CHAPTER 28 EXAM Flashcards
What is monospermy and how do humans prevent polyspermy?
One sperm per oocyte. Oocyte membrane block and zona reaction.
What is oocyte membrane block?
When a sperm binds to a sperm-binding receptor on oocyte, it causes oocyte to shed all other sperm-binding receptors. Other sperm can no longer bind to oocyte
What is zona reaction (slow block).
Entry of sperm triggeres surge of calcium. Oocyte is activated to prepare for secondary meiotic division. ZIPs are released (Zonal inhibiting proteins), they destroy sperm-binding receptors. Fragments bind water and swell, detaching any other sperm still around
What is the corpus luteum maintained by what what is its involvement in pregnancy?
Maintained by HcG. Prevents menstruation during the implantation phase. Secretes progesterone during the early stages of pregnancy
How long is an egg able to be fertilized?
12 to 24 hours
What are the endoderm, mesoderm and ectoderm?
Primary germ layers present in the embryo
First cells that enter displace hypoblast of yolk sac and form _____. Cells that follow push laterally forming ______. Cells that remain on the embryo’s dorsal surface form _______.
Endoderm, mesoderm, ectoderm
What does ectoderm form?
Becomes nervous system and skin epidermis
What does endoderm form?
Becomes epithelial linings of digestive, respiratory and urogenital systems and associated glands
What does mesoderm form?
Everything else. Vertebra, muscles, ribs, dermis, kidneys, gonads.
How is luteinizing hormone involved in menstrual cycle and pregnancy?
Triggers ovulation and the release of an egg from the ovary. During pregnancy, LH levels typically decrease and remain low. This is because pregnancy disrupts the normal menstrual cycle, preventing ovulation from occurring.
Follicle stimulating hormone involvement in menstrual cycle and pregnancy?
Stimulates the growth and development of follicles in the ovaries during the early part of the menstrual cycle. FSH typically decreases during pregnancy because it is no longer needed.
Human chorionic gonadotropin involvement in menstrual cycle and pregnancy?
Prompts corpus luteum to continue secretion of progesterone and estrogen. Levels rise until the end of 2nd month. Levels spike early in pregnancy. Not typically used in menstrual cycle but important in pregnancy
The significance of calcium?
Levels within the sperm begin to rise, triggering the release of acrosomal enzymes. Increased calcium triggers exocytosis of cortical granules which hardens the zona pellucida and destroys it’s sperm binding receptors.
What happens at 8 weeks (end of embryonic period)
Head nearly as large as body. First brain waves. Liver large. Limbs present, webbed toes/fingers. Ossification begun, spontaneous muscle contractions occur. Cardiovascular system functional. 30mm and 2 grams.
