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MD3002 Physiology > Spermatogenesis and Spermiogenesis > Flashcards

Spermatogenesis and Spermiogenesis Flashcards

1
Q

What are found in between the seminiferous tubules?

A

Peritubular compartments (leydig cells found here)

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2
Q

What are the 2 major compartments of the testes?

A
  • Seminiferous tubules

- Interstitial spaces

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3
Q

Why are the seminiferous tubules and interstial spaces seperate?

A

Create a blood-testis barrier

  • Prevents immune reaction to spermatozoa
  • Separates fluids of different composition
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4
Q

What do the interstitial spaces contain?

A
  • Leydig cells

- Blood and lymph vessels

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5
Q

Where is the blood-testis barrier made?

A

Formed through interactions between tight junctions, zonular junctions and filament bundles between neighbouring sertoli cells, spermatogonia reside on one side of the blood-testis barrier, as development procedes it travels through it

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6
Q

What are the 3 stages to produce a mature spermatozoa?

A
  • Mitotic proliferation
  • Meiotic divisions
  • Cell modeling (spermiogenesis)
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7
Q

What are the undifferentiated germ cells called which spermatozoa are derived from?

A

Primordial germ cells

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8
Q

What are the names of all the cells from primordial germ cell to spermatozoa?

A
  • Primordial germ cell
  • Spermatogonia
  • Primary spermatocyte
  • Secondary spermatocyte
  • Spermatid
  • Spermatozoa
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9
Q

What does the primary spermatocyte do?

A

Enters meiosis 1

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10
Q

How long is the spermatogenic cycle?

A

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

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11
Q

How many days does it usually take to initiate spermatogenesis?

A

16 days (occurs in waves)

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12
Q

How long does it take for the spermatogonium to develop into the primary spermatocyte?

A

25 days

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13
Q

How long does the meiotic division 1 take (primary to secondary spermatocyte)?

A

9 days

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14
Q

How long does it take for the secondary spermatocyte to develop into a spermatozoa?

A

21 days

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15
Q

What is spermiogenesis?

A

Process that remodells the spermatid into the spermatozoa, during this period where the sperm develops the machinary required for sperm motility

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16
Q

How much sperm is made in 1 day roughly?

A

200 million

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17
Q

What structures surround the middle piece?

A

Sheathes of ring shaped mitochondria

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18
Q

What is the acrosome fprmed by?

A

The golgi

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19
Q

What does fluid secreted by sertoli cells do?

A

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

  • 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 perstaltic muscle contractions
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20
Q

Why would ejaculated sperm not fertilize an oocyte in vitro immediately?

A
  • Need to undergo capacitation (normally occurs in reproductive tract (2-6h)
  • Glycoprotein coat gained in the epidymis is stripped
  • Head then aquires the capacity to initiate the acrosome reaction
  • Hyperactivation (increased flagellar beats)
21
Q

What percentage of sperm show normal morphology under a microscope?

A

~ 4 - 14%

22
Q

If normal morphology drops below what level does fertilisation rates obtained with IVF reduced?

A

4%

23
Q

Infertility in men is primarily diagnosed by semen analysis comprising of what?

A
  • Determination of sperm concentration/total count
  • Motility
  • Morphology
24
Q

What level of sperm count would make a man sub-fertile?

A

Below 15 million

25
Q

What is oligozoospermia?

A

Reduced sperm count (< 15 million/ml)

26
Q

What is azoospermia?

A

Absence of sperm in ejaculate

27
Q

What is asthenozoospermia?

A

Reduced sperm motility (<50% moving)

28
Q

What is teratozoospermia?

A

Reduced percentage of sperm with normal morphology

29
Q

What is antisperm antibodies?

A

Abnormal immune response to sperm (combinations of these abnormalities afre common)

30
Q

What cells in the testicles does mumps affect?

A

Sertoli cells

31
Q

How much lower is the temperature of the scrotum in relation to the rest of the body?

A

2-3 degrees lower

32
Q

What stimulates the anterior pituitary gonadotropins?

A

Pulsatile secretion of Gonadotropin-releasing hormone (GnRH) from the hypothalamus

33
Q

What are the pituitary gonadotrophins?

A
  • Lutenizing hormone (LH)
  • Follicle stimulating hormone (FSH)
  • They control testicular function
34
Q

What cells have LH receptors?

A

Leydig cells (stimulate synthesis and secretion of testosterone)

35
Q

What happens to testosterone if LH secretion is low?

A

Testosterone is low (spermatogenesis halts)

36
Q

What does FSH do?

A

Acts on Sertoli cells and maximises sperm production

37
Q

WHat are the functions of FSH on Sertoli cells?

A
  • Increased RNA and protein synthesis
  • Increased energy metabolism
  • Increased inhibin secretion
  • Increased cAMP
  • Increased ABP secretion
  • Increased fluid secretion
  • Increased androgen receptors
  • Increased FSH receptors
38
Q

What is more important for sperm production FSH or LH?

A

LH

39
Q

What can testosterone be converted into?

A

Dihydrotestosterone or estrogens

40
Q

What are estrognes made by?

A

Sertoli and Leydig cells

41
Q

What is are inhibins produced by?

A

Peptide hormone released by Sertoli cells (feedback loop to control hormone levels)

42
Q

WHat is oxytocin (peptide hormone) produced by?

A

Leydig cells

43
Q

What does oxytocin do?

A

Contraction of Smooth muscle of the genital tract

44
Q

Where will spermatogenesis fail if testosterone is blocked?

A

When primary spermatocyetes enter meiotic prophase

45
Q

What will happen if blood testosterone is low?

A

Fewer stem cells will begin cell division but the whole process will still take 74 days

46
Q

Where does testosterone act on to negatively feedback?

A

Hypothalamus and anterior pituitary

47
Q

What perecentage of infertile men are actually provided a causal diagnosis?

A

~ 28%

48
Q

What are the causes of male infertility that can often be diagnosed?

A
  • Gonadotoxic chemo or radio therapy (10%)
  • Testosterone abuse or other chronic diseases (e.g diabetes) (14%)
  • Genetic disorders (Klinfelter, Karyotype 47, XXY or microdeletions on the Y chromosome) (4%)
49
Q

What is thought to be one of the causes of congenital hypogonadotrpic hypogonadism?

A

Mutated genes involved in the migration and function of GnRH neurons or their upstream regulators, can include anosmia

MD3002 Physiology (24 decks)

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