Colon

Absorption of water, sodium, and other minerals, but also production and absorption of volatile fatty acids, takes place in the colon [1]. Furthermore, the colon harbours the largest population of microorganisms in the digestive tract. These bacteria produce essential vitamins; for example, vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B12 (cobalamin), and vitamin K, which are then absorbed by the colon.

Colon morphology varies between species with different diets. Carnivores generally have short and smooth colons (Fig. 1). Herbivores, on the other hand, tend to have long and sacculated colons [1–4]. Colonic morphology in omnivores is highly variable. Whereas some have short and smooth colons similar to those of carnivores (e.g., rats), others (e.g., pigs) have either long or medium-sized colons, which are also sacculated [1].

The role of diet in colon morphology becomes clear when considering that even within the same order of mammals, differences can occur. Such is the case within the order of primates: more carnivorous primates have simple and smooth-walled colons, while frugivorous primates have an elongated, sacculated colon [4].

What about humans?

The human colon, like that of herbivores, is long and sacculated [1].

Digestive tracts of carnivores and herbivores

 

Fig. 1:  Digestive tracts of carnivores and herbivores (ruminant and non-ruminant; from [3]).

Anatomy of the human colon

 

Fig. 2:  Anatomy of the human colon (from [5]).
 

REFERENCES:

[1] Kararli, Tugrul T. "Comparison of the gastrointestinal anatomy, physiology, and biochemistry of humans and commonly used laboratory animals." Biopharmaceutics & drug disposition 16.5 (1995): 351–380.

[2] Alvarez, Walter C. "An Introduction to Gastro-Enterology. Paul B. Hoeber, Inc., New York (1940).

[3] Feldhamer, George A. Mammalogy: adaptation, diversity, ecology. JHU Press, 2007.

[4] Chivers, David J., and Claude Marcel Hladik. "Morphology of the gastrointestinal tract in primates: comparisons with other mammals in relation to diet." Journal of Morphology 166.3 (1980): 337–386.

[5] Blausen.com staff. “Blausen gallery 2014”. Wikiversity Journal of Medicine (2014).