Mod.A Embryology Lec2 Flashcards
Before birth, the primordial/primary follicle is formed of two main parts
primary oocyte and follicular cells
At puberty, a pool of primordial follicles developed into growing
follicles
Each month, 15 to 20 follicles mature and a cavity appear in between follicular cells, containing follicular fluid, this follicle is called
mature secondary follicle
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are
gonadotropins hormones, produced by the anterior pituitatry gland.
These two hormones act on the ovaries producing cyclic changes
in the ovaries (development of the ovarian follicles, ovulation and
formation of the corpus lutum).
Ovulation follows within 24 hours of a surge of
LH hormone
What is ovulation ?
liberation of the secondary oocyte/ovum outside the follicle along with the follicular fluid.
Shortly after ovulation, the ovarian follicle
collapses and develops into a glandular
structure called
corpus luetum
what is Menstrual cycle
cyclic changes in the endometrium under the effect of progesterone and estrogen that are secreted from follicle and corpus luteum
Phases of menstrual cycle
1- Menstrual phase
2- Proliferative phase
3- Luteal phase
4- Ischemic phase
Menstrual phase:
- no hormones
- endometrium sheds and bleeding occurs
- 1-5 days
Proliferative phase:
- development of endometrium under effect of ESTROGEN
Luteal phase:
after ovulation, thickness of the endometrium increases under the effect of PROGESTERONE
Ischemic phase:
decrease in blood supply after decrease in estrogen and progesterone levels
Fertilization (def,site,time)
It is fusion of sperm and ovum to form a zygote.
Site: Lateral 1/3 of the follapian tube.
Time: within 24 hours from ovulation.
Steps of fertilization:
1- Sperm conditioning; Capacitation and Acrosome reaction.
2- Sperm penetration;
- Phase 1: Penetration of the corona radiata.
- Phase 2: Penetration of the zona pellucida the zona reaction or zona block.
- Phase 3: Penetration of vitelline membrane.
3- Fusion of pronuclei then segmentation.
Results of fertilization:
1- Completion of the second maturation division of the ovum.
2- Restoration of the diploid number of chromosomes.
3- Sex determination.
4- Initiation of the cleavage.
5- The zona and cortical reactions occur.
