Development of the GI System Flashcards
Endoderm forms what part of the GUT
Mucosal Epithelium and GI glands (all only NOT lower 1/3 of anus)
Splanchnic Mesoderm forms what part of the GUT
CT
Vasculature
SM wall
Ectoderm forms what part of the GUT
Enteric Ganglia, N, and Glia (by neural crest cells)
Epithelium of lower 1/3 anus
Foregut
Esophagus, stomach, liver, gallbladder, pancreas, upper duodenum
Foregut Blood supply
Celiac Trunk
Midgut
Lower duodenum, Jejunum, Ileum, Cecum, Appendix, Ascending Colon, proximal 2/3 transverse colon
Midgut Blood supply
SUPERIOR MESENTERIC A.
Hindgut
Distal 1/3 transverse colon, Descending colon, Sigmoid colon, rectum, upper anal canal
Hindgut Blood supply
INFERIOR MESENTERIC A
Visceral Peritoneum
directly around each organ
Parietal Peritoneum
directly around the Peritoneal Cavity with includes the organs inside
Dorsal Mesentery Derivatives
Greater Omentum (gastrosplenic, Gastrocolic, Splenorenal Ligaments) SI mesentary Mesoappendix Transverse mesocolon Sigmoid Mesocolon
Ventral Mesentary Derivatives
LESSER UMENTUM ( hepatoduodenal, hepatogastric Ligaments)
Flaciform Ligament of Liver
Coronary Ligament of Liver
Triangular Ligament of Liver
Intraperitoneal Organs
organs in the mesentery, surrounded by the peritoneal cavity
EX: abd esophagus, liver, stomach, gallbladder, cecum, sigmoid, appendix, jejunum, Ileum
Retroperitoneal organs
organs outside the peritoneal cavity
Ex: thoracic esophagus, Rectum
Secondarly Retroperitoneal organs
organs that were initially in the mesentery (interperitoneal) and then fused with the body wall
EX: Ascending + Descending colon, Duodenum, most of Pancreas
ALL RETROPERITONEAL (INCLUDING SECONDARY)
SADPUCKER Suprarenal (Adrenal) Glands Aorta/ IVC Duodenum (2nd+3rd part) Pancreas (not tail) Ureter Kidneys Colon (ascending +descending) Esophagus - thoracic Rectum
How does the developing stomach rotate
Stomach rotates 90 degrees
LEFT= VENTRAL
RIGHT= DORSAL
Greater curvature- attached to greater omentum
Lesser curvature- attached to lesser omentum
Left Vagus N
Anterior Stomach
Right Vagus N
Posterior Stomach
Lesser sac
behind stomach
Greater Omentum
connects stomach to transverse colon
double layer of peritoneum
lesser Omentum
connects stomach to the liver and duodenum
double layer of peritoneum
Hypertrophic Pyloric Stenosis
What happens
narrowed opening from stomach to duodenum due to thickened muscle
- NCC dont migrate to ganglion enteric cells = sphincter cant relax
- muscularis externa hypertrophy = narrowing pyloric lumen
Hypertrophic Pyloric Stenosis Sx:
Sx: starts a few months after birth olive mass over right costal margin projectile vomiting few + smaller stools X gain weight, can loose weight
Where does the liver form from
Hepatic Diverticulum from GUT ENDODERM
GUT ENDODERM 3 parts
- connects to Foregut : common bile duct
- Endoderm: Hepatocytes, Bile ducts, Hepatic ducts
- Splanchnic mesoderm : stromal cells, Kupffer cells, stellate cells
Liver formation happens when
week 10, it takes over hematopoiesis
very love anomalies
Where does the Gallbladder and Bile duct from from
Cystic Diverticulum of the CYSTIC ENDODERM
- it outpatches from the common bile duct—> ventral mesentery +cyctic duct (connection to bile duct)
- Recanilzation of bile duct
- bile forms week 12
- right above the Ventral Pancreatic Fold
Biliary Atresia
Fibro-inflammatory obstruction of extra-hepatic bile duct
obliterated bile duct
SX: immediate jaundice in infants
white clay stool
Dark urine
12-19mo lifespan
How is the Pancrease form and from what
- inferior to the cystic diverticulum, 2 endodermal buds from FOREGUT form
- Ventral Pancreatic Bud: uncinate process and grows —> VENTRAL MESENTERY
- Dorsal Pancreatic Bud: Pancreatic Head, Body, and Tail and grows —-> DORSAL MESENTERY - both exocrine and endocrine portions form
- ducts fuse
Week 5 of pancreatic formation
The Ventral pancreas (under cystic diverticulum) migrates around posteriorly to the dorsal pancreas bud
- Ventral Pancreatic Duct= main Pancreatic duct + connects to Duodenum
- Dorsal Pancreatic Duct = Accessory Pancreatic Duct
Pancreas Divisum
Ventral and dorsal parts dont fuse by week 8
