Flashcards in Lecture 17: Establishing the Body Cavities and Formation of the Diaphragm Deck (29):
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
The brain and tail regions grow quicker than the rest of the body, causing the embryo to fold into itself around the yolk sac
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
What embryonic coelem is called after lateral folding is complete
Mesoderm lining the anterior body wall
somatic mesoderm layer
Suspends the gut tube (former yolk sac) within the periteneal cavity from dorsal side in caudal, foregut, midgut, hindgut
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
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
dorsal mesentery of the esophagus
muscular growth of lateral body wall
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.
After lateral folding, this is the remaining communication between the gut-tube and the yolk sac/amnion vesicle
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
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)