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Module 2 The Digestive Tract
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Overview of the digestive system
In this module we look at the process of digestion
in the dog and cat. After food is eaten it must first be broken down to simple
molecular compounds, a process which we call digestion, which can then be
absorbed into the body. The digestive system is a term used for the system
of organs involved with digestion and absorption of food.
The Digestive Tract
In all animals, the digestive tract is a tube which shows
modifications in different species to enable them to digest their particular
diet. Although dogs belong to the carnivore group of animals, they are actually
omnivorous. They can feed not only on animal tissue like meat, but they can
also feed on vegetable material. Cats, on the other hand, are true carnivores,
and must have animal tissue in their diets. In evolutionary terms, cats have
been such successful hunters that they can always catch prey. Since they have
had no need to branch out in terms of their nutritional requirements, their
digestive profile is quite narrow and they do not cope well on vegetarian
diets. Whereas dogs, because they have evolved as scavengers, as well as hunters,
can cope with a wide range of food materials.
Two important features should be noted from the table below.
Firstly, the similarity of the dog's intestinal structure to that of humans.
Secondly, that cats have a relatively short intestine and a short retention
time of food in their gut. However, the cat compensates by having very efficient
absorption. The dog has some capacity to ferment food in its gut, but the
cat's intestine has little capacity for fermentation, due to its almost non-existent
caecum.
Intestinal Lengths and Transit Times for Digesta
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Dog |
Cat |
Human |
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Small Intestine (m) |
3.9 |
1.7 |
7.0 |
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Large Intestine (m) |
0.6 |
0.4 |
1.8 |
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Total length (m) |
4.5 |
2.1 |
8.8 |
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Body length (m) |
0.75 |
0.5 |
1.75 |
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Total length:body length |
4-5 |
3 |
5 |
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Mean retention time (hours) |
22.6 ± 2.2 |
13 |
45.6 ± 11.1 |
To understand the digestive process
fully, it is necessary to follow the passage of food right through the digestive
tract. Click here to take a journey down the digestive
tract and learn about the basic processes of digestion.
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