Blood Vessel Structure And Function Flashcards
5 main blood vessels
Arteries - conducting
Arterioles- resistance vessels , BP
Capillaries
Venules
Veins- capacitance
3 layers
TUNICA INTIMA/ INTERNA
Innermost and contacts the blood.
Epithelial lining, connective tissue + elastic fibres
TUNICA MEDIA
Smooth muscle + different connective tissue
Most variable
TUNICA EXTERNA / ADVENTITIA
Connective tissue sheath
Stabilising system to bind blood vessels to things
Artery vs vein
Vein= thinner walls , larger lumen
Vein not uniform shape and arteries are round
Veins have valves
Veins = lower bp
Veins less resilient - can’t withstand high pressure
arteries = very elastic, dilate or constrict from ANS + hormone signals
ARTERIES
Muscular = medium sized vein size , 0.5mm, more numerous
Elastic= larger arteries eg, aorta, common carotid, pulmonary and common iliac , up to 2.5cm
Tunica intima= many elastic fibres to expand and recoil and withstand pressure
Tunica media= more smooth muscle - varies from muscular or elastic arteries
Tunica externa= collagen + elastic fibres , withstand pressure and alterations
Blood propels forwards + even out pressures
ANS + hormones vasodilation + vasoconstriction
Arteries are 3 things
CONDUCTING vessels = deliver blood to specific areas and large radius so little resistance
PRESSURE RESERVOIR = collagen fibres + tensile strength and elastic fibres + elastic recoil
Regulate flow = smooth muscle contract and relax
ARTERIOLES
30nm in diameter
Less elastic + collagen as pressures evened out in arteries
More smooth muscle and sphincters to redistribute blood
Regulate blood pressure, distribute blood and lead into capillaries
Capillaries
Thin walls
Oxygen. Co2 and wastes exchanged
Only tunica intima
Blood flow slow
Blood and interstitial fluid
One arterioles gives rise to a large capillary network
Millions of capillaries reduces pressure
Pre-capillary sphincters on arterioles redistribute blood
Eg, exercise causes sphincters to open up and capillary beds so more oxygen to tissues
Sphincters in arterioles and capillary beds of gut will close in exercise
Venules
Only 1nm diameter
Some have only tunica intima, as you get further layers build up
Veins
Regulate and return blood to heart via venous return
Three layers
Walls thin as pressure lower and can’t withstand high pressures
Medium sized veins are 2-9mm and similar size to muscular arteries
Minimal smooth muscle - skeletal muscle pump used for venous return
Valves - valve faces flow of blood + will shut if blood tries to come back. AIDS venous return
Capacitance vessels, less muscle and large radius = reservoir for blood
VENOUS RETURN
UPper limb = gravity assisted
Blood pressure low in veins so veins can’t oppose gravity.
To aid venous return, we use valves (folds of tunica intima) and pressure from skeletal muscle pump. Muscle contracts, squeezes vein and pushes blood upwards.
Also respiratory pump = inspiration means pressure in thorax dropps and draw air in. At same time as pressure drop in lungs, blood is drawn up through veins
BLOOD PRESSURE
Cardiac output X peripheral resistance
How much blood pumped out heart and how tight your vessels have become
So heart pumps too hard or arteries tighten too much then blood pressure rises
Blood pressure regulated by ANS and hormones
ANS= Baroreceptors in blood to detect pressure
Hormone response= Adrenal gland hormones above kidneys (controls constricting and relaxing of blood vessel walls).
More
120/80 is normal
Hypertension = 140/90 or above
Pre high = 121-139/81-89
Hypotension is below 120/80. Only problems are symptoms which are dizziness, faint feeling, sickness, light headed etc
Types of hypertension
Essential and secondary
Essential= no medial cause of it. Related to age, gender, genetics, race and environment or pathology.
Lifestyle factors like smoking, alcohol, obesity , stress etc
Secondary = specific medial condition causes it eg, COPD
Some of essential can be prevented Not always - genetic link Low socio economic Black African 40-45% Age - older Men more likely Smoking , raises bp and HR Obesity Alcohol good in moderation not excessive
20-30% all people get hypertension
5-10% have secondary hypertension, eg chronic kidney disease , renovascular etc
80-95% have essential hypertension , lifestyle and risk factors causing it.
Symptoms of hypertension
180/110 mmhg that causes symptoms
HEADACHE SOB CHEST PAIN + Palpitations Nosebleeds Visual problems Irregular heartbeat Blood in urine
1 in 3 adults have hypertension
1 in 3 adults with hypertension don’t know thy have it
1 in 3 adults with it can’t get it down to below 140/90mmHg
Management
Lifestyle changes
ABCD meds
ACE INHIBITORS- works on adrenal gland to decrease bp by hormones
Beta blockers - Blcoks release of adrenaline and noradrenaline in areas of body. Slows HR and lowers bp
Calcium ion channel blockers- prevent calcium ins entering cells of heart + blood vessel walls so lower bp
Diuretics- increase urine production so lower bp to remove excess salt + water
Pathologies of arterial walls
ARTERIOSCLEROSIS= harden and loss of elasticity of large and medium arteries
ARTERIOLOSCLEROSIS= hardening and loss of elasticity of arterioles
ATHEROSCLEROSIS= hardening of artery due to deposition of atherosclerotic plaques.
Atherosclerosis - slow inflammatory disease Tunica intima now rough Lots of LDLs is bad for you Catch on the roughened tunica intima Inflammatory response produced and WBCs
1- Endothelial cells have adhesion molecules + gather inflammatory cells
2- Monocytes migrate, turn into macrophages and ingest lipids = foam cells
3- Foam cells foreign so more macrophages to area
4- ingest even more foam cells and area larger- plaque
5- larger plaque pushes away from tunica intima, into media and externa layers
6- Starts to block the inner vessel so reduced blood flow through arteries - angina may appear
7- pushed into tunica media so some elasticity lost
8- fibroblasts at area + calcium build up - area rock hard , artery can’t expand
9- increaseS blood pressure
10- high bp knocks off sone plaque , then blocks further down the vessel - platelets form blood clot
11- the blood clots cause atherosclerosis as they block blood supply to brain and heart- stroke or MI
Aneurysm
Localised enlargement in an artery caused by weakness in arterial wall
Can’t control pressure + may rupture
Commonly- CEREBRAL ANEURYSM (cerebral bleed) AORTIC ANEURYSM (8/10 with this ruptured will die)
Deep vein thrombosis
Thrombus formed in large veins - stagnant blood
Risk factors;
IMMOBILITY- by being immobile you may get DVT and pulmonary embolisms
RECENT SURGERY- NBM can Dehydrate you so blood stickier
FAMILY HISTORY- you may be more likely
OBESITY
Symptoms -
Discolouration
Heavy aching pain
Swelling
Should do the Homan’s test- dorsiflexion ankle and pain felt in calf
Treatments- stockings, anticoagulants, raise legs and exercise
Varicose veins
Valves don’t work as well, so blood flows backwards, you get bulging and swelling of veins
Chronic venous insufficiency
Valves don’t work properly for long time
Build up of wastes and necrosis of tissues, may get DVT
Symptoms: Swollen legs, skin colour and texture changes and venous ulcers
Varicose veins + CVI use exercise treatment (muscle pumps and respiratory pumps)
Compression stockings
Venous insufficiency caused by faulty valves + varicose veins. Common in women, stand for a while, obesity and pregnancy. Family history.
Lots of hormones, blood volume and excessive weight
