoa despite long maturation time.
  • A single spermatogonial stem cell enters mitosis every 16 days.
18
Q

What is the function of LH?

A

Stimulates production of testosterone from Leydig cells

19
Q

What hormones are involved in regulating spermatogenesis?

A
  • FSH
  • Testosterone
20
Q

What are the interactions of FSH and testosterone with Sertoli cells?

A
21
Q

What are the feedback loops involved in male gametogenesis?

A
22
Q

What is the function of negative feedback in male gametogenesis?

A

Allows maintenance of constant levels of gonadotrophin and testosterone production for constant spermatogenesis.

23
Q

What is the structure of the spermatozoal tail?

A
  • Central microtubule bundle (axoneme) contains:
    1. 2 central singlets
    2. 9 peripheral doublets
  • Axoneme surrounded by 9 dense outer fibres
24
Q

What is the structure of spermatozoal midpiece?

A

Spermatozoal tail fibres are surrounded by helical mitochondria

Human Reproduction (21 decks)

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