GI - First Aid Flashcards
The foregut is the…
pharynx to the duodenum.
The midgut is the…
duodenum to the proximal 2/3 of the transverse colon.
The hindgut is the…
distal 1/3 of the transverse colon to the anal canal above the pectinate line.
Failure of rostral fold closure causes…
stenral defects.
Failure of lateral fold closure causes…
ompholocele and gastroschisis.
Failure of caudal fold closure causes…
bladder exstrophy.
Duodenal atresia is due to…
failure to recanalize. (associated with trisomy 21)
Jejunal, ileal, and colonic atresia is due to…
vascular accident. (apple peel atresia)
During the 6th wk, the midgut will…
herniate through the umbilical ring.
During the 10th wk, the midgut will…
return to the abdominal cavity and rotate around the SMA.
Gastroschisis
extrusion of abdominal contents through abdominal folds; not covered by peritoneum
Ompholcele
persistence of herniation of abdominal contents into umbilical cord; sealed by peritoneum
The most common tracheoesophageal anomaly is…
esophageal atresia with distal tracheoesophageal fistula. (EA w/ TEF)
EA w/ TEF results in…
drooling, choking and vomiting with the first feed.
TEF allows…
air to enter the stomach (visible on CXR).
Cyanosis is seen in EA w/ TEF secondary to…
laryngospasm (to avoid reflux-related aspiration).
Clinical test for EA w/ TEF
failure to pas NG tube into stomach
In H-type tracheoesophageal anomaly, it is…
a fistual alone (no atresia).
In pure atresia (no TEF), the CXR shows…
gasless abdomen.
Congenital pyloric stenosis is when…
hypertrophy of the pylorus causes obstruction.
Features of congenital pyloric stenosis
-palpable “olive” mass in epigastric region -nonbilious projectile vomiting at 2-6 wks old (common in firstborn males)
Treatment for congenital pyloric stenosis
surgical incision
The pancreas is derived from the…
foregut.
Ventral pancreatic buds contribute to…
the pancreatic head and main pancreatic duct.
The uncinate process is formed by..
the ventral bud alone.
The dorsal pancreatic duct becomes…
everything else (body, tail, isthmus and accesory duct).
Annular pancreas
ventral pancreatic bud abnormally encircles the 2nd part of the duodenum and forms a ring of pancreatic tissue that may cause duodenal narrowing
Pancreas divisum
ventral and dorsal parts fail to fuse at 8 wks
The spleen arises in…
the mesentery of the stomach (hence, mesodermal) but is supplied by the foregut (celiac artery).
Retroperitoneal structures include GI structures that…
lack a mesentery and non-GI structures.
Injuries to retroperitoneal structures can cause…
blood or gas accumulation in the retroperitoneal space.
Retroperitoneal structures (10)
SAD PUCKER 1. Suprarenal (adrenal) glands 2. Aorta and IVC 3. Duodenum (2nd through 4th parts) 4. Pancreas (except tail) 5. Ureters 6. Colon (descending and ascending) 7. Kidneys 8. Esophagus (lower 2/3) 9. Rectum
Falciform ligement connects…
liver to anterior abdominal wall.
Falciform ligament contains…
the ligamentum teres hepatis (fetal umbilical vein).
Falciform ligament is a derivative of…
ventral mesentery.
The hepatoduodenal ligament connects the…
liver to the duodenum.
Structures in the hepatoduodenal ligament
Portal triad: Hepatic artery, portal vein and common bile duct
Pringle Maneuver
the hepatoduodenal ligament may be compressed between the thumb and index finger placed in the omental foramen to control bleeding.
The hepatoduodenal ligament borders the…
omental foramen which connects the greater and lesser sacs.
Gastrohepatic ligament
-connects liver to lesser curvature -contains gastric arteries -separates greater and lesser sacs on the right -may be cut during surgery to access the lesser sac
Gastrocoli ligament
-connects greater curvature to transvere colon -contains gastroepiploic arteries -part of greater omentum
Gastrospenic ligament
-connects greater curvature and spleen -contains short gastrics and left gastroepiploics -separates greater and lesser sacs on the left
Splenorenal ligament
-connects spleen to posterior abdominal wall -conatins splenic artery, splenic vein and tail of pancreas
Layers of the gut wall (inside to outside)
- Mucosa 2. Submucosa 3. Muscularis externa 4. Serosa (adventitia)
The mucosa contains…
epithelium (for absorption) lamina propria (for support) muscularis mucosa (for motility)
The submucosa contains…
the submucosal nerve plexus (Meissner).
The muscularis externa contains…
myenteric nerve plexus (Auerbach).
