1 Part 6: Rabbit Abdominal Viscera – Supplemental

Supplemental: Self-Study of Rabbit Abdominal Viscera

Comparative Note: Rabbit abdominal viscera shows some similarity to the horse due to a very large cecum with prominent sacculations, however the bands are more subtle. A couple of interesting anatomical features associated with the cecum are also worth noting.

1. On the isolated rabbit viscera, identify the cecum, sacculations, sacculus rotundus, and appendix.
   • Similar to the equine, the rabbit has a very large cecum (the largest of all animals relative to body size) with prominent sacculations, however the bands are more subtle. Identify the cecum and its sacculations.
   • Identify the sacculus rotundus. This round dilatation of the cecum marks the ileocecal junction.
   • The cecum has a long vermiform (worm-like) appendage on the apical (apex) end which resembles the human appendix, and is referred to as the appendix of the cecum. This structure is unique for domestic animals. Identify the appendix on the isolated rabbit viscera.
   • Note the abrupt change from the sacculated cecum to the smooth surfaced appendix; massive amounts of lymphoid tissue reside within its walls.
2. On the isolated rabbit viscera, identify the colon. Identify the proximal colon and the distal colon.

• • In the rabbit, identify the colon which is only about half the diameter of the cecum.
  • The colon is divided into a sacculated proximal colon (with well-defined bands) and a non-sacculated distal colon. Identify these two regions of the colon on the rabbit viscera.
  • Note that rabbits produce dry hard feces and soft mucoid feces.
    • The soft mucoid feces are the so-called ‘night feces’, or cecotrophs, that come from the cecum and pass through the colon with little water absorption. Goblet cells in the colon add mucous to the cecotrophs.
    • In contrast, water absorption in the colon is responsible for production of dry feces.
  • Coprophagy, the consumption of feces/stools, is abnormal in many species but normal in rabbits. The cecotrophs are eaten as they pass through the anus and are swallowed whole without chewing. The mucous coating prevents digestion while the cecotrophs ferment in the fundus of the stomach.

Figure 5-23.  Rabbit gastrointestinal tract, a schematic illustration.