Shoulder

Brachium

Antebrachium

Facial and Masticatory Muscles

Thorax and Heart

Brain

Body Wall

Hip and Thigh

Shank and Foot

Digestive System

Urinary and Reproductive Systems

Hip and Tail

Digestive system of the Cat (Felis catus)

Photos and text by Adam Hartstone-Rose

Introduction:

Cats are the most carnivorous members of Carnivora, and meat is one of the easiest foods to digest [1].  As such, the cat gut (stomach and intestines) is extremely short and simple compared to those of some of the highly specialized herbivores.  However, as meat contains a substantial amount of fat and concentrated toxins (the higher up an animal is on the trophic pyramid the more concentrated toxins become), cats have relatively large gallbladders (to store the gall necessary to emulsify the fats) and livers (to produce the large amounts of gall and filter the toxins out of the blood returning from the gut) [2].

Table 1.  Comparison of digestive systems among mammals.

Dissection Technique:

To visualize the abdominal viscera in situ, retract the skin and abdominal wall (made up of the different layers of musculature, see abdominal wall lab) with forceps and nick with either scissors or a scalpel.  Continue the incision along the midline, cranially to the xiphoid process and caudally to the pubic symphysis.  Be careful not to damage any of the deep structures.  Cut laterally perpendicularly at the two ends of the midline incision.  Retract the two sides of the abdominal wall and observe the viscera in their life position.

Gut tube:

The gut tube enters the abdomen as the esophagus pierces the diaphragm close to the vertebral column and enters, almost immediately, into the stomach.  The digestion process really begins in the mouth, where enzymes are mixed into the food (in most mammals, food is physically broken into smaller pieces through mastication, but most carnivores, as is true in the cat, consume large bites of meat with little chewing).  The esophagus does little or no digestion.  Once in the stomach, the food is broken down further by acids and other enzymes.  In the pangolin, the pyloris (the last part of the stomach) has a calcified region that actually serves to crush the insects it eats in the absence of masticatory teeth in the mouth.  As the bolus leaves the stomach it is mixed with other enzymes and emulsifiers from the liver, gall bladder and pancreas.  In the ileum and jejunum of the small intestine, nutrients begin to be absorbed.  In cats the bolus then moves directly into the large intestine where more nutrients and water are extracted before excretion.  In many herbivorous mammals, the gut is complicated by various pockets in which food is allowed to sit and ferment [2].  However, this is unnecessary in the digestion of meat.

Hepatic system:

If your animal is “triple injected” then the hepatic portal system will be dyed a different color than the rest of the vasculature, thus making it easier to differentiate.  The hepatic portal system essentially allows the body to separate the blood with toxins absorbed from the guts and the blood returning from the lower extremities.  As such, all of the blood draining from the mesenteries of the intestines and the stomach is sent into the hepatic portal vein and through the liver before it is incorporated into the inferior vena cava and circulated through the body.  In my specimen, all of the hepatic portal veins were dyed yellow (see figure).

Spleen:

The spleen is close to and shares a substantial supply of blood with the stomach.  It is a highly vascularized organ that is primarily responsible for recycling blood – cleaning it and producing new cells.  In the adult, all of its functions can be performed by other anatomical structures, and thus it is a rather redundant organ. [2]

Conclusion:

The gut is essentially a tube running from the mouth to the anus.  The body’s challenge has is to remove the maximum amount of energy and nutrients from the food as it passes through this system.  As such, the tube is differentiated into regions with specific tasks of breaking down food for better absorption or to absorb different nutrients from that food.  Several organs produce and dump different chemicals into the bolus on its journey.  Other organs take the distilled nutrients and remove the harmful chemicals from them.

Depending on the food source, different elements of the system need to be emphasized.  If food is tough and nutrient poor (like leaves and grasses), then it needs to be physically and chemically broken down into the smallest pieces possible (as is done by fermenting animals) or consumed at a greater rate to compensate for the reduction in calories captured per bite.  If the food is simple to break down (small molecules with little structural complexity), then the gut can be emphasized.  Herbivores have the challenge of breaking down easily obtainable but difficult to digest food.  Therefore their guts are highly developed where their stealth need not be.  Frugivores rely on patchy food that maybe hard to get into but that is generally easily digested.  Thus, their guts are not as complicated as some other herbivores’ are, but their food procuring senses and dental morphology may be more highly modified.  For carnivores, the task of digestion is easiest, but the procurement of their food is the most difficult.  Thus they have short guts but highly tuned senses and weapons to capture their prey.

References:

1. Turner, A. 1997.  The Big Cats and Their Fossil Relatives.  New York: Columbia Univ.

2. Walker, W. F. 1970. Vertebrate Dissection.  Philadelphia: W. B. Saunders Co.