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Year 2 Reproduction > Gametogenesis > Flashcards

Gametogenesis Flashcards

1
Q

Describe the process of spermatogenesis

A

Spermatagonium divide (mitosis) to give primary spermatocytes (2n). Then they divide again by meiosis to give two 1n secondary spermatocytes. The second round of meiosis is what gives 4 spermatids. Then spermeiogenesis will differentiate them into spermatozoa.

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2
Q

Distinguish between a spermatogenic cycle and a wave.

A

A cycle is a measure of time- time taken for reappearance of the same stage of spermatogenesis to appear at a specific location within the tubule- 16days.
A wave is a measure of space- distance between the same stage of spermatogenesis within a tubule.

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3
Q

What is the role of the rete testis?

A

Concentrates sperm

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4
Q

What is the function of the epidydimus?

A

Stores the sperm

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5
Q

What is the function of the reproductive tube in males that cystic fibrosis patients may lack?

A

Transport the sperm out of the scrotum to the urethra. It is in the Vas Defrens that the seminal vesicles make their secretions.

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6
Q

What are the bulbourethral glands?

A

The Cowper glands contribute to <1% of the ejaculate by producing mucoproteins that lubricate and neutralise any acidity from urine in the distal urethra.

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7
Q

What do the seminal vesicles add to the ejaculate?

A

70% of ejaculate is the amino acids, fructose, citrate and prostaglandins secreted here.

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8
Q

How does the prostate change the ejaculate?

A

Proteolytic enzymes and zinc.

Zinc may be there to slow sperm down until hey reach the female genital tract. 25% of final ejaculate.

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9
Q

Outline the anatomical relationship between the prostatic urethra and the prostate.

A

The urethra runs through the prostate gland.

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10
Q

Describe the ovarian cycle

A

Prenatal stage, astral and preovulatory stage

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11
Q

How is ovulation controlled.

A

LH surged

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12
Q

What happens in ovulation?

A

The oocyte perforates the ovary. Fimbriae catch the oocyte and fuel it into the infundibulum

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13
Q

Contrast oogenesis and spermatogenesis.

A

Females produce few gametes (1/cycle), Males produce 200 million sperm/day
Males make 4 spermatids from meiosis, women make one oocyte and 3 polar bodies.
Oogenesis starts as a foetus, spermatogenesis only starts at puberty.
Lifelong or till menopause
Motile gametes- sperm, fixed ovum.
Last meiosis stage in gonads for men, oviduct for women
Males continuously produce sperm, women intermittently ovulate (only 400 opportunities to reproduce)

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14
Q

What is spermiation?

A

Spermatids released into seminiferous tubule

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15
Q

What is the name given to the process of spermiation remodelling of spermatids to spermatazoa and the movement of the sperm through the peristaltic epidydimus?

A

Spermiogenesis

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16
Q

Outline the structure of sperm.

A

Nucleus covered by plasma membrane and acrosome.
Midconnecting piece mae up of centriole and mitochondria.
The motile tale.

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17
Q

Outline the structure of sperm.

A

Nucleus covered by plasma membrane and acrosome.
Midconnecting piece mae up of centriole and mitochondria.
The motile tail.

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18
Q

What is the final maturation step for a sperm to become motile?

A

Capacitation-removal of glycoproteins and cholesterol from its membrane. This allows sperm to bind zona pellucida.

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19
Q

What stimulates capacitation by the sperm signalling pathway?

A

The environment of the female genital tract.

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20
Q

What is the acrosome reaction?

A

Allows sperm to penetrate zona pellucida.

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21
Q

What is the final maturation step for a sperm to become motile?

A

Capacitation-removal of glycoproteins and cholesterol from its membrane. This allows sperm to bind zona pellucida.
This must be faked in IVF or sperm aren’t fertile

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22
Q

How do female gamete stocks vary?

A

100% before birth.
Stock declines due to atresia
Menopause

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23
Q

When does maturation of oocytes start?

A

Before birth- germ cells arise from the yolk sac, colonise the gonad cortex and become oogonium.

24
Q

How do oogonia proliferate?

