structure and function of the cardiovascular system

functions of the cardiovascular system

deliver O₂ to the muscles and remove CO₂, transport nutrients to organs and muscle cells to remove waste, maintain an even body temperature (homeostasis), fight disease, transport hormones

circulation of blood to the body

during exercise, blood flow redistributes to the working muscles so that 80-90% of total cardiac output is directed to working muscles, arteries open up (vasodilate) and constrict (vasoconstriction) to allow more or less blood to reach certain body areas

hypothermia

body becomes too cold and heat needs to retained, blood flow to the skin is restricted

hyperthermia

body becomes too hot, the cardiovascular system directs blood flow to the skin so heat is lost to the environment by sweating

Heart

muscular pump which contracts continuously to drive blood around the body, protected by ribs, sternum and vertebral column, separated into two sides, 4 chambers: left and right atrium & left and right ventricle

left atrium

receives oxygenated blood

right atrium

receives deoxygenated blood

left ventricle

pumps oxygenated blood

right ventricle

pumps deoxygenated blood

valves

located between the atrium and ventricles which ensures blood flows in only one direction

cardiac cycle

two separate circuits (systemic and pulmonary), left and right sides of the heart function as two separate pumps

systemic circulation

carries blood from the heart to all parts of the body (except lungs), and back again, left side pumps oxygenated blood via aorta, deoxygenated blood returns from the right side via vena cava.

pulmonary circulation

carries blood from the heart to the lungs and back again, ride side of the heart pumps deoxygenated blood to the lungs via pulmonary artery, oxygenated blood returns into the heart from the lungs via pulmonary vein

blood vessels

arteries, veins and capillaries

arteries

carry blood away from the heart (oxygenated), pushed through the arteries caused by contractions

pulse

flow or surge of blood through the arteries felt near the skin

veins

blood towards the heart (deoxygenated), valves allow the return but not back flow of blood

capillaries

blood vessels reach every cell of the body, allow passing of tissues and removal of carbon dioxide

structure of arteries

thick muscular walls, no valves, blood under high BP

structure of veins

thin, collapsible walls, valves present, blood under low BP

structure of capillaries

very thin walls (only one cell thick), branch from arterioles and venules to form a network

blood functions

transport of nutrients and waste products, regulation of body temp, protection of the body (white blood cells)

components of blood

plasma, white blood cells, red blood cells, platelets

plasma

appox 55% of total blood volume, clear yellow liquid, 90% water, carries blood cells which continually passes through capillary walls and into tissues

white blood cells

approx <1% of total blood volume, responsible for moving to sites of infection where they destroy bacteria and other disease causing organisms

red blood cells

approx 45% of total blood volume, red colour, responsible for carrying oxygen to the cells and the removal of carbon dioxide away from muscles and organs

platelets

very small percentage, produced in the bone marrow and cause the blood to clot when a vessel is damaged to prevent excess bleeding

cardiac output equation

stroke volume (ml/beat) x heart rate (bpm) = cardiac output (L/min)

heart rate

measured by combining the pulse rae, blood flow pushed through the arteries by heart

carotid pulse

located at the neck

radial pulse

located at the wrist

resting heart rate (RHR)

heart rate at rest, lying down but awake, not having recently exerted yourself, typically 60-80 bpm

maximum heart rate (MHR)

number of beats per min when the heart is working at maximum, calculated as 220-age=MHR

target heart rate zone (THR)

age specific heart rate range to be maintained during aerobic exercise to receive physical benefits

stroke volume

measured in litres (L). L/beat, average at rest is 70-90 ml

blood pressure

pressure of the blood in the arteries as the heart pumps it around the body, during exercise, blood pressure increases due to an increase in cardiac output (Q)