Arteries, Veins and Control of Peripheral Vascular Resistance Flashcards
What types of blood vessels are in the CV system?
- Large arteries
- Capillaries
- Arterioles
- Venules
- Veins
Is the structure of blood vessels in the CV system adapted to their role?
YES
What are the components of blood vessels?
- Endothelial cells
- Vascular smooth muscle
- Elastin and collagen
What does endothelial cells do in blood vessels and why are they important?
- Line all vessels and inside of heart chambers
- Important for local blood pressure control
- Prevent platelet aggregation and blood clot formation
- Angiogenesis and vessel remodelling
- Permeability barrier for nutrients/fluid between plasma and interstitial fluid
What does vascular smooth muscle do in blood vessels and why are they important?
- Present in all vessels with exception of smallest capillaries
- Determine vessel radius by contracting and relaxing
- Secrete an extracellular matrix which gives vessels their elastic properties
- Can multiply in some diseases
Why is elasticity important in vascular smooth muscle?
To allow large arteries to act as a pressure resevoir.
Prevents pressure falling to 0 as blood leaves arteries during diastole.
What is an example of a clinical defect in vascular smooth muscle?
-Calcification in human artery; caused by healing response to the presence of dead cells. Reduces elasticity of vessel- BP affected.
Age also reduces elasticity of vessel.
In what area of arteries and veins is elastin and collagen type III?
They have a tunica externa level composed of elastin and collagen type III.
What is blood pressure?
Circulation of fluid contained within a space of definite volume.
When does blood pressure fall during circulation?
Pressure falls as blood circulates from left ventricle to right ventricle (systemic circulation).
And right ventricle to the left ventricle (pulmonary circulation).
What do we need to supply our basic metabolic demands in terms of blood?
We require a certain volume/min.
What is the normal blood pressure?
120/80 (systolic/diastolic)
This varies with age, environment etc.
What unit can be used to quote blood pressure?
mmHg.
What is mean arterial pressure(MAP) and how can it be calculated?
MAP is average pressure pushing blood round the system.
Calculated as MAP=CO X TPR (total peripheral resistance)
MAP= diastolic BP + 1/3 pulse pressure (PP)
Which feature of aorta and arteries allow them to contain a small ammount of blood at high pressure?
Very thick walled/elastic
What sort of resitance does arterioles have?
A variable resistance system which distributes the blood - dissipates most of the pressure.
What sort of surface area do capillaries have?
Have a vast surface area where the interchange of substances with the extracellular fluid of the tissues occurs (are as little as one cell thick).
What do the venules, veins and venae cava do?
A collecting and resevoir system which contains most of the blood (70%) at low pressure.
What is the function of capillaries and the features that allow this?
Perform exchange of nutrients/waste products in the CV system.
- Just wide enough for erythrocyte
- One cell thick to allow rapid exchange with tissues
- Flow depends on supply from arterioles
What factors influence transport between capillaries and tissues?
-The blood in the capillaries exerts a pressure on the capillary wall (hydrostatic pressure)
This tends to favour movement of fluid (small molecules) out of the capillary.
-The plasma has an intrinsic osmotic pressure due to plasma proteins (colloid pressure)
Tends to favour movement of fluid into capillary
What happens to hydrostatic pressure and colloid pressure as blood pressure drops?
Hydrostatic pressure decreases
Colloid pressure will remain the same as plasma protein are too big to leave capillary.
What is the exceptions of the pressure systems in the CV system?
In pulmonary system
- Pulmonary hydrostatic pressures are much lower than systemic pressure
- Colloid pressure equivalent
- Therfore have a net fluid of transfer at both ends.
- Prevents pulmonary oedema.
What is a clinical defect that may result from pressures in the pressure system in the heart?
Anything that increases capillary hydrostatic pressure eg. heart failure can lead to pulmonary oedema.
What happens to tissue fluid?
We dont get it all back, we have net loss.
A build up in tissues would lead to oedema.
Lymphatic system move this fluid back to blood, also responsible for moving asorbed fat into the circulation.
Where are main baroreceptors?
Carotid sinus and aortic arch
