GI Flashcards
Foregut develops into
Pharynx to duodenum
Midgut develops into…
duodenum to transverse colon
Hindgut develops into…
Distal transverse colon to the rectum
Developmental Defect of Anterior Abdominal Wall Due to Failure of
Rostal Fold Closure:
Lateral Fold Closure:
Caudal Fold Closure:
Rostal Fold Closure: Sternal Defects
Lateral Fold Closure: Omphalocele, Gastroschisis
Caudal Fold Closure: Bladder Exstrophy
Duodenal atresia What is it? Genetics? Presentation XR
Failure to Recanalize
Trisomy 21 (Down Syndrome)
Early bilious vomiting with proximal stomach distention
“Double Bubble” on XR
Jejunal, Ilial, or Colonic Atresia
What causes them?
Vascular accident (apple peel atresia)
Timing of midgut development
6th week: Midgut Herniates through umbilical ring
10th week: Returns to abdominal cavity and rotates around SMA
Gastroschisis
What is it?
Peritoneum?
Extrusion of the abdominal contents through the abdominal folds; not covered by peritoneum
Omphalocele
What is it?
Peritoneum?
Persistance of herniation of abdominal contents into umbilical cord; covered by peritoneum
Most common Tracheoesophageal anomaly?
Esophageal atresia with distal tracheoesophageal fistula (85%)
Esophageal atresia with distal tracheoesophageal fistula Presentation XR Cyanosis? Clinical test?
Drooling, choking, vomiting with first feeding
Air in stomach visible on XR (TEF allows air into stomach)
Cyanosis secondary to laryngospasms (to avoid reflux-related aspiration)
Clinical test: failure to pass NG tube into stomach
H type Tracheoesophageal anomaly
Fistula alone
CXR in pure atresia type Tracheoesophageal anomaly?
In pure atresia (esophageal atresia only) CXR shows gasless abdomen
Congenital Pyloric Stenosis What causes it? Presentation? Physical exam? Treatment Occurrence? More often in...
Hypertrophy of pylorus Nonbilious projectile vomiting at 2 weeks of age Palpable olive mass in epigastric region Surgical incision Occurs 1/600 live births More often in first born males
Pancreas Derived from
Foregut
Ventral Pancreatic bud contributes to
Pancreatic head and main pancreatic duct
Uncinate process of pancreas formed by the
Ventral bud alone
Dorsal pancreatic bud becomes
Body, tail, isthmus and accessory pancreatic duct
Annular Pancreas
What is it?
What may it cause?
Ventral pancreatic bud abnormally encircles 2nd part of duodenum
May cause duodenal narrowing
Pancreas divisum
Ventral and dorsal parts of pancreas fail to fuse at 8 weeks
Where does the spleen arise from?
What kind of tissue is this?
Where does it get its blood supply from?
Arises in mesentery of stomach
Mesodermal tissue
Supplied by foregut (celiac artery)
Do retroperitoneal structures have a mesentery?
No
Injuries to retroperitoneal structures can cause
Blood or gas accumulation in the retroperitoneal space
List of Retroperitoneal Structures
"SAD PUCKER" Suprarenal gland (adrenal) Aorta and IVC Duodenum (2nd and 3rd parts) Pancreas (except the tail) Ureters Colon (descending and ascending) Kidneys Esophagus (lower 2/3) Rectum (lower 2/3)
Falciform Ligament
Connects
Structures Contained
Derivative of
Connects liver to abdominal wall
Contains ligamentum teres hepatis (from fetal umbilical vein)
Derivative of ventral mesentery
Hepatoduodenal Ligament
Connects
Structures Contained
Connects liver to duodenum
Contains portal triad
Portal Triad
Hepatic Artery, Portal Vein, Common Bild Duct
Omental Foramen
Name
What is it?
What is inside of it?
Epiploic Foramen of Winslow
Connects Greater and Lesser Sacs
Hepatoduodenal Ligament is inside of it
Pringle Maneuver
Compression of Hepatoduodenal ligament in omental foramen to control bleeding
Gastrohepatic Ligament Connects? Structures contained? Separates? Surgery?
