Embryology GI (Funk) Flashcards
formation of the intraembryonic body cavity forms within what layer
lateral plate mesoderm
divides lateral plate into parietal (somatic) and visceral (splanchnic) mesoderm
body wall defects occur when what happens?
when the ventral body wall fails to fuse and viscera herniate through the defect
what is cantrell’s pentology
cleft sternum ectopic cordis gastroschisis or omphalocele diaphragmatic hernia (anterior) congenital heart defects
what are the dorsal mesentery derivatives
DORSAL MESENTERY DERIVATIVES: Mesoesophagus Greater omentum (gastrocolic, gastrosplenic, gastrophrenic ligaments) Splenorenal ligament Phrenicosplenic ligament Phrenicocolic ligament Mesentery proper Mesoappendix Transverse mesocolon Sigmoid mesocolon
what are the ventral mesentery derivatives
Lesser omentum (hepatogastric, hepatoduodenal ligaments)
Falciform Ligament
Coronary Ligaments
Right and Left Triangular Ligaments
what is a mesentery
double layer of peritoneum
provides pathway for vessels, nerves to organs
what is the function of the dorsal mesentery
suspends gut tube to posterior body wall
extends from caudal foregut to hindgut
what is the function of the ventral mesentery
suspends gut tube to anterior body wall
extends from caudal to foregut to proximal duodenum
what are the three types of peritonealization
primary retroperitoneal
secondary retroperitoneal
peritonealized
what are organs that are primary retroperitoneal
kidney
ureter
bladder
what are organs that are secondary retroperitoneal
parts 2-3 of duodenum
ascending colon
descending colon
pancreas
what are examples of organs that are peritonealized
stomach spleen parts 1 and 4 of duodenum jejunum ileum transverse and sigmoid colon
what is the septum transversum and what does it form in the adult
plate of mesoderm that separates the throacic and peritoneal cavities (forms from somites 3, 4 and 5)
will form bulk of diaphragm (muscle and central tendon)
note it does not
what do the pleuropericardial membranes separate in the embryo
pleural and pericardial cavities
what do pleuorperitoneal membranes separate in the embryo
pleural and and peritoneal cavities
what are the sources that contribute to the formation of the diaphragm
septum transversum
pleuroperitoneal membrane
the mesoderm of the diaphragm forms from what and what is the positional changes of the diaphragm
where does the diaphragm sit at week 8
cervical somites 3-5
differential growth of the body leads to a descent of the diaphragm into the thorax
by week 8 sitting at level of 1st lumbar vertebra
what is the motor innervation to the diaphragm
sensory?
motor - phrenic
sensory = phrenic n to central tendon
intercostal nn to muscu. diaphragm
what is a bochdalek defect
posterolateral defect –> incomplete formation of pleuroperitoneal membranes (often on left side)
small intestine or viscera herniate through
the lugns and heart are compressed
common cause of pulmonary hypoplasia
what is a morgagni defect
parasternal hernia
anterior defect in muscular portion of diaphragm
small and sometimes not detected until child is several years old
what are two causes of congenital diaphragmatic hernias
failure of pleuroperitoneal membranes to form
small gap between sternal and costal portion of diaphragm
what is eventration of the diaphragm
weakness of diaphragm due to failure of myotome migration (lack of muscle differentiation)
allows abdominal viscera to ballon into thoracic cavity
all three germ layers contribute to the formation of the gut tube. what do each of the three layers make
endoderm- epithelium and glands
mesoderm - CT and muscle
ectoderm– epithelium at ends of tubes (mouth, lower 1/2 of anal canal)
what comprises the foregut 8
Pharynx Esophagus Stomach ½ duodenum (parts 1 and 2) Spleen Pancreas Liver gallbladder
when does the oropharygneal membrane rupture
4th week
when does the cloacal membrane (anus) rupture
7th week
what comprises the mid gut 7
½ duodenum (parts 3 and 4)
Jejunum Ileum Cecum /appendix Ascending colon 2/3 transverse colon
what comprises the hindgut 5
distal 1/3 of transverse colon decending colon sigmoid colon rectum proximal anal canal
during what week does the esophagus become partly obliterated
week 5
recanalizes by week 8
what is the cause of esophageal atresias and stenoses and tracheoesophageal fistula
malformation of tracheoesophageal septum
–> leads to development of esophageal fistula
incomplete recanalizaiton of distal esophagus
-during week five the canalization occurs in which the endoderm proliferates very rapidyly and produces an epithelial plug
by week 8 it will recanalize
incomplete –> stenosis
absent recanalizaiton–> atresia
what is the cause of a congenital hiatal hernia
esophagus fails to elongate, pulls stomach through diaphragm into thorax
what is the rotation of the stomach
rotates 90 degreses clockwise aroudn longitudinal axis (greater curvature is now left, lesser curvature is not right)
rotates around its anterioposterior axis
pyloric part moves upward and to right
fundus part moves down and to left
what is going on with the omental bursa as the stomach is developing
as the stomach rotates it stretches dorsal mesentery and the omental bursa comes to lie inferior and posterior to the stomach
during later development the layers of the greater omentum fuse
what is the cause of pyloric stenosis
hypertrophy of smooth muscle around pyloric sphincter
forcible vomiting of stomach contents after eating
what does the spleen form from
mesenchymal cells within the two layers of dorsal mesogatrium
what is the hepatic diverticulum
an outgrowth from second portion of duodenum
endoderm derived portion of the liver is what?
