physiology notes:
Development
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- Pregnancy: period of time from fertilization until birth
Conceptus: developing offspring
Gestation: time of development
- Embryo: age of conceptus from 1 week to 8 weeks.
Fetus: conceptus from week 9 to birth
- Capcitation is the breakdown of the membrane surround the acrosome or cap of the
sperm to allow the release of hyaluronidase.
- Acrosomal reaction: release of enzymes in the area of the oocyte; intercellular
matrix (hyaluronic acid) is penetrated allowing passage of sperm of the oocyte
surface
- Polyspermy: when many sperm enter the egg. Monospermy is mechanism in
humans. Fusion of one sperm with oocyte membrane→ depolarization preventing
additional sperm from entering. Also cortical reaction produces enzymes that
destroy sperm receptors.
- Male and female pronuclei: sperm and ovum nuclei before they fuse.
- Cleavage: cell divisions without growth following fertilization; results in smaller
cells produced called blastomeres.
- Blastocyst: a single layere sphere filed with fluid; has trophoblast outer layer and
Inner cell mass→ embryo.
9.Morula: berry-shaped ball of cells of 16 cells formed about 3 days after conception.
10. Implantation: blastocyst arrives in uterus (endometrium) ; trophoblast cells attach to lining and release digestive enzymes and becomes enclosed with. HCG from trophoblast cells→ corpus luteum→ progesterone; eventually, placenta takes over estrogen and progesterone function. Pregnancy tests use HCG levels for determination.
11. Human Chorionic Gonadotropin: see #10
12. Placenta: contains embryonic part (trophoblast layer= chorion) and maternal (endometrium); serves as a an organ for nutrition, respiration, excretion.
13. Gastrula: 3 cell layered embryo.
14. Functions of:
a. amnion: membranous sac surrounding the embryo
b. yolk sac: not a great source of nutrients; it does produce the first blood cells primordial germ cells
c. allantois: becomes part of the umbilical cord; develops into urinary bladder
d. chorion: encloses the other membranes; part of placenta
15. Three primary germ layers: p. 1126 chart
Ectoderm: forms skin, nervous system
Mesoderm: forms blood, muscles, bone, urogenital system
Endoderm: digestive, respiratory
16. Primitive streak: formed during process of gastrulation; determines axis of embryo
17. Neurulation:
a. neural plate: thickening of overlying ectoderm above notochord
b. neural folds: sides of neural groove rise up
c. Neural tube: formed from closing of neural folds.
d. Neural crest: migratory cells that form cranial and spinal nerves and adrenal medulla.
18. Endoderm structures: see #15
19. Mesoderm specialization: notochord→backbone; somites form sclerotome→
vertebra, dermatome→ dermis and myotome→ skeletal muscles
20. Teratogens: chemicals that can cause degeneration of developing fetal structures (alcohol, drugs, nicotine; German measles, thalidomide)
21. Relaxin: placental hormone causing relaxation of pelvis ligaments and pubic symphysis
22.Distinguish between:
a. Human placental lactogen: stimulates breasts for milk production (also called human chorionic somatomammotropin)
b. human chorionic thyrotropin: increases maternal metabolism
23. Oxytocin: from fetus: causes placenta→ prostaglandins which cause muscular contractions; posterior pituitary also releases oxytocin= more contractions
24. 3 stages of labor:
a. dilation stage: beginning of labor to dilation of cervix (10 cm); may last 6-12 hours
b. expulsion stage: full dilation to delivery; average time is 2 hours; crowning; episiotomy possible
c. placental stage: removal of placenta (30 minutes after delivery)
25. Prolactin effect: causes milk production in mammary glands
26. Colostrum: secretion in mother’s milk containing proteins, minerals and antibodies
27. Ectopic pregnancy: embryo
implants outside the uterine lining; often happens