Anatomy - Unit 1 - Chapter 3 - Embryology

embryology

development before birth

prenatal period and the three stages

38 weeks of human development

pre embryonic period

embryonic period

fetal period

pre embryonic period

first 2 weeks after fertilization to form blastocyst and ends w implantation into uterine wall

zygote

name used right when egg is fertilized

cleavage

series of mitotic divisions

morula

16 cell stage that is a solid mass of cells, will enter the uterine cavity

blastocyst

fluid filled cavity of cells, once it goes into uterine cavity and will implant

2 layers

1. trophoblast - outer ring of cells

2. embryoblast - inner mass agaist the wall

trophoblast

outer ring of cells in blastocyst that forms chorion

embryoblast

inner mass of cells in blastocyst that will form the embryo

these are pluripotent

pluripotent

can differentiate into any cell type in the body, stem cells

implantation

happen at the end of week 1, implants into edometrium (uterine lining), enzymes in blastocyst release enzymes to break down and impant into the wall, process is done by day 9

bilaminar germinal disc

created by day 8 to make hypoblast and epiblast, in week 2

hypoblast

layer of small cubiodal cells facing the blastocyst, below

epiblast

layer of columnar cells deep to the hypoblast, above

yolk sac

sit fro eraly blood cell an vessel formation, attached to hypoblast

amniotic sac/amnion

surrounds developing embryo and fetus, connected to epiblast layer

chorion

forms placenta, outermost membrane, comes from trophoblast

placenta

vascular organ for communication between mother and baby with blood flow for nutrints, antibodies, and baby waste removal

produces estrogen for 2ndary sex characteristics and progesterone for maintaining uterine lining during pregnancy

embryonic period

3-8 weeks, form 3 primary germ layers, organ systems are developed by end of this stage, increases in comlexity

gastrulation

process in which cells are rapidly dividing for 3 primary germ layers going from bilaminar to trilaminar, all 3 layerz come from epiblast, forms primitive streak and primitive node and pit

primitive streak

forms in epiblast, goes up towards cranial region but not all the way, stops at indentation

primitive node

cephalic end of primitive streak, pit is the depression in the node

ectoderm

forms from ectoderm, top part, has amniotic cavity, nerveous system and skin

mesoderm

middle layer, becomes bones and muscles and stays on the inside

endodoerm

bottom, has yolk sac, becomes inner linings of body

embryo

can be called this when all 3 germ layers are present

invagination

inward movement of cells from epiblast layer through primitive streak between epiblast and hypoblast layers

embryonic disc

the 3 layers

neurulation

formation of neural tube begins from overlying ectoderm cells

notochord

will form deep to primitive streak goes towards heart, sends signals for tissues and cells to differentiate

embryonic period

notochord forms

neural tube

develops into the CNS

cephalocaudal folding

head to tail folding, brings heart to correct location below mouth

transverse folding

lateral folding to make ectoderm on the outside and endoderm to the inside

organogenesis

organ development

teratogens

substances that can negatively impact developments after week 2 because that is when they start sharing blood, causes congenital malformations

thalidomine

medication for mornign sickness that prevents development of blood vessels

fetal period

week 9 to birth, maturation and growth of tissues and organs, head grows first and then body