Large Intestine Histology

Overview
  • The large intestine possesses all of the basic histological layers of the GI Tract (See: GI Tract Histology). The histological architecture of all sections of the large intestine, in which we include the rectum, are largely uniform throughout.
Basic Layers
  • Large Intestine Mucosa:
    • The large intestinal mucosa is architecturally arranged as a layer of deep, densely packed, straight glands that do not extend villi into the lumen. The large intestine epithelium is a simple columnar epithelium composed of two basic cell types responsible for the distinct functions of water resorption and mucus secretion. Near the neck of the large intestinal glands lie cells primarily responsible for water resorption while the base is populated with Goblet cells that produce a mucous critical for lubricating the propulsion of increasingly solidified feces. Large numbers of intraepithelial lymphocytes are observed throughout the epithelium and combat the rich bacterial flora of the colon. The large intestine lamina propria lies between the densely arranged colonic glands and is richly invested with capillaries and lymphatics necessary for fluid resorption. Occasionally lymphoid aggregates of MALT are observed. The large intestine muscularis mucosa is a flat surface that lies just beneath the terminal portions of colonic glands, known as intestinal crypts, and is composed of a thin layer of smooth muscle cells.
  • Large Intestine Submucosa:
    • The large intestinal submucosa is a largely collagenous layer with occaional aggregations of MALT and larger vasculature and lymphatics.
  • Large Intestine Muscularis Propria:
    • This is perhaps the most prominent layer of the large intestine and is responsible for the powerful peristaltic activity of the colon, required for propulsion of increasingly solid feces. The muscularis propria possesses the traditional inner circular layer and outer longitudinal layer of smooth muscle cells common to all GI tract segments. However, except for the rectum, the majority of the large intestine's outer longitudinal layer is bundled into three equidistant strips running the length of the colon termed taeniae coli.