Human Circulatory System Flashcards
Why may humans need a circulatory system
The surface area to volume ratio is not large enough for diffusion alone to occur and supply substances like glucose and oxygen to the body and cells
What are the 2 pumps of the heart
Atrium
Ventricle
What is the atrium
Thin walled and elastic, can stretch when filled with blood
What is the ventricle
Thick muscular walls to pump blood around the body or lungs
Why are 2 pumps needed
To maintain blood pressure around the whole body
One pump would be too slow as blood passes the lungs causing it to loose pressure
What are the 4 main vessels connecting the heart
Aorta
Pulmonary artery
Pulmonary vein
Vena cava
What does the aorta do
Connected to the left ventricle and carries oxygenated blood to all parts of the body except for the lungs
What does the pulmonary artery do
Connected to the right ventricle and carries deoxygenated blood to the lungs where it is oxygenated and the carbon dioxide is removed
What does the pulmonary vein do
Connected to the left atrium and brings deoxygenated blood back from the tissues except the lungs
What are the 5 blood vessels
Arteries
Arterioles
Capillaries
Venules
Veins
Structure and function of arteries
Thick walls to withstand high blood pressure
Contains elastic tissue to stretch and recoil enabling smooth blood flow
Lined with smooth endothelium to reduce friction and ease the flow of blood
Small lumen to maintain high blood pressure
Structure and function of aterioles
They branch off arteries
Have thinner and less muscular walls
Their role is to feed blood into capillaries
Structure and function of capillaries
Smallest blood vessels
Site of metabolic exchange
Very thin walls one cell thick to keep the diffusion pathway short
What are venules
Larger than capillaries but smaller than veins
What do veins do
Carry blood with low oxygen from the body to the heart
Structure and function of veins
Wide lumen to maximise volume of blood carried to the heart
Thin walls due to low blood pressure
Have valves to prevent backflow of blood
Little elastic tissue as no need for stretching and recoiling
What are the 3 stages of the cardiac cycle
Atriole systole
Ventricular systole
Diastole
Describe atriole systole: stage 1 of the cardiac cycle
Atrium muscle contracts
Ventricles relax
Increased pressure and decreased volume
Atrial ventricular valve opens so blood enters ventricle
Describe ventricular systole: stage 2 of the cardiac cycle
Ventricle muscle contracts
Atria relaxes
Decrease volume and increased pressure
Semi lunar valve opens
Av valve closes to prevent backflow
Blood leaves via arteries
Describe diastole: stage 3 of the cardiac cycle
Atria and ventricle relax
Semi lunar valve closes
High artery pressure and low volume
Blood enters via veins
Cardiac output formula
Stroke volume x heart rate