A

mitosis

25
Q

What is the arrangement of oogonia by the 3rd month of gestation in a female embryo?

A

Clusters surrounded by flat epithelial cells.

26
Q

When oogonium go into meiosis 1 in utero, at what stage do they arrest?

A

Prophase 1

27
Q

Oogonium that arrest in prophase 1 are now called what?

A

Primary oocytes

28
Q

Oogonium that arrest in prophase 1 are now called what?

A

Primary oocytes

92 chromatids, 46 chromosomes

29
Q

The maximum germ cell number in a female embryo is reached by?

A

Mid-gestation

30
Q

Oocyte degeneration is known as what?

A

Atresia- results in cell death and declining germ cell number and the majority of oogonia have been lost at 7 months gestation.

31
Q

How many primary oocytes are made?

A

2 million

32
Q

What is a primordial follicle?

A

Primary oocyte (arrested in prophase 1) are individually wrapped up by flat epithelial cells known as follicular cells

33
Q

Atresia of oocytes occurs through most of childhood until 40000 remain at ?

A

Puberty

34
Q

How many oocytes mature each month after onset of menarche?

A

15-20 oocytes

35
Q

What are the 3 stages of oocyte maturation each month?

A

Preantral
Antral
Preovulatory

36
Q

What happens at the preantral stage?

A

Primordial follicle cell growth
Follicular cells change from simple flat to stratified cuboidal granulosa cells.
The granolas cells secrete glycoproteins making the zone pellucida

37
Q

Development continues after the prenatal stage by what happening in the astral stage?

A

Fluid filled sac forms between granulosa cells, this space is the antrum.

38
Q

Lots of follicles enter the prenatal stage but only one reaches maturity, what happens to the others?

A

Atresia

39
Q

What happens in the preovulatory stage?

A

Surge in LH causes growth.
Meisosis 1 completes so haploid gamete formed. (2 unequal size cells- one cell with most of the cytoplasm, the other is a polar body)
Metaphase 2 arrest 3 hours before ovulation.

40
Q

How long after ovulation do the oocytes degenerate?

A

24 hours (unless fertilised)

41
Q

When do oocytes complete meiosis?

A

Fertilisation

42
Q

What role do FSH and LH have in the preovulatory phase?

A

Rapid growth

43
Q

What role do FSH and LH have in the preovulatory phase?

A

Rapid growth

LH stimulates collagenase activity

44
Q

What is a graafian follicle?

A

2.5cm in diametre mature follicle

45
Q

What role do prostaglandins do in ovulation?

A

Increases response to LH and causes ovarian wall contractions

46
Q

In ovulation what is releaced/

A

The oocyte

47
Q

In ovulation what is released/

A

The oocyte

48
Q

What is the corpus luteum?

A

Remaining granolas cells and theca externa get vascularised after ovulation. Lutein cells form. The corpus luteum secretes oestrogen and progesterone. Dies after 14 days

49
Q

What effect does the corpus luteum have on the uterine lining?

A

Uterine mucousa enters secretory phase in preparation for implantation

50
Q

How are oocytes transported?

A

fimbriae sweep over the ovarian surface. Uterine tube contracts rhythmically. Oocyte carried by fimbriae and cilia. Mucosa undergoes peristaltic contraction and moves oocyte along. If fertilisation happens will reach the uterus by day 3-4

51
Q

What is corpus albicans?

A

The corpus luteum degenerates and makes fibrous scar tissue if there is no fertilisation. Progesterone secretion reduces and stimulates menstrual bleeding

52
Q

What happens to the corpus luteum if fertilisation happens?

A

Human chorionic gonadotrophin hormone secreted by the embryo supports the corpus luteum. It grows to make the corpus luteum graviditatis, the cells secret progesterone till 4 months gestation and then the placenta can take over.

53
Q

LH surge causes what?

A

Ovulation

54
Q

Drop in progesterone causes what?

A

Menstruation

55
Q

FSH causes the follicle to …. and ….

A

Grow

Mature

56
Q

LH surge causes what?

A

Ovulation

Corpus luteum development

Year 2 Reproduction (8 decks)

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