Reproductive Flashcards
1
Q
What are the basic steps in oogenesis?
A
- No primary oocytes form after birth, primordial germ cells in fetal development replicate ~2.5 mil primary oocytes present at birth (arrested in prophase (4n, crossing over occurred, prior to ovulation)
- 36-48 hrs before ovulation, first meiotic division occurs, now 2’ ooctye and degenerating polar body
- At ovulation, 2nd meiotic division begins and stops at metaphase
- At fertilization, second meiotic division completes and second polar body extruded
Summary: 1 primary oocyte -> 1 ovum
2
Q
What are the basic steps involved in spermatogenesis
A
- Primordial germ to base of seminiferous tubules where they are spermatogonia
- At puberty spermatogonia undergo mitotic divisions -> clonal expansion
- Entry into first meiotic division -> primary spermatocytes (4n)
- Each primary spermatocyte divides into 2 secondary spermatocytes (2n)
- Secondary spermatocytes enter into second meiotic division, producing 2 spermatids (1n)
- Further maturation of spermatid into mature sperm in epididymis
Summary: 1 primary spermatocyte -> 4 spermatozoa
3
Q
Summarise the steps involved in fertilization
A
- Ovulated egg has jelly cumulus (sperm swin through) and tough zona pellucida
- Acrosome on sperm head eats through zona pellucida
- Contact with cell membrane and sperm fuse -> triggers electrical signal that causes mucus secretion and coating of egg to prevent any other sperm penetrating it
- Sperm head disintegrates revealing chromosomes & egg completes 2nd meiotic division
- Fusion of pronuclei
4
Q
Summarise the steps of blastocyst implantation into endometrium
A
- During first 3-4 days, zygote still in ampula
- During this time, mitosis occurs forming morula
- Progesterone produced by corpus luteum builds up nutrients in endometrium (purpose of waiting 3-4 days) and leads to relaxation of oviduct
- (After 3-4days) -> morula descent
- Morula developes into blastocyst
- Trophoblast makes contact with endometrium, secretion digestive enzymes
- Digestive enzymes allow penetration of endometrium by finger like trophoblastic cells
- Carves out hole for blastocyst and implanted completed in endometrium