The outer layer of the gut wall is called the…
serosa when intraperitoneal and adventitia when retroperitoneal.
Ulcers extend into…
the submucosa, inner or outer muscular layer.
Erosions only are in..
the mucosa.
Frequencies of basal electric rhythm
Stomach - 3 waves/min Duodenum - 12 waves/min Ileum - 9 waves/min
Histology of the Esophagus
nonkeratinized stratified squamous epithelium
Histology of the Stomach
gastric glands
Histology of the Duodenum
-villin and microvilli -Brunner glands (submucosa) -cryps of lieberkuhn
Histology of the Jejunum
-plicae circulares -crypts of lieberkuhn
Histology of the Ileum
-Peyer patches (lamina propria, submucosa) -plicae circulares -crypts of Lieberkuhn
The ileum has the largest number of…
goblet cells in the small intestine.
Histology of the colon
-crypts of lieberkuhn -NO villi -numerous goblet cells
Arteries supplying GI structures branch from the aorta…
anteriorly while those supplying non-GI structures branch laterally.
Superior Mesenteric Artery (SMA) Syndrome occurs when…
the transverse portion (3rd segment) of the duodenum is entrapped between the SMA and aorta causing intestinal obstruction.
Artery supply, PNS innervation and vertebral level of the foregut
-Celiac artery -vagus nerve -T12/L1
Artery supply, PNS innervation and vertebral level of the midgut
-SMA -vagus nerve -L1
Artery supply, PNS innervation and vertebral level of the hindgut
-IMA -pelvic nerve -L3
Organs included in foregut supplies
-liver -gallbladder -pancreas -spleen
In the hindgut, the splenic flexure is…
a watershed region.
Branches of the celiac trunk
-common hepatic -splenic -left gastric (these consitute the main blood supply of the stomach)
If the splenic artery is blocked, the short gastrics have…
poor anastomoses.
In the gastric circulation, strong anostomses exist between…
-left and right gastroepiploics -left and right gastrics
If branches off the abdominal aorta are blocked, these arterial anastomoses compensate (4):
- superior epigastric w/ inferior epigastric 2. superior pancreaticoduodenal w/ inferior pancreaticoduodenal 3. middle colic w/ left colic 4. superior rectal w/ middle/inferior rectal
3 Portosystemic anastomosis sites
- Esophagus 2. Umbilicus 3. Rectum (show varices and seen w/ portal HTN)
Clinical sign of anastomosis at the esophagus is…
esophageal varices. Anastomosis between left gatric and esophageal.
Clinical sign of anastomosis at the umbilicus is…
caput medusae. Anastomosis is between paraumbilical and small epigastric veins of wall
Clinical signs of anastomosis at the recutm is…
anorectal varices. Anastomosis is between superior rectal and middle/inferior rectal.
Treatment for Portosystemic anastomoses/varices is…
transjugular intrahepatic portosystemic shunt (TIPS) between the portal vein and hepatic vein which can relieve portal HTN by shunting blood to the systemic circulation.
The pectinate line is formed where…
the endoderm (hindgut) meets the ectoderm.
Pathology that occurs above the pectinate line includes…
internal hemorrhoids and adenocarcinoma.
Arterial supply above the pectinate line is from…
the superior rectal artery (a branch of the IMA). Venous drainage is to the superior rectal vein (to the IMV to the portal system). (Lymphatic drainage to deep nodes)
Internal hemorrhoids receive….
visceral innervation and are therefore not painful.
Pathology below the pectinante line includes…
external hemorrhoids, anal fissures and SCC.
Arterial supply below the pectinate line is from..
the inferior rectal artery (branch of the pudendal artery). Venous drainage is to the inferior rectal vein (to internal pudendal vein to internal iliac to IVC). (lymphatic drainage to superficial inguinal nodes)
External hemorrhoids recieve…
somatic innervation (inferior rectal branch of pudendal nerve) and are therefore painful.
Anal fissue is a…
tear in the anal mucosa below the pectinate line. Features include pain while pooping and blood on toilet patper. Occur posteriorly bc this area is poorly perfused.
The apical surface of hepatocytes faces…
bile canaliculi.
The basolateral surface of hepatocytes faces…
sinusoids.
Zone I of the hepatocyte
Periportal zone -affected 1st by viral hepatitis (and ingested toxins)
Zone II of the hepatocyte
Intermediate Zone
Zone III of the hepatocyte
Pericentral vein Zone -affected 1st by ischemia -contains CYP450s -most sensitive to metabolic toxins -site of alcoholic hepatitis (acetaminophen toxicity)
Gallstones that reach the ampulla of vater can…
block both the bile and pancreatic ducts.
Tumors that arise in the head of the pancreas can…
cause obstruction of the common bile duct.
