Embryology Of The Gastrointestinal System

Front 1

The early gut tube is formed by what?

Back 1

Incorporation of part of the yolk sac during folding of the embryo

Front 2

Why is the vitelline duct maintained in the fetus?

Back 2

As a connection between the gut tube and the yolk sac

Front 3

Patterning of the regions of the digestive system is based on the orderly expression of what?

Back 3

Homeobox genes

Front 4

What transcription factors code for the esophagus, duodenum/pancreas, small intestine, and large intestine?

Back 4

SOX2 - esophagus
PDX1 - duodenum and pancreas
CDXC - small intestine
CDXA - large intestine

Front 5

In addition to regionalization, development of the gut tube includes what else?

Back 5

Continuous elongation
Herniation past the body wall
Rotation and folding for efficient packing
Histiogenesis of further maturation of epithelial lining

Front 6

What is derived from the endoderm of the gut tube?

Back 6

Epithelial lining
Glands

Front 7

What layers are derived from splanchnic mesoderm?

Back 7

Lamina propria
Muscularis mucosa
Submucosa
Muscularis externa
Serosa

Front 8

What three parts is the primitive gut tube divided into?

Back 8

Foregut
Midgut
Hindgut

Front 9

What suspends the primitive gut tube from the dorsal and ventral body walls?

Back 9

Dorsal and ventral mesentery

Front 10

What structures make up the foregut?

Back 10

Esophagus
Stomach
Liver
Gallbladder
Pancreas
Upper duodenum

Front 11

Branches of what vessel supply the foregut?

Back 11

Branches of the celiac artery

Front 12

What structures make up the midgut?

Back 12

Lower duodenum
Jejunum
Ileum
Cecum and appendix
Ascending colon
2/3 transverse colon

Front 13

Branches of what artery supply the midgut?

Back 13

Superior mesenteric artery

Front 14

What structures make up the hindgut?

Back 14

1/3 transverse colon
Descending colon
Sigmoid colon
Rectum
Upper part of anal canal

Front 15

Branches of what artery supply hindgut?

Back 15

Inferior mesenteric artery

Front 16

What is esophageal atresia?

Back 16

Narrowed or occluded esophagus due to incomplete recanalization, usually found in the lower 1/3

Front 17

What can be done to fix esophageal atresia?

Back 17

Colon interposition - take a section of colon and join it to the esophagus above and stomach below
Gastric tube esophagoplasty - Longitudinal segment taken from the stomach which is swung up into the chest to join the esophagus
Gastric transposition - Whole stomach is freed and moved into the chest

Front 18

The abdominal esophagus and stomach start as a straight tube. The __________ side of the tube grows rapidly, expands, and there is _____________ rotation of 90 degrees.

Back 18

Dorsal
Clockwise

Front 19

Due to the rotation, the left side of the stomach lies __________ and the right side lies ______________.

Back 19

Anterior
Posterior

*Left vagus becomes anterior vagal trunk and right vagus becomes posterior vagal trunk

Front 20

What is hypertrophic pyloric stenosis?

Back 20

Overgrowth of musculature at the sphincter regulating passage of food from stomach to duodenum. *Non-bilious projectile vomitting presents 2-3 weeks after birth*

Front 21

What is a duplication cyst?

Back 21

A tubular structure with an internal lining of GI epithelium, smooth muscle in its wall and adherence to some portion of the alimentary tract

Front 22

Where do the liver, gallbladder, and bile ducts develop?

Back 22

Ventral mesentery

Front 23

All foregut endoderm has the potential to express liver specific genes and to differentiate into liver tissue. What blocks expression where the liver should NOT be and what blocks the inhibiting factors where the liver should be?

Back 23

Blocked by unknown signals from the trunk mesoderm and ectoderm
These inhibiting factors are blocked in the area of the liver by FGF2 secreted by cardiac mesoderm and BMPs secreted by septum transversum

Front 24

Hepatic cords coalesce around extraembryonic veins to form what?

Back 24

Sinuosoids

Front 25

The gallbladder and cystic ducts are outgrowths of what common structure?

Back 25

The bile duct

Front 26

What fetal structure is the falciform ligament? Ligamentum teres hepatis?

Back 26

Obliterated Umbilical vein
Obliterated left umbilical vein

Front 27

What adult structure does the ductus venosus become after birth?

Back 27

Ligamentum venosum

Front 28

What is extrahepatic biliary atresia and what are its symptoms?

Back 28

Incomplete canalization of the bile duct
Jaundice - high bilirubin in blood
Dark urine - bilirubin filtered by kidney and excreted
Pale stool - no bilirubin being emptied into intestine
Treatment: surgical correction

Front 29

What is Menke's disease? Wilson's disease?

Back 29

Menke's - decreased ability to absorb copper
Wilson's - copper is not eliminated properly (kayser-fleishcer ring)

Front 30

What are PAX 4 and PAX 6?

Back 30

PAX4 - cells secretig insulin, somatostatin and pancreatic polypeptide
PAX6 - cells secreting glucagon

Front 31

What is annular pancreas and how is it caused?

Back 31

Ring around the duodenum causing an obstruction caused by the ventral and dorsal pancreatic buds forming around the duodenum

Front 32

Describe rotation of the foregut.

Back 32

Stomach moves to the left
Liver moves to the right
Right side of peritoneal cavity gets smaller

Front 33

What typically causes atresia/stenosis in the upper duodenum?

Back 33

Failure to recanalize

Front 34

What is apple peel atresia?

Back 34

10% of all atresias
Proximal jejunum
Intestine is short and portion distal to the defect is coiled around the mesenteric remnant
Associated with low body weight and other abnormalities

Front 35

When does rapid growth of the midgut begin?

Back 35

About 6 weeks

Front 36

T or F: Rapid growth of the midgut produces a normal physiologic hernia.

Back 36

True

*Gut loops into umbilical cord and rotates 90 degrees counter clockwise around superior mesenteric artery

Front 37

What happens to the midgut at around 10 weeks?

Back 37

The herniated loops return to the abdominal cavity and rotate an additional 180 degrees (270 total)

Front 38

What is malrotation?

Back 38

Partial rotation of midgut
Presents within first week as duodenal obstruction with bilious vomiting

Front 39

What is volvulus?

Back 39

Abnormal twisting of the intestine causing obstruction
Compromises intestine and blood flow

Front 40

What is an omphalocele?

Back 40

Herniation of abdominal contents through enlarged umbilical ring
Midgut loop fails to return to abdominal cavity and a pale shiny sac protrudes from base of umbilical cord

Front 41

What is gastroschisis?

Back 41

Failure of anterior abdominal wall musculature to close during folding

Front 42

What is a common triad of features for prune belly or Eagle-Barrett syndrome?

Back 42

Deficient or absent muscle of anterior abdominal wall
Urinary tract anomalies
Bilateral cryptorchidism

*Occurs almost exclusively in males

Front 43

What are the two hypotheses for the cause of prune belly syndrome?

Back 43

Urinary tract obstruction - leads to distention of bladder which causes ab damage and undescended testes

Primary mesodermal developmental defect - Insult between weeks 6 and 10 disrupting development of intermediate and lateral plate mesoderm

Front 44

What is an Ileal diverticulum (Meckel's diverticulum)? How does patient present?

Back 44

A small bulge in the small intestine
Remnant of vitelline duct that failed to close

Fecal discharge through umbilicus

Front 45

What is Hirschsprung's disease and what causes it?

Back 45

Congenital aganglionic megacolon
Failure of migration of the neural crest cells that form the colonic ganglion cells

*Functional obstruction

Front 46

In which part of the gut is Hirschsprungs most prevalent and why?

Back 46

Cranial parts 70%-80% descending and sigmoid colon

Decreased occurrence in proximal parts due to higher mortality rate

Front 47

How is Hirschsprungs disease treated?

Back 47

Surgery. Resect the part of the colon with ganglia and reconnect the good ends

Front 48

What does it mean to be primarily retroperitoneal?

Back 48

Any organ that developed outside the abdominal cavity which never had a mesentery to begin with (kidney)

Front 49

What does it mean to be secondarily retroperitoneal?

Back 49

Portions of the gut tube whose mesentery has fused with lining peritoneum

Front 50

What does it mean to be intraperitoneal?

Back 50

Organs with a mesentery

Front 51

The cloaca partitions into what?

Back 51

Urogenital sinus
Rectum

*Rathke fold and Tourneux fold

Front 52

What is anal agenesis?

Back 52

Anal canal ends as a blind sac below the pelvic diaphragm

Front 53

What is anorectal agenesis?

Back 53

Rectum ends as a blind puch above the pelvic diaphragm (most common)

Front 54

What is imperforate anus and what are the signs and symptoms?

Back 54

Absence or misplaced anal opening
No passage of first stool within 24 to 48 hours after birth
Stool passed by way of vagina, base of penis or scrotum, or urethra
Abdominal distention

Front 55

What is the prognosis for imperforate anus, rectourethral fistula, and rectovesical fistula?

Back 55

Imperforate - colostomy at birth, prognosis is excellent
Rectourethral - colostomy before repair period, long term prognosis for normal function is good
Rectovesical - have poorly developed sacral bones and sphincters, prognosis for normal bowels is poor