Connects Liver to lesser curvature of the Stomach
Contains gastric arteries
Separates greater and lesser sacs on the Right
May be cut during surgery to access lesser sac
Gastrocolic Ligament
Connects?
Structures contained?
Part of?
Connects greater curvature of stomach to transverse colon
Contains gastroepiploic arteries
Part of greater omentum
Gastrosplenic Ligament
Connects?
Structures contained?
Function?
Connects greater curvature of stomach to the spleen
Contains short gastrics and Left gastroepiploic vessels
Separates greater and lesser sacs on the left
Splenorenal Ligament
Connects?
Structures contained?
Connects Spleen to Posterior Abdominal Wall
Splenic artery and vein. Tail of pancreas
Layers of Gut Wall
From Inside to Outside: “MSMS”
Mucosa, Submucosa, Muscularis Externa, Serosa (when intraperitoneal)/Adventitial (when retroperitoneal)
Layers of Gut Mucosa and function of each layer
Epithelium (absorption), Lamina Propria (support), Muscularis Mucosa (motility)
What is included inside the submucosa?
Submucosal Nerve Plexus (Meissner’s)
Glands
What is included inside the Muscularis externa?
Myenteric Nerve Plexus (Auerbach’s)
Ulcers extend into
submucosa, inner or outer muscular layers
Erosions extend into
Mucosa only
Frequency of basal electric rhythm?
Stomach
Duodenum
Ileum
Stomach: 3 waves/min
Duodenum: 12 waves/min
Ileum: 8-9 waves/min
Histology of the Esophagus
Non-Keratinized Stratified Squamous Epithelium
Histology of the Stomach
Gastric Glands
Histology of the Duodenum
Villi and Microvilli
Brunner’s Glands (in submucosa)
Crypts of Lieberkuhn
Histology of the Jejunum
Plicae Circulares
Crypts of Lieberkuhn
Histology of the Ileum
Peyer’s Patches (lamina propria, submucosa)
Plicae Circulares (proximal ileum)
Crypts of Lieberkuhn
Largest # of goblet cells in SI
Histology of the Colon
Crypts by no villi
Numerous goblet cells
Branches of the abdominal Aorta that supply GI structures branch in which direction?
Anteriorly
Branches of the abdominal Aorta that supply non-GI structures branch in which direction?
Laterally
SMA Syndrome
Transverse portion (3rd part) of Duodenum entrapped between SMA and Aorta –> Intestinal Obstruction
Level of Celiac Trunk
T12
Level of SMA
L1
Level of Left Renal Artery
L1
Level of IMA
L3
Bifurcation of Abdominal Aorta occurs at what level?
L4
Foregut Artery Parasympathetic Innervation Vertebral Level Structure supplied
Celiac
Vagus
T12/L1
Stomach to proximal duodenum, Liver, Gallbladder, Pancreas, Spleen (mesoderm)
Midgut Artery Parasympathetic Innervation Vertebral Level Structure supplied
SMA
Vagus
L1
Distal duodenum to proximal 2/3 of transverse colon
Hindgut Artery Parasympathetic Innervation Vertebral Level Structure supplied
IMA
Pelvic
L3
Distal 1/3 of transverse colon to upper portion of rectum
Splenic flexure
Bend between transverse and descending colon
Watershed region
Branches of Celiac Trunk
Common Hepatic, Splenic, Left Gastric
Strong anastomoses in stomach blood supply
L and R Gastroepiploics
L and R Gastrics
Poor anastomoses in stomach blood supply
Short Gastrics (if splenic artery is blocked)
Collateral circulation if abdominal aorta is blocked?
