The Cardiovascular System 2 Flashcards
what makes up the arterial system and venous system
- Arteries and arterioles
- Veins and venules
what are the 3 walls of blood vessels called
inner - Tunica intima
middle - Tunica media
outer - Tunica externa
describe the Tunica intima
- made of 2 layers, endothelium and a connective tissue layer
- in arteries the connective tissue layer has elastic fibres
what role does the endothelium have and play
- releases vasoactive substances which affect the vascular tone
- the vascular tone is the state of being constricted or dilated
- this affects blood pressure and flow maintaining vascular homeostasis
name 2 vasoactive substances and what they cause
Nitric oxide - causes vasodilation
Endothelin - causes vasoconstriction
Describe the Tunica media
- Concentric sheets of smooth muscle in a loose connective tissue of collagen or elastic (arteries)
- this encircles the endothelium binding the inner and outer membranes together
how does the Tunica media differ in arteries and veins
- in arteries the smooth connective tissue between the muscles are elastic not collagen
- there is an additional elastic membrane between the Tunica media and externa in arteries
describe the tunica externa
- Anchors vessels to adjacent tissues
- contains collagen fibres, elastic fibres and smooth muscle in veins
What does the term vasa vasorum refer to?
- these are the small arteries and veins that carry blood to and away from the tunica media and tunica externa
how do arteries change as they get further from the heart?
- they transition from more elastic to more muscular
name the 3 types of capillaries
- continuous capillary
- fenestrated capillary
- sinusoid capillary
what 2 features do all capillaries have
- basement membrane
- endothelial cells
describe a continuous capillary and what can pass out of one
- no pores or gaps between endothelial cells
- only permits the diffusion of water, small solutes and lipid soluble things
- blocks blood cells and plasma proteins
where are continuous capillaries found?
- all tissues except epithelia and cartilage
- specialised continuous capillaries in CNS and thymus have special permeability
describe a fenestrated capillary and where they are found
- have pores in the endothelial lining
- large pores allow rapid exchange of water and larger solutes
- found in endocrine organs, kidneys and intestinal tract
describe sinusoid capillaries and where they are found
- have large gaps between endothelial cells
- free exchange of water and large plasma proteins through gaps
- gaps are guarded by phagocytes
- found in liver, spleen, bone marrow and endocrine organs
what is a thoroughfare channel
- when an arteriole directly connects to a venule without a capillary bed to separate them
what makes up the valves of the veins
- folds of tunica intima
what is the condition varicose veins
- when the vein wall weakens near the valve
how do you calculate total capillary blood flow
total capillary blood flow = cardiac output = heart rate*stroke volume
what is the pressure gradient
- the difference in blood pressure between one end of the vessel to the other
what is the typical pressure gradient?
85mmHg
what is and what makes up total peripheral resistance
- resistance to blood flow
made by: vascular friction, blood viscosity, turbulence
what is hypertension?
- abnormally high blood pressure
