MCAT Chapter 3 BIOL

Development

ampulla

widest part of fallopian tube

where fertilization occurs

fertilization membrane

depolarized and impenetrable membrane of the zygote

dizygotic twins

two zygotes formed from two eggs being fertilized by two sperm

monozygotic twins

one egg fertilized by one sperm but the zygote splits

cleavage

the zygote undergoes mitosis and becomes an EMBRYO

indeterminate cleavage

can differentiate into complete organisms

determinate cleavage

(in protostomes) each blastocyst has a developmental fate

process of development

egg/sperm → zygote→ embryo (blastomere→ morula→blastula→gastrula)

trophoblast cells

type of blastocyst that differentiates into placenta

inner cell mass

blastula that forms organism

chorion

forms placenta

amnion

tough membrane filled with amniotic fluid that protects fetus from shock

gastrulation

development of three distinct germ layers

ectoderm

germ layer that forms skin, nervous system, lens of eye, hair , nails

endoderm

germ layer that forms epithelial and intestinal linings as well as respiratory

mesoderm

germ layer that forms the muscles, circulatory system, and most of excretory system

induction

ability of cells to cause specific differentiation of nearby cells

neuralation

notochord (mesoderm) stimulates the ectoderm to differentiate into the neural tube (CNS) and neural crest cells (PNS)

determination

commitment of cell to a specific type through differentiation

morphogens

cause neighboring cells to follow developmental pathway

embryonic cells cause controversy

because they can cause embryo to stop development

potency goes

totipotent→ pluripotent→ multipotent

inducers

growth factors that function on a specific cell type

when does apoptosis occur in development?

when a cell disintegrates so that it can be absorbed and used by another cell

complete regeneration

a stem cell migrates to the area to fully differentiate into structure

liver tissue

incomplete regeneration

newly formed structure is not identical to previous cells that had been damaged

ie. heart

Why should maternal and fetal blood stay separate?

They might have different blood types which could cue immune responses

fetal blood cells contain

fetal hemoglobin which has a greater affinity for O2

Umbilical cord

has two arteries and one vein

Fetal gas exchange occurs

across the placenta

placenta produces

hCG, progesterone, estrogen to maintain pregancy

Umbilical arteries

carry DEOXYGENATED Blood away from the fetus

UMBILICAL VEIN

carries blood to fetus

foramen ovale

one way valve that connects fetal atriums

ductus arteriosis

shunts leftover blood from pulmunary artery to aorta

liver is bypassed via

ductus vensus

first trimester

brain develops, heart begins to develop, most of the organs are formed

~8 weeks

afterward called a FETUS

second trimester

fetus grows a lot

third trimester

rapid growth and brain development

hormones that cause labor

oxytocin and prostoglandins