Internal Thoracic (mammary) –> Superior epigastric ↔ Inferior epigastric –> External iliac
Celiac Trunk –> Superior pancreaticoduodenal ↔ Inferior pancreaticoduodenal – SMA
SMA –> Middle Colic ↔ Left Colic –> IMA
IMA –> Superior Rectal ↔ Middle and Inferior Rectal –> Internal Iliac
Portosystemc Anastomoses
L Gastric Vein ↔ Esophageal Vein –> Azygos
Paraumbilical Vein ↔ Superficial and Inferior Epigastric (below umbilicus) and Superior Epigastric and Lateral Thoracic (above umbilicus)
Superior Rectal ↔ Middle and Inferior Rectal
SMV and IMV drain into
Portal Vein
Varices of Portal HTN
Varices of “Gut, Butt, and Caput”
Esophageal varices, Internal hemorrhoids, Caput medusae
Surgical treatment of Portal HTN
“TIPS” Transjugular Intrahepatic Portosystemic Shunt between Portal Vein and Hepatic Vein percutaneously
What is the Pectinate (Dentate) Line
Where endoderm (hindgut) meets ectoderm
Above the pectinate line What kind of hemorrhoids? What kind of cancer? Arterial Supply Venous drainage
Internal Hemorrhoids
Adenocarcinoma
Superior Rectal Artery from IMA
Superior Rectal Vein –> IMV –> Portal Vein
Below the pectinate line What kind of hemorrhoids? What kind of cancer? Arterial Supply Venous drainage
External Hemorrhoids
Squamous Cell Carcinoma
Inferior Rectal Artery from Internal Pudendal
Inferior Rectal Vein –> Internal Pudendal Vein –> Internal Iliac –> IVC
Internal Hemorrhoids
Innervation?
Pain?
Lymphatic drainage?
Visceral Innervation, therefore NOT painful
Drained by Deep Nodes
External Hemorrhoids
Innervation?
Pain?
Lymphatic drainage?
Somatic Innervation (inferior rectal branch of pudendal nerve) and therefore Painful Drained by Superficial Inguinal Lymph Nodes
Apical Surface of hepatocytes face
Bile Canaliculi
Basolateral Surface of hepatocytes face
Sinusoids
Zones of Liver
What is each one vulnerable to?
I: periportal –> Affected 1st by viral hepatitis
II: intermediate
III: pericentral vein (centrilobular)
Affected 1st by ischemia, Contains P450 system, most sensitive to toxin injury, site of alcoholic hepatitis
Common Hepatic Duct
Formed from
Goes to
R and L Hepatic Ducts
Joins Cystic duct to form Common Bile Duct
Common Bile Duct
Formed from
Goes to
Cystic Duct + Common Hepatic Duct
Joins Main Pancreatic Duct at Ampulla of Vater in Duodenum
Ampulla of Vater
Where the Main Pacreatic Duct joins the Common Bile Duct in the 2nd part of the Duodenum
Sphincter of Oddi
Sphincter around ampulla of vater
Gallstones lodged in ampulla of Vater block
Both bile and pancreatic ducts
Tumors that arise near the head of the pancreas near the duodenum can cause
Obstruction of the common bile duct
Organization of Vessels in Femoral Region
Lateral to Medial to find your “NAVEL”
Nerve, Artery, Vein, Empty space, Lymphatics
Femoral Triangle contains
Femoral Vein, Artery, and Nerve
Femoral Sheath
Location
Contents
3-4cm below inguinal ligament
Contains femoral vein, artery, and canal (deep inguinal lymph nodes) but not the femoral nerve
Relation between IVC and the Aorta
IVC is to the R of Aorta in MRI/CT
Contents of Inguinal Canal
Ilioinguinal nerve
Male: Spermatic Cord
Female: Round Ligament
Diaphragmatic Hernia
Definition
Think what kind of pt?
Most common kind of DH?
Abdominal structures enter the thorax
May occur in infants a a result of defective development of pleuroperitoneal membrane
Most commonly a Hiatal Hernia (stomach herniates through esophageal hiatus of diaphragm)
Sliding Hiatal Hernia
Frequency?
Results in what?
