body folding embryo Flashcards
what does growth involve?
cell division &elaboration of cell products
what does morphogenesis involve?
development of shape, size, and other features of a particular organ or part or the whole body
what is morphogenesis controlled by?
gene expression & regulation in an orderly sequence
what is Differentiation ?
cells are organized in a precise pattern of tissues & organs that are capable of performing specialized functions
what is the first step in body folding?
Primordium of the intraembryonic coelom (embryonic body cavity) appears
Isolated coelomic spaces Coalesce to form the intraembryonic coelom
intraembryonic coelom divides lateral mesoderm into what?
Somatic (parietal) layer of lateral mesoderm
Splanchnic (visceral) layer of lateral mesoderm
what is the somatopleure?
somatic mesoderm& overlying embryonic ectoderm form body wall
what is the splanchnopleure?
splanchnic mesoderm & underlying embryonic endoderm form embryonic gut
how does folding occur?
cranial & caudal ends, & sides occurs simultaneously
why is folding significant? whats important about the lateral edges
Folding is significant for creating correct body form
Embryo increases in length, but lateral edges cannot keep pace
when does embryo elongate?how?
cranially & caudally (4thweek/day 22)
overgrowth of neural folds over oropharyngeal membrane causes what?
moves septum transversum, primordial heart, pericardial coelom, & oropharyngeal membrane to ventral surface
Endoderm forms what when it is incorporated into foregut?
primordium of pharynx, esophagus, & lower respiratory system
after head folding has occured, what position is embryo in?
Pericardial cavity is ventral
- Pericardioperitonealcanals run dorsally on each side of the foregut
- Intraembryonic & extraembryonic coeloms are in communication
folding of caudal end of embryo is due to what?
growth of the distal neural tube
tail folding causes what change in position?
caudal eminence(tail region) projects over thecloacal membrane (future anus)
primitive streak lies caudal to cloacal membrane
Allantois is partially incorporated
Connecting stalk attached to ventral surface
terminal hindgut forms what?
cloaca
what produces the R/L lateral folds
Rapid growth of SC & somites
Extend ventrally toward the midline
Creates a cylindrical embryo
what happens to abdominal wall as a result of lateral folding?
incorporates endoderm to form themidgut
how is omphaloentericduct formed due to lateral folding?
Connection btwnumbilical vesicle & midgutis reduced
as a result of lateral folding what happens to amnion?
Amniotic cavity expands, obliterates most of extraembryonic coelom
Amnion forms epithelial covering of umbilical cord
Gastroschisis,what happens?
Protrusion of viscera; site of the abdominal defect is to the right of the umbilical cord
bowel is uncovered and floating in the amniotic fluid
lateral folding deficiency
Congenital epigastric hernia, what happens?
Midline bulge of abdominal wall located between the xiphoid process & umbilicus
Bowel is not exposed to the amniotic fluid
intraembryonic coelom will be divided into what?
pericardial cavity, pleural cavities, & peritoneal cavity
Parietal wall is derived from what?
somatic mesoderm
visceral wall is derived from what?
splanchnic mesoderm
pericardial cavity does what during head folding?
relocated ventrally, anterior to the foregut
opens into pericardioperitonealcanals (2), located dorsal to the foregut
now cranial to septum transversum
where are Pericardioperitonealcanals after headfolding?
dorsal to septum transversum
dorsal mesentery does what after head folding?
suspends Caudal foregut, midgut, & hindgut in the peritoneal cavity
partitions in pericardioperitonealcanal are called what?
Pleuropericardial folds (cranial)
Pleuroperitonealfolds (caudal)
Pericardial cavity and pleural cavities separated how?
pleuropericardial Membranes fuse with mesenchyme ventral to esophagus (7thweek)
Bronchial buds grow into what to split mesenchyme?
what does it split into?
pericardioperitonealcanals
Outer layer → thoracic wall
inner layer → fibrous pericardium
Pleuroperitoneal Membranes are formed how?
Pleuroperitoneal folds enlarge, project into pericardioperitoneal canals
Form as developing lungs & pleural cavities expand/invade the body wall
how are Pleuroperitoneal Membranes closed?
Fuse with dorsal mesentery of esophagus & septum transversum in week 6
Myoblasts migrateinto the pleuroperitonealmembranes & completes closure process
Septum transversum forms what ? how?
fuses with dorsal mesentery of the esophagus & pleuroperitonealmembranes
central tendon of diaphragm
Pleuroperitonealmembranes form what?
primordial diaphragm
dorsal mesentery forms what?
median portion of diaphragm
Myoblasts form what?
cruraof the diaphragm
how is innervation of diaphragm formed? how is the phrenic nerve related to this?
Pleuropericardial membranes contain cardinal veins AND myoblasts migrating through diaphragm
Myoblasts pull ventral rami (C3-C5) with them.
Phrenic subsequently lies on fibrous pericardium
what is a congenital diaphragmatic hernia?
Viscera bulge into pleural cavity
Lung maturation may be delayed; polyhydramnios may be present
diaphragm doesnt close !
Left side typically impacted (80%)
Can be corrected at birth
