HEART AND CIRCULATION Chapter 30 Sections 3 and 4

If you were to lay out all of the arteries, capillaries and veins in one adult, end-to-end, they would stretch about 60,000 miles If you were to lay out all of the arteries, capillaries and veins in one adult, end-to-end, they would stretch about 60,000 miles - By comparison, the circumference of the Earth is about 25,000 miles (40,000 km). That means a person's blood vessels could wrap around the planet approximately 2.5 times!

FLOW OF BLOOD THROUGH THE HEART 1.) Blood returns from the body and enters the heart through the Superior or Inferior Vena Cava 2.) Blood enters the right atrium 3.) Blood moves into the right ventricle, by going through the tricuspid valve 4.) Blood then moves to the lungs via the pulmonary artery. - Blood gets oxygenated 5.) Blood returns from lungs and enters the left atrium 6.) Blood then moves into the left ventricle via the mitral valve 7.) Blood leaves the heart through the aorta, and goes to the body

Heart is the main propulsive organ to force blood around the body through veins, arteries, and capillaries Heart is the main propulsive organ to force blood around the body through veins, arteries, and capillaries What is blood? What is blood? - - Plasma: the fluid portion of blood, containing proteins, nutrients, and other solutes - -Formed Elements: red and white blood cells and platelets Components of Blood

BLOOD CIRCULATION Divided into two distinct processes Divided into two distinct processes - Pulmonary Circulation: Pumps blood between the heart and lungs - Systemic Circulation: Pumping of blood to the rest of body (besides lungs) Blood supplies all body tissues with the substances needed for survival, so it is vital that blood delivery is ample for tissue demands. Blood supplies all body tissues with the substances needed for survival, so it is vital that blood delivery is ample for tissue demands.

FUNCTIONS OF BLOOD CIRCULATION Transport of nutrients Transport of nutrients - From digestive tract to tissues, to and from storage organs - From digestive tract to tissues, to and from storage organs Transport of metabolites Transport of metabolites - Lactic acid from muscle to liver - Lactic acid from muscle to liver Transport of excretory products Transport of excretory products - From tissues to excretory organs - From tissues to excretory organs Transport of gases Transport of gases - Respiratory organs to/from tissues - Respiratory organs to/from tissues Transport of hormones Transport of hormones Transport of cells - Including cells of non-respiratory function Transport of heat Transport of force - e.g., locomotion (earthworms, spiders), erection of penis Coagulation

BLOOD PRESSURE Force blood exerts against the wall of a blood vessel. Force blood exerts against the wall of a blood vessel. - Pressure is highest at the heart end of any artery. - Pressure decreases in the blood vessels furthest from the heart Heart chambers fill during diastole (relaxation of the heart) and pump blood out during systole (contraction of the heart). Heart chambers fill during diastole (relaxation of the heart) and pump blood out during systole (contraction of the heart). Normal blood pressure 120/80 mmHg ( book states 120/70 mmHg) Normal blood pressure 120/80 mmHg ( book states 120/70 mmHg) - Various factors can cause an increase or decrease in blood pressure

PERIPHERAL RESISTANCE Opposition of blood flow - measure of the degree to which the blood vessel hinders or resists the flow of blood Main factors in Peripheral Resistance 1.) Blood vessel radius 2.) Blood vessel length 3.) Blood viscosity

RADIUS Single most important factor in determining blood flow resistance Smaller the blood vessel radius, the greater the resistance - due to frictional drag between the blood and the vessel walls Lipid deposits (fats) can cause the radius of an artery to decrease - Atherosclerosis - Can lead to coronary heart disease, heart attack, stroke, or death

LENGTH OF BLOOD VESSEL The the vessel length, the greater the resistance The longer the vessel length, the greater the resistance - Due to friction between the blood and vessel walls - The length of a person’s blood vessels change only as a person grows; otherwise, length generally remains constant.

BLOOD VISCOSITY Measurement of the “thickness” of blood. Blood viscosity depends mainly on hematocrit, or the fractional contribution of red blood cells to total blood volume. - The higher the hematocrit, the more viscous the blood is; - The lower the hematocrit, the less viscous the blood. Temperatures also has a significant effect on viscosity - As temperature decreases, viscosity increases