Crohn's and Hirschprung's Disease
Symptoms: abdominal pain in central and right lower quadrant. Diarrhea, weight loss, and
lassitude. Required iron supplements and intramuscular injections of vitB12. Eventually got
intestinal obstruction and had parenteral nutrition. Developed gallstone disease later.
1. What is the basic defect in Crohn's disease and which parts of the GI tract are affected?
Expand on the function of the different segments on the intestinal tract on the absorption
of different nutrients.
Crohn's disease is an autoimmune disease causing inflammation of the SI. All parts of the GI
tract can be affected from the mouth (aphthous ulcers of mucosa and tongue) to anus (skin tags,
fistulas). The main affected area is the terminal ileum, but in the intestines many things occur:
Thickening of walls (obstruction)
Cobble stone mucous membrane
Mesenteric lymph nodes enlarge (Peyer's patches in jejenum)
Note: Vitamin B12, vitamin C, and bile salts are absorbed in the ileum. B12 is important for the
production of healthy RBCs and bile salts are important for fat absorption.
2. Why did the patient suffer from weight loss and tiredness? Damage to the small intestine can cause fibrosis and damage of enterocytes, leading to
malabsorption of fat, carbohydrates, vitamins, and minerals. A fistula can cause a bypass of some
of the small intestine leading to further malabsorption. This leads to weight loss and fatigue. The
patient is also anemic and tired.
3. Why injections of B12 and iron were given?
The terminal ileum was damaged and chronic gastrointestinal bleeding leads to iron deficiency
anemia so iron must be injected. B12 is also absorbed here so it must be injected as well.
4. What could be the cause of gall stone disease in this patient?
Bile salts are mainly absorbed in the terminal ileum. With it damaged, there is no recycling of
bile salts and the liver can't keep up with de novo synthesis of conjugated bile salts. Micelle
formation is impaired and cholesterol precipitates out, creating a gall stone.
Questions: Colon bacteria, motility of SI, laxatives, defecation reflex
Overview of small intestine (6.5m in vivo, 7.5m after death because loss of muscle tone)
Duodenum is 25cm. Has intestinal glands like crypts of lieberkuhn and glands of Brunner
Jejunum=2.5m and ileum is 3.75m with anatomical separation. The microvilli are
smaller, and have Peyer's patches (contain immune cells like macrophages). They are on
a mesentery (double layer of peritoneum separating the jejunum and ileum from posterior
wall of abdomen)
Superior mesenteric artery feeds the SI
o Blood flow is about 10% of cardiac output, but increases 50-300% during a meal.
o Controlled by nerves (vagus), hormones, and paracrine factors
o Drains into portal veins
Microvilli increase area which increases permeability as in Fick's equation
o Has a venule, an arteriole, and lacteal
Function: mixes digestive juices with chyme and moves contents to colon
1. Spontaneous contractions
a. Due to uneven amplitude of the oscillating MP,
b. Influenced by ACh and stomach contractions
c. 12x minute (tonic), contracts even if no food present
2. Migrating myoelectric complex MMC
a. Triggers every 1.5h that lasts 10min
b. Contraction of the whole intestine aborally (toward colon) c. Occurs even when not in a meal
Segmentation tries to mix the food in the SI
Peristalsis a wave that pushes the chyme down, a propagating wave
Motility results from:
Intrinsic nerves of intramural plexus