Most common hiatal hernia
GE junction is displaced upwards resulting in a hourglass stomach
Paraesophageal Hernia
GE junction is normal
Fundus protrudes into the thorax
Indirect Inguinal Hernia Goes through Location Occurs in what kind of pt? Follows path of? What is it covered by?
Goes through internal (deep) inguinal ring, external (superficial) inguinal ring and into the scrotum.
Enters internal inguinal ring lateral to the inferior epigastric artery
Occurs in male infants owing to failure of processus vaginalis to close (from hydrocele)
Follows path of descent of the testes
Covered by all 3 layers of spermatic fascia
Direct Inguinal Hernia Definition Location Occurs in what kind of pt? Goes through What is it covered by?
Protrudes through inguinal (Hesselbach’s) Triangle
Bulges directly through abdominal wall medial to inferior epigastric artery
Older men
Goes through external (superficial) inguinal ring only
Covered by external spermatic fascia
Location of Direct vs Indirect Inguinal Hernias?
“MDs don’t LIe”
Medial to inferior epigastric = Direct
Lateral to inferior epigastric = Indirect
Femoral Hernia Location Goes through Most common in Leading cause of
Protrudes below inguinal ligament
Goes through Femoral Canal below and lateral to pubic tubercle
Most common in Women
Leading cause of bowel incarceration
Hesselbach’s Triangle
Inferior epigastric vessels
Lateral border of rectus abdominis
Inguinal ligament
Gastrin
Source
Location of Source
Action
G Cells in Antrum of stomach
↑ Gastric H secretion (through ECL cells that release Hist)
↑ Growth of gastric mucosa
↑ Gastric motility
Gastrin
↑ by
↓ by
What syndrome produces ↑ Gastrin secretion?
↑ by stomach distention, alkalinization, AA (esp Phenylalanine and Tryptophan), peptides, vagal stimulation
↓ by stomach ph < 1.5
↑↑ in Zollinger-Ellison Syndrome
Chronic Proton Pump Inhibitors (PPI) lead to
↑ Gastrin production
Cholecytokinin Source Location of Source Action Regulation
I cells in the duodenum and jejunum
↑ pancreatic secretion (via muscarinic pathways) and gallbladder contraction
↓ gastric emptying
Relaxes sphincter of Oddi
CCK secreted in response to ↑ FA and AA in duodenum
Secretin Source Location of Source Action Regulation
S cells in duodenum
↑ pancreatic bicarb secretion, bile secretion
↓ gastric acid secretion
Secretion ↑ w/ acid and FA in duodenum
Pancreatic enzymes function at what pH
Basic pHs
Somatostatin Source Location of Source Action Regulation Affects Re Growth?
D cells in pancreatic islets and GI mucosa
↓ gastric acid and pepsinogen secretion, pancreatic and small intestine fluid secretion, gallbladder contraction, insulin and glucagon release
Secretion is ↑ by acid
Secretion is ↓ by vagal stimulation
Antigrowth hormone (inhibits digestion and absorption of substances needed for growth)
Glucose Dependent Insulinotropic Peptide AKA Source Location of Source Exocrine Endocrine Regulation
Gastric Inhibitory Peptide (GIP) K cells in duodenum and jejunum Exocrine: ↓ Gastric H secretion Endocrine: ↑ insulin release Secretion is ↑ by FA, AA, and oral glucose
Vasoactive Intestinal Polypeptide Source Location of Source Action Regulation
Parasympathetic ganglia in sphincters, gallbladder and SI
↑ intestinal water and electrolyte secretion and ↑ relaxation of intestinal smooth muscle and sphincters
Secretion is ↑ by distention and vagal stimulation
Secretion is ↓ by adrenergic input
VIPoma
Kind of cells
Presentation
non-α, non-β islet pancreatic tumors secrete VIP
“WDHA”
Copious Watery Diarrhea, HypoK, and Achlorhydria (no gastric acid produced)
Nitric Oxide
Actions in GI tract
Especially present in
Implicated in what disorder
Smooth muscles relaxation
Especially in lower esophageal sphincter
Loss of NO secretion is implicated in achalasia
Motilin Location of Source Action Regulation Agonists? Uses of agonists?
