CGRN GI Anatomy and Pathophysiology 2 — Questions and Answers
Question 1: Which layer of the GI tract wall contains the submucosal plexus (Meissner's plexus) responsible for regulating secretions?
- Mucosa
- Submucosa (Correct answer)
- Muscularis externa
- Serosa
Correct answer: Submucosa
The submucosal plexus (Meissner's plexus) is located in the submucosa and primarily controls GI secretions and local blood flow.
The GI tract wall has four primary layers: mucosa, submucosa, muscularis externa, and serosa. The submucosa contains the submucosal plexus (Meissner's plexus), which is part of the enteric nervous system. This plexus primarily regulates glandular secretions and submucosal blood flow.
Question 2: A patient presents with steatorrhea and fat-soluble vitamin deficiencies. Which portion of the small intestine is most likely affected?
- Duodenum
- Jejunum (Correct answer)
- Ileum
- Cecum
Correct answer: Jejunum
The jejunum is the primary site for absorption of fats, carbohydrates, and proteins.
The jejunum makes up approximately the middle 40% of the small intestine and is the primary site for absorption of most nutrients including fats, amino acids, sugars, and fat-soluble vitamins (A, D, E, K). The duodenum absorbs iron and calcium. The ileum is specialized for bile salt and vitamin B12 absorption.
Question 3: What is the primary function of the sphincter of Oddi?
- Prevent reflux from the colon to the ileum
- Regulate the flow of bile and pancreatic juice into the duodenum (Correct answer)
- Control gastric emptying into the duodenum
- Separate the esophagus from the stomach
Correct answer: Regulate the flow of bile and pancreatic juice into the duodenum
The sphincter of Oddi regulates the flow of bile and pancreatic secretions into the duodenum through the ampulla of Vater.
The sphincter of Oddi is a smooth muscle valve located at the ampulla of Vater in the second portion of the duodenum. It controls the flow of bile from the common bile duct and pancreatic juice from the pancreatic duct into the duodenal lumen.
Question 4: Which condition is characterized by transmural inflammation that can affect any portion of the GI tract from mouth to anus?
- Ulcerative colitis
- Crohn's disease (Correct answer)
- Irritable bowel syndrome
- Microscopic colitis
Correct answer: Crohn's disease
Crohn's disease is characterized by transmural inflammation and can affect any part of the GI tract, most commonly the terminal ileum and colon.
Crohn's disease involves transmural (full-thickness) inflammation that can involve any segment of the GI tract. It presents with skip lesions, fistulas, strictures, and non-caseating granulomas. Ulcerative colitis involves only mucosal and submucosal inflammation limited to the colon and rectum.
Question 5: The portal vein is formed by the confluence of which two veins?
- Hepatic vein and inferior vena cava
- Superior mesenteric vein and splenic vein (Correct answer)
- Left gastric vein and right gastric vein
- Inferior mesenteric vein and hepatic vein
Correct answer: Superior mesenteric vein and splenic vein
The portal vein is formed behind the neck of the pancreas by the union of the superior mesenteric vein and the splenic vein.
The hepatic portal vein is formed by the confluence of the superior mesenteric vein (draining the small intestine, cecum, ascending and transverse colon) and the splenic vein (draining the spleen, pancreas, and portions of the stomach) behind the neck of the pancreas.
Question 6: Which cells in the gastric mucosa are responsible for producing intrinsic factor and hydrochloric acid?
- Chief cells
- Parietal cells (Correct answer)
- G cells
- Mucous neck cells
Correct answer: Parietal cells
Parietal (oxyntic) cells produce both hydrochloric acid and intrinsic factor, essential for vitamin B12 absorption in the ileum.
Parietal cells are found primarily in the body and fundus of the stomach. They produce hydrochloric acid via the H+/K+ ATPase proton pump and secrete intrinsic factor necessary for vitamin B12 absorption. Chief cells produce pepsinogen, G cells produce gastrin.
