Blood Vessel Structure And Function

Question 1

5 main blood vessels

Answer 1

Arteries - conducting

Arterioles- resistance vessels , BP

Capillaries

Venules

Veins- capacitance

Question 2

3 layers

Answer 2

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

Question 3

Artery vs vein

Answer 3

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

Question 4

ARTERIES

Answer 4

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

Question 5

Arteries are 3 things

Answer 5

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

Question 6

ARTERIOLES

Answer 6

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

Question 7

Capillaries

Answer 7

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

Question 8

Venules

Answer 8

Only 1nm diameter

Some have only tunica intima, as you get further layers build up

Question 9

Veins

Answer 9

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

Question 10

VENOUS RETURN

Answer 10

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

Question 11

BLOOD PRESSURE

Answer 11

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).

Question 12

More

Answer 12

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

Question 13

Types of hypertension

Answer 13

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.

Question 14

Symptoms of hypertension

Answer 14

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

Question 15

Management

Answer 15

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

Question 16

Pathologies of arterial walls

Answer 16

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

Question 17

Aneurysm

Answer 17

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)

Question 18

Deep vein thrombosis