Small Intestine
Produced migrating motor complexes
Secretion ↑ in fasting state
Agonists like erythromycin used to stimulate intestinal peristalsis
Intrinsic Factor
Source
Location of Source
Action
Parietal Cells in Stomach (Body)
Vit B12 binding protein
Where is Vit B12 absorbed?
Bound to IF in terminal ileum along with bile acids
Autoimmune destruction of parietal cells leads to
Chronic gastritis and pernicious anemia
Gastric Acid Source Location of Source Action Regulation
Parietal Cells in Stomach
↓ stomach pH
Secretion ↑ by Hist, ACh, Gastrin
Secretion ↓ Somatostatin, GIP, prostaglandins, secretin
Gastrinoma
Gastrin secreting tumor that causes high levels of acid secretion and ulcers
Pepsin Source Location of Source Action Regulation
Chief Cells in Stomach (Body)
Protein digestion
Secretion is ↑ by vagal stimulation and local acid
Activation of pepsinogen
Converted to pepsin in presence of H+
Bicarb Source Location of Source Action Regulation
Mucosal cells of stomach, duodenum, salivary glands, pancreas and Brunner’s Glands (in the duodenum)
Neutralizes acid
Secretion is ↑ from pancreatic and biliary secretion with secretin
Mucus that covers the gastric epithelium traps what?
Traps bicarb
Saliva
Secreted from
Stimulated by
Parotid, Submandibular and Sublingual glands
Supplied by sympathetic (β –> cAMP) and parasympathetic activity (M –> IP3)
Components of Saliva with function
Amylase digests starch
Bicarb neutralizes bacterial acids
Mucin lubricates food
Tonicity of Saliva
Normally hypotonic because of absorption but more isotonic with higher flow rates (less time for absorption)
How would Atropine affect parietal cells vs. G cells
Atropine –/ parietal cells
Atropine leaves G cells unaffected because the Vagus nerve releases GRP, not ACh to activate them
Brunner’s Glands
Location
Function
Hypertrophied in…
Duodenal submucosa
Secrete Alkaline mucus
Hypertrophied in peptic ulcer disease
Receptors on Parietal Cells
ACh –> M3 –> Gq –> IP3 –> ATPase
Gastrin –> CCKB –> Gq –> IP3 –> ATPase
Hist –> H2 –> cAMP –> ATPase
Prostaglandins/misoprostol Receptors –> Gi –/ cAMP
Somatostatin Receptors –> Gi –/ cAMP
Pancreatic Secretions
Tonicity of Fluid
How does [electrolyte] change with flow?
Isotonic fluid
Low flow –> High [Cl]
High flow –> High [HCO3]
Pancreatic Secretions
Names and Roles
α amylase –> Starch digestion (secreted in active form)
Lipase. Phospholipase A, Colipase –> fat digestion
Proteases
Trypsinogen –> Activation of proenzymes (including trypsinogen)
Pancreatic Proteases
Names
Secreted as…
Trypsin, Chymotrypsin, Elastase, Carboxypeptidase
Secreted as proenzymes (zymogens)
What converts trypsinogen into trypsin
Enterokinase/enteropeptidase and then trypsin itself
Where is enterokinase/enteropeptidase secreted from?
Duodenal mucosa
Salivary Amylase
Role
MoA
Yields
Starts digestion
Hydrolyzes α(1-4) linkages to yield disaccharides (maltose and α-limited dextrins)
Pancreatic Amylase
Concentrated in
MoA
Highest concentration in duodenal lumen
Hydrolyzes starch to oligosaccharides and disaccharides
Oligosaccharide Hydrolase
Location
Role
MoA
At brush border of intestines
Rate limiting step in carbohydrate digestion
Produces monosaccharides from oligo- and disaccharides