Flashcards in Lecture 7: Blood Vessels - Structure and Function Deck (41):
what is the basic arterial vessel wall structure
tunica intima - endothelial cell layer, basement memb, sub endothelial CT layer, internal elastic lamina
tunica media - smooth muscle cells & elastic fibres in concentric layers, external elastic lamina
tunica adventitia - CT blends with surrounding tissue, contain smaller blood vessels in larger arteries = vasa vasorum
what is the function of the tunica intima
prevents plasma membranes escaping
secretes vasoactive mediators
what is the function of the tunica media
what is the function of the tunica adventitia
tethers vessel to surrounding tissue
what is the functional significance of the smooth continuous endothelium
low frictional resistance
what is the functional significance of the elastic lamina and elastic fibres?
elasticity during pulsate pressure changes
what is the functional significance of the smooth muscle cells
regulate internal calibre of vessel lumen
what is the functional significance of the collagen fibres
protection against stresses
what are the five functional groups of blood vessels?
1. conducting arteries
2. distributing arteries
3. resistance vessels
4. exchange vessels
5. capacitance vessels
list three features of conducting arteries
1. large and thick walled
2. very distendable - lots of elastic
3. most compliant ARTERIES - can stretch and recoil important for the changing blood pressure
what are some examples of conducting arteries?
what is compliance ?
the degree of volume change when distending pressure increases.
C = Delta V/ Delta P
veins are more compliant than arteries
why is arterial compliance important?
important in converting pulsative flow from the heart
elastic arteries act as a pressure reservoir, continues driving blood forward during diastole
what are two features of distributing arteries
1. muscular - tunica media has more smooth muscle (relative to lumen) than conducing arteries
2. rich sympathetic innervation
what is the primary role of the distributing arteries?
conduct flow to the smaller arteries
what are some examples of distributing arteries?
femoral artery, internal carotid artery
where does the most major fall in blood pressure occur?
over the resistance vessels
what are examples of resistance vessels?
arterioles and metarterioles
what is the role of the arterioles?
regulate total peripheral resistance, control blood flow to the capillary beds with metarterioles
what is the wall structure of the arterioles
tunica intima - fenestrated endothelium
tunica media - 1-2 layers of smooth muscle
tunica adventitia - loose CT
what is the role of the metarterioles?
regulate total peripheral resistance, co-op with arterioles to control blood flow to capillary beds
what is the wall structure of the metarterioles?
tunica intima - fenestrated endo
tunica media - single intermittent layer of smooth muscle or no smooth muscle
tunica adventitia - not recognised
what is resistance?
the opposite of flow
= difference in mean pressure needed to drive one unit of flow.
the largest blood pressure decrease is found in the arterioles vessels, pulsative flow also disappears here -- this is where the largest resistance is.
describe the rate of blood flow (L/min)
remains the same across all vascular beds
in individual capillary speeds is very slow but same volume is maintained
what is TPR?
resistance to flow through the entire systemic circulation
TPR = (mean aortic pressure - Vena cava pressure/ CO)
what is CO?
CO = HR x TPR
what are some determinants of TPR?
MAP = CO x TPR
MAP = diastolic pressure e+ 1/3rd pulse pressure
what are two features of exchange vessels?
high cross sectional area
what is the function of exchange vessels?
metabolic exchange takes place across the walls of exchange vessels, CO2, O2 and Metabolites
how are capillaries classified
1. position in vascular bed
2. nature of endothelial lining
what is the x2 essential components of capillary wall structure
1. thin endothelial layer
2 basement membrame
how can the endothelial lining differ
- continuous with thick or thin endothelium = lipid soluble
- discontinuous = proteins can come through
what are sinusoids
discontinuous endothelial layer and basement membrane
= allow easy interchange of macromolecules and fluid
characteristic of liver and haemopoietic tissue
what are post capillary venules
drain several capillaries
continuous endothelial layer and basement membrane, surrounded by persecutes, no or few SMC
promote migration of WBC due to leaky joins b/w cells
what are capacitance vessels?
large volume and low pressure
return blood to heart
includes all muscular venules and veins
what is the wall structure of the capacitance vessels?
tunica intima - same as arteries but no internal elastic lamina
tunica media - relatively small amounts of SMC and elastic fibres
usually abundant collagen fibres
no external elastic lamina
tunica adventitia - many large collagen fibres in the CT
often the thickest layer
what factors influence venous return?
smooth muscle contraction- induce vasoconstriction
skeletal muscle pump effect
one way valves
thoracic and cardiac pressure: incl pressure gradient between veins and heart
valves in the lumen of veins
composed of two cusps
valves present in medium size veins.
opening of pocket directed towards the heart
standing animal, weight bearing limbs extend well below heart, would lead to pooling and excessive filtration bt the valves convert the column of the vein into short segments reducing hydrostatic pressure
--> even blood vol in each segment
valves make sure theres an equal amount of blood in each segment
increase VR prevent back flow and pooling
skeletal muscle pump
contraction of the muscles in the limb applies pressures to the veins. promotes movement of blood towards the heart since the valves prevent the movement away from the heart
respiratory activity and cardiac suction
mechanism work by increasing pressure gradient between the veins and the heart