Development Of ody Cavities, Respiratory, And Digestive Systems Flashcards
Intraembryonic coelom
. Forms as space btwsplanchnic and somatic layers of lat. plate mesoderm
. Subdivided into pericardial, pleural, and abdominopelvic cavities
When is transverse folding of embryo complete?
end of Week 4
Lateral body wall folds vs. lateral splanchnic folds
. Body wall folds from somatic mesoderm plus overlying ectoderm, fuses closing ventral body wall, parietal serous membrane from somatic mesoderm
. Splanchnic folds from splanchnic mesoderm plus underlying endoderm fuses forming gut tube, visceral serous membrane from splanchnic mesoderm
Dorsal mesentery
. Where parietal and visceral serous membranes are continous w/ one another
. Suspends gut tube from post. Body wall
. Derived from splanchnic mesoderm
Ventral mesentery
. Present along foregut
. Persists in area of future stomach and liver
. Derives from septum transversum
Septum transversum
. Thick plate mesoderm proliferates in space btw thoracic cavity and yolk sac
. Partially separates thoracic and abdominopelvic cavities
Pericardioperitoneal canals
. Bilateral openings in septum transversum on either side of foregut
. Lung buds from gut tube project into these canals
Pleuropericardial folds
. Bilateral mesodermal folds projecting from lat. wall of thoracic cavity ant. To lung buds and post. To developing heart
. Expand med. to come pleuropericardial membranes
Pleuropericardial membranes
. Engulf phrenic n. And common cardinal v.
. Fuse at midline w/ roots of lungs
. Fusions divides thoracic cavity into pericardial cavity and 2 pleural cavities
. Incorporate into fibrous pericardium
Formation of thoracoabdominal diaphragm
. Pleuroperitoneal folds (mesodermal) project into caudal ends of pericardioperitoneal canals and extend med. and ventrally
. Pleuroperitoneal membranes form post. Part of Diaphragm in week 7
. Membranes, septum transversum, and mesentery of esophagus fuse o separate pleural and peritoneal cavities
. Myoblasts (C305 somites) migrate along lat. wall and into membranes to form muscular part
. Fibers of C3-5 spinal nn. Migrate in myoblasts to form phrenic n.
. Septum transversum becomes central tendon
Congenital diaphragmatic hernia
. Most common diaphragm hernia
. Failure of pleuroperitoneal membranes to close off pericardioperitoneal canals
. Abdominal contents protrude into abdominal cavity and compress heart and lungs
. High mortality from units not forming well
Parasternal hernias
. Small defects in muscle fibers of diaphragm permit intestinal loops to enter chest btw sternal and costal parts of diaphragm
Esophageal hernias
. Congenitally short esophagus causes upper stomach to remain in thorax
Endoderm in gut tube
. Forms epithelial lining of GIa nd respiratory tracts
Splanchnic mesoderm in gut tube gives rise to ___
. . Smooth muscle, CT of GI and respiratory tracts
. Organs that arise as outpouching of these tracts
. Dorsal mesentery of gut tube
When does Vitelline duct incorporate into umbilical cord and degenerate w/ yolk sac?
Months 2-3
Epithelial lining in gut tube evolution
. Lining proliferates and temporarily occluded lumen
. Growth of tube and apoptosis causes re-canalizations of tube by week 9
Stomodeum
. Primitive oral cavity
. Gets separated from gut tube by oropharyngeal membrane that ruptures in week 4
Proctodeum
. Primitive lower part of anal canal
. Separated from the distal end of gut tube by cloacal membrane that breaks down to form anal opening in week 7
Respiratory diverticulum
. Endodermal outpouching off ventral aspect of foregut
. Elongates to form trachea
. Splits into R/L lung buds that are surrounded by splanchnic mesoderm
Bronchial buds
. From lung buds
. Form R/L primary bronchi
. Continue to branch to form respiratory tree
What regulates growth of respiratory tree via biomolecular signaling
Splanchnic mesoderm
Tracheoesophageal fistula
. Abnormal/incomplete separation of trachea from esophageal foregut
. Identified shortly after birth when infant chokes or regurgitates milk while feeding
Maturation of fetal respiratory system
. Not developed before 26 weeks
. Proliferation of primary resp. Alveoli in weeks 26-40 (have enough after week 26 to survive)
. Surfactant from type II cells made
. Need adequate pulmonary vasculature for survival
When does stomach growth start to appear?
