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gametogenesis Flashcards

1
Q

What is gametogenesis?

A

The process by which the mature gametes are formed from the primitive germ cells

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2
Q

What is gametogenesis in females called?

A

Oogenesis

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3
Q

What is the gametogenesis in males called?

A

Spermatogenesis

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4
Q

Where does gametogenesis occur?

A

In the gonads

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5
Q

What happens to the cytoplasm in primitive germ cells during gametogenesis?

A

In the ovum, the cytoplasm increases

In the sperm, the cytoplasm decreases

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6
Q

What happens to the nucleus of primitive germ cells during gametogenesis?

A

It undergoes mitotic division to reduce the number of chromosomes it has to itself

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7
Q

When does spermatogenesis start ?

A

At puberty and continues till old age

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8
Q

How many days does it take for a spermatogonium to develop into a mature spermatozoon?

A

Approx 74 days

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9
Q

How many sperm cells are produced daily?

A

Around 300 million

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10
Q

Where does spermatogenesis occur?

A

In the seminiferous tubules in the testis and completed in the epididymis

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11
Q

What do sertoil cells do ?

A

Support and protect the germ cells,

Participate in nutrients and assist in the release of mature spermatozoa

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12
Q

What hormone regulates spermatogenesis?

A

LH

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13
Q

What does LH do in men ?

A

Stimulate testosterone production and promote spermatogenesis

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14
Q

What does FSH do in men?

A

Stimulate testicular fluid production and synthesis of androgen receptor proteins

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15
Q

What is the purpose of spermatogenesis?

A

To reduce number of chromosomes from diploid to haploid
Change the shape of the germ cells to produce a highly motile sperm
Production of a large number of sperms
Determine the sex of the sperm

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16
Q

What are the stages of spermatogenesis?

A

Spermatocytogenesis

Spermiogenesis

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17
Q

What is spermatocytogenesis?

A

The process by which primitive germ cells differentiate into spermatids

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18
Q

What is spermatocytogenesis?

A

The process by which primitive germ cells differentiate into spermatids

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19
Q

How many chromosomes are in spermatogonial stem cells?

A

46

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20
Q

Where are spermatogonia cells found ?

A

In the Walls of the seminiferous tubules of the testis, supported by sertoil cells

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21
Q

What is produced when spermatogonial stem cells undergo mitotic division?

A

Spermatogonia type A

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22
Q

What happens to spermatogonia type A?

A

It’s continues to divide to give spermatogonia type B

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23
Q

What happens to spermatogonia type B ?

A

Divides by mitosis to give primary spermatocytes

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24
Q

What happens to primary spermatocytes?

