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S3) Gametogenesis Flashcards

(56 cards)

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1
Q

What are the starting cells for spermatogenesis and how long are they available for?

A
  • Spermatogonia
  • 70 years
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2
Q

Spermatogonia divide by mitosis to give rise to two types of cells.

Identify and describe them

A
  • Ad spermatogonium: reserve stock (resting)
  • Ap spermatogonium: maintain stock (active)

– require different stock because a male always needs sperm on the go as female isn’t always fertile

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3
Q

What do ap spermatogonia do?

A

From puberty onwards, ap spermatogonia produce type B spermatogonia which give rise to primary spermatocytes

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4
Q

Briefly describe the process of spermatogenesis

A
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5
Q

What is spermiation?

A

Spermiation is the release of spermatids into the lumen of seminiferous tubules

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6
Q

What is spermiogenesis?

A

Spermiogenesis is when a haploid spermatid differentiates into a spermatozoon

– mainly occurs in the seminiferous tubules

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7
Q

Outline the steps involved in spermiogenesis

A

⇒ Spermiation

⇒ Spermatid remodelling (seminiferous tubule)

⇒ Spermatid moves through rete testis and ductuli efferentes and into the epididymis

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8
Q

What is the spermatogenic cycle?

A

Spermatogenic cycle is the time taken for reappearance of the same stage (of spermatogenesis) within a given segment of the seminiferous tubule

– each different part appears at different times so you just look at one

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9
Q

How long is the spermatogenic cycle in adult humans?

A

16 days

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10
Q

What is the spermatogenic wave?

A

Spermatogenic wave is the distance (in the tubule) between the same stage of spermatogenesis

  • along the seminiferous tubule
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11
Q

How does the spermatogenic wave move?

A

Waves move in corkscrew-like spirals towards the inner part of the lumen

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12
Q

How do spermatids reach the epididymis in the process of spermiogenesis?

A
  • Spermatids are non-motile
  • Transported by Sertoli cell secretions assisted by peristaltic contraction

– they learn how to become motile in the epididymis

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13
Q

Identify the different structures in the pathway for the delivery of sperm

A

Seminiferous tubules → Rete testis → Ductuli efferentes → Epididymis → Vas deferens → Urethra

this whole process is known as spermiogenesis

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14
Q

Identify the contents of seminal vesicle secretions (~70%) and where are they in relation to the journey of the sperm?

A
  • Amino acids
  • Citrate
  • Fructose
  • Prostaglandins
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15
Q

Identify the contents of prostate gland secretions (~25%)

A
  • Proteolytic enzymes
  • Zinc
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16
Q

What is the function of the bulbourethral gland (<1%)?

A

Secrete mucoproteins to help lubricate and neutralise acidic urine in distal urethra

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17
Q

What is the overall contribution of sperm to semen?

A

2-5% of overall volume

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18
Q

How many sperm are there per ejaculate?

A

200-500 million

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19
Q

Which glands secrete into the urethra?

A
  • Prostate gland
  • Bulbourethral gland
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20
Q

Which gland secretes into the vas deferens?

A

Seminal vesicle

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21
Q

What is sperm capacitation?

A
  • Sperm capacitation refers to the physiological changes spermatozoa must undergo in order to fertilise an egg
  • The final maturation step for sperm
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22
Q

Which three processes are stimulated by the female genital tract?

A
  • Removal of glycoproteins and cholesterol from sperm membrane
  • Activation of sperm signalling pathways
  • Allow sperm to bind to zona pellucida of oocyte
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23
Q

When does oocyte maturation begin?

24
Q

What are oogonia and what do they do?

