Circulatory System TransportationRegulationProtection

Open vs. Closed Systems Open-not confined to vessels Closed- confined to vessels 42.2

Vertebrate Circulatory Systems Fish-2 chambered heart, single circulation Amphibians, some reptiles- 3 chambered heart, double circulation Mammals, birds-4 chambers, complete separation of oxygenated and deoxygenated blood. 42.3

Mammalian double circulation Atrioventricular valves (AV) are between the atrium and the ventricle. Semilunar valves are at the exits of the heart. Valve defects may cause a heart murmur-detected as hissing as the blood leaks back through a valve. 42.4

Blood Vessels Arteries, arterioles- thicker, leave heart Veins, venules- have valves to keep blood flowing to heart- varicose veins- valve failure. Capillaries- endothelial tissue only. All exchanges take place here Capillary Bed Pix Vein valve pix

Blood Blood is a connective tissue Cells are suspended in plasma Plasma- Mostly water, 55% of blood Formed elements (cells and platelets), 45%. Platelets are cell fragments pinched off from cells in the bone marrow. pH of 7.4

Blood Composition 42.14

Stem Cells If there is not enough oxygen to the cells the kidneys convert a plasma protein to a hormone- erthropoietin- causes more RBC’s to be made

Blood Clotting 42.16

Cardiac Cycle One complete sequence of pumping and filling Systole-contraction Diastole-relaxation 42.6

Cardiac Output Cardiac Output is the volume of blood pumped per minute from the left ventricle. Depends on –Heart rate-# of beats per minute –Stroke volume-amount of blood pumped from the left ventricle per contraction

Electrical Excitation and Contraction Cardiac muscle cells are connected by intercalated discs. 42.7

Blood Flow and Pressure Follows fluid laws Pressure drops in capillary beds-total diameter increases Speeds up again in vein as cross sectional area decreases again. Constricted blood vessels raise blood pressure. (Stress can cause this constriction) 42.12

Blood Flow Dynamics 42.10

Normal artery (left) and one showing atherosclerosis (right) Plaques develop on inner walls and narrow it. Fibrous connective tissue, and lipids like cholesterol. Increases B.P. due to narrowing and reduced elasticity. In arteriosclerosis the plaque is hardened with Ca-”Hardening of the arteries.” Clots or thrombus are more likely to form here and be caught here

Cardiovascular Disease Leading cause of death in the US. Heart Attack-death of cardiac muscle caused by blockage of coronary arteries Stroke- death of nervous tissue in brain- rupture or blockage of artery in the head