GI Week 1 Flashcards
Which of the following layers of the GI tract contains the myenteric (also known as Auerbach) nerve plexus?
- Mucosal
- Submucosal
- Muscularis externis
- Serosa
c. Muscularis externis
The myenteric nerve plexus innervates the smooth muscle of the muscularis externis. The mucosa contains the lamina propria and muscularis mucosae, the submucosa contains the submucosal or Meissner’s plexus which supplies the glands in the mucosa and submucosa, and the serosa contains squamous epithelium, connective tissue, and adventitia.
SM 125b Histology GI System (Pezhouh)
A 40-year-old white man presents to the emergency department complaining of burning retrosternal chest pain after meals. His pain is relieved by antacids. The patient’s ECG is normal, and his x-ray of the chest is remarkable for an 8-cm hiatal hernia. This patient is at risk for developing which of the following types of sequalae?
- Adenocarcinoma of the esophagus
- Squamous cell carcinoma of the esophagus
- Stomach carcinoma
- Myocardial infarction
- Bacterial infection
A) Adenocarcinoma of the esophagus.
The quality and location of this patient’s pain, combined with alleviation with medication and the radiographic findings, are suggestive of gastroesophageal reflux disease (GERD)/reflux esophagitis (RE). This disorder increases the risk of developing esophageal mucosal metaplasia, called Barrett’s esophagus. In turn, patients with Barrett’s esophagus are at increased risk for developing adenocarcinoma of the esophagus.
Squamous cell carcinoma (b) and stomach carcinoma (c) are not known to correlate with gastroesophageal reflux disease. Squamous cell carcinoma is thought to be associated with tobacco and alcohol use. Myocardial infarction (d) is also not associated with GERD.
Infection with H. pylori (e) is a risk factor for the development of peptic ulceration and distal gastric cancer, which is similar to the patient’s symptoms, but infection would come before these complications.
SM 126b Pathology of Esophageal Disorders (Bandy)
Objective Define Barrett’s esophagus, the main etiology of Barrett’s esophagus, approach to follow-up Barrett’s esophagus patients, and why Barrett’s esophagus patients need to be follow-up. [MKS-1b]
Adapted from First Aid Q&A 2012
What is contained within the foregut, midgut, and hindgut of the digestive system? What arteries and nerves supply each section?
Foregut – esophagus, stomach, first half of duodenum, liver, pancreas. Supplied largely by celiac truck (artery) and vagus nerve (parasympathetic innervation)
Midgut – second half of the duodenum, jejunum, ileum, ascending colon, proximal 2/3 of transverse colon. Supplied by superior mesenteric artery and vagus nerve.
Hindgut – distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum. Supplied by inferior mesenteric artery and pelvic splanchnic nerves (sacral outflow).
SM 127b GI Development & Organization (COCHARD)
Objective Describe how organs, arteries, and nerves relate to the foregut, midgut, and hindgut. (MKS1a)
Label the following structures
A-Celiac trunk
B-Esophageal
C-Short gastric
D-Splenic
E-Left gastro-epiploic
F-Right gastro-epiploic
G-Gastroduodenal
H-Hepatic proper
SM 128b Structure of the Abdomen (COCHARD)
Objective Identify the arterial supply of the abdominal foregut, midgut, and hindgut. (MKS1a)
Label the following structures
Answers
A Pancreas
B Greater peritoneal sac
C Superior mesenteric vessels
D Duodenum
E Aorta
F Left kidney
G Right kidney
H Inferior vena cava
I Duodenum
SM 128b Structure of the Abdomen (COCHARD)
Objective Describe the spatial relationships between the abdominal foregut, midgut, and hindgut organs. Describe how the surface of the abdomen is subdivided in the physical exam and how organs project on the surface. (MKS1a)
Explain why direct inguinal hernias occur in adults, while indirect hernias are more likely to occur in newborns and babies. Consider how the anatomy differs between the two.
Direct hernias are medial to the spermatic cord and under the conjoined tendon and are due to weakness in the abdominal wall, which can occur in older men. Meanwhile, indirect hernias in newborns occurs as a result of a patent processus vaginalis, which allows the hernia to pass into the inguinal ring.
SM 129b Abdominal Wall and Inguinal Hernia (Cochard)
Objective Describe the origin of the tunica vaginalis testis and how it relates to indirect inguinal hernia. Describe the location of a direct inguinal hernia and how it differs from an indirect hernia. Indicate the fate of the gubernaculum in males and females.
What begins contraction in the digestive system and which muscles are important for achieving it?
Contraction begins by the distention of GI tract with food. Alternating activity of the circular and longitudinal muscles allow for bolus to be pushed through the digestive tract.
