Spermatogenesis and fertilisation Flashcards

1
Q

Is phase 4 of spermatogenesis more or less rapid than oogenesis

A

More rapid

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2
Q

Where does spermatogenesis begin?

A

Seminiferous tubules of testers after puberty

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3
Q

What are type A spermatogonia?

A

mitotically active throughout reproductive life

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4
Q

How are spermatogonia kept at edge of semiferous epithelium?

A

Interlocking sertoli cells connected by intercellular cytoplasmic bridges

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5
Q

What are type B spermatogonia termed as when they enter meiosis

A

Primary spermatocytes

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6
Q

How long do spermatocytes take to complete meiosis 1

A

24 days

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7
Q

What happens during meiosis 1

A

spend this time making mRNA for later protein production

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8
Q

What is the result of early translation into protein

A

Sterility

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9
Q

What is produced from meiosis 1

A

Secondary spermatocytes

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10
Q

What is produced from meiosis 2

A

Spermatids

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11
Q

How are spermatids converted to spermatozoa

A

Spermiogenesis

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12
Q

How does spermatid changes as it becomes spermatozoa

A
  • Reduction in nuclear size
  • Golgi apparatus condense
  • Flagellum grows from centriole
  • Cytoplasm streams away from nucleus
  • Mitochondria in spiral arrangement around flagellum
  • Head partitioned into domains
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13
Q

What is the final step of sperm maturation

A

Capacitation

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14
Q

Where does capacitation occur

A

Female genital tract (requires contact with secretions of the oviduct)

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15
Q

What does LH stimulate

A

Testosterone production by Leydig cells

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16
Q

What are the main targets of testosterones and FSH

A

Sertoli cells which secrete androgen binding fluids

17
Q

What do androgen binding fluids do

A

Binds to testosterone and carries to seminiferous tubule: stimulates spermatogenesis

18
Q

Where is sperm deposited?

A

Cervical ovarian sphincter

19
Q

What propels the sperm up the uterine canal?

A

Uterine cilia

Sperms propulsion

20
Q

Describe the steps of the acrosome reaction

A
  • Sperm fuses with overlying plasma membrane
  • Enzyme released allow passage through zona pellucida
  • Finishes jounry between zp and oocyte (oolemma)
  • Sperm becomes enveloped
  • Fusion
  • Large increase in intracellular cacium forms wave across the egg
21
Q

How does fusion occur

A
  • Binds with egg receptors once acrosome reaction complete
  • Cortical vesicle fuses with plasma membrane undergo exocytosis
  • Releases contents into peri-vitelline spae
  • Modified fertilisation detaches and rises
  • Sperm pulled into egg by fertilisation cone
  • Microtubules from the centrosome associated w male pronucleus
  • Fuses with female pro nucleus
22
Q

How do mature egg and sperm finding each other

A

Chemotaxis

23
Q

How do cells with each other in a species specific way

A

In mammals there is a glycoprotein called ZP3 found in zona pellucida
Capacitated sperm are species specific in their binding to ZP3
Binding triggers changes in calcium and pH in sperm

24
Q

How is number of cell fusing restricted

A

Production of second messenger on sperm/ egg binding triggers blocking
Calcium wave triggers cortical release and activation of cell division

25
Q

What happens at 16-32

A

Polarisation of 2 cell populations

Outer cells form trophoblast precursors and inner cell are pluriblast (morula)

26
Q

What happens at 32-64 cell stage

A

This is blastocyst

Has to hatch off the hardened zona pellucida

27
Q

What attach itself to uterine wall

A

7-9 days post ovulation