BIOL 240W Study Guide - Midterm Guide: Corpus Luteum, Chemiosmosis, Carbon Fixation
bio 240 // exam 3
1. development pt. 2
a. gastrulation results in a disk made of 3 layers of embryonic cells + extra
membranes
i. ectoderm
ii. mesoderm
iii. endoderm
iv. extra membranes:
1. chorion → trophoblast and mesoderm, gas exchange
2. amnion → mesoderm and ectoderm, surrounds and cushions
embryo
3. yolk sac → hypoblast and mesoderm, site of early blood cell
production
4. allantois → endoderm and mesoderm, becomes umbilical cord
b. weeks 3-8 → organogenesis. head and bottom visible by week 4, all other organs
visible by week 8. at this point it is called a fetus
i. neural tube → nervous system
ii. notochord → spinal column
iii. somites → vertebrae + ribs
iv. coelom → abdominal and thoracic cavities
v. archenteron → digestive tract
c. know where the following tissues come from:
i. nervous system → mesoderm
ii. skeletal system → mesoderm
iii. muscular system → mesoderm
iv. liver → endoderm
v. touch receptors in skin → ectoderm
vi. circulatory system → mesoderm
vii. lining of gi tract → endoderm
viii. lining of mouth → endoderm
d. first trimester → first 13 weeks. everything that happens is stated above
e. second trimester → second 3 months.
i. fetus becomes very active
ii. placenta takes over estradiol and progesterone production + corpus
luteum degenerates
iii. fetuses birthed at this stage have a high rate of survival if appropriate
NICU is available, birthed before 24 weeks = low survival rate
