Development Of ody Cavities, Respiratory, And Digestive Systems

Question 1

Intraembryonic coelom

Answer 1

. Forms as space btwsplanchnic and somatic layers of lat. plate mesoderm
. Subdivided into pericardial, pleural, and abdominopelvic cavities

Question 2

When is transverse folding of embryo complete?

Answer 2

end of Week 4

Question 3

Lateral body wall folds vs. lateral splanchnic folds

Answer 3

. 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

Question 4

Dorsal mesentery

Answer 4

. Where parietal and visceral serous membranes are continous w/ one another
. Suspends gut tube from post. Body wall
. Derived from splanchnic mesoderm

Question 5

Ventral mesentery

Answer 5

. Present along foregut
. Persists in area of future stomach and liver
. Derives from septum transversum

Question 6

Septum transversum

Answer 6

. Thick plate mesoderm proliferates in space btw thoracic cavity and yolk sac
. Partially separates thoracic and abdominopelvic cavities

Question 7

Pericardioperitoneal canals

Answer 7

. Bilateral openings in septum transversum on either side of foregut
. Lung buds from gut tube project into these canals

Question 8

Pleuropericardial folds

Answer 8

. 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

Question 9

Pleuropericardial membranes

Answer 9

. 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

Question 10

Formation of thoracoabdominal diaphragm

Answer 10

. 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

Question 11

Congenital diaphragmatic hernia

Answer 11

. 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

Question 12

Parasternal hernias

Answer 12

. Small defects in muscle fibers of diaphragm permit intestinal loops to enter chest btw sternal and costal parts of diaphragm

Question 13

Esophageal hernias

Answer 13

. Congenitally short esophagus causes upper stomach to remain in thorax

Question 14

Endoderm in gut tube

Answer 14

. Forms epithelial lining of GIa nd respiratory tracts

Question 15

Splanchnic mesoderm in gut tube gives rise to ___

Answer 15

. . Smooth muscle, CT of GI and respiratory tracts
. Organs that arise as outpouching of these tracts
. Dorsal mesentery of gut tube

Question 16

When does Vitelline duct incorporate into umbilical cord and degenerate w/ yolk sac?

Answer 16

Months 2-3

Question 17

Epithelial lining in gut tube evolution

Answer 17

. Lining proliferates and temporarily occluded lumen

. Growth of tube and apoptosis causes re-canalizations of tube by week 9

Question 18

Stomodeum

Answer 18

. Primitive oral cavity

. Gets separated from gut tube by oropharyngeal membrane that ruptures in week 4

Question 19

Proctodeum

Answer 19

. 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

Question 20

Respiratory diverticulum

Answer 20

. Endodermal outpouching off ventral aspect of foregut
. Elongates to form trachea
. Splits into R/L lung buds that are surrounded by splanchnic mesoderm

Question 21

Bronchial buds

Answer 21

. From lung buds
. Form R/L primary bronchi
. Continue to branch to form respiratory tree

Question 22

What regulates growth of respiratory tree via biomolecular signaling

Answer 22

Splanchnic mesoderm

Question 23

Tracheoesophageal fistula

Answer 23

. Abnormal/incomplete separation of trachea from esophageal foregut
. Identified shortly after birth when infant chokes or regurgitates milk while feeding

Question 24

Maturation of fetal respiratory system

Answer 24

. 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

Question 25

When does stomach growth start to appear?

Answer 25

Week 4

Question 26

Dorsal mesogastrium

Answer 26

. Subdivision of dorsal mesentery | . Suspends stomach from post. Body wall

Question 27

Ventral mesogastrium

Answer 27

. Subdivision of ventral mesentery . Suspends stomach from ventral wall . Encloses developing liver

Question 28

Stomach rotations during embryonic development

Answer 28

. 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

Question 29

Lesser peritoneal sac formation

Answer 29

. Forms as longitudinal rotation of stomach pulls ventral mesogastrium to the right and dorsal mesogastrium to left . Creates space post. Tot stomach

Question 30

Greater omentum formation

Answer 30

. 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

Question 31

Less omentum and falciform ligament derive from ____

Answer 31

Ventral mesogastrium

Question 32

Hepatic diverticulum

Answer 32

. 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

Question 33

Outgrowth of embryonic bile duct forms ___

Answer 33

Gallbladder and cystic duct

Question 34

Liver formation

Answer 34

. 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

Question 35

Bare area of liver

Answer 35

. Location where liver contacts inf. Surface of diaphragm and visceral and parietal peritoneal membranes fuse together

Question 36

Epiploic foramen

Answer 36

. Allows continuity btw greater and lesser peritoneal sacs | . Hepatoduodenal ligament on inf. Rim

Question 37

Pancreas formation

Answer 37

. 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

Question 38

Spleen formation

Answer 38

. Develops btw 2 layers of dorsal mesogastrium btw stomach and dorsal body wall

Question 39

Small and large intestine formation

Answer 39

.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

Question 40

Volvulus

Answer 40

. from abnormal gut rotations . Portion of gut twists about it’s mesentery . May cause bowel obstruction or ischemia in affected segment

Question 41

Meckel’s diverticulum

Answer 41

. 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

Question 42

Omphacele

Answer 42

. 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