Embryology Flashcards
what is the intraembryonic body caivty derived from
lateral plate mesoderm
what does the lateral plate mesoderm divide into
parietal and visceral mesoderm
what does parietal mesoderm form? visceral?
parietal serous membranes
visceral becomes visceral serous membranes and muscles of organs
what causes fusion of the body wall ventrally
body folding
when does the intraembryonic cavity become completely separate from extra embryonic cavity
week 12
what causes body wall defects
ventral body wall fails to fuse and viscera herniate through defect
what are examples of body wall defects
ectopic cordis
gastroschisis
bladder/cloacal exstrophy
cantrell’s pentology
what are the characteristics of cantrell’s pentology
cleft sternum ectopic cordis gastroschisis diaphragmatic hernia congenital heart defects
what is a mesentery
double layer of peritoneum
what is derived from the dorsal mesentery
mesoesophagus greater omentum splenorenal lig phrenicosplenic lig phrenicocolic lig mesentery proper mesoappendix transverse mseocolon sigmoid mesocolon
what suspends the gut tube
ventral mesentary to anterior body wall
dorsal mesentary to posterior body wall
what are derivatives of ventral mesentery
lesser omentum
falcifom lig
coronary and triangular lig
what organs are primary retroperitonealized
kidneys, ureters and bladder
what organs are secondary retroperitonealized
duodenum, ascending, descending colon, pancreas
what organs are peritonealized
stomach, spleen, parts 1 and 4 of the duodenum, jejunum, ileum, transverse and sigmoid colon
what are the two main steps in partitioning of the intraembryonic body cavity
septum transversum
pleuropericardial and pleuroperitoneal membranes
what separates the thoracic and peritoneal cavities
plate of mesoderm (septum transvedsum)
what does the septum transversum for
bulk of diaphragm, muscle and central tendon
what is still left after septum transversum
leaves pericardioperitoneal canals on either side of the foregut
what does the pleuropericardial membranes separate
pleural and pericardial cavities
what does the pleuroperitoneal membranes separate
separate pleural and peritoneal cavities
what somites form the mseoderm of the diaphragm
cervical somites 3-5
what causes descent of diaphragm into thorax
differential growth
by week 8, the diaphragm is at what vertebral level
1st lumbar vertebra
What is the innervation of the diaphragm
motor- phrenic
sensory- phrenic n to central tendon, intercostal nn to muscular diaphragm
What is a bochdalek hernia
posterolateral defect, congenital diaphragmatic hernia
what causes bochdaleks hernia
incomplete formation of pleuroperitoneal membranes
small intestine or other viscera, herniate through defect into pleural cavity
lungs and heart are compressed, common cause pulmonary hypoplasia
what is a morgagni hernia
parasternal hernia, anterior defect in muscular portion of diaphragm, small sometimes not detected at very young ages
what is eventration of the diaphragm
weakness of diaphragm due to failure of myotome migration
allows abdominal visceral to “balloon” into the thoracic cavity
what germ layers contribute to formation of gut tube
endoderm- epithelium and glands
mesoderm- CT and smooth mm
ectoderm- epithelium at ends of tube
when do the rostral and caudal ends reopen
4th and 7th week
What are the portions of the gut
foregut, midgut and hindgut
what is included in the foregut
pharynx, esophagus, stomach, parts one and two of duodenum, liver, gallbladder, pancreas, spleen
what artery supplies most of foregut
celiac artery
what structures are included in midgut
3-4 duodenum, SI, cecum, appendix, ascending colon and proximal 2/3 transverse colon
what supplies most of midgut
SMA
what structures are included in hindgut
distal 1/3 transverse colon to upper anal canal
what artery supplies most of hindgut
inferior mesenteric a
when does the esophagus lumen become obliterated and then recanalize?
