placenta and development of major body cavities Flashcards
what are the 3 layers of the uterine wall
- endometrium - inner layer - mucosa
- myometrium - middle - muscular
- perimetrium - outer - CT/ supportive
what are the 2 zones of the endometrium in the uterine wall
- basal layer
- functional layer
what is the basal layer in the endometrium
deeper layer, not sloughed off during menstruation but functions as a regenerative zone after its rejected
- supplied by straight arteries
what is the functional layer of the endometrium
superficial layer, 80% of thickness and is sloughed off during menstruation
- site of cyclic changes
- supplied by spiral arteries
where does the blastocyst attaches
functional layer of endometrium
what happens when the blastocyst invades the basal layer of endometrium
placenta accerta
what happens when the blastocyst invades the myometrium
placenta increta
what happens when the blastocyst invades the perimetrium
placenta percenta
what is decidua
portion of the uterine wall that is lost at parturition
what are the 3 types of decidua
- decidua basalis
- decidua capsularis
- decidua parietalis
what is decidua basalis
position of the decidua underlying the embedded embryo and where chorionic villi are anchored
what is decidua capsularis
portion of the decidua that covers the embryo as it bulges into the uterine cavity
what is decidua parietalis
decidua that lines the remainder of the uterus
what is the cytotrophoblast
stem cell layer that contributes to the growing synctiotrophoblast layer
what is the Syncytiotrophoblast layer
mass of cytoplasm filled with nuclei
- unbroken barrier that protects the fetus
- recreates enzymes to invade maternal tissue
what to blastocysts produce
human chorionic gonadotrophin (hCG) which signals corpus luteum which creates progesterone in the ovaries to continue its life
what is the function of stromal cells
- in contact with villi
- differentiate into decidual cells which are filled with glycogen
what fills the lacunae become filled with when growth occurs
maternal blood
what do the first primitive vessels of the yolk sac do
the first site of hematopoiesis
what do the primordial germ cells do in the yolk sac
migrate to the bees of the gonads
what is chorion
fetal tissue that forms the placenta
- Syncytiotrophoblast
- Cytotrophoblast
- Extraembryonic somatopleuric mesoderm
how are chorionic villi formed
1) cytotrophoblast invades the strands of syncytiotrophoblast and coverts it to primary villi
2) maternal blood from the eroded maternal blood vessels fills the lacunae which forms intervillus spaces
3) extraembryonic mesoderm invades the villi forming secondary villi
what are primary villus
central core of cytotrophoblast surrounded by syncytiotrophoblast
what are secondary villus
primary mesoderm invade primary villi forming central core
- central core of mesoderm + cytotophoblast + syncytiotrophoblast
what are tertiary villus
formation of fetal blood vessels in the central core of mesoderm
what happens to tertiary villus
undergo degeneration except the villi adjacent to the decidua basalis where they continue to grow
what tissue does the core of tertiary villi contain
- loose CT with fetal capillaries
- fibroblasts
- few phagocytic cells called cells of Hofbauer
what are Hofbauer cells
large cells with large nuclei
what are the parts of chorion
- chorion frondosum
- chorion laeve
what is the chorion frondosum
bushy chorion, part under the implanted embryo
- between embryo and myometrium
what is the placenta
disk shaped organ composed of maternal side bassalis and dental side
what is the fetal surface covered by
amnion - smooth where the umbilical cord is attached too
what does the fetal part of the placenta consist of
- branching chorionic plate
- amniotic membrane
- tertiary chorionic villi
what does the maternal part of the placenta consist of
- modified basal lamina of endometrium
- lacunae - filled with maternal blood
- connected tissue septae - separate colyledons
- cotyledons - placnetal lobes
what are the functions of the placenta
- respiratory function
- nutrition function
- excrete waste products
- barrier function - heparin and insulin do not pass
- production of hormones
- immune - IgG antibodies transferred giving passive immunity
- production of enzymes
when does the placental barrier form
at 4 months
what passes through the placental barrier
nutrients, hormones and viruses
what cannot pass through placental barrier
drugs and bacteria
what are the components of the placental barrier
- syncytiotrophoblast,
- cytotrophoblast,
- basal lamina of cytotrophoblast,
- CT (mesodermal, mesenchymal layer) of villus,
- basal lamina of the blood vessel,
- endothelium of the fetal blood vessel.