Week 4
Dorsal mesogastrium
. Subdivision of dorsal mesentery
. Suspends stomach from post. Body wall
Ventral mesogastrium
. Subdivision of ventral mesentery
. Suspends stomach from ventral wall
. Encloses developing liver
Stomach rotations during embryonic development
. Rotates 90 degree clockwise around longitudinal axis causing left side to face ant. And right post.
. Curvatures from as new left side and grow faster than right side
. Rotates around AP axis so pyloric part shifts to the right and upward and cardiac portion moves left and downward
. Stomach ends diagonal from upper left to lower right
Lesser peritoneal sac formation
. Forms as longitudinal rotation of stomach pulls ventral mesogastrium to the right and dorsal mesogastrium to left
. Creates space post. Tot stomach
Greater omentum formation
. AP rotation has dorsal mesogastrium form double-layered sac that drapes ventral to transverse colon and SI
. Layers fuse together and w/ mesentery of colon
Less omentum and falciform ligament derive from ____
Ventral mesogastrium
Hepatic diverticulum
. Endoermal outpouching off foregut in week 3
. Forms liver and gallbladder
. Hepatocytes from endoderm
. Kupffer cells and CT from mesoderm of septum transversum
. Bile duct from narrowing of initial diverticulum
Outgrowth of embryonic bile duct forms ___
Gallbladder and cystic duct
Liver formation
. liver bud attaches to ant. Body wall via ventral mesentery
. Liver enlarges and ventral mesentery thins becoming falciform ligament
. Longitudinal rotation of foregut has liver swing right
. Contacts parietal peritoneum overlying IVC and peritoneal membranes fuse so liver anchors to post. Body wall
Bare area of liver
. Location where liver contacts inf. Surface of diaphragm and visceral and parietal peritoneal membranes fuse together
Epiploic foramen
. Allows continuity btw greater and lesser peritoneal sacs
. Hepatoduodenal ligament on inf. Rim
Pancreas formation
. Ventral pancreatic bud branches from hepatic diverticulum
. Dorsal pancreatic bud that branches directly from foregut
. Longitudinal rotation of foregut pulls ventral bud post. To duodenum
. Dorsal and ventral buds fuse together and pancreas pressed against post. Body wall
. Visceral and parietal peritoneum fuse and pancreas is secondarily retroperitoneal
. Main pancreatic duct from ventral bud
. Accessory pancreatic duct from dorsal bud
Spleen formation
. Develops btw 2 layers of dorsal mesogastrium btw stomach and dorsal body wall
Small and large intestine formation
.Elongation of gut tube/mesentery forms primary intestinal loop
. Loop remains in connection w/ Vitelline duct at loop apex
. Loop rotates 90 degrees clockwise around sup. Mesenteric a. (SMA)
. Week 10 intestine loops return to body cavity and rotate 180 degrees about SMA
. Prox. Jejunum 1st part to return
. Distal colon pushed L forming descending colon
. Cecum rotates caudally to final position
. De/ascending mesocolon fuses w/ dorsal body wall to become 2ndary retroperitoneal
. Mesentery transverse colon fuses w/ dorsal greater omentum
Volvulus
. from abnormal gut rotations
. Portion of gut twists about it’s mesentery
. May cause bowel obstruction or ischemia in affected segment
Meckel’s diverticulum
. Blind outgrowth off ileum
. Asymptomatic usually
. Can become inflamed and have similar symptoms as appendicitis
. If it Attaches to body wall it can form volvulus
Omphacele
. Abdominal all defect
. Caused by guy viscera not returning to body cavity aftern herniation in umbilicus
. Intestinal loops or other viscera in sac formed by amnion outside body
. Occur in 1/3500 births