mesoderm portion is what ?
what does the liver function as during 2nd month
when does bile formation begin
endoderm–> perenchyma
mesoderm –> stroma
hematopoietic organ–> 2nd month
bile formation–> 12 week
what does the gallbladder from from
because of rotation of the gut, where does the bile duct pass in relation to the duodenum
forms from evagination of bile duct
rotation–> bile duct passes posterior to duodenum
what is the development of the pancreas like? from what portion of the gut
how does rotation of the gut effect pancreatic development
arises from two endodermal outgrowths of duodenum (ventral and dorsal buds)
ventral bud forms lower portion of head and uncinate process
dorsal bud forms most of pancreas
what is the main pancreatic duct derived from
ventral pancreatic duct and distal dorsal pancreatic duct
what is the accessory pancreatic duct derived from
proximal part of dorsal pancreatic duct
what is the problem with accessory pancreatic tissue
can degrade surrounding tissue
what is annular pancreas
“ring” around the duodenum
bifid ventral pancreatic duct
during rotation the bifid bud encircles the duodenum
after fusion of the pancreas the annular tissue can constrict the duodenum
what occurs in gestational diabetes
fetal insulin=secreting cells are exposed to high levels of maternal glucose
as a result, insulin-secreting cells hypertrophy and increase rate of insulin secretion
what does the duodenum derive from
caudal end of foregut (parts 1 and 2)
rostal end of the midgut (parts 3 and 4)
stomach rotates –> pulls duodenum superiorly and to the right
pancreas grows rapidly causing C-shape
what is the cause of duodenal stenosis
how does it present
how does a pregnant mother present
failure to recanalize
usually affects parts 3 and 4
digested food + bile are forcibly vomited (green-colored)
distended epigastrium due to overfilled stomach
infant is not swalloing amniotic fluid so mother presents with polyhydramnios
what happens during week 5 of midgut development
midgut loop forms
what happens during week 6 of midgut formation
midgut loops physiologically herniates through the umbilical ring (gut around the superior mesenteric artery herniates) into the extraembryonic cavity
what occurs later after the week 6 and before week 10 in midgut development
what happens in terms of peritonealization to the midgut at this point
the primary intestinal loop undergoes a rotation of 270 degrees counterclockwise
mesentery proper becomes twisted and the ascending and descending colon becomes secondarily retroperitoneal
what happens in midgut develpement around week 10-12
midgut loop retracts into the abdominal cavity
jejunum first and lies on the left side
cecum returns last and lies in the upper quadrant
what is the path of the cecum after it retracts back into the abdomen
returns last and lies in the upper right quadrant
the cecum then descends to lie in the lower right quadrant
the appendix forms after the midgut returns to the abdomen as the cecum is descending
thus retrocecal position
what is omphalocele
results from failure of midgut to return to abdominal cavity
tssue protrudes through umbilicus and is covered by the amniotic membrane***
often prognosis of this is poor and is associated with other congential abnormalities
what is gatroschisis
results when gut herniates through weakness in body wall
typically occurs lateral to umbilicus (to right)
usually results from incomplete fusion of ventral body wall during folding
herniated bowel is not covered by amniotic membrane *** bathed in amniotic fluid
what is an umbilical hernia
occurs when gut herniates into umbilical cord after returning to abdominal cavity
loops of bowel herniate through an imperfectly closed umbilicus (along midline)
herniated tissue covered by skin subcutaneous tissue
what is meckel’s diverticulum
what does it present similar to
persistence of vitelline duct
RULE OF 2’s
occurs in 2% of population
2x more likely in males
found within distal 2 feet of ileum
usually about 2 inches long
2 percent become symptomatic before age of 2
2 types of tissue (gastric and pancreatic)
presents very similar to appendicitis
what occurs with malrotation of the gut
may results in volvulus (twisting of intestine)
or potential loss of blood supply
can stenoses and atresia occur in the midgut
yes anywehre along intestine
resulting from vascular compromise or failure to re-canalize
what is the problem with failure of the ascending colon to become retroperitoneal
results in long mesocolon which may allow for abnormal movements and potentially volvulus of the colon
retrocolic hernia (entrapment of small intestine behind colon) may also result
what is the cloaca and what is it lined with
what does it contribute to forming
distal most portion of the gut tube
endoderm lined cavity which will contribute to formation of the hindgut and urogenital system
what does the urorectal septum do
divides cloaca into urogenital sinus and anorectal canal
when does the cloacal membrane rupture
during week 7
what is the pectinate line demarcating
marks division between ectoderm/endoderm
what is Hirschprung’s disease
aka congenital mesocolon
failure of neural crest cells to migrate into caudal large intestine or rectum
absence of parasymapthetic ganglia b/c neural crest cells typically form into parasympathetic nerves
soo…. the area proximal to the paralyzed portion will have a build up of fecal matter
fistulas and atresias of the cloaca result from what?
improper formation of urorectal septum
what do rectourethral and rectovaginal fistulas result from ?
anterior displacement of the hindgut
rectoanal atresias (abnormally closed or absent) result from what?
loss of vascular supply or failure of recanalization
how does an imperforate anus occur
failure of cloacal membrane to degenerate