what happens to the placental barrier after 4 months
cytotrophoblast and mesoderm thin out and leaves a thin layer of syncytiotrophoblast and fetal capillary endothelium
where does the umbilical cord develop from
connecting stalk - part of extrambryonic mesoderm
where is the mesodermal bar of connecting stalk attached to
roof of amniotic cavity at one end and trophoblast at the other
what are the 3 blood vessels in the umbilical cord
- 2 umbilical arteries - branched from iliac arteries carry deoxygenated blood from fetus to placenta
- 1 umbilical vein - supplies oxygenated blood from placenta to fetus into the inferior vena cava via ductus venosus
what is the amnion
large sac containing amniotic fluid whee the umbilical card is suspended
what are the functions of amniotic fluid
- absorbs jolts
- allows for fetal movement
- prevents adherence of the embryo to surrounding tissue
how is amniotic fluid produced
dialysis through placental and fetal blood vessels or fetal urine
how is amniotic fluid absorbed
feral swallowing
when is the maximum amount of amniotic fluid reached
36 weeks
what is amniocentesis
procedure where amniotic fluid is aspirated from amniotic cavity for diagnostic purposes
- done at 14-15 weeks
what is the purpose of amniocentesis
- examine chromosomes
- detect defective enzymes
- neural tube defects
- sex of a fetus
- study fetal enzymes and hormones
what are the abnormalities with amniotic fluid
- severe hydaamios - excess - may indicate genetic defects eg. CNS or blockage to gastrointestinal tube
- oligohydramnios - not enough - problem with fetal development
what are dizygotic twins/ fraternal
come from two zygotes
what are monozygotic twins/ identical
one zygote
what are the reasons for hyperovulation
- height - taller people more likely
- high body weight - increases estrogen
- maternal age - older women more likely
- subsequent births - people who have given birth several times
- race
what happens to the placenta with dizygotic twins
- separate placentas but fuse due to being so close together
what happens when dizygotic twins have different sexs
testosterone from male can affect female development
- square jaws
- large teeth
how does conjoined monozygotic twins form
embryonic disc doesn’t divide completely of discs fuse
what are the types of conjoined monozygotic twins
- craniopagus - twins united with head
- thoracopagus - twins fused at thorax
- pygopagus - fusion of sacral region
- cephalothoracopagus - function of throat and head
what are parasitic twins/ heteropagus
conjoint twin that have one large and another smaller parasitic twin
what are vanishing twin
- fetus becomes mummified and resembles parchment paper
what is the intraebroyonic mesoderm subdivided into
- paraxial mesoderm (somite),
- intermediate mesoderm (nephrogonatome),
- lateral plate mesoderm.
what does lateral plate mesoderm form
body wall and body cavities
- initially involved in formation of intraembryonic celom
what is the itraembryonic celom
all cavities fuse together to form one large horseshoe shaped cavity
when does the intramebryonic celom divide
during 2nd month
what does the intraembronic celom divide into
- somatopleuric mesoderm - development of body wall
- splanchnopleuric mesoderm - development of walls of viscera
- intraembryonic mesoderm - development of liver and diaphragm
what is the canal connecting the pericardial and peritoneal cavities called
pericardioperitoneal
canals
What do two fused primitive peritoneal cavities form
Single peritoneal cavity
When does the intraembryonic celom form
End of 3rd week
What is the structure of the intraembryonic celom
Horseshoe-shaped cavity in the lateral plate mesoderm
How does folding of the embryo occur
- pericardial cavity lined ventrally and two pericardioperitoneal canals pass on either side of the foregut
- two long buds arising from foregut invaginate the pericardioperitoneal canals
- growth and enlargement of lung buds expands the canals forming the pleural cavities
What components form the diaphragm
- septum transversum
- paired pleuropeitoneal membranes
- dorsal mesentry of esophagus
- mesoderm of body wall