Organization of the Femoral Region
Lateral to Medial: Nerve, Artery, Vein, Lymphatics
The femoral triangle contains….
the femoral vein, artery and nerve.
The femoral sheath is a…
fascial tube 3-4 cm below the inguinal ligament. It contains the femoral vein, artery and canal (deep inguinal LNs) but NOT the nerve.
A hernia is a…
protrusion of peritoneum through an opening.
Diaphragmatic hernia
abdominal structures enter the thorax; may occur in infants as a result of defective development of pleuroperitoneal membrane
A diaphragmatic hernia is most commonly a…
hiatal hernia in which the stomach herniates upward through the esophageal hiatus of the diaphragm.
A sliding hiatal hernia is the..
most commono type. The GE junction is displaced upward. **hourglass stomach
A paraesophageal hernia is when…
the fundus protrudes into the thorax; GE junction is normal.
An indirect inguinal hernia goes through…
the internal inguinal ring, external inguinal ring and into the scrotum. Enters the internal inguinal ring lateral to the inferior epigastric artery.
An indiriect inguinal hernia occrus in…
infants owing to failure of the processus vaginalis to close and is much more common in males.
An indirect inguinal hernia follows…
the path of testicular descent and is covered by all 3 layers of spermatic fascia.
A direct inguinal hernia protrudes through the…
inguinal (Hesselbach) triangle. It bulges directly through the abdominal wall medial to the inferior epigastric artery and only goes throut the external inguinal ring.
Direct inguinal hernias are covered by…
external spermatic fascia and are usually seen in older men.
Femoral hernias protrude…
below the inguinal ligament through the femoral canal below and lateral to the pubic tubercle. More common in females.
Femoral hernia is the leading cause of…
bowel incarceration.
Hesselbach triangle is formed by…
the borders of the inferior epigastric vessels, the lateral border of the rectus abdominis and the inguinal ligament.
CCK source
I cells in the duodenum and jejunum
CCK actions (4)
- increase pancreatic secretion 2. increase gallbladder contraction 3. decrease gastric emptying 4. increase sphincter of Oddi relaxation
CCK regulation
increased by fatty acids and amino acids
To cause pancreatic secretion, CCK acts on..
neural muscarinic pathways.
Gastrin source
G cells in the antrum of the stomach
Gastrin actions (3)
- increase gastric H+ secretion 2. increase growth of gastric mucosa 3. increase gastric motility
Regulation of Gastrin
increased by stomach distention, alkalinization, amion acids, peptides, vagal stimulation decreased by stomach pH
Gastin is increased by…
chronic PPI use, phenylalanine and tryptophan.
Gastrin is greatly increased in…
Zollinger-Ellison Syndrome.
Glucose-dependent insulinotropic peptide (GIP) source
K cells in the duodenum and jejunum
GIP actions
Exocrine: decrease gastric H+ secretion Endocrine: increase insulin release
GIP regulation
increased by fatty acids, amino acids, and oral glucose
An oral glucose load is used more rapidly that the equivalent given by IV due to…
GIP secretion.
Motilin source
small intestine
Motilin action
produces migrating motor complexes
Motilin regulation
increased in fasting state
Motilin receptor agonists are used to…
stimulate intestinal peristalsis (ex. erythromycin).
Secretin source
S cells int he duodenum
Secretin actions (3)
- increased pancreatic HCO3- secretion 2. decreased gastric acid secretion 3. increased bile secreton
Secretin regulation
increased by acid, fatty acids in lumen of duodenum
Increased HCO3- in the duodenum, stimulated in response to secretin, acts to…
neutralize gastric acid allowing pancreatic enzymes to function.
Somatostatin source
D cells in pancreatic islets and GI mucosa
Somatostatin actions (4)
- decrease gastric acid and pepsinogen secretion 2. decrease pancreatic and small intestine fluid secretion 3. decrease gallbladder contraction 4. decrease insulin and glucagon release
Somatostatin regulation
increased by acid decreased by vagal stimulation
Somatostatin is an inhibitory hormone that…
has antigrowth hormone effects (inhibits digestion and absorption of substances needed for growth).
Nitric oxide action
increases smooth muscle relaxation, includeing lower esophageal sphincter
Loss of NO secretion is implicated in…
increased LES tone of achalasia.
