HEART AND BLOOD VESSELS

BLOOD VESSELS

Arteries From heart to tissue Usually carry oxygenated blood Branch into arterioles

Veins From tissues back to heart Usually carry deoxygenated blood Venules

Capillaries Small, thin Allow diffusion into tissues

ARTERIES & ARTERIOLES

3 layers of tissue Endothelium Connective tissue and smooth muscle Connective tissue with elastic/collagen fibers

Smooth muscles in arterioles control blood pressure and volume of blood to tissues: Vasoconstriction Vasodilation

Exercise increases vasodilation in arterioles of muscles

VEINS AND VENULES

Blood flows from capillaries to venules to veins

Large diameter, some smooth muscle

Pressure is lower, farther from heart

Valves prevent back flow

HEART

Basic Structure: Atrium – receiving chamber Ventricle – pumping chamber

Evolution Fish

1 atrium, 1 ventricle Single circuit of blood vessels

Amphibians, Most Reptiles 2 atria, 1 ventricle Double circuit Conus arteriosus separates oxygen rich & poor blood

HEART, CONT.

Birds, Mammals & crocodilians 2 atria, 2 ventricles Conus arteriosus aorta & pulmonary arteries Ventricle separated by septum Double circuit

http://trc.ucdavis.edu/biosci10v/bis10v/media/ch22/circulatory_systems.html

http://trc.ucdavis.edu/biosci10v/bis10v/media/ch22/blood_circulation.html

HUMAN HEART

Hollow, muscular organ

Cardiac Muscle

Enclosed by the pericardium

Septum separates left and right sides of heart In fetal heart, foramen ovale allow blood to flow

from right to left atrium Why?? Closes and leaves fossa ovalis

HEART VALVES

AV valves Right – tricuspid Left -mitral valve or bicuspid

Chordae tendinae hold valves in place

As blood enters atria, pressure forces valves to open

As ventricles contract, back pressure forces valves closed

HEART VALVES, CONT.

Semilunar valves Exit from heart Aortic Pulmonary

As ventricles contract, valves open

As ventricles relax, blood pressure in arteries is higher, valves close

http://www.bostonscientific.com/templatedata/imports/HTML/CRM/heart/interact_4.html

PATTERN OF CIRCULATION

Vena cava returns blood from body to heart

Right atria, right ventricle to pulmonary artery

Lungs gas exchange

Pulmonary vein to left atrium to left ventricle

Aorta to body

YOUR HEART IN ACTION

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