1. Development

2. Ejaculation the release of semen
-Approximately 2 teaspoons (10 mL)
-280 million sperm
-Most die in the vagina within minutes after ejaculation
-Once they move through the cervix into the uterus, they can survive longer, up to 5 days.
-Outside the body sperm will die within minutes.

3. SPERM STRUCTURE Head contains nucleus
an organelle “cap” called an Acrosome (contains digestive enzymes)
Tail
flagellum – whipping motion provides motility.
Base of tail contains a coiled mitochondrion to provide power for movement.

4. Capacitation: readying the sperm
Sperms cannot fertilize oocytes when they are newly ejaculated.
The acrosome is not active
Chemicals in the uterus cause the acrosome to become active

5. Ovulation-
Secondary oocyte (nuclues contains 1/2 the chromosomes)
Folicle cells (make up the corona radiata)
Zona pellucida (protects the “egg”)

6. At the cervix Helping the sperm:
At ovulation, the muscus that normally covers the opening of the cervix thins out
This allows sperm to pass through the cervical opening.
It is also thought to help guide the sperm
Passage of sperm:
Since sperm can only move 2 to 3 mm per minute using their own power, they must be helped along somehow. At the shortest, sperms can be found in the oviducts only 5 minutes after ejaculation. Other sperms can take 45 minutes.
The Natural Family Planning method of attempting pregnancy relies on changes in mucus thickness for the timing of intercourse—the character of the mucus is a good indicator of the presence of a viable egg.

7. Stage 1 of fertilization:
Sperm come in contact with the follicle cells of the corona radiata
Enzyme action from multiple acrosomes help sperm pass through
Flagella action also aids corona radiata penetration

8. Stage 2 of fertilization:
Penetration of the zona pellucida around the oocyte:
Acrosomal enzymes: cause lysis of the zona pellucida
Once sperm penetrates zona pellucida, the zona reaction occurs:
This reaction makes the zona pellucida impermeable to other sperms.
Zona pellucida begins to harden
When more than one sperm manages to enter the ovum (dispermy = 2; triploidy = 3), the fetus nearly always aborts.

9. Corona radiata
Figure 7.8

10. Stages 3 of fertilization:
Fusion of plasma membranes of oocyte and sperm
Causes action potential of the seconadary oocyte membrane
2nd meiotic division of oocyte is completed
The secondary oocyte was previously arrested in metaphase of the 2nd meiotic division, and now forms the mature ovum and another polar body.

11. Twins: still 1 sperm per egg
Monozygotic (monoovular):
A fertilized, single egg splits into two developing zygotes at a very early stage.
Identical twins; same sex.
Dizygotic (polyovular):
Result from the fertilization by two sperm of two separate ova that have reached maturation at the same time.
Not identical twins; can be different sexes
Incidence increases with age of the mother

12. Cleavage is cell splitting The cells continue “splitting” by mitosis
Cleavage begins
Cleavage is cell splitting
The cells continue “splitting” by mitosis
The size of the embryo does not change, but the number of cells does
This is all occurring in the oviduct
Zona pellucida is hard
Day

13. MORULA Cleavage stage ends now called a morula (Latin for raspberry)
It is a solid ball of cells (about the size of the tip of your pen)
It will continue to be called a morula as long as it is a “solid ball”
Day 4 - 5

14. Blastocyst The Morula hollows out as cells move outward.
The inside fills with liquid (the liquid is produced by the cells)
Cells are too many and too small to be seen at this point
This is now a blastocyst

15. Inside the Blastocyst
Inner Cell mass: will become develop into the child
Blastocoel: empty space of liquid is inside (-coel means empty space)
Trophoblast: outer layer of cells which will become membranes
Parts of the blastocyst:
wrtk/handbook.html

16. Human Hatching The blastocyst will “hatch” from the hardened zona
pellucida mm

17. Implantation embryo attaches to uterine lining
Embryo produces pregnancy hormone (hCG) (human chorionic gonadotropin )
Found in blood and urine
Approximately 6-8 days after fertilization

18. Hormonal Control of Pregnancy
Initially the trophoblast cells secrete Human Chorionic Gonadotrophin (HCG)
Functions of HCG:
Prevents the degeneration of the corpus luteum
Stimulates the growth of the CL.
Increase secretion of both estrogen and progesterone
Prevents mestruation

19. Small chorionic villa (finger-like projections) grab on to the endometrium

20. These projections make contact with the maternal blood supply, becoming the pipeline through which the fetus derives nutrients and oxygen, and rids itself of carbon dioxide and wastes. The placenta has not formed yet.

22. The process of: Gastrulation
A hole forms at the top of the blastocyst near the inner cell mass
This hole is called the blastopore
Cells begin to migrate inward forming layers (forming shape- morph)
The blastocyst is now becoming a gastrula

24. Cell to cell interaction lines up the cells properly
3 layers are formed
Ectoderm
Mesoderm
Endoderm

26. Differentiation Cells are now committed
Each layer will only become what it has been programmed to become (by your DNA)

28. Neurulation Brain and spinal cord are forming
At 19 dys – photo about 25 dys: 2.5 mm
Brain and spinal cord are forming
The skull will not completely close until months after birth
WHY?
What do we call these spots?

29. Neurula Brain regions can be found
Neural groove, which will become the spinal column
Heart begins to develop
Hematopoiesis begins
Neurula
Day 28
2-3.5 mm