Ovarian Cycle: Follicular phase – Ovulation – Luteal phase

Uterine Cycle: Menstruation – Proliferation – Secretory

1. Follicle Stimulation Hormone (FSH)

• Produced by anterior pituitary gland
• Stimulates primary follicles to develop

2. Estrogen

• Produced by primary follicles
• Endometrium to proliferate
• Stop production of FSH so that other primary follicle don’t develop
• Stimulate production of LH (Luteinizing Hormone)

3. Luteinizing Hormone (LH)

• Produced by anterior pituitary gland
• Stimulates ovulation
• Rest of Graffian follicle forms corpus luteum – produces progesterone

4. Progesterone

• Maintain thick endometrium (secretory phase of endometrium)

NB:

• If fertilized, corpus luteum will form corpus luteum of pregnancy – produces progesterone and is maintained by gonadotropic hormones produced by the embryo until placenta takes over to produce progesterone
• If not fertilized, corpus luteum will form corpus albicans which will then degenerate
• Reduction in production of progesterone leads to menstruation
• Reduction in production of estrogen leads to FSH production
• Proteolytic enzymes prevent coagulation of blood during menstruation

1. Germinal period – 2 weeks; formation of 3 germ layers
2. Embryonic period – 3rd week to 3rd month; differentiation of the 3 germ layers into organs and systems
3. Fetal period – growth of various organs and systems

1st week after fertilization

Zygote →Cleavage division → Morula → Blastocyst → Hatching (degeneration of zona pellucida) → Late blastocyst

Inner cell mass forms embryoblast

Outer cell mass forms trophoblast; which has 2 poles:

• Embryonic pole – faces site of implantation
• Abembryonic pole – opposite pole

Process of Implantation:

1. Trophoblast erodes endometrium
2. Penetration defect in endometrium
3. Blastocyst embedded in endometrium of uterus
4. Penetration defect closed by fibrin clot

Clinicals:

1. Ectopic Pregnancy – implantation can occur in the abdomen, ovarian and fallopian tube
2. Blighted ovum – dead embryoblast
3. Downs syndrome – Trisomy of chromosome 21
4. Turners syndrome – monosomy of x chromosome
5. Triple x syndrome