SM 131b GI Motility I & SM 132b GI Motility II (MCKENNA)
Objective Describe how luminal pressure and stretch of the gut initiate reflexes in GI organs and how these inputs are integrated by intrinsic and extrinsic neural pathways. [MKS-1a]
A 75-year-old male presented with a 6-month history of early satiety and with upper abdominal discomfort for many years. Physical examination revealed mild epigastric tenderness. Esophago-gastro-duodenoscopy showed a large, ulcerated mass in the upper stomach, which was found to be cancerous. Surgery resulting in the removal of the gastric fundus was performed. After successful surgery, the patient was advised to eat small portions and to drink small volumes because of which of the following?
(A) almost complete absence of gastric motility
(B) distorted emptying of liquids
(C) inadequate mixing of large food boluses
(D) lack of receptive relaxation in the stomach
(E) weaker and slower propulsion of food toward the pylorus
(D) lack of receptive relaxation in the stomach
The receptive relaxation reflex is a feature of the orad stomach, composed of the fundus and upper stomach body. Without food, the orad stomach shows low frequency, sustained contractions that are responsible for generating a basal pressure within the stomach. When food enters the stomach, a reflex is initiated, which allows gastric accommodation of large increases in volume with only small increases in intragastric pressure.
The tonic contractions of the orad stomach also contribute to some extent to gastric emptying (choice B), since they generate a pressure gradient from the stomach to the intestine. However, neural and hormonal components play a more important role in regulating gastric emptying, which makes this not the best choice. Since the lower stomach is not affected by the surgery, characteristic motility patterns of the distal stomach remain (choice A). Features of the distal stomach include strong peristaltic waves of contractions, which cause the mixing of the chyme with digestive secretions (choice C), the grinding of the particles to a small size, and the propulsion through the gastroduodenal junction (choice E). All these motility patterns would still be a feature of the remaining stomach.
SM 131b GI Motility I & SM 132b GI Motility II (MCKENNA)
Objective Describe how luminal pressure and stretch of the gut initiate reflexes in GI organs and how these inputs are integrated by intrinsic and extrinsic neural pathways. [MKS-1a]
Taken from Lange USMLE step
A 30-year-old woman presents to her physician complaining of chest pain and difficulty swallowing. Results of ECG and x-ray of the chest were normal, but the following image was seen during a barium swallow study. Which of the following actions is most likely absent in this patient?
(A) Contraction of the lower esophageal sphincter
(B) Contraction of the upper esophageal sphincter
(C) Initiation of swallowing in the oropharynx
(D) Relaxation of the lower esophageal sphincter
(E) Relaxation of the upper esophageal sphincter
The correct answer is D. The barium swallow study shows esophageal dilatation and a “bird’s beak” sign of the distal esophagus, which are characteristic of achalasia. This disease presents with difficulty swallowing, abnormal contractions of esophageal muscles, absence of peristalsis, and absence of relaxation of the lower esophageal sphincter on swallowing.
Answer A is incorrect. In achalasia, the lower esophageal sphincter fails to relax. If the lower esophageal sphincter fails to close completely, a patient may experience symptoms of gastroesophageal reflux and not achalasia.
Answer B is incorrect. In achalasia, the lower esophageal sphincter is affected, not the upper esophageal sphincter.
Answer C is incorrect. There is no difficulty with initiation of swallowing in achalasia.
Answer E is incorrect. In achalasia, the lower esophageal sphincter is affected, not the upper esophageal sphincter.
SM 136b Disorders of GI Motility (HIRANO) and SM 135b Clinical Features of Esophageal Disorders (GONSALVES)
Objective Describe how diseases affecting the autonomic nervous system, enteric nervous system or smooth muscle result in region specific or generalized GI motility disorders.
From First Aid Q&A 2012
A 68-year-old woman with type 2 diabetes mellitus and a 13.6-kg (30-lb) weight loss over the past 2 months presents to the physician with a history of nausea and bloating. Symptoms are most prominent following a meal. An outpatient gastric emptying study shows esophageal dysmotility. What most likely causes this patient’s current condition?
- Degeneration of NO producing neurons
- Autonomic neuropathy
- Atrophy of muscularis propria
- Failure of neural crests cells to populate distal digestive tract
Answer: (B) Patient has diabetic gastroparesis which can include gastric body and antral hypomotility and pylorospasm leading to symptoms such as regurgitation, nausea, vomiting,
abdominal pain and early satiety. This condition is thought to be caused by autonomic neuropathy.
(A) Degeneration of NO producing neurons is seen in achalasia
(C) Atrophy of muscularis propria is seen in scleroderma
(D) Failure of neural crest cells to migrate the distal digestive tract is seen in Hirschsprung’s disease leading to the internal anal sphincter to be unable to relax. This produces a functional obstruction of the anorectum leading to proximal colonic dilation often referred to as “megacolon.”
SM 136b Disorders of GI Motility (HIRANO) and SM 135b Clinical Features of Esophageal Disorders (GONSALVES)
Objective Describe how diseases affecting the autonomic nervous system, enteric nervous system or smooth muscle result in region specific or generalized GI motility disorders.
Adapted from First Aid Q&A 2012
