How long is a human pregnancy and how many stages are in it
9 months, first trimester second trimester, third trimester, embryonic period and fetal
what does the blastocyte contain
contains Inner cellular mass and trophoblast
what happenes to the blastocyte contents after implantation
ICM forms embryionic disk and a space called the amniotic cavity
Trophoblast forms cytotrophoblast, syncytiotrohpoblast and chorion
what are the two layers of the embryonic disk, where does the embryonic disk come from what do the two layers do
embryonic disk comes from the ICM
epiblast - becomes the embryo proper
hypoblast - forms extraembrionic membrane like the yolk sac
what does the cytotrophoblast do
adheres to the endometrium and burrows trough the uterine wall
secretes factors that attract maternal blood vessels
remodels the maternal blood vessels
what does the syncytiotrophoblast do
multinucleited body that digests uterine tissue
what does the chorion do
embryionic contributions to the placenta
membrane that surroinds all others
what does the amniotic cavity do?
coushining and shock absorption
temprature regulation
what does the yolk sac do?
- Supplies nutrients that it extracts from the trophoblast
- primitive blood circulation for 2nd and 3rd week
- placenta takes over nutrition after 4th week and yolk sac reduces in size
- sources blood cells from primordial germ cells
- contains the alantonis which is a outpocketing that serves as the primitive excretory duct that eventually becomes part of the urinary bladder.
what happens during gastrulation
two layers to three layers from
pluripotent to multipotent
primitive streak or indentation forms on the surface of the embryo
cells migrate towards primitive streak and form two layers
what are the two layers formed by gastrulation and whats left over when it is atracted to the primitive streak
first layer formed is the endoderm which displaces the hypoblast
seccond layer is the mesoderm that fills the midle layer
ectoderm forms with the epiblast that did not migrate
what does the endoderm layers become
- digestive system
- pancreas
- liver
-lungs inner layer
what does the mesoderm become
dermis of skin
circulatory system
skeletal system
muscular sysem
what does the ectodem become
hair nails skin nervous system
how does the placenta connect to the embryo
via umbelical cords, two arteries that carry deoxygenated blood and waste from fetus
one vein to carry oxigentated blood and nutrients
how is the maternal blood vessels remodeled other than cytotrophoblasts and why does it happen
chorionic (from trophoblast) membranes with finger like villy burrow into the endometrium and remodell the maternal blood vessels.
what forms the umbelical cord
fetal cells derived from mesoderm fill villi and differentiate into blood vessels, including those of the cord
where does the tissues come from the mom
decidua basalis portion of endometrium
what is the big 3 functions of the placenta
nutrition and digestion,
respitaration
endocrine function
what does the placenta do in nutrition and digestion
mediates diffusion of glucose, amino acids, fatty acids, vitamins and minerals, stores nutrients during early preganancy so that it can be used in later stages. excertes fetal wastes into the maternal blood
What ddoes the placenta do in endocrine funtion
secretes hcg, estrogen and progestreone to develope fetus and mother and maintain pregnancy,
what is the pathway from maternal blood to fetal blood
chorionic epithelial cells, fetal connective tissue, fetal endothelial cells, fetal blood
why are there several structures from maternal blood to fetal blood
barier to high molecular wiegth like most maternal hormones
barrier to some infectious agents
but many substances cross as it is a lipid soluable substance.
what things cross into the fetus by simple diffusion
oxygen, co2, lipid soluble
