human fertilization

19 Nov. 2008 Fertilization.ppt 1

Fertilization & Development

19 Nov. 2008 Fertilization.ppt 2

Coitus & Sperm Transfer

• 2-3 phases– Erection/engorgement: Parasympathetic reflex– Plateau– Orgasm: Sympathetic reflex

• Heart rate, contractility increase (pulse & BP)• Intense pleasure• Ejaculation by male

19 Nov. 2008 Fertilization.ppt 3

Fertilization

• Contact of sperm & secondary oocyte occurs in uterine tube– Sperm penetration– Oocyte completes

meiosis II– Nuclear fusion

19 Nov. 2008 Fertilization.ppt 4

Fertilization

• Sperm penetration• Why so many?

19 Nov. 2008 Fertilization.ppt 5

Fertilization

• Oocyte completes meiosis II

• Nuclear fusion– 1n + 1n 2n

19 Nov. 2008 Fertilization.ppt 6

Early Development

• Cleavage in uterine tube

19 Nov. 2008 Fertilization.ppt 7

Early Development

• Implantation– 6-7 days after

fertilization– Trophoblast forms

placenta– “Inner cell mass”

forms embryo

– (pp. 1118-1119)

19 Nov. 2008 Fertilization.ppt 8

Early Development

• Implantation– Trophoblast forms

placenta– “Inner cell mass”

forms embryo

19 Nov. 2008 Fertilization.ppt 9

Early Development• Placenta

– Provides large area for exchange of O2, CO2, nutrients, metabolic wastes between fetal and maternal blood

19 Nov. 2008 Fertilization.ppt 10

Pregnancy

• Pregnancy lasts 39-40 weeks, – 280 days from last

menstrual period– 3 trimesters

• Hormonal changes

19 Nov. 2008 Fertilization.ppt 11

Labor & Delivery• Dilation

– Cervix dilates to ~ 10 cm diameter

– Effacement– Descent of fetus into

birth canal (“Station”)• Expulsion• Placental stage

– “afterbirth”