Page 17 - (DK) The Dog Encyclopedia

CARDIOVASCULAR AND DIGESTIVE SYSTEMS

Where the blood flows in and out of the
paws, the arteries and veins are in very close TEETH
proximity. As warm arterial blood passes
By the age of 7 to 8 months, most dogs Carnassial
into the paws, it transfers its heat to the
have a full set of 42 adult teeth, all teeth
cooler returning venous blood, so the heat
adapted for eating meat. At the front, Hidden
is retained in the body rather than lost to the upper and lower jaws have six canine root
the environment. Known as counter-current incisors flanked at either side by a Incisor
heat exchange, the same mechanism single large canine tooth that was tooth
once used for grasping, holding, and
operates in the skin of walruses and in
piercing prey. Along the sides of the
penguins’ feet, allowing them to survive
jaws are the premolars and molars.
in freezing polar environments. The fourth upper premolar and lower
first molar on each side of the jaw are
DIGESTING FOOD called carnassial teeth and are a feature
A healthy dog wastes no time in clearing its of all mammals belonging to the Canine
Carnivora order. These teeth act like a tooth
food bowl, gulping down one mouthful
pair of scissors and are used for cutting
after another without stopping to chew Premolars Molars
and shearing through hide and bone.
anything. Canids are programmed to eat fast,
not out of greed but out of necessity—in the
wild the slowest feeder risks losing its meal to process of digestion even before swallowing. much more quickly and easily digested than
ravenous pack mates. Humans tend to savor Dogs, which have relatively few taste buds plant material. A dog’s stomach contains
the food in their mouths, chewing it and compared to humans, simply grab large high levels of digestive acids that break
mixing it well with saliva, which starts the chunks of food and swallow them whole. To down meat, bone, and fat rapidly, reducing
mitigate this, they also have an excellent gag food to a liquid that then passes into the
reflex. If they eat something unpleasant they small intestine. Once there, digestive
Sharp teeth bite off lumps can simply throw it up. enzymes produced by the liver and pancreas
of meat, which are mixed
with saliva and swallowed The canine digestive tract is aid the breakdown of food into nutrients
whole without chewing
short and designed specifically that can be absorbed into the bloodstream
for processing meat, which is through the intestinal walls. Any undigested
material moves through the large intestine
to be eliminated as feces. In dogs, the transit
Pancreas produces more
enzymes and substances that time of food through the digestive tract,
neutralize the stomach acid on
entering the duodenum from eating to elimination, takes around
8 to 9 hours, compared with an average
of 36 to 48 hours in humans.
Muscular contractions of
the esophagus move the
lumps of food down into
the stomach

Stomach has rings of muscle at its
entrance (cardiac sphincter) and exit Large intestine absorbs
(pyloric sphincter) and produces enzymes, excess liquid. Feces are
formed and are passed
and mucus that coats its walls, protecting from the body
them from the acid it produces to break
down the fibrous tissue in meat
Liver produces bile to help break
down fat into molecules that can
then be absorbed by the blood
Nutrients are absorbed
through the walls of the
small intestine into the
bloodstream

Digestive system
Structurally simple—essentially the gut is a long
tube—but functionally complex, the digestive
system processes food, releasing its nutrients so
they can be absorbed into the blood stream.

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