Heart Cardiac Cycle And Circulatory System Essay

Describe the function of the heart, cardiac cycle and circulatory system

Function of the heart

The heart is a muscular organ that pumps and circulates blood throughout the body via a transport system of arteries and veins and capillaries. As the blood circulates throughout the body it supplies oxygen and nutrients to the tissues as well as removing carbon dioxide and harmful waste products (Tucker, 2015).

The structure of arteries

Arteries have thick muscular walls and a small lumen passage. According to L. Tucker they are constructed with three layers:

• A fibrous outer layer

• A middle layer of muscle and elastic tissue

• A lining made of squamous epithelial tissue

The epithelial lining has a smooth surface to reduce friction and

The walls of veins are far thinner and the lumen passage much larger. The walls are not muscular and blood is pushed through the vessels by the action of skeletal muscles. Veins carry deoxygenated blood (dark red) to the heart, except for the pulmonary veins which carry oxygenated blood. Blood pressure is very low in the veins, so there are valves in the endothelial layer which prevent the back flow of blood (Tucker, 2015).

The structure of capillaries

Capillaries are the smallest blood vessels in the body. The walls are only one cell thick and porous, which allows the passage of oxygen to body tissues and collection of waste products, mainly carbon dioxide and urea. They also deliver nutrients (e.g. sodium and potassium) and hormones to body tissues. The blood is brick red in colour because it has oxygen and carbon dioxide. I understand this from reading L. Tucker’s book.

The cardiac cycle

The cardiac cycle is the sequence of events that occur when the heart beats. According to L. Tucker, the following occurs during the cardiac cycle:

• The left and right atria contract, forcing blood into the