Pulmonary circuit
- blood vessels that carry blood to and from the lungs
Systemic circuit
- blood vessels that carry blood to and from all body tissues
Ventricles
right - pulmonary circuit (lungs)
left - systemic circuit (body)
coronary circulation
- blood supply to the heart muscle
- supplies oxygen and nutrients to the heart muscle cells
- veins of heart all drain into the coronary sinus
- coronary sinus then opens directly into the right atrium
Ventricular diastole
- blood enters both atria
- ventricles are relaxed and tricupsid & bicupsid valves open
- passive filling of blood into ventricles- 80% ventricular filling
- both atria contract causing blood to enter ventricles- remaining 20% of ventricular filling
- semilunar valves closed
ventricular systole
- ventricles both contract causing blood to exit heart and atria relax (atrial diastole)
- tricupsid & bicupsid valves- closed, semilunar valves open
- ventricles relax at end of this stage - cycle begins again
Heart sounds - S1
(lub)
- louder longer sound
- atrioventricular valves close
- onset of ventricular systole (contraction)
Heart sounds - S2
(dub)
- short and sharper sound
- semilunar valves close
- onset of ventricular diastole (relaxation)
Blood vessel structure - tunica intima
- inner layer
- thin layer of tissue
- endothelium lines the blood vessel
Blood vessel structure - tunica media
- middle layer
- contains smooth and elastic fibres
- amount varies depending on type of blood vessel
- thicker in arteries compared to veins
blood vessel structure - tunica externa (adventitia)
- external layer
- contains collagen fibres
- anchors blood vessel to its surroundings.
Blood vessels - artery
- thick wall rich in elastic fibres and smooth muscle
- transport blood away from heart
- subject to high blood pressure from heart
Blood vessels - vein
- thin wall
- larger lumen
- valves present
- transport blood towards heart
- subject to low blood pressure
blood bessels - capillary
- smallest blood vessels
- single cell wall thick
- gas exchange takes place
arterioles
- smallest arteries
- smooth muscle in blood vessel wall
- arteriole diametre controls blood flow into capillaries
- arterioles dilate- blood flow into capillaries increases
- arterioles constrict- blood flow into capillaries decreases
venules
- smallest veins
- blood flowing out of capillaries enters venules
Blood flow
- volume of blood flowing through blood vessels or organ in given period
blood pressure
- force exerted on a vessel wall by the blood as it is pumped by the heart.
- measured in mm Hg
- systolic (ventricular contraction)
- diastolic (ventricular relaxation)
- pulsepressure is diff between systolic and diastolic
resistance
- opposition to flow of blood through vessels
- blood viscosity, blood vessel length, blood vessel diametre
blood pressure in arteries
- highest blood pressure compared to other blood vessels
- highest blood pressure in aorta
blood pressure in capillaries
- very low pressure
- extremely fragile blood vessels
- high pressure would rupture capillaries
blood pressure in veins
- very low pressure
factors that impact resistance - blood viscosity
- thickness of blood
- greater the thickness > inc resistance > increase difficulty in blood flow
- increase blood viscosity due to dehydration or elevated blood cholesterol
> heart must work harder to force thickened blood to move through the blood vessels
factors that impact resistance - blood vessel length
- longer vessel > greater resistance
- obese individuals have longer blood vessels
> heart must work harder to force blood to move through the blood vessels to reach the end
