Lecture 17: Establishing the Body Cavities and Formation of the Diaphragm Flashcards Preview

Structures > Lecture 17: Establishing the Body Cavities and Formation of the Diaphragm > Flashcards

Flashcards in Lecture 17: Establishing the Body Cavities and Formation of the Diaphragm Deck (29):

Intraembryonic Coelem

Formed at beginning of fourth week. Vesicles in the lateral mesoderm coalesce, forming a horse-shoe shaped cavity


Functions of Intraembryonic Coelem

Continuous with extra-embryonic coelem (the space external to the yolk-sac), gives space for organs to grow into


Cranial-Caudal folding

The brain and tail regions grow quicker than the rest of the body, causing the embryo to fold into itself around the yolk sac


Lateral folding

The lateral edges of the germ disk fold towards each other, ventrally, caused by rapid growth of amnion and somites. Fuse in the midline. The yolk sac (made of endoderm) pinches off and becomes narrow and more tubular.


Regions of yolk sac after lateral folding

Foregut, midgut, hindgut


Mesoderm lining periteneal cavity

splanchnic mesoderm layer


Periteneal Cavity

What embryonic coelem is called after lateral folding is complete


Mesoderm lining the anterior body wall

somatic mesoderm layer


Dorsal Mesenteries

Suspends the gut tube (former yolk sac) within the periteneal cavity from dorsal side in caudal, foregut, midgut, hindgut


Ventral mesenteries

Suspends the gut tube from ventral side, only present in proximal foregut (stomach and doedunum)



A double layer of periteneum that connects organs to the body wall. Vessels and nerves travel through the mesentery, especially those supplying the gut


parts of embryonic body cavity

Pericardial cavity, peritoneal cavity, connected by 2 pericardial-peritoneal canals


Arterial supply to fore-gut

celiac artery


arterial supply to midgut

Superior mesenteric artery


Arterial supply to hindgut

Inferior mesenteric artery


Physiological herniation of midgut

The midgut sticks into the extraembryonic coelem from the intraembryonic coelem until week 10, at which point the intestine retreats into the intraembryonic coelem. After lateral folding the communication between the two coelems becomes much narrower, and only exists in one cross-section.


Parts of the diaphragm

The Septum transversum
Pleuroperitoneal membrane
dorsal mesentery of the esophagus
muscular growth of lateral body wall


Septum Transversum

Thick plate of mesodermal tissue, occupies the space between the pericardial cavity and the omphaloenteric duct. Originally were cranial to the developing heart, after cranio-caudal folding migrates to sit to above location.


Omphaloenteric duct

After lateral folding, this is the remaining communication between the gut-tube and the yolk sac/amnion vesicle


Pleuropericardial folds

Folding in of the tissue between the pleural cavities (where lungs will form) which are inferior and posterior to the pericardial cavity (where heart will form). They separate the former pleuroperitoneal canals from the pericardial cavity, and create the pleural space.


Pleuropericardial membrane, origin and what they contain

Pleuropericardial folds become these membranes. These membranes contain common cardinal veins and phrenic nerves


What does septum transversum become?

the central tendon of the diaphragm


pleuroperitoneal membrane

Originates from pleuroperitoneal folds, grows in from lateral body wall to merge with septum transversum and dorsal mesentery of esophagus. There are small openings closed by migrating myoblasts


Crura of diaphragm

pair of muscle bundles that originate from myoblasts that migrate into the dorsal mesentary


dorsal mesentary contributes what to diaphragm

Forms median part of diaphragm


Lateral Body wall muscular ingrowth contribution to diaphragm

Forms the peripheral edges of the diaphragm


Formation of costo-diaphragmatic recesses

Also called costophrenic angles, formed by descending pleural space during development


Innervation of diaphragm

2 phrenic nerves (motor&sensory, C3, C4, C5). Spinal nerves migrate with septum transversum, lengthen to 30 cm as diaphragm descends during development.
Intercostal nerves to the body wall (sensory)


Congenital Diaphragmatic Hernia

1/2200 newborns, 85% of time on left side bc that side closes later than right side; viscera herniates into thorax