HUMAN REPRODUCTION:
Sequence of milk conduction in mammary glands:
Mammary alveoli → mammary tubules → mammary duct → mammary ampulla → lactiferous duct.
Spermatogenesis
Structure of sperm
- Acrosome: Releases lytic enzymes to penetrate the layers of ovum.
- Mitochondria: Provides energy for tail movement.
Oogenesis
Structure of ovum (egg)
3 membranes:
- Plasma membrane
- Zona pellucida
- Corona radiata
Sectional view of a seminiferous tubule
Structure of ovary
- Primary sex organ.
- Produce ovum and oestrogen & progesterone.
MENSTRUAL CYCLE (REPRODUCTIVE CYCLE)
Phases |
Days |
Main events |
1. Menstrual phase |
1-5th day |
Menstrual flow (bleeding). |
2. Follicular (Proliferative) phase |
5-13th day |
o Primary follicles → Graafian
follicles. o
Proliferation of ruptured uterine endometrium. |
3. Ovulatory phase |
14th day |
LH surge → rupture of
Graafian follicle → ovulation. |
4. Secretory (Luteal)
phase |
15-28th
day |
Corpus luteum forms → progesterone
→ endometrium maximum vascular, thick and soft |
- Menarche: The first menstruation during puberty.
- Menopause: Permanent stopping of menstrual cycle at the age of 50.
FERTILIZATION AND IMPLANTATION
Zygote → cleavage → morula (8-16 blastomeres) → blastocyst → embryo
- 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.
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