Study These Flashcards
A
  • Germ cells arise from yolk sac and colonise the gonadal cortex, differentiating into oogonia
  • Oogonia proliferate rapidly by mitosis
25
Describe the arrangement and actions of oogonia by the end of 3rd month
- Arranged in **clusters** surrounded by **flat epithelial cells** - Majority continue to divide by **mitosis** but some enter **meiosis**
26
What are primary oocytes?
**Primary oocytes** are oogonia that have arrested in prophase of meiosis I
27
What is the maximum number of germ cells in the female? When is this value reached?
- ~7 million germ cells - Reached by mid gestation
28
What are primordial follicles?
**Primordial follicles** are surviving primary oocytes which are individually surrounded by a layer of follicular cells
29
What are follicular cells?
**Follicular cells** are the layer of flat epithelial cells that surround individual primary oocytes in late gestation
30
Define follicular atresia
**Atresia** is the degeneration of those ovarian follicles which do not ovulate
31
Describe atresia in females
- **After mid gestation,** many oogonia and primary oocytes degenerate - **By 7th month gestation**, ~5 milion oogonia have degenerated
32
How many oocytes are left by the start of puberty?
~40,000 (most oocytes undergo atresia during childhood) * roughly females have 400 periods so 400 chances too get pregnant
33
How many oocytes mature each month from puberty onwards?
~15-20 oocytes start to mature each month – in the end only one will mature enough to be fertilised
34
Identify the 3 stages in oocyte maturation
1. Preantral 2. Antral 3. Preovulatory
35
What happens in the pre-antral stage?
- Primordial follicle grows to form the **primary follicle** - Follicular cells change and proliferate to form a **stratified cuboidal epithelium of granulosa cells**
36
Describe the function of granulosa cells
**Granulosa cells** secrete layer of glycoprotein on oocytes forming the **zona pellucida**
37
What happens in the antral stage?
- **Fluid-filled spaces** appear between granulosa cells - These spaces coalesce to form the **antrum**
38
What induces the preovulatory growth phase?
Surge in LH
39
What happens during the preovulatory stage?
- Meiosis I completion results in 2 haploid cells of unequal size - One cell receives most of cytoplasm the first polar body receives practically none
40
When does meiosis II occur in oogenesis?
- Before ovulation, cell then enters meiosis II but arrests in **metaphase** - After ovulation, meiosis II is only completed if oocyte is fertilized, otherwise cell degenerates
41
Which substances stimulate the rapid growth of the follicle?
- Follicle stimulating hormone (FSH) - Luteinising hormone (LH)
42
What is a Graafian follicle?
- A **Graafian follicle** is a mature follicle in the ovary that gets released - It is ~2.5cm in diameter
43
What role does LH have in ovulation?
- LH surge increases collagenase activity - Prostaglandins increase response to LH & cause local muscular contractions in ovarian wall
44
What happens to the oocyte in ovulation?
**Oocyte** is extruded & breaks free from ovary
45
How is the corpus luteum formed?
- After ovulation, remaining **granulosa** and **theca interna** cells become vascularized - They develop a yellowish pigment and change into **lutein cells**, which form the corpus luteum
46
What does the corpus luteum do?
- Secrete **oestrogen & progesterone** - Stimulates **uterine mucosa** to enter secretory stage in preparation for embryo implantation - **Dies** after 14 days if **no fertilisation** occurs
47
How is the oocyte transported from the ovary?
- Oocyte carried into tube by sweeping movements of **fimbriae** and **mucosal cilia** - Oocyte then propelled by peristaltic muscular contractions of **uterine tube** (contract rhythmically) and by **mucosal cilia**
48
What happens to the corpus luteum if no fertilisation occurs?
- Corpus luteum degenerates - Forms corpus **albicans** – mass of fibrotic scar tissue - Progesterone production decreases - Menstrual bleeding occurs
49
The corpus luteum does not degenerate if fertilisation occurs. Explain why
Degeneration prevented by **human chorionic gonadotropin**, secreted by developing embryo
50
What role does the corpus luteum have post-fertilisation?
The corpus luteum continues to grow and forms the corpus luteum of pregnancy (**corpus luteum graviditatis**)
51
When does the corpus luteum stop secreting progesterone and why?
Cells continue to secrete **progesterone** until ~ 4th month until the placenta takes over
52
Outline the four steps involved in the ovarian cycle
⇒ Hypothalamic **GnRH** stimulates anterior pituitary to release **FSH** and **LH** ⇒ **FSH** stimulates follicle growth ⇒ **FSH** and **LH** stimulate follicle maturation ⇒ **LH** surge triggers ovulation & promotes development of the corpus luteum
53
Compare and contrast oogenesis and spermatogenesis in terms of the following: - Commencement - Completion - Gamete motility - Daughter cells - Stages - Overall yield
54
what is a primary spermatocyte?
* each forms 4 haploid spermatids * the spermatids differentiate into spermatozoa
55
at which point is meiosis II completed In oogenesis
at fertilisation.
56
what element of the developing follicle is next to the developing oocyte
granuloma cell

SA reproductive (22 decks)

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