Human Reproduction | Plus 2 Zoology| Exam Capsule Notes (Web and PDF)

December 25, 2020

2

HUMAN REPRODUCTION:

CHAPTER AT A GLANCE

Sequence of milk conduction in mammary glands:

Mammary alveoli → mammary tubules → mammary duct → mammary ampulla → lactiferous duct.

Spermatogenesis

Structure of sperm

Oogenesis

Structure of ovum (egg)

3 membranes:

Sectional view of a seminiferous tubule

Structure of ovary

MENSTRUAL CYCLE (REPRODUCTIVE CYCLE)

Phases	Days	Main events
1. Menstrual phase	1-5^th day	Menstrual flow (bleeding).
2. Follicular (Proliferative) phase	5-13^th day	o Primary follicles → Graafian follicles. o Proliferation of ruptured uterine endometrium.
3. Ovulatory phase	14^th day	LH surge → rupture of Graafian follicle → ovulation.
4. Secretory (Luteal) phase	15-28^th day	Corpus luteum forms → progesterone → endometrium maximum vascular, thick and soft

FERTILIZATION AND IMPLANTATION

Zygote → cleavage → morula (8-16 blastomeres) → blastocyst → embryo

Blastocyst

A. Inner cell mass: Becomes embryo.
B. Trophoblast: Gives nourishment to inner cell mass. Also, it is attached to endometrium.

After attachment, blastocyst is embedded in endometrium. It is called implantation.

PREGNANCY AND EMBRYONIC DEVELOPMENT

Placenta: A structural & functional unit b/w foetus & uterine wall formed by interdigitation of chorionic villi & uterine tissue.

Functions of placenta:

Supply O2, nutrients etc. from mother to foetus.
Remove CO2 and excretory wastes from foetus.
Acts as an endocrine gland. It secretes Human chorionic gonadotropin (hCG), human placental lactogen (hPL), oestrogens, progesterone & relaxin.

Changes in embryo during pregnancy:

After one month: Heart is formed.
End of second month: Limbs and digits are developed.
End of 12 weeks (first trimester): Major organs (limbs, external genital organs etc.)
5th month: Hair on the head. First movement of foetus.
End of 24 weeks (2nd trimester): Fine body hair, eyelids separate and eye lashes are formed.
End of 9 months: Ready for delivery.

PARTURITION AND LACTATION

Signals from foetus & placenta → mild uterine contractions (fetal ejection reflex) → oxytocin from pituitary → stronger uterine muscle contractions → further secretion of oxytocin → Parturition (giving birth).
Lactation: Production of milk from mammary glands.
Colostrum: Yellowish milk produced during the initial few days of lactation. It is rich in antibodies essential to develop resistance for the new born babies.