Page 419 - Concise Pathology for Exam Preparation ( PDFDrive )

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404 SECTION II Diseases of Organ Systems
Jejunum and Ileum

• Lack Brunner’s glands
• Ileum has Peyer’s patches in the lamina propria.
• Small intestine is the site where most nutrients from ingested food are absorbed. It is
arranged in folds called plicae circularis which are distinct from rugae, as they are not
permanent, allowing distention and contraction of the small intestine.
• From the plicae circularis, project microscopic finger-like villi. Jejunal villi are long;
whereas, ileal villi are short.
• The small intestinal mucosa is lined by simple columnar epithelium and the epithelial
cells also have finger-like projections known as microvilli.
• The function of the plicae circularis, villi and microvilli is to increase the amount of
surface area available for secretion of enzymes and absorption of nutrients.
COLON

• It consists of the ascending, transverse, descending and sigmoid colon. Colon from
caecum to the splenic flexure (the junction between the transverse and descending co-
lon) is also known as the right colon. The remainder is known as the left colon.
• There is increase in the thickness of mucosa from caecum to rectum.
• Surface epithelium is composed of absorptive tall columnar epithelium with goblet cells
and endocrine cells.
• Columnar cells and goblet cells are present in the ratio of approximately 4:1.
• Paneth cells are most prominent in the caecum and proximal colon (usually confined to
crypt bases).

Q. Define and classify malabsorption syndrome.

Ans. Malabsorption syndrome is associated with impaired absorption of nutrients like fat,
fat-soluble and other vitamins, proteins, carbohydrates, electrolytes, minerals and water.

Classification

1. Defective intraluminal digestion of fat, proteins and carbohydrates (enzyme deficiency).
Normally, the process starts in the oral cavity (saliva) and continues as gastric digestion
as well as digestion in the small intestine (aided by pancreatic enzyme secretion and
emulsifying action of bile).
Causes
• Pancreatic insufficiency (pancreatitis and cystic fibrosis)
• Zollinger–Ellison syndrome (inactivation of pancreatic enzymes by excess gastric
acid secretion)
• Defective bile secretion
2. Defective mucosal absorption of fat, proteins, carbohydrates, water and minerals.
Causes
• Primary mucosal cell abnormalities: Defective terminal digestion and defective
epithelial transport, eg, disaccharidase deficiency (lactose intolerance) and bacte-
rial overgrowth with brush border damage.
• Reduced small intestinal surface area: Crohn disease, celiac sprue and surgery
• Lymphatic obstruction: Lymphoma and tuberculosis
• Infections like tropical sprue, Whipple disease and parasitic infestation

Clinical Features
Depend on the type of malabsorption; signs and symptoms may be related to specific
nutrient deficiency or may be due to generalized deficiency and are as follows:
• Passage of bulky, frothy, greasy, yellow or grey stools, abdominal distension and flatus
• Weight loss and muscle wasting
• Anaemia from iron, pyridoxine, folate or vitamin B 12 deficiency
• Bleeding (petechiae and purpura) due to vitamin K deficiency

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