The circulatory system consists of the heart and blood vessels, and circulates blood throughout the body. Blood is pumped from the heart to the lungs to pick up oxygen and to organs to deliver oxygen and nutrients and pick up waste. The circulatory system includes arteries, veins, and capillaries that form closed loops to circulate blood, as well as heart chambers and valves that keep blood flowing in one direction. Blood carries red blood cells, white blood cells, platelets, and plasma to tissues and removes waste products.

1. “Circulatory System”
 Circulation is the process of sending blood:
 To the lungs to pick up oxygen
 To the digestive system to pick up
nutrients
 For delivery of oxygen and nutrients to
all organ systems of the body
 The circulatory system consists of the heart
and blood vessels.
 This system also circulates waste products to
certain organ systems so these wastes can be
removed from the blood.
Heart Coverings
 Pericardium - covers the heart and large
blood vessels
 Visceral pericardium - innermost layer
 Parietal pericardium - lays on top of the
visceral pericardium
Heart Walls
 Epicardium - the outermost layer
 Myocardium - the middle layer
 Endocardium - the innermost layer
Heart contains four hollow chambers
 Two atria – left and right
 Two ventricles – left and right
Heart Valves
 Tricuspid valve - prevents blood from flowing back into the right atrium when the right ventricle
contracts
 Bicuspid valve - prevents blood from flowing back into the left atrium when the left ventricle
contracts
 Pulmonary valve - prevents blood from flowing back into the right ventricle
 Aortic valve - prevents blood from flowing back into the left ventricle
Arteries and Arterioles
 strongest of the blood vessels
 carry blood away from the heart easily and are under high pressure
 have thick walls
Veins and Venules
 no pressure in veins - does not move very easily
 valves in veins prevent blood from flowing backwards
Blood Pressure
 Systolic pressure - ventricles contract, blood pressure is greatest in the arteries
 Diastolic pressure - the ventricles relax, blood pressure in arteries is at its lowest
 Reported as the systolic number over the diastolic number
Paths of Circulation
 Pulmonary Circuit
right atrium --> right ventricle --> pulmonary trunk --> pulmonary arteries --> lungs -->
pulmonary veins --> heart (left atrium)
 Systemic Circuit
left atrium --> left ventricle --> aorta --> arteries --> arterioles --> capillaries --> venules -->
veins --> vena cava --> heart (right atrium)
Components of Blood
A type of connective tissue:

2.  Red blood cells (erythrocytes)
 White blood cells (leukocytes )
 Platelets-contains cell fragments
 Plasma - fluid part of blood (55% of blood)
Nervous System