Lecture 2: Body Folding and Cavities Flashcards
(23 cards)
Where does the intraembryonic coelom (cavity) appear?
Between the lateral plate of the mesoderm
*horse-shoe shaped
What does the intraembryonic coelom (cavity) divide?
Divides lateral mesoderm into:
1) Somatic (parietal) layer
2) Splanchnic (visceral) layer
What does the somatic (parietal) layer line?
Body wall
What does the splanchnic (visceral) layer line?
Body gut
Describe the consequences of cranial folding.
Cranial folding happens much faster compared to rest of the embryo, allowing:
1) Moves oropharyngeal membrane (future mouth) to correct position
2) Moves primordial heart and surrounding structures to correct position
3) Endoderm is incorporated into foregut
After cranial folding, what happens to the intraembryonic coelom?
Has 3 portions:
- Pericardial cavity (ventral)
- 2 Pericardioperitoneal canals (dorsal) on each side of foregut
Describe the consequences of caudal folding.
1) Primitive Streak now caudal to cloacal membrane
2) Moves cloacal membrane (future anus) to correct position
3) Endoderm is incorporated into hindgut
What folding is happening in the median plane?
Cranial/Caudal Folding
What folding is happening in the horizontal plane?
Lateral Folding
Describe the consequences of lateral folding.
Umbilical vesicle is compressed and pinches off.
Eventually the gut tube is enclosed.
What is gastroschisis?
Birth defect of the abdominal wall
- Baby’s intestines are found outside of the body right of umbilical cord (not midline)
- Organs are uncovered, which is bad because amniotic fluid is corrosive to the organs
What is congenital epigastric hernia?
Birth defect of the abdominal wall
- Midline bugle of abdominal wall
- Bowel is not exposed to amniotic fluid and is covered by skin
What is the function of the pericardioperitoneal canals?
Connects pericardial cavity to peritoneal cavity
What is the function of dorsal mesentery?
Suspends caudal foregut, midgut, and hindgut in peritoneal cavity
What does the septum transversum eventually become?
Central tendon of diaphragm
Where is the pericardioperitoneal canals located compared to the septum transversum?
Pericardioperitoneal canals is DORSAL to septum transversum
*and lateral to foregut
What is the function of the pleuropericardial folds?
Separates heart from lungs and lungs from each other
What is the function of the pleuroperitoneal folds?
Separates abdomen from lungs
With what structures do the pleuroperitoneal folds fuse with to close the canal?
Dorsal mesentery of esophagus and septum transversum
What are the function of myoblasts migrating into the pleuroperitoneal folds?
Completes closure of pleuroperitoneal folds
What embryological structures make up the diaphragm?
1) Septum transversum: central tendon
2) Pleuroperitoneal membranes: primordial diaphragm
3) Dorsal mesentery: median portion of diaphragm
4) Myoblasts: Crura of diaphragm
What innervates the diaphragm?
Phrenic Nerve (ventral rami C3-C5)
What is a congenital diaphragmatic hernia?
Defect of diaphragm
- Viscera will bulge into pleural cavity
- lung maturation may be delayed
- left side typically impacted
