04 Circulatory System

Circulatory System: The Heart
The body has about 5 liters of blood continuously traveling through it by way of
the circulatory system. The circulatory system consists of the blood, blood vessels and
the heart. It is important to provide transport of oxygen, nutrients, hormones and waste
products (carbon dioxide and toxins); helps fight infection; and helps regulate body
temperature. This is accomplished through a network of about 60,000 miles of blood
vessels and a fist sized organ, the heart which pumps more than 2,000 gallons of blood
each day.
The heart is responsible for pumping the blood to every cell in the body. In the
pulmonary circulation, blood from the right side of the heart is low in oxygen and travels
along pulmonary arteries to the lungs, where it receives oxygen and returns to the heart
through pulmonary veins. In the systemic circulation, blood leaves the heart through the
aorta, goes to all organs of the body through the systemic arteries (carry oxygenated
blood) and then returns to the heart through the systemic veins (carry deoxygenated
blood). It is supplied by coronary arteries, which arise from the aorta and eventually
branch into capillary beds that course throughout the heart walls and supply heart
muscles with oxygenated blood. The coronary veins return blood from the heart muscles,
which empty directly into the right atrium.
The heart has to have enough pressure to get blood down to your fingertips and to
the tip of your toes. It contracts and relaxes at about 70 times a minute at rest and it will
contract more during exercise. It pumps blood through its four chambers and bloodstream
via its blood vessels to reach the cells.
Exercise promotes health to the body. It increases total blood volume so that the
body is better equipped to transport oxygen, likewise lung capacity increases which is
associated with greater longevity. The heart muscle grows stronger that with each heart
beat there is an increase in stroke volume which means that it pumps more oxygenated
blood through the circulatory system. Thus exercise cause changes in the circulatory
system to increase the delivery of oxygen to muscle cells, by increasing heart rate, blood
flow to muscle tissues, arterial pressure, body temperature and breathing rate, but
decreasing blood flow to non-muscular tissue.