blood vessels structure and function Flashcards
5 main types of blood vessel
arteries (conducting/ distributing vessels) arterioles (resistance vessels) capillaries (exchange vessels) venules (collecting vessels) veins (capacitance vessels)
walls of blood vessels- tunica interna/intima
inner layer- has direct contact with blood, has epithelial lining and supporting connective tissue and sometimes elastic fibres
walls of blood vessels- tunica media
middle layer- smooth muscle and different connective tissue, binds inner and outer together most variable layer
walls of blood vessels- tunica externa/adventitia
outer layer, has connective tissue sheath for protection has anchoring system so blood vessels are stuck to something and stay in position
different between veins and artery structure
veins are larger in diameter (larger lumen)
veins have thinner walls
veins are more collapsed- less uniform
veins have valves
veins have a lower amount of BP and are less resilient
arteries are elsatic and respond to pressure changes (vasoconstrict/contract)
why are arteries important to stop bleeding
they can contract to stop bleeding
what do arteries do
they carry blood pumped from the heart to the body, they are able to accommodate high pressure, able to propel blood onwards, able to even out pressure changes, able to vasoconstrict/ dilate
different types of artery
elastic (larger arteries such as aorta) and muscular (size of medium vein)
walls of arteries
tunica media- thick muscular to elastic, more smooth muscle and will be thick
inner layer has a large number of elastic fibres meaning it can change diameter and take pressure
external layer is strong- contains collagen and elastic fibres to withstand alterations to blood flow
arteries- conducting vessesl
large radius to offer little resistance to blood flow
arteries- pressure reservoir
collagen fibres for tensile strength, elastic fibres to provide elastic recoil
what are arterioles
smaller branches of arteries, lead into capillaries, resistance vessels- regulate arterial blood pressure and distribute blood, have sphincters that can constrict or dilate depending on where blood is needed
what are capillaries
they are smallest with thin walls, microscopic capillary networks permute all active tissues, exchange vessels of the cardiovascular system, materials diffuse between blood and interstitial fluid, where the arterial and venous system
capillary layers
only has 1 layer- tunica interna to allow exchange to occur
how are capillaries arranged
found in clumps- capillary networks/beds/plexus, one arteriole gives rise to lots of these clumps, capillary networks help to reduce the pressure, entry to the capillary is guided by precapillary sphincters- meaning blood can be redistributed to where required
what are venules
smallest branches of veins, come out of other side of capillary, allows blood to return to the capillary bed to the venous system, have the same function as veins
layers of venules
only have 1 layer if close to capillary- further away they have 3 layers
what are veins
they regulate and return blood to the heart (venous return), unable to withstand high pressures, requires skeletal muscle pumps to asset venous return, valves prevent backflow and aid venous return
layers of vein
same 3 layers- don’t have a lot of smooth muscle so requires muscle pump to keep blood moving, have valves to prevent backflow
veins- capacitance vessels
large radius and little musculature and reservoir for blood- due to large diameter
Resistance of veins
little resistance, small to large, venous pressure is low
venous reurn
lower body must overcome gravity-
valves- prevent backflow, muscle pump- helps to push blood upwards, muscle contracts and squeezes veins to push blood upward (blood cannot flow upwards due to veins)
respiratory pump- only takes effect when exercising- when inhaling pressure drops in thorax drawing air in, and drawing blood up
what is the equation for blood pressure
cardiac output X peripheral resistance= blood pressure
increasing either makes blood pressure go up
what are the main factors that influence blood pressure
cardiac output, peripheral resistance, blood volume
blood pressure- barrow receptors
barrow receptors within blood vessels detect pressure in them, hormonal responses are to do with adrenal gland that produce hormones that communicate with smooth muscles in blood vessels (constrict/ dilate)
normal blood pressure
120 (systolic- when hear contracts) / 80 (when heart relaxes- pressure in vessels when heart relaxes)
what is hypertension (essential and secondary)
BP greater than 140/90mmhg, essential hypertension- no medical cause, no specific reason for it, mainly related to risk factors, secondary hypertension- specific conditions causing it (e.g. COPD)
risk factors- hypertension
genetic- if it runs in family more likely to have it, environmental- socioeconomic group (availability to poor diet), age, gender, pathology
lifestyle factors- hypertension
smoking causes change in blood vessel, diet (salts and fats), alcohol, sedentary lifestyle, obesity, stress
symptoms of hypertension
headaches, shortness of breath, chest pain and palpitations, nose bleeds, distributed vision,
first line of management for hypertension
lifestyle changes
medication for hypertension
A and E inhibitors (work on adrenal gland decrease blood pressure through hormone regulation), B blockers, calcium channel blocker, diuretics, rest on smooth muscle of blood vessels
consequences of long term hypertension
blood vessel damage (damage to tunica interna- atherosclerosis), heart attack/ failure, kidney failurem stroke
pathology of arterial walls- arteriosclerosis
hardening and loss of elasticity of large and medium arteries
pathology of arterial walls- arteriolosclerosis
hardening and loss of elasticity or arterioles
pathology of arterial walls- atherosclerosis
hardening of an artery due to depostion of an atheroscleortic plaque
risk factors and consequences and treatment of atherosclerosis
risk- smoking, HBP, diabetes, high cholesterol
can cause angina, TIA (stroke), intermittent claudication- can result in amputations of limbs, can cause hemorrhage
with lifestyle changes can be reversed
development of atherosclerosis- 1
if blood is pushed through tunica interna at high pressure it is no longer smooth, giving the ability for things to catch to it, if you are eating a diet with a high LDL consumption- these circulate in blood and get caught on tunica interna
development of atherosclerosis- 2
this causes WBC to be sent in this area, this leads to macrophages eating away at LDL’s, they don’t manage to move away/ get stuck, they are then called foam cells, this sets up chronic inflammatory process- as body sends more macrophages
development of atherosclerosis- 3
the first response is to push away from blood vessel- it pushes away from the internal areas of blood vessel- into tunica media, plaques encroaches on internal part of blood vessel, because of the elastic properties begin to be lost, fibroblasts can be laid down and calcium that circulates in blood- leads to build up becoming rock hard
consequences of atherosclerosis
leads to an increased BP and hypertension, due to high blood pressure blood flow in artery- plaque can become displaced- platelets recognise this as damaged- platelets are sent and cause blood clots- block arteries to brain and heart
what is an aneurysm
excessive localised enlargement of an artery caused by weakness in arterial wall- meaning it could rupture, can be linked
common locations of aneurysm
aortic aneurysm and cerebral aneurysm
what is deep vein thrombosis
thrombus (blood clot) formed in large veins
risk factors of deep vein thrombosis
family history, immobility, recent surgery, obesity
symptoms of deep vein thrombosis
Discolouration- red, pain, swelling, homan’s test- if positive it is likely to have it- when dorsiflexing ankle will have severe pain
pathologies of the venous system- varicose veins
bulging veins- valves become incompetent- don’t stop backflow
pathologies of the venous system- chronic venous insufficiency
leg swelling, skin colour and texture change, venous ulcers
What treats varicose veins and chronic venous insufficiency
both treated with exercise- muscle pump working and compression stockings
causes of venous insufficiency
faulty valves, varicose veins, standing for long periods of time, women more than men, obesity, pregnancy, family history
