Lecture 17: Body Cavities/Diaphragm Flashcards
when intraembryonic coelom begins to develop
early 4th week
what intraembryonic coelom becomes
embryonic body cavities
where in embryonic tissue intraembryonic coelom develops
lateral mesoderm- spaces within this coalesce to form coelom
what happens in intra-extraembryonic coelom communication space
organs will develop there
location of extraembryonic coelom
chorionic cavity
where intraembryonic and extraembryonic coeloms communicate
lateral mesoderm
2 major body folds, week 3
cranio-caudal
lateral
why cranio-caudal fold occurs
because of large size of brain developing relative to rest of embryo
why lateral fold occurs
- rapid growth of amniotic cavity
2. somites around notochord growing at rapid rate
what disconnects during lateral folding of embryo
intraembryonic and extraembryonic endoderms disconnect
allantois
extends from embryonic coelomic cavity into body stalk
when does orophorengeal membrane develop
intraembryonic coelom folding
layer of embryonic tissue lining amniotic cavity
surface ectoderm, a thin layer of mesodermal tissue
how embryonic body cavity forms
lateral/cranial-caudal folding
partitioned cavities of embryonic body cavity will be
pericardial cavity
2 pleuro-pericardial canals
peritoneal cavity
2 layers of lining of embryonic body cavity
somatic mesoderm (parietal layer) and splanchnic mesoderm (visceral layer)
mesentery
double layer of peritoneium that connects an organ to the body wall
what is within mesentery
blood vessels, nerves
dorsal mesentery
mesentery closer to embryo’s back
suspends acudal foregut, mindgut, an hindgut in peritoneal cavity
ventral mesentery
mesentery that largely disappears in embryo
disappears except in proximal foregut (stomach and proximal duodenum)
layer of embryonic tissue that forms gut/intestines
embryonic endoderm
3 major arteries to primitive gut and their location
celiac - foregut
superior mesenteric - midgut
inferior mesenteric - hindgut
all in dorsal mesentery
physiologic herniation of midgut - how/why occurs
midgut must form outside of embryo (extraembryonic coelom) and then travel back in (intraembryonic coelom), at 10th week of embryonic development
tissue that separates pleuropericardial cavities
mesoderm
what drags with mesodermal tissue to create delineation between pleuropericardial cavities
veins
cardinal veins
early blood vessels in pleuropericardial membranes
what pleuropericardial membranes contain
common cardinal veins, phrenic nerves
what separates pericardial and pleural cavities
mesenchyme ventral to esophagus, in midline
diaphragm function in embryo
divide chest from abdomen
2 halves of diaphragm
left crus, right crus
why diaphragm needs holes
so aorta blood supply can go from chest to abdomen
so esophageal space exists for food to get from top to bottom
important embryonic components of diaphragm
- septum transversum
- pleuperitoneal membranes
- dorsal mesentery of esophagus
- muscular in-growth from lateral body walls
septum transversum
mesodermal structure, primordium to central tendon of the diaphragm, that begins cranial to heart but migrates below heart during cranial-caudal folding, and separates heart from liver
pleuroperitoneal membrane
membrane separating embryonic pleural and peritoneal cavitiesz
grows in from lateral body walls
fuses with dorsal mesentery of esophagus and septum transversum
myoblasts
muscle forming cells in pleuroperitoneal membrane that will become diaphragm’s muscles - make it able to contract
close the pleuroperitoneal openings
effect of pleuroperitoneal membranes- fetus vs adult
large effect-fetus; small effect-adult
dorsal mesentery of esophagus
muscle fibers that surround vena cava and aorta
forms median part of diaphragm
what crura of diaphragm form from
myoblasts that migrate from dorsal mesentery
septum transversum, in adult
central tendon
as pleural cavities grow, divide body wall into 2 parts
external layer- definitive body wall
internal layer- peripheral diaphragm
division of pleural cavities creates
costodiaphragmatic recesses aka costo phrenic angles
how many phrenic nerves
2- motor and sensory- 1 on each side of the embryo
what septum transversum pulls down with it
from cranial end where it develops, pulls spinal nerves
phrenic nerve root value
C3, 4, 5
congential diaphragmatic hernia (CDH) - description
when L side of diaphragm doesn’t close, can have herniation of abdominal contents into chest cavity - dangerous because if abdominal contents are in chest cavity, lungs don’t have space to form, and child gets pulmonary hypoplasia- cannot breathe
CDH incidence
1/2200
diaphragm close order re: right/left
right then left
clinical sequelae of CDH
pulmonary hypoplasia, polyhydramnios
CDH treatment options
pre-natal: in utero surgery; tracheal occlusion
post-natal: deliver in 3o care center; ECMO; immediate surgical repair
