What 2 things are needed for the LES to function properly?
1) Inner circular esophageal muscle layer 2) Loop of diaphragm around esophagus
Why does the LES not work well when there is a Hiatal Hernia?
Because part of its function depends upon the diaphragm circling around it
What vein drains the foregut, midgut and hindgut?
The portal vein
Cirrhosis causes portal hypertension, what is the significance of this condition?
Blood can’t get through the liver effectively, so it shunts it through the Azygous and Hemiazygous veins in order to get it back to the heart. Blood also backs up into other structures like the esophageal veins, this causes esophageal varices.
The Vagus nerve has been surgically cut (ligated) in the past before it’s function was fully understood. Why did we do this?
The Vagus nerve releases Ach in the stomach, and the stomach in turn produces HCl. If someone had ulcers that could not be treated in any other way, the nerve would be cut… stopping the release of Ach and thus stopping acid production.
Why do esophageal cancers metastasize so quickly?
No serosa
What cell type normally lines the esophagus?
Stratified Squamous epithelium
Why are most esophageal cancers NOT squamous cell carcinoma?
Intestinal metaplasia occurring in invading columnar epithelium from the stomach causes Barrett’s esophagus and thus adenocarcinoma.
How can having a hiatial hernia ultimately lead to cancer?
Acid reflux leads to intestinal metaplasia (influx of columnar epithelium from the stomach)
What are the tissue layers of the GI tract? Name them from inner to outer.
From inner to outer:
Mucosa (stratified squamous epithelium, lamina propria, muscularis mucosa)
Submucosa
Circular muscle
Longitudinal muscle
Serosa or adventitia (except esophagus)
What structure causes the plica circulares to form?
Muscularis mucosa
What layer of GI tissue houses the glands?
Submucosa
What is the blood supply to the foregut?
Celiac a.
What is the blood supply to the midgut?
Superior mesenteric a.
What is the blood supply to the hindgut?
Inferior mesenteric a.
What defines the boundaries of the gut?
The blood supply
Which Vagus nerve can be seen on the anterior surface of the stomach?
Clockwise rotation makes the left branch of the Vagus anterior
Which divisions of the gut have both dorsal and ventral mesogastrium?
Note that the foregut is the only place where the structures are tethered both dorsal and ventral by their respective mesogastrium
Why is the greater omentum important?
Walls off inflammatory processes in the abdomen
What artery comes off the aorta cephalad (towards the head or anterior) to the pancreas?
Celiac
Which artery comes off caudad to the body of the pancreas, but cephalad to the insula?
SMA
Why is the antrum of the stomach sometimes removed, and where is it located?
Inferior portion of stomach leading to pyloric valve. Intractable peptic ulcer disease
Where is the pylorus and what does it do?
Valve separating the stomach from the duodenum. Regulates the rate of entry of chyme into the sm. intestine
Describe the greater and lesser curvatures, the direction the muscle layers travel, and the folds that increase surface area in the stomach.
Why does the stomach have 3 muscle layers, not two, like the rest of the GI?
Helps churn food
What do flattened rugae indicate?
If the rugae, folds, are flattened, it may indicate stomach inflammation (gastritis)
Why do babies with pyloric stenosis have non-bilious vomiting?
Bile is released by the common bile duct in the duodenum, so the bile cannot get backwashed into the stomach as the enlarged pyloris prevents this.
What is the classic metabolic disturbance in pyloric stenosis and why?
Blood tests will reveal hypokalemic, hypochloremic metabolic alkalosis from the loss of gasric acid (which contains hydrocholic acid and potassium) via persistent vomiting.
If you find an ulcer at location V, what location is this and what is associated with causing it?
Type V are located in the body of the stomach. Type V occur with NSAID use.
Type I-IV ulcers are found where? What causes them?
Type I,II inferior to LES. Type II also duodenum. . Type III Superior to pyloris, along lesser curvature. Type IV in fundus. 75% on lesser curvature. Most have normal acid but abnormal mucosal defense. Type A blood associated with Type I ulcers, Type O blood associated with all others.
Where is iron absorbed?
In the duodenum
Where does the foregut end?
The foregut ends after the first portion of the duodenum, a location when the bile and pancreatic ductsdrain into the duodenum.
Why do anterior duodenal ulcers perforate and posterior duodenal ulcers bleed?
The peritoneal or abdominal cavity is located anterior to the duodenum. Therefore, if an anterior ulcer grows deep enough, it will perforate; whereas if a posterior ulcer grows deep enough, it will perforate the gastroduodenal artery and bleed. The largest arterial supply generally comes from the posterior surface of a hollow viscus (intestines and stomach).
When does pancreatic cancer occur in most people and what are its symptoms?
In their 50s and 60s. Pain radiating to the spine.
Why are pancreatic tumors inoperable?
The tumor has encased the SMA and SMV