Vasoactive Intestinal Polypeptide (VIP) source
parasympathetic ganglia in sphincters, gallbladder and small intestine
VIP actions
increase intestinal water and electrolyte secretion increase relaxation of intestinal smooth muscle and sphincters
VIP regulation
increased by distention and vagal stimulation decreased by adrenergic input
VIPoma is a…
non-alpha, non-beta islet cell pancreatic tumor that secretes VIP See copious watery diarrhea, hypokalemia and achlorhydria
Intrinsic factor source
parietal cells
Intrinsic factor action
vitamin B12-binding protein (IF is required fro uptake of B12 in the terminal ileum)
Autoimmune destruction of parietal cell leads to…
chronic gastritis and pernicious anemia.
Gastric acid source
parietal cells
Gastric acid action
decrease stomach pH
Gastric acid regulation
increased by histamine, ACh and gastrin decreased by somatostatin, GIP, prostaglandin and secretin
Gastrinoma
gastin-secreting tumor that causes high levels of acid secretion and ulcers refractory to medical therapy
Pepsin source
chief cells
Pepsin action
protein digestion
Pepsin regulation
increased by vagal stimulation and local acid
Inactive pepsinogen is converted to…
pepsin by H+.
HCO3- source
mucosal cells (stomach, duodenum, salivary glands, pancreas) Brunner glands (duodenum)
HCO3- action
neutralize acid
HCO3- regulation
increased by pancreatic and biliary secretion with secretin
Gastin increases acid secretion primarily through its action on…
enterochromaffin-like (ECL) cells, which leads to histamine release, rather than through its direct effects on parietal cells.
Atropine blocks vagal stimulation of…
parietal cells but NOT G cells because a different transmitter is used at G cells (GRP, not ACh).
Brunner glands secrete…
alkaline mucus.
Hypertrophy of Brunner glands is seen in…
peptic ulcer disease.
Pancreatic secretions
isotonic fluid low flow = high chloride high flow = high HCO3-
alpha-amylase role
starch digestion (secreted in active form)
lipase, phospholipase A, colipase role
fat digestion
Proteases role
protein digestion
Proteases include..
trypsin, chymotrypsin, elastase and carboxypeptidase. These are secreted as proenzymes (zymogens).
Tyrpsinogen is converted to…
active trypsin which acts to activate other proenzymes and cleaving additional trypsinogen to make more trypsin (positive feedback).
Trypsinogen is converted to trypsin by…
enterokinase/enteropeptidase (a brush border enzyme on duodenal/jejunal mucosa).
Enterocytes absorb only…
monosaccharides (glucose, galactose and fructose).
Glucose and galactose are taken up by…
SGLT1 (Na+ dependent).
Fructose is taken up by…
facilitated diffusion by GLUT-5.
All monosaccharides are transported to blood by…
GLUT-2.
D-xylose absorption test distinguishes…
GI mucosal damage from other causes of malabsorption.
Iron is absorbed as….
Fe2+ in the duodenum.
Folate is absorbed in..
the jejunum (and ileum).
B12 is absorbed in…
the terminal ileum along with bile acids (requires intrinsic factor).
Peyer patches are…
unencapsulated lymphoid tissue found in the lamina propria and submucosa of the ileum.
Peyer patches contain…
specialized M cells that sample and present antigens to immune cells.
In the germinal centers of Peyer Patches, there is stimulation of…
B cells that differentiate into IgA-secreting plasma cells which ultimately reside in the lamina propria.
IgA from Peyer Patches receives…
a protective secretory component and is then transported across the epithelium ot the gut to deal with intraluminal antigen.
Bile is composed of…
bile salts (bile acids conjugated to glycine or taurine, making them water soluble), phospholipids, cholesterol, bilirubin, water and ions.
The rate limiting step of bile synthesis is catalyzed by…
cholesterol 7alpha-hydroxylase.
Functions of bile (3):
- digestion and absorption of lipids and fat soluble vitamins 2. cholesterol excretion 3. antimicrobial activity
Bilirubin is a product of…
heme metabolism.
Bilirubin is removed from the blood by…
the liver, conjugated with glucuronate and excreted in bile.
Direct bilirubin
-conjugated with glucuronic acid -water soluble
Indirect bilirubin
-unconjugated -water insoluble
Salivary gland tumors are generally…
benign and occur in the parotid glands.
3 types of salivary gland tumors
- Pleomorphic adenoma 2. Warthin tumor 3. Mucoepidermoid carcinoma
Pleomorphic adenoma is composed of…
chondromyoid stroma and epithelium.
Pleomorphic adenoma presents as a..
painless, mobile mass. It will recur if incompletely excised or ruptured intraoperatively.
Warthin tumor is a…
benign cystic tumor with germinal centers.
Mucoepidermoid carcinoma is the most common..
malignant salivary gland tumor and has mucinous and squamous components.
Mucoepidermoid carcinoma presents as…
a painless, slow-growing mass.
Achalasia is due to..
failure of relaxation of LES due to loss of myenteric plexus.