obliterate week5 and recanalize week 8
what are congenital anomalies of the esophagus and what causes them
atresias- no recanalization at all in week 8
stenosis- incomplete recanalization
both can also be caused by malformation of tracheoesophageal septum
what causes a congenital hiatal hernia
esophagus fails to elongate and pulls the stomach through diaphragm
describe the rotation of the stomach
stomach rotates 90 degrees clockwise pushing the greater curvature (dorsal) left and the lesser curvature (ventral) right
which way does the stomach orient around the anterioposterior axis
plyoric part moves upward to the right and cardiac down to the left
where is the omental bursa
inferior and posterior to the stomach
what is pyloric stenosis
hypertrophy of smooth m around pyloric sphincter
forcible vomiting of stomach contents after eating
what is the spleen derived from
mesenchymal cells within 2 layers of dorsal mesogastrium
what causes the spleen to be in ULQ
rotation of gut
What is the hepatic diverticulum
outgrowth from second portion of duodenum
what 2 germ layers form the liver and what parts
endoderm becomes parenchyma and mesoderm becomes stroma
when does the liver start functioning as a hematopoietic organ
2nd month
when does bile formation begin in liver
week 12
what forms the gall bladder
evagination of bile duct
where is the bile duct in relation to duodenum and why
posterior to duodenum because rotation of foregut
what does the pancreas arise from
2 endoermal layers of duodenum. ventral and dorsal buds
what leads to fusion of the pancreatic buds
rotation of duodenum
majority of the pancreas is derived from what bud
dorsal, the ventral forms lower portion of head and uncinate process
where is the main pancreatic duct derived form? accessory?
main is from ventral pancreatic and distal dorsal
accessory pancreatic duct is derived from proximal part of dorsal pancreatic duct
What can cause acessory pancreatic tissue
abnormal migration of tissue during gut rotation
What is a annular pancreas and what can be a result
bifid ventral pancreatic bud that encircles duodenum during rotation and can constrict duodenum after fusion
What occurs with maternal diabetes
fetal insulin secreting cells see high glucose and hypertrophy because of increased rate of insulin secretion
What portions of the gut gives rise to the duodenum
foregut (parts 1 and 2)
midgut (parts 3 and 4)
what happens in the 2nd moth to the duodenum
obliterated and recanalizes
how can you predict if a fetus has duodenal stenosis
polyhydramnios becuase baby cannot swallow
how can you predict at what level the duodenal stenosis is in an infant
if vomit is green most likely from 3rd/4th part because pass the ampulla
if vomit is white then most likely from 1st or 2nd part (milk)
how long is the midgut in comunication with yolk sac via vitelline duct
week 10 they separate
what happens with physiologic herniation of the midgut during week 6
gut around superior mesenteric a herniates through umbilical ring into extraembryonic cavity
what occurs during midgut rotation
primary intestinal loop undergoes 270 degree rotation counterclockwise resulting in a twisted mesentery proper and ascending/descneding colons become secondarily retroperitoneal
when do the herniated intestinal loops of midgut retract
during week 10
where does the cecum retract to initially and then how does it change
retracts to URQ but then descends and the appendix thus gets dragged behind it
what is omphalocele
failure of midgut to return to abdominal cavity
tissue will protrude through the umbilicus and is covered in amniotic membrane
What is gastroschisis
when gut herniates through weakness in body wall
lateral to umbilicus
results from incomplete fusion of ventral body wall during folding
NOT covered by amniotic membrane
What is an umbilical hernia
results when gut herniates into umbilical cord after returning to abdominal cavity
skin covering hernia
What is Meckel’s diverticulum
persistence of vitelline duct- connection to umbilicus
2% population, 2x more likely in ales
2 feet of ileum, 2 inches long
2% symptomatic BEFORE AGE 2
What can malrotation of midgut result in
volvulus and potential loss of blood supply
what can lead to stenoses and atresias of the midgut
failure to recanalize
What results from a failure of the ascending colon to becom retroperitoneal
long mesocolon allowing for abnomral movements and potential volvulus of colon
or retrocolic hernia (entrapment of SI behind colon)
what germ layer lines the hindgut
endoderm
What structure forms the hindgut
cloaca
what are the steps of hindgut development
urorectal septum divides cloaca into urogenital sinus and anorectal canal
cloacal membrane ruptures week 7
What marks the division between ectoderm/endoderm
pectinate line
What is Hirschprungs disease
failure of neural crest cells to imigrate into caudal large intestine or rectum
What results from improper formation of urorectal septum
fistulas and atresis of cloaca
What causes rectourethral and rectovaginal fistulas
anterior displacement of hindgut
what can cause rectoanal atresias
loss of vascular supply or failure of recanalization
what causes an imperforate anus
failure of cloacal membrane to degenerate