Circulatory System

Parts and functions

Heart

-          It is made of cardiac muscle tissue, nerve tissue and connective tissue.

-          Covered by epithelial tissue that reduces friction and allows blood to flow through the heart freely.

-          It pumps the blood around the body where it is used along with food to make energy.

Blood vessels

Three types: arteries, veins, and capillaries.

Blood vessel	Description
Arteries	-Carry blood away from the heart -Arteries walls required to be thicker because blood is pumped from the heart so they are under pressure. -Carry red and oxygenated blood, except of pulmonary artery.
Veins	-Carry blood back to the heart -Veins walls are thinner and lined with valves that prevent the blood from flowing backwards. -Carry blue and de-oxygenated blood, except of pulmonary vein.
Capillaries	-Tiny and thin blood vessels. -Allow nutrients and oxygen to flow from the blood with nutrients and oxygen to the tissues to flow again into the blood with wastes.

Blood

Type of blood	Description
Red	-Carry oxygen -Contains hemoglobin molecules that allow the cell to transport oxygen throughout the body. -Oxygen gives blood its red colour. -Half the volume of the blood
White	-White blood consists of infection fighting cells. -Recognizes and destroys invading bacteria and virus.
Platelets	-Small cells that help in blood clotting.
Plasma	-It is a protein rich liquid that carries the blood cells -Nearly half of the blood volume.