BIOL BC 1500x Lecture Notes - Lecture 14: Egg Cell, Amniotic Sac, Oviduct
10 Oct 2016
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General model: animals go from egg to adult through a series of steps. Development of frogs eggs => tadpole => adult frog. All changes occur by thyroxin, hormone from the thyroid gland. Initiated by steroids from adrenal cortex, testes, and ovaries. Begins at 7-10 weeks old in embryonic development. Endocrine control: gonadotropic releasing hormones (gnrh) from hypothalamus flow to anterior pituitary. Testosterone triggers secondary sexual characteristics (hair, deep voice, muscle mass, etc. ) Estrogen stimulates secondary sex characteristics (breasts, redistribution of fat and muscles, hair, etc. ) Phases: menstrual phase (flow phase), beginning of menstrual flow (menses) At end: low levels of ovarian hormones, high fsh and increasing lh: follicular phase biggest follicle dominates and grows. Ratios of lh and fsh stimulates high production of estrogen. Estrogen stimulates thickening of uterine lining (required if there is an embryo forming: ovulation. Stimulated by high amounts of estrogen stimulation of hypothalamus to produce more.
