Development of the Coelomic Cavity

▪During _____ week -Coelomic spaces appear within lateral embryonic mesoderm and ________ mesoderm -Fuse into a single horseshoe shaped cavity ▪Intraembryonic coelom

3rd , cardiogenic

Innervation of the diaphragm ▪During _____th week -Septum transversum lies opposite 3rd - 5th cervical somites ▪During _____th week -Myoblasts from somites invade septum bringing nerve fibers that join to form phrenic nerves ▪During _____th week -Diaphragm is at level of thoracic somites ▪During ____th week -Diaphragm is at level of 1st lumbar vertebra ▪As four parts of diaphragm fuse _________ invades other three parts ▪Costal border receives sensory fibers from lower intercostal nerves due to muscular ingrowth from lateral body wall

4, 5, 6, 8, mesenchyme from septum transversum

▪Pericardioperitoneal canals -Lie lateral to proximal foregut -Dorsal to septum transversum ▪Plate of mesodermal tissue between thoracic cavity and omphaloenteric duct ▪Future central tendon of diaphragm -Growth of bronchial buds into canals forms pair of membranous ridges ▪_______ -Superior to developing lungs -Separate pericardial from pleural cavities ▪________ -Inferior to developing lungs Separate pleural from peritoneal cavities

Cranial pleuropericardial folds, Caudal pleuroperitoneal folds

· Describe the common malformations that occur during descent of the testes o _______ - hidden testes § ______—most commonly within inguinal canal § Most common defect in neonates, especially those born prematurely

Cryptorchidism, Undescended testes

Development of Diaphragm extended -Muscular ingrowth from lateral body walls ▪Formed by growth of lungs and pleural cavities into lateral body walls and splitting them into two layers -External layer that becomes ________ -Internal layer that contributes to ________ -Also results in costodiaphragmatic recesses

abdominal wall, diaphragm

▪Pleuroperitoneal folds -Enlarge and become membranous ▪Pleuroperitoneal membranes -Separate pleural cavities from peritoneum -Produced as developing lungs invade the body wall -Attached dorsolaterally to _______ -Extend ventromedially to fuse with ________

abdominal wall, septum transversum and dorsal mesentery of esophagus

o Congenital epigastric hernia -

bulging of anterior abdominal wall (▪between xiphoid process and umbilicus), bowel not exposed to amniotic fluid

· Describe the development of the dorsal and ventral mesenteries and their importance relative to peritoneal cavity and diaphragm o The dorsal and ventral mesenteries divide the peritoneal cavity into right and left halves, but the ventral mesentery disappears except where it is attached to the caudal part of the foregut (stomach and proximal duodenum). The peritoneal cavity then becomes a continuous space. The arteries supplying the primordial gut: _______ pass between the layers of the _______ which suspends the_______ to the posterior abdominal wall

celiac artery, superior mesenteric artery, and inferior mesenteric artery; dorsal mesentery; foregut, midgut, and hindgut

o Diaphragm: § Formed from four embryonic structures a Septum transversum → _________ b Pleuroperitoneal Membranes (_______) c Dorsal Mesentery of the Esophagus - _______ d Body Wall → _________

central tendon and gives rise to mesenchyme that migrates out to form most of the diaphragm muscle; minimal adult contribution, crura of the diaphragm, peripheral diaphragm (muscular ingrowth)

o Diaphragm 2: a Body Wall → peripheral diaphragm (muscular ingrowth) § Pleural cavity erodes downward a bit to form ________ § The diaphragm is innervated by the phrenic nerve (C3-5) because the _______; the costal border also receives sensory fibers from ________ nerves due to the muscular ingrowth from the lateral body wall

costodiaphragmatic recesses, septum transversum originally lies opposite cervical somites 3-5, lower intercostal

o Gastroschisis - congenital fissure of anterior abdominal wall § Failure of _____ to fuse § Bowel is exposed to_____

lateral body folds, amniotic fluid

· Describe the development of the extra- and intraembryonic coelom (see past lectures also)

o Extraembryonic coelom: § Extraembryonic coelomic spaces appear in the extraembryonic mesoderm and fuse to form one extraembryonic coelom that surrounds amnion o Intraembryonic coelom: § Intraembryonic coelomic space appears in the lateral mesoderm and splits it to form the somatopleure and splachnopleure

o Cranial pleuropericardial folds - separate the _________

pericardial from pleural cavities

Embryonic folding ▪Head fold relocates heart and pericardial cavity ventrally and anterior to foregut ▪Pericardial cavity opens into ________ -Pass dorsal to foregut ▪Lateral embryonic folding causes _________ to be suspended in peritoneal cavity from dorsal abdominal wall Dorsal mesentery

pericardioperitoneal canals, caudal foregut, midgut, and hindgut

o Caudal pleuropericardial folds - separate the_______

pleural from peritoneal cavities

· Describe the common malformations that occur during development of the abdominal wall and diaphragm o Posterolateral defect of the diaphragm - the pleural cavity and the peritoneal cavity remain continuous § Failure of ______ to fuse with the other three parts of the diaphragm § Diaphragm extends into lung space and lungs ______ § Associated with _____ can be life threatening.. bc lung dvel probs, usually unilateral

pleuroperitoneal membranes, do not develop properly, congenital diaphragmatic hernia (most common on left posterolateral side)

o Eventration of diaphragm - diaphragm musculature defect where abdominal contents can _____ § Caused by problems with _____ myoblast resulting in weak diaphragm muscle

push on aponeurotic sheet and cause it to extend into thorax, septum transversum

o The dorsal and ventral mesenteries divide the peritoneal cavity into ________, but the ventral mesentery disappears except where it is attached to the _______ The peritoneal cavity then becomes a _______.

right and left halves, caudal part of the foregut (stomach and proximal duodenum), continuous space

o Diaphragm: § Formed from four embryonic structures

septum transversum, pleuroperitoneal membranes, dorsal mesentary of the esophagus, muscular ingrowth from lateral body walls

o Congenital hiatal hernia -

stomach herniates through overly large esophageal hiatus

· Describe the embryologic development of the peritoneal cavity, abdominal mesenteries, diaphragm and ventral body wall o Peritoneal cavity: § During horizontal folding, the limbs of the intraembryonic coelom are brought together on the ________ aspect of the embryo. The________ degenerates in the region of the future peritoneal cavity. The peritoneal cavity is continuous with extraembryonic coelom at the umbilicus until the_______ when the intestines return to the abdomen

ventral, ventral mesentery, 11th week

o Abdominal mesenteries: § Mesenteries are double layers of parietal peritoneum that begin as an extension of viscera peritoneum. In the abdominal region the umbilicus gets in the way ________ resulting in ventral mesenteries for the ______ but not the midgut or hindgut. The dorsal mesenteries extend the ________.

ventrally (everywhere except cranially), foregut, full length

· Describe the structures that subdivide the intraembryonic coelom into its derivate cavities o The intraembryonic coelom becomes ___________

§ Pericardial cavity (for heart) § Two pericardioperitoneal cavities (pleura for lungs) § Peritoneal cavity (for gut)

▪Describe the development of the extra- and intraembryonic coelom ▪Describe the structures that subdivide the intraembryonic coelom into its derivate cavities ▪Describe the embryologic development of the peritoneal cavity, abdominal mesenteries, diaphragm and ventral body wall

▪Describe the development of the dorsal and ventral mesenteries and their importance relative to peritoneal cavity and diaphragm ▪Describe the common malformations that occur during development of the abdominal wall and diaphragm ▪Describe to path of the testes from the abdomen into the scrotum ▪Describe the common malformations that occur during descent of the testes