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Large Intestine

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Microscopic view of large intestine mucosa, hematoxylin and eosin staining, capturing distinct layers. Top: Tall columnar epithelial cells. Below: Connective tissue with striated muscle fibers. Bottom Layer: Loose connective tissue with some clusters of clear adipose tissue. Image is overall light pink with denser pink areas highlighting cell & fiber structures.
Figure 1: Intestine mucosa. Microscopic view shows layered tissue structure dyed pink.

The large intestine, also known as the colon, is the final portion of the digestive tract responsible for absorbing water and electrolytes from undigested food material, forming feces, and facilitating their elimination from the body

Mucosa

 Like the small intestine, the mucosa of the large intestine is lined with simple columnar epithelium. However, unlike the small intestine, it lacks villi. Instead, it contains numerous tubular intestinal glands (crypts of Lieberkühn) that extend into the lamina propria. Mucus cells are abundant in the epithelium of the large intestine. They secrete mucus, which lubricates the fecal material. This mucus also protects the epithelial surface from mechanical damage and dehydration.  Although fewer in number compared to the small intestine, there are still absorptive cells (enterocytes) in the large intestine. They absorb water and electrolytes from the luminal contents.  The mucosa also contains the tubular intestinal glands (crypts of Lieberkühn), which extend deep into the underlying tissue.

Submucosa

Much like the small intestine, the large intestine focuses on absorption. It has a submucosa richly vascularized with capillaries. Its function is to reabsorb as much water as can be extracted from feces.  However, lacteals are not present.

Muscularis Externa

The muscularis externa of the large intestine consists of inner circular and outer longitudinal layers of smooth muscle. This structure is similar to the small intestine.  The outer longitudinal layer forms three bands of smooth muscle called taeniae coli. These bands run longitudinally along the length of the colon. They contribute to its pocketed appearance (haustra).

Serosa

The outermost layer of the large intestine is covered by serosa. Serosa is a serous membrane consisting of mesothelial cells and connective tissue.  In the retroperitoneal portions of the large intestine (e.g., ascending and descending colon), the outermost layer is covered by adventitia instead of serosa.

Histological section of large intestine mucosa, stained with hematoxylin and eosin (H&E). Vertical columns of crypts dominate the composition, featuring columnar epithelial cells with basal nuclei. Lamina propria with inflammatory cells is present between crypts. Image displays cellular morphology under magnification.
Figure 2: Microscopic view of large intestine mucosa, stained pink and purple, showing cellular structure and arrangement.
Photomicrograph of large intestine submucosa, stained with hematoxylin and eosin (H&E). Left: columnar epithelium of intestines. Middle: fibromuscular connective tissue exhibiting collagen fibers and small blood vessels. Right: muscle layer. Image is evenly illuminated and is composed of pink and shades of purple. Field of view is approximately 500x magnification.
Figure 3: Microscopic view of large intestine submucosa showing different tissue layers stained in pink and purple hues.
Micrograph of the large intestine's muscularis externa. Tissue is stained primarily pink, with darker areas and white lines. The upper area of the image displays smooth muscle bundles with evident striations and collagen. In the lower area, the smooth muscle arrangement is more disorganized, appearing web-like. A vessel is visible.
Figure 4: Microscopic view of the large intestine’s muscularis externa, stained pink.
Microscopic image of large intestine serosa, stained pink. Predominantly collagen fibers with a wavy, swirling pattern; hematoxylin and eosin (H&E) stain highlights nuclei and cellular components. Blood vessels visible as circular structures. Image composition: high magnification, showing layered tissue structure.
Figure 5: Serosa of the large intestine under a microscope, showing collagen fibers, blood vessels and nuclei stained pink. Tissue structure visible.

Functions

Water reabsorption
Vitamin Harvesting

Specializations

Haustra
Tena Coli
Epiploic appendages

Figure 1-5: Large intestine (colon), H&E, 40X Slide 176
All by University of Michigan Histology, licensed under CC BY-NC-SA 3.0.

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Large Intestine
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