A

They undergo 1st meiotic division to produce two secondary spermatocytes ,

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25
What happens to secondary spermatocytes?
They undergo 2nd mitotic division to produce two spermatids 22+X 22+Y
26
What is spermiogenosis?
The morphological unstructural changes resulting in the transformation of spermatids into spermatozoa
27
How is the sperm head formed?
Condensation of the nucleus Shedding most of the cytoplasm Formation of acrosomal cap from Golgi apparatus around half of the nucleus
28
How is the middle piece of the sperm formed?
Formed from mitochondrial sheet
29
What is the junction between the head and the middle piece of the sperm called?
The neck
30
How is the tail of the sperm formed?
It is formed by elongation of one of the centrioles
31
What is oogenesis?
production of a mature ovum ready for fertilization
32
What does oogenesis occur?
In the cortex of the ovary
33
What is the aim of oogenesis?
Reduction of number of chromosomes from diploid to haploid | Increase the size of the ovum from 30 to 120 microns
34
What cells divide by mitosis and differentiate into oogonia?
PGCs | Primordial germ cells
35
What are primary oocytes?
Enlarged oogonia
36
When so all the primary oocytes start prophase of meiosis 1?
Near the time of birth
37
What are primordial follicles?
Flat epithelial cells that surround the primary oocytes
38
How many primary oocytes are there at birth ?
0.7 to 2 million
39
How many oocytes are present at the beginning of puberty?
Approximately 400,000
40
How many oocytes will be ovulated?
Fewer than 500
41
What are the two processes of oogenesis?
Maturation of the primary oocyte itself | Maturation of the follicular cells
42
How is the primary follicle formed? | The maturation of the follicular cells
The simple flat epithelium which surrounds the primary oocyte begins to grow It changes from flat to cuboidal epithelium Proliferate to produce stratified epithelium of granulosa cells
43
Where do granulosa cells rest?
Basement membrane
44
How is the Zona pellucida formed?
Granulosa cells and the oocyte secrete and layer of Glock proteins on the surface of the oocyte
45
What do the cells of the theca folliculi organize into ?
Inner layer ~ theca interna | Outer layer ~ theca externa
46
How was the secondary follicle formed? | The maturation of the follicular cells
Fluid-filled spaces appear between granulosa cells which coales forming The antrum
47
What is the cumulus oophorus ?
The layer of granulosa cells that surround the oocyte ~ after the second follicle formation, these cells stay intact and form the cumulus oophorus
48
What does LH do?
When the secondary follicle is mature, It's induces the preovulatory growth phase
49
What is the result at the end of meiosis one? | Maturation of his primary oocytes itself
The secondary oocyte receives most of a cytoplasm | The first polar body receives small amount of cytoplasm
49
What is the result at the end of meiosis one? | Maturation of his primary oocytes itself
The secondary oocyte receives most of a cytoplasm | The first polar body receives small amount of cytoplasm
50
How long does the cell stay in metaphase during meiosis 2 before ovulation?
Approximately 3 hours
51
How long after ovulation does the cell degenerate if not fertilized?
24 hours
52
What is the ovarian cycle controlled by?
The hypothalamus
53
Where is GnRH produced and what does it do?
Produced in the hypothalamus | Epsom salts of the anterior pituitary gland which secretes gonadotropins
54
What are the two types of gonadotrophins ?
FSH and LH
55
How many days does it take to complete one ovarian cycle?
28
56
What are the three phases of the ovarian cycle?
a. follicular phase b. Ovulation c. luteal phase
57
Describe the pre-opulatory phase ( the follicular phase)
It's the first half of ovarian cycle At the beginning the anterior pituitary secretes FSH Normally only one follicle reaches maturity and only one oocyte is ovulated - the others degenerate FSH also stimulates maturation of follicular cells The growing full of cells secretes estrogen Feedback effects on the anterior pituitary FSH secretion stops The generation of primary follicles
58
What is ovulation?
It is the rupture of the Graafian follicle with extrusion of the ovum from the surface of the ovary
59
How many days before the next menstruation does ovulation happen?
Exactly 14 days
60
Does ovulation occur during pregnancy?
No
61
What is the name of the degenerated follicles?
Corpus atreticum
62
What happens in ovulation during the LH surge?
Graffian follicle will enlarge and become nearer to the surface The follicle enters the preovulatory stage The primary oocyte complete meiosis one to form the secondary outside and small polar body Meiosis 2 is also initiated but the oocyte stops in metaphase for 3 hours before ovulation
63
What is the stigma?
When the surface of the ovary begins to bulge locally a vascular spot called the stigma appears on the apex
64
What hormone increases collagenase activity?
LH
65
What causes muscular contractions in the ovarian wall?
An increase in Prostaglandin due to LH surge
66
How is Corona radiata formed?
The oocyte, In metaphase phase of meiosis 2, is discharged from the ovary together with a large number of cumulus oophorus cells some of them arrange themselves around the zona pellucida to form the Corona radiata
67
Describe the luteal phase
It is the second half of the cycle Due to LH, the ruptured graafian follicle is transformed into a yellow body called Corpus luteum The corpus luteum secrete progesterone and a bit of estrogen to inhibit FSH and LH Progesterone causes the uterine mucosa to enter the progestational stage in preparation for implantation of the embryo
68
What happens if fertilization does not occur?
The corpus luteum lives for 9 days only after ovulation, then shrinks and degenerates forming a fibrotic scar tissue called Corpus albicans This leads to decrease the level of progesterone in the blood precipitating menstrual bleeding
69
What happens if fertilization does occur?
Degeneration of the Corpus luteum is prevented by hCG secreted by the embryo The Coopers luteum continues to grow and forms the corpus luteum of pregnancy Luteal cells continue to secrete progesterone until the end of the fourth month of pregnancy
70
Why is progesterone important?
It is essential to maintain pregnancy | The removal of the corpus luteum before the fourth month usually leads to an abortion
71
What happens at the end of the fourth month of pregnancy?
The corpus luteum of pregnancy regress slowly as secretion of progesterone by the placenta becomes adequate for maintenance of pregnancy
72
What are three layers that the wall of the uterus consists of?
Endometrium or mucosa - lining the inside wall Myometrium - a thick layer of smooth muscle Perimetrium - peritoneal covering of the outside wall
73
What is the uterine cycle?
The monthly cichlid changes comparing in the endometrium in response to cyclic changes which occur simultaneously in the ovaries during ovarian cycle
74
What are the stages that the uterine endometrium pass through?
Follicular or proliferative phase Secretory or progestational phase Menstrual phase
75
Describe briefly the follicular phase
Begins at the end of the menstrual phase and is under the influence of estrogen and parallel growth in the ovarian follicles
76
Briefly describe the secretory phase
Begins approximately 2 to 3 days after ovulation in response to progesterone produced by Corpus Luteum
77
Briefly describe what happens in the menstrual phase
The fertilization does not occur shedding of the endometrium occurs If fertilization does occur the endometrium assists in implantation and formation of the placenta
78
What happens to the uterus at the time of implantation?
The mucosa of the uterus is in the secretory phase during which the uterine glands and arteries become coiled and the tissue becomes succulent
79
What are the three layers that form in the uterus at the time of implantation?
A superficial compact layer An intermediate spongy layer A thin basal layer
80
Where does the human blastocyte implant?
In the endometrium along the anterior and the posterior wall of the body of the uterus
81
At the time of implantation, what happens if the oocyte is not fertilized?
Venules and sinusoidal spaces gradually become packed with blood cells During the menstrual phase blood escapes from the superficial arteries and pieces of the stroma and glands breakaway During the following three or four days the compact and spongy layers are expelled and the basal layer is the only part of the endometrium that is retained
82
What are the arteries that supply the basal layer with blood ?
Basal arteries

Embryology (3 decks)

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