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Repro > Spermatogenesis > Flashcards

Spermatogenesis Flashcards

1
Q

What is the function of the testes?

A
  • To produce sperm and store it
  • To produce hormones which regulate spermatogenesis
  • Sperm production
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2
Q

Why is the scrotum outside of the body cavity?

A
  • For the optimum temperature for sperm production is 1.5-2.5 degrees below body.
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3
Q

What happens if there is overheating of the testes?

A

Reduces sperm count

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4
Q

What is the normal volume of the testes and how is this measured?

A

15-25 ml and measured by an orchidometer

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5
Q

What percentage of the testis is seminiferous tubules and what is the function of these tubules?

A

95%, and the site of spermatogenesis

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6
Q

How long are the seminiferous tubules in the testes?

A

600 m long

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7
Q

Where do the tubules in the testis lead to?

A

the epididymis and ultimately the vas deferens

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8
Q

Where are the spermatogonia located?

A

On the basememnt membrane

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9
Q

What are the walls of the seminiferous tubule made of?

A

tall columnar endothelial cells called sertoli cells

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10
Q

What are the tight junctions between the seminiferous tubules and what is their function?

A

Adluminal compartments for a specific enclosed environment for spermatogenesis that is filled with secretions from sertoli cells.

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11
Q

What is filled between the tubules?

A

Blood and lymphatic vessels, Leydig cells and interstitial fluid

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12
Q

Summarise Meiosis

A
  • S-phase the chromosomes are replicated and stay attached to the originals forming identical sister chromatids.
  • Homologous chromosomes group together in pairs ab=nd exchange genetic material that gives rise to new chromosomes a mixture of maternal and paternal genes.
  • Sister chromatids remain attached and may differ from one another if cross over.
  • Cell division creates two haploid daughther cells, but each chromosome is two sister chromatids and are no longer identical due to crossing-over.
  • Sister chromatids separate as cell divides giving haploid gametes.
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13
Q

What is spermatogonia?

A

Germ cell on basement membrane, capable of mitotic or meiotic division to produce primary spermatocytes or more spermatogonia by mitosis. They are diploid.

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14
Q

What are primary spermatocytes?

A

They move into the adluminal compartment and duplicate their DNA to produce sister chromatids which exchange genetic material before entering meiosis I. They are 46XY diploid.

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15
Q

What are secondary spermatocytes?

A

Have undergone meiosis I to give 23X to 23Y haploid number of chromosomes arranged as sister chromatids.

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16
Q

What are spermatids?

A

Meiosis II occurs to give 4 haploid spermatids. Round spermatid to elongated spermatid differentiation

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17
Q

What is spermatozoa?

A

Mature sperm extruded into the lumen

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18
Q

How often does a new spermatogenesis cycle occur?

A

Every 16 days

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19
Q

How long does spermatogenesis take?

A

74 days

20
Q

What allows for the synchronous development of sperm?

A

A syncytium - formed from the cells remaining connected to one another by cytoplasmic bridges.

21
Q

What is the difference between oogonia and spermatogonia?

A
  • Spermatogonia and oogonia is laid down in foetus.
  • Spermatogonia begins to make spermatocyte after puberty or divide mitotically to make more spermatogonia whereas oogonia begin meiosis after birth and cannot make more mitotically.
  • There is a lifetime supply of spermatogonia whereas a limited supply of oogonia.
22
Q

Describe the feedback mechanism of spermatogensis hormones

A

Hypothalamus releases GnRH into the pituitary this releases LH/FSH to the testis. This then produces testosterone/DHT which acts in a negative feedback manner.

23
Q

What is the primary role of Leydig cells?

A

They contain LH receptors and primarily convert cholesterol into androgens.

24
Q

How do androgens control spermatogenesis?

A

They cross-over to and stimulate sertoli cell function.

25
Q

What is the function of sertoli cells?

A

They contain FSH receptors and convert androgens to oestrogen.

26
Q

What does FSH do?

A

It establishes a quantitatively normal Sertoli cell population.

27
Q

What do the androgens do?

A

They initiate and maintain sperm production.

28
Q

What can interfere with negative feedback?

A

Taking anabolic steroids will reduce FSH/LH from pituitary leading to testicular atrophy.

29
Q

What causes erection and ejaculation?

A
  • Vasodilation of the corpus cavernosum
  • Partial constriction of the venous return
  • Autonomic nervous system causes co-ordinated smooth muscle contractions of vas deferens, glands and urethra.
30
Q

Which system controls erection?

A

Parasympathetic

31
Q

What does the sympathetic nervous system control?

A

Movement of sperm into epididymis, vas deferens, penile urethra (emission)

32
Q

What does the somatic nervous system do?

A
  • Explusion of the glandular secretions

- Evacuation of urethra

33
Q

What nerves control the somatic nervous system in the penis?

A

The perineal branch of the pudendal nerve from nerve roots S2-S4.

34
Q

How much sperm is produced per day on average?

A

300 million

3500 per second

35
Q

What is the volume of ejaculate?

A

1.5 ml to 6 ml

Around 1/3 or just over a teaspoon full

36
Q

How much sperm is lost before reaching the ampulla of the uterine tube?

A

99.9% - the first portion of the ejaculate is the most sperm rich.

37
Q

What does the seminal fluid contain?

A

It contains seminal vesicles, prostate, bulbo-urethral gland combined with epididymal fluid.

38
Q

What is the function of the bulbo-urethral gland?

A
  • Produces a clear viscous secretion high in salt - known as pre-ejaculate.
  • This helps to lubricate the urethra for spermatozoa to pass through, neutralising traces of acidic urine.
39
Q

What is the composition of the seminal vesicle secretion?

A
  • Contains proteins, enzymes, fructose, mucus, vitamin C and prostaglandins.
40
Q

What is the function of the fructose in the seminal secretions?

A

Provide energy source

41
Q

What does the high pH in the seminal secretion do?

A

It protects against acidic environment in the vagina.

42
Q

What is the function of the prostate?

A

It secretes milky or white fluid roughly 30% of the seminal fluid.

43
Q

What is the protein content of the prostate secretions?

A

Less than 1% and includes proteolytic enzymes, prostatic acid phosphatase and prostate-specific antigen.

44
Q

What do prostate-specific antigen do?

A

It is involved in liquefaction.

45
Q

What element is in prostate fluid that is useful?

A

A high zinc concentration (500-1000 times more than blood) for antibacterial purposes.

46
Q

Structure of spermatozoon

A

Head - containing acrosome, nucleus and connecting piece.
Sperm Tail - Midpiece, Principal Piece and End piece
Midpiece - contains the mitochondrial sheath.
It is all surrounded by a plasma membrane.

Repro (11 decks)

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