1. REPRODUCTIVE SYSTEM - 2
LECTURE 19

2. Female Reproductive Organs

4. Oogenesis

6. Over 300 million sperm enter the female at ejaculation.
Only about 100 of these live to enter the fallopian tube.
In order to fertilize the ovum, a sperm must become capacitated. This takes at least 7 hours after ejaculation.
pH increases
Hyperactivation of the flagellum
Capacitated sperm are guided to the oocyte by chemotaxis and thermotaxis

7. Sperm Sperm Oocyte Sperm
(b) Sperm surround the oocyte, attacking its defensive barriers.
Oocyte
Sperm

8. When the sperm enters the oocyte, Ca2+ is released from the endoplasmic reticulum.
A calcium wave travels through the oocyte to the opposite side from the entry of the sperm
The Ca2+ has several effects:
Prevents other sperm from entering the oocyte (polyspermy)
Activates the oocyte to finish meiosis to become a haploid ovum

10. Implantation

11. Ectoderm – epidermis and neural tissue
16 DAYS
Ectoderm – epidermis and neural tissue
Mesoderm – connective tissue and muscle
Endoderm – epithelium of lungs and gut

12. A Comparison of bird with human sacs

13. Placenta and Amniotic Sac Formation
As the blastocyst develops, the endometrium also changes to form the decidua basalis.
This joins with the chorion frondosum to form the placenta.

14. Molecule exchange across the placenta
Umbilical arteries deliver fetal blood to placental vessels.
This blood circulates within the placenta and returns to the fetus via the umbilical vein.
Maternal blood is also delivered to/from the placenta.
In this way, maternal and fetal blood do not mix, but are separated by only two cell layers.
Molecules diffuse across tissues of the placenta for exchange.

15. Amniocentesis
Samples from the amniotic fluid can help diagnose genetic abnormalities such as Down syndrome.
Samples are taken at week 16

17. Pregnancy Averages 38 weeks from fertilization
Takes 2 weeks for blastocyst to form
Weeks 3 to 8: embryonic period
Weeks 9 to birth: fetal period

18. LABOR AND PARTURITION