Page 7 - Health & Physical edu- 8

carbon dioxide to the lungs. Similarly, the blood increases the immunity of the
body and balances the level of water, minerals, salt and temperature. It takes the
hormones to the appropriate parts of the body.

Blood Circulation Process

The heart functions as a pump in order to circulate the blood to the body parts. The
impure blood from the upper part of the body reaches the heart through superior
venacava and such blood from the lower part of the body reaches the heart through

inferior venacava. Both these venacava take the blood to the right atrium. When
the heart relaxes, the blood flows to right ventrical through the tricuspid valve.
When the heart contracts, the same blood moves from right ventricle to the lungs
through the pulmonary artery. The blood in the lungs reaches the air sacs through the
capillaries in it. At that time, the blood gets purified mixing the oxygen and leaving
the carbondioxide (Co ) there. The purified blood reaches the left atrium through
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pulmonary vein. This type of circulation of the blood from the heart to the lungs

and from lungs to the heart is also called pulmonary blood circulation. The blood
collected at left atrium moves to the left ventricle through the bicuspid valve when
the heart relaxes. After the contraction of the heart, the same blood is pumped to
all the organs, tissues and cells through aorta. The cells consume the oxygen of the
blood and the carbondioxide or other unnecessary elements mixed into the blood.
That blood finally moves to the right atrium of the heart through capillaries to veins
and veins to venacava from different parts of the body. This process is known as
systemic blood circulation.

Glandular System

Gland is a group of special cells that produce enzymes and hormones. The enzymes
and hormones produced by the glands affect in digestion, physical activities, etc.
Enzymes secreted by exocrine glands do not directly mix into the blood. They secrete
enzymes into ducts and reach the necessary parts through ducts. Glands such as
salivary glands, sweat gland, pancreas, and stomach are the examples of such glands.

Endocrine Glands

The hormones secreted by endocrine glands directly mix into the bloodstream
and reach the parts of the body through it. The types of such glands are described
below.
Health & Physical Education, Class-8 3