Page 16 - (DK) The Dog Encyclopedia

INTRODUCTION TO DOGS | CARDIOVASCULAR AND DIGESTIVE SYSTEMS

Cardiovascular and

digestive systems

The major body systems that keep a dog, and all other mammals, up and running can
function only by working together. Oxygen drawn in by the lungs and nutrients
contributed by the digestive system are the essential fuels of life and must be
transported to every part of the body. Circulating blood, driven through a network of
arteries and veins by the steady beating of the heart, provides the vital supply line.

CIRCULATION AND RESPIRATION dioxide, produced by cell activity. Blood warm air that causes saliva in its mouth to
A dog’s heart functions in the same way as flows in a continuous circuit, picking up evaporate—latent heat is lost, and the dog’s
our own, pumping with a regular rhythm to oxygen from inhaled air in the lungs, and body temperature decreases as a result.
keep blood moving around the body. Inside then carrying it, together with nutrients Also invaluable for dogs, especially
the muscular walls of the heart there are absorbed through the intestinal walls, cold-climate spitz breeds, is an adaptation
four chambers that contract and relax in a around the entire body. At the same time to the cardiovascular system that prevents
sequence with each heartbeat. This forces that oxygen is collected in the lungs, carbon excessive loss of body heat through the
blood out of the heart through the arteries dioxide diffuses out of the bloodstream and paws when in contact with cold ground.
and into circulation and allows the heart to is expelled from the body in exhaled breath.
refill with blood returning via the veins. The respiratory system also has a vital role
This circulatory, or cardiovascular, system in preventing a dog’s body from overheating.
operates in conjunction with the respiratory Because a dog has only a few sweat glands,
system to bring oxygen to every cell in the mostly in its paws, it cannot keep cool by
body and to remove waste, such as carbon perspiring. Instead, a dog pants, exhaling

Trachea carries inhaled air
from the nostrils or mouth
to the lungs and exhaled
air back out

Jugular vein

Carotid artery carries up to
20 percent of the heart’s
blood to the brain

Pulmonary vein, in contrast to all
other veins, carries oxygenated
blood (from the lungs to the heart)
Lungs have a large surface
Femoral artery and
vein are the main area and rich blood supply to Aorta has thick, elastic walls to
blood vessels of the maximize gaseous exchange carry blood under pressure as
hind legs it leaves the heart

Pulmonary artery, in contrast to all
other arteries, carries Subclavian artery and vein
deoxygenated blood (to the lungs are the main blood
from the heart) vessels of the forelegs

Rib cage protects
heart and lungs
Circulatory system
Oxygenated blood is carried from
the heart to all parts of the body in a
Heart contracts and relaxes regularly to
pump blood around the body; its size and branching network of arteries (red),
shape vary with the breed and returns in a similar network of
veins (blue) carrying carbon dioxide.

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