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Y2S2 REPRO > Spermatogenesis > Flashcards

Spermatogenesis Flashcards

1
Q

Testes have two major compartments:

A

Seminiferous tubules

Interstitial spaces

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2
Q

Seminiferous tubules

A
  • ~250 m total length
  • Developing germ cells
  • Sertoli cells
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3
Q

Interstitial spaces

A
  • Leydig cells (synthesize androgens)

* Blood and lymph vessels

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4
Q

what separates the two compartments

A

“Blood-testis barrier”
• Prevents immune reaction to spermatozoa
• Separates fluids of different composition

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5
Q

Spermatogenesis

A

Production of mature spermatozoa from undifferentiated germ

cells (primodial germ cell)

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6
Q

what re the three stages of spermatogenesis

A

1) Mitotic proliferation
2) Meiotic divisions
3) Cell modeling (spermiogenesis)

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7
Q

The Spermatogenic cycle is

A

~74 days (from 1st mitotic division to release of spermatozoa)

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8
Q

when is spermatogenesis initiated

A

every 16 days and occurs waves

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9
Q

Rate of each developmental stages is not uniform:

A
  • Spermatogonium > 1 ̊ spermatocytes = 25 days
  • Meiotic division 1 > 2 ̊ spermatocytes = 9 days
  • Development > spermatids = 19 days
  • Differentiation > spermatozoa = 21 days
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10
Q

At end of differentiation: in spermiation

A
  • Cytoplasmic links are broken
  • Spermatozoa released into tubule lumen
  • Sperm virtually immobile
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11
Q

what flushes spermatozoa from seminiferous tubules, through the rete testis into the epididymis:

A

Fluid secreted by Sertoli cells

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12
Q

what happens when the fluid flushes spermatozoa from seminiferous tubules, through the rete testis into the epididymis:

A
  • Capacity for motility by the time they reach the tail of the epididymis
  • Motility is suppressed by epididymal fluid
  • Instead movement through reproductive tract is aided by peristaltic muscle contractions
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13
Q

capacitation:

A
  • Normally occurs in the female reproductive tract (2-6h)

Glycoprotein coat gained in the epididymis is stripped

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14
Q

what changes occur in capacitation

A
  • Head acquires the capacity to initiate the acrosome reaction
  • Hyperactivation (increased flagellar beats)
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15
Q

Infertility in men is primarily diagnosed by semen analysis comprising of:

A
  • Determination of sperm concentration/total count
  • Motility
  • Morphology
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16
Q

Oligozoospermia

A

• Reduced sperm count (< 15 million/ml)

17
Q

Azoospermia

A

• Absence of sperm in the ejaculate

18
Q

Asthenozoospermia

A

• Reduced sperm motility (< 40% moving)

19
Q

Teratozoospermia

A

• Reduced percentage of sperm with normal morphology

20
Q

Anti-sperm antibodies

A

• Abnormal immune response to sperm

–

21
Q

where are the hormones released from

A

Hormones released by the hypothalamus, pituitary and testes are regulated by complex feedforward and feedback loops

22
Q

Hypothalamic secretion of Gonadotrophin-releasing hormone (GnRH) stimulates

A

the release of gonadotropins from ant. Pit.

23
Q

Pituitary gonadotrophins, luteinizing hormone (LH) and follicle stimulating hormone (FSH) control what

A

control testicular functions

24
Q

High GnRH pulse amplitude and frequency preferentially stimulates

A

LH synthesis and secretion whereas low GnRH pulse frequency stimulates FSH synthesis and secretion

25
Q

1)

Anterior pituitary

A 
Gonadotrophs
– Secrete LH and FSH (glycoproteins)
– Most cells secrete one or other, but some secrete both
Lactotrophs
– Secrete prolactin (protein)
26
Q

Posterior pituitary

A

Neurosecretory neurones

– Secrete arginine vasopressin (AVP) andoxytocin (peptides)

27
Q

Leydig cells

A

in the testes have receptors for LH

– stimulates synthesis and secretion of testosterone

28
Q

If LH secretion is too low

A

testosterone is low

– spermatogenesis halts

29
Q

FSH is required for

A

FSH is required for maximum sperm production – acts on Sertoli cells

30
Q

Testosterone (steroid) by Leydig cells

A

• In some tissues do not exert direct effects, but are converted to dihydrotestoterone or estrogens

31
Q

2) Estrogens (steroid)

A

) by Sertoli and Leydig cells

32
Q

3) Inhibins (peptide hormone)

A

by Sertoli cells

• feedback loop to control hormone levels

33
Q

4) Oxytocin (peptide hormone)

A

by Leydig cells

• contraction of smooth muscle of the genital tract

34
Q

Role of testosterone

A

– If production prevented spermatogenesis ceases

– Blocked when primary spermatocytes enter meiotic prophase

35
Q

If blood [testosterone] is low

A

hen fewer stem cells will begin cell division but the whole process will still take 74 days.

Y2S2 REPRO (25 decks)

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