Sx: asymptomatic
prone to abd pain and pancreatitis
Having an accessory pancreatic duct
33% population
Annular Pancreas
Poor migration of pancreas = pancreatic ring around duodenum (2nd part) Sx: duodenal obstruction +necrosis Bilious Vomiting (in annulus is inferior to bile duct) Low birth weight
= basically the ventral pancreatic bud migrates some posteriorly and some anteriorly to the dorsal pancreatic bud forming a ring when it fuses
what does the spleen form from and what happens week 4
dervied from mesoderm
1. mesenchymal condensation in the dorsal mesogastrium
spleen formation week 5
fully formed
Midgut formation in general
week 6: herniates out from umbilicus
week 10: goes back to ABD
How does the midgut rotate week 6
week 6: rotated 90 degrees counterclockwise
- proximal part: right and convoluted
- distal left and develops cecum
How does the midgut rotate week 10
week 10: proximal portion of loop returns to abd going under the distal portion = 90 counterclockwise turn
- cecum : URQ
- ascending colon : anterior to duodenum
How does the midgut rotate week 11
week 11: distal portion of loop returns to the abd = 90 counterclockwise turn
- cecum: LRQ
- ascending colon : right side of abd.
Omphalocele
higher risk if trisomy 13 or 18
Hermiated bowel does not fully go back into abd
SX: herniation through the umbilicus, covered by perietal peritoneum
Gastroschiscis
Abnormal lateral body folding and fusion = wall weakness and bowel herniated
OR
CT of skin and hypaxial muscles of body wall doesnt form normally = wall weakness
Bowel not covered by parietal peritoneum
Meckel’s Diverticulum
Yolk sac (vitelline duct) connection to midgut doesnt go back to abd. = midgut is still connected to umbilicus SX: asymptomatic abd swelling, intestinal obstruction, GI bleeding
*basically a little string of midgut tissue connected to the body wall of the umbilicus
RULE OF 2 for all Sx:
Malrotation/ Non-Rotation of the Midgut loop
only completes first week 6 90 degree rotation
(still return to abd.)
Sx: left sided colon
right sided SI
= formation of Ladd Bands –> volvulus +duodenal obstruction
Reverse Gut Rotation
Initial midgut week 6 90 degree rotation is normal
other 2 are clockwise rotations
Sx: Duodenum : anterior to Transverse Colon
Volvulus
Bowel twists around its mesentary high risk of gut rotation anomalies CT= Coffee bean sign SX: acute, abd pain, Vomit, GI bleeding - can lead to bowel obstruction and Infarction
Cloaca separates to
part of hindgut and separates to rectum and urogenital sinus
how does the Hindgut form
- Urorectal septum (b/w hindgut and urogenital sinus) grows fork like extensions to separate the cloaca
- Cloaca becomes VENTRAL urogenital Sinus
DORSAL anorectal canal - Cloaca membrane ruptures = opens both parts to outside
Ventral Urogenital Sinus becomes the
bladder and urethra
how does the anus and rectus form
- anal rectal lumen closed by ENDOTHELIAL ANAL PLUG
- MESODERM around opening grows out and forms anal pit
- Anal pit is lined by ECTODERM
what does the Pectineal Line Divide
the hindgut and anal pit inside anal canal
1. Superior 2/3 : ENDODERM, IMA artery and Internal Iliac Artery - superior and middle rectal arteried
(RECTUM)
2. Inferior 1/3 : ECTODERM, Puedendal Artery - inferior rectal arteries
(ANUS)
Imperforate Anus
X anal opening, anal membrane (endoderm) is still there
there is low, intermediate and high malformation = due to LEVATOR ANI MUSCLES and pelvic bone
Abnormal Urorectal Septum : Rectovaginal
Females
rectum goes to vagina canal
Abnormal Urorectal Septum : Rectovestibular
Females
rectum opens at vaginal opening
Abnormal Urorectal Septum : Rectoperineal
Females and Males
rectum opens however ventral to the anus (so no anus in opening)
Abnormal Urorectal Septum : Rectovesical
Males
rectum opens into prostate
Abnormal Urorectal Septum : Rectourethral
Males
rectum opens into sperm canal to exit the penis
Hirschsprung’s Disease (congenital Aganglionic Megacolon)
NCC dont migrate = X Ganglionic plexus in GI
X peristalsis (COLON does not relax)
SX: hypertrophy of Intestinal wall proximal to aganglionic segment
Megacolon: dilated colon
X pass meconium - first poop of newborn
