Lecture 11: Gametogenesis and Fertilization Flashcards
1
Q
Primordial germ cells are progenitors
A
gametes
2
Q
Primordial germ cells from yolk sac ______ migrate to ____ ___ which will become _____ _____.
A
- Endoderm
- Genital ridge
- Indifferent gonad
3
Q
Intermediate mesoderm gives rise to
A
- Part of urogenital organs
- Leydig cells, sertoli cells, follicular cells, ovary, testis, ducts, uterus
4
Q
Urogenital sinus endoderm gives rise to
A
- Terminal internal parts of genital organs
- Vesicular, prostate and bulbourethral glands
5
Q
Mullerian ducts are also called
A
Paramesonephric
6
Q
Mullerian ducts develop into
A
Fallopian tubes, uterus, cervix
7
Q
Mullerian ducts in male
A
Disappear under the influence of anti-paramesonephric hormone
8
Q
Seminiferous cords consist of
A
- Sertoli cells
- Primordial germ cells - stem cells for spermatogenesis and stay dormant till puberty
9
Q
Two parts of the prepuberal testis
A
- Seminiferous cords
- Inactive interstitial cells of leydig
10
Q
Cryptorchidism
A
- Testes fail to descend into the scrotum
- Inherited as a sex-linked autosomal recessive trait
- Cryptorchid can be unilateral (fertile) or bilateral (sterile)
11
Q
Scrotal hernia
A
- Type of inguinal hernia
- Congenital weakness in abdominal wall
12
Q
Primitive sex cells
A
- Spermatogonia
- Oogonia
13
Q
Primitive sex cells have complete
A
DNA complement
14
Q
How are more oogonia and spermatogonia made
A
Mitosis
15
Q
Purpose of spermocyte and oocyte meiosis
A
Insure variation and provide 1/2 of the chromosome in both male (1N) and female (1N) sex cells (gametes)
16
Q
Fertilization
A
Joining of sex cells
17
Q
Fertilization creates
A
Zygote, which restores DNA complement (2N) and initiates cleavage
18
Q
Mitosis results in formation of
A
2 daughter cells, each having diploid set of chromosomes, the same number of chromosomes as in the mother cell
19
Q
Meiosis results in
A
Gametes - daughter cells that are haploid
20
Q
Are gametes haploid or diploid
A
haploid
21
Q
Two goals of meiosis
A
- Reduction of diploid set chromosomes into haploid in gametes
- An exchange of genetic material between make and female chromatids in prophase of meiosis I (crossing over) which results in 4 daughter cells with four different genetic makeups
22
Q
Oogenesis and spermatogenesis both have (4)
A
- Multiplication of spermatogonia and oogonia
- Meiosis
- Extensive morphological differentiation
- Incapacity of surviving for very long if fertilization doesn’t occur
23
Q
Sperm supply is
A
Continuously renewed
24
Q
One Io spermatocytes produces
A
4 sperm
25
In sperm, initial large cell results in
small cells
26
Do sperm move
motile cells
27
Chromosome of sperm
X or Y sex chromosome
28
Are oocytes made after birth?
No
29
One Io oocyte produces
1 ovum and 2-3 polar bodies
30
In oocytes, initial small cell
grows into a large cell
31
Do oocytes move?
Nope
32
In mammals, chromosome for oocyte
X chromosome
33
Where does oogenesis occur?
Ovary
34
Oogonia
Prenatal mitosis and differentiation
35
Basic plan of oogenesis
1. Oogenia
2. Folliculogenesis
3. Meiosis II
36
Second step of oogenesis
All are primary oocytes (4N) arrested in meiosis I until puberty. At ovulation, meiosis I is completed except in dogs and mares who ovulate primary oocytes
37
Third step of oogenesis
In uterine tube, secondary oocyte (2n) awaits fertilization (1st polar body is present). Meiosis II is completed on sperm contact, resulting in ovum (1n) and second polar body (1n)
38
At puberty, hormone influence on folliculogenesis leads to
ovulation
39
Primordial follicles
- Resting follicles
| - Oocyte I + single layer of squamous follicular cells
40
Primary follicles
- Activated or growing follicles
| - Zona pellucida forms
41
Secondary follicles
- Secretory
- Antral follicles
- Fluid filled spaces are formed among the granulosa cells
42
Tertiary mature (Graafian) follicle
- One antrum containing liquor folliculi
| - Have an eccentric cumulus oophorus which contains a primary oocyte
43
Zona pellucida acts as
An immunologic protective barrier for the developing egg and early embryo
44
After ovulation, the follicular space fills with
Blood and clots
45
Corpus hemorrhagicum
- Bloody body
| - Is replaced by infiltrating luteal cells to become the corpus luteum
46
Corpus luteum produces
Progesterone some estrogen
47
How does the corpus luteum produce progesterone and some estrogen
1. Granulosa luteal cells = large luteal cells
2. Theca luteal cells = small luteal cells
These cells infiltrate the space left by the ruptured follicle
48
Purpose of progesterone
- Maintains pregnancy
- Stimulates mammary development
- Locally down regulates the immune system
49
The corpus luteum regresses during
diestrus
50
Corpus albicans (white body)
Connective tissue scar that remains during the regression of the corpus luteum
51
Atretic follicle
If a follicle is not selected to complete maturation, if will undergo a programmed destruction. The fate of many follicles
52
Ovulation
1. The oocyte departs the ovary, leaving behind a structure known as the corpus hemorrhagicum which becomes..
2. The corpus luteum of theca and granulosa cells
53
5 steps of the basic plan of spermatogenesis
1. Spermatogonium (2n): mitosis, differentiate
2. Primary spermocyte (4n): meiosis I - crossover
3. 2 Secondary spermatocytes (2n): meiosis II
4. 4 Spermatids (1n): do not divide, but undergo spermiogenesis (metamorphosis)
5. 4 spermatozoa (sperm, sperm cells)
54
Testis secrete _____ under the influence of ___
Testosterone
| LH
55
Sertoli cells are activated by
Follicle-stimulation hormone
56
During fetal cells, sertoli cells secrete
Anti-Mullerian hormone to inhibit uterus formation
57
After puberty, sertoli cells secretes
Inhibin and activins to regulate FSH secretion from pituitary
58
In males, sertoli cells secrete
Androgen binding proteins to bind testosterone, increase concentrations in the seminiferous tubules, and stimulate spermatogenesis
59
What do sertoli cells do for spermatids
Provide support, protection, and nutrition until spermatids transform into mature spermatozoa
60
The size and shape of sperm cell heads is
Species-specific
61
Sperm cell head is disc-like in
ruminants
62
Sperm cell head is pear shaped in
man, stallion
63
Sperm cell head is hook-like in
rodents
64
Sperm cell head is spoon-like in
guinea pids
65
Sperm cell head is filiform in
birds
66
Axonema
Core of cilia and sperm flagellum
67
Axoneme of cilia/sperm flagella is a derivative of
a modified centriole (basal body)
68
Axoneme consists of
- A pair of central microtubules
| - Outer ring of 9 doublets with dynein arms
69
How long does it take for sperm to be to be transported through the epididymis?
2 weeks
70
In most mammals, spermatogenesis takes place in orderly
waves
71
Almost every animal produces approx. ____ sperm per gram of testicular tissue per day
25 million
72
Humans produce only about ___ sperm per gram of testicular tissue per day
4 million
73
Spermatogenesis is very sensitive to (6)
1. Temperature (cryptorchids)
2. X ray irradiation
3. Nutrition (vitamin A)
4. Infection and non-infectious diseases
5. Stress
6. Drugs
74
Sperm defects are often categorized by
the infertility rates associated with them
75
5 difference between spermatogenesis and oogenesis
1. Spermatogonia remain dormant until puberty vs oogonia completing proliferation in early embryonic stage
2. Meiosis is completed within testes vs by birth all oogonia entered meiosis I but their development is arrested in Meiosis I until puberty. Thus, females are born with primary oocytes. Meiosis I is completed in fallopian tube
3. Each spermatogonium gives rise to multiple (64-256 spermatozoa) vs one oocyte giving rise to only one ovum
4. Spermatids undergo metamorphosis vs ova do not
5. Spermatogenesis may continue throughout the whole life of the animal vs oogenesis stops after the ovary is exhausted of germ cells
76
When does oogenesis stop in dogs?
10-12 years
77
When does oogenesis stop in cattle?
14-16 years
78
When does oogenesis stop in mares?
20-22
79
Three parts of fertilization
1. Capacitation
2. Acrosome reaction
3. Fusion
80
Capacitation
- Occurs in uterine environment
| - Sperm cells gain the ability to fertilize theoocyte
81
Acrosome reaction
-Release of acrosmal enzymes (acrosin)to digest way through zona pellucida
82
Fusion
- Sperm contacts oocyte most commonly in fallopian tube
| - Sperm plasma membrane and the vitelline membrane of oocyte
83
Cortex of oocyte below oolemma contains
cortical granules
84
Another name of ovum
Oocyte II
85
Sperm contact with oocyte plasma membrane causes
release of proteases from cortical granules whih modify the zona pellicuda, which is then a barrier to other sperm penetration
86
What causes oocyte to complete Meiosis II
Ca++ wave
87
Nuclear material of sperm and ootid is called
Male/female pronuclei
88
Syngamy
Union of male and female pronuclei. They merge restoring diploid set of chromosomes and enter the first mitotic division
