Heart Flashcards
Closed circulatory
system
Blood remains within blood vessels
Name different types of blood vessels
Arteries, arterioles, capillaries, venules and veins
Structure of arteries
Thick muscular layer thick elastic layer thick outer layer small luman
no valves
Capillary endothelium
Extremely thin
one cell thick
contains small gaps for small molecules to pass through (e.g. glucose, oxygen)
Capillaries
Form capillary beds
narrow diameter (1 cell thick) to slow blood flow
red blood cells squashed against walls shortens diffusion pathway
small gaps for liquid / small molecules to be forced out
Arterioles
Branch off arteries
thickest muscle layer to restrict blood flow
thinner elastic layer and outer layer than arteries as pressure lower
Tissue fluid
Liquid bathing all cells contains water, glucose, amino acids, fatty acids, ions and oxygen
enables delivery of useful molecules to cells and removal of waste
Tissue fluid formation
At arteriole end, the smaller diameter results in high hydrostatic pressure
small molecules forced out (ultrafiltration)
red blood cells / large proteins too big to fit through capillary gaps so remain
Reabsorption of tissue fluid
Large molecules remaining in capillary lower its water potential
towards venule end there is
lower hydrostatic pressure due to loss of liquid
water reabsorbed back into capillaries by osmosis
Role of the lymph in tissue fluid reabsorption
Not all liquid will be reabsorbed by osmosis as equilibrium will be reached
excess tissue fluid (lymph) is absorbed into lymphatic system and drains back into bloodstream and deposited near heart
Cardiac muscle
Walls of heart having thick muscular layer
unique because it is:
myogenic - can contract and relax without nervous or hormonal stimulation
never fatigues so long as adequate oxygen supply
Coronary arteries
Blood vessels supplying cardiac muscle with oxygenated blood branch off from aorta
if blocked, cardiac muscle will not be able to respire, leading to myocardial infarction (heart attack)
Structure of the heart
Adaptation of left ventricle
Has a thick muscular wall in comparison to right ventricle enables larger contractions of muscle to create higher pressure
ensures blood reaches all body cells
Veins connect to the heart
Pulmonary artery - carries deoxygenated blood from right ventricle to lungs
Aorta - carries oxygenated blood from left ventricle to rest of the body
Valves within the heart
Ensure unidirectional blood flow semilunar valves are located in aorta and pulmonary artery near the ventricles
atrioventricular valves between atria and ventricles
Opening and closing of valves
Valves open if the pressure is higher behind them compared to in front of them.
AV valves open when pressure in atria > pressure in ventricles SL valves open when pressure in ventricles > pressure in arteries
The Septum
Muscle that runs down the middle of the heart
separates oxygenated and deoxygenated blood maintains high concentration of oxygen in oxygenated blood maintaining concentration gradient to enable diffusion to respiring cells
Cardiac output
Volume of blood which leaves one ventricle in one minute.
heart rate = beats per minute
Cardiac output= heart rate x stroke volume
Stroke volume
Volume of blood that leaves the heart each beat
measured in dm^3
Cardiac cycle
Consists of diastole, atrial systole and ventricular systole
Diastole
Atria and ventricular muscles are relaxed
when blood enters atria via vena cava and pulmonary vein increasing pressure in atria
Atrial systole
Atria muscular walls contract, increasing pressure further. pressure atria > pressure ventricles
atrioventricular valves open and blood flows into ventricles ventricular muscle relaxed
Ventricular systole
After a short delay (so ventricles fill), ventricular muscular walls contract
pressure ventricle > atria pressure and artery pressure atrioventricular valves close and semi-lunar valves open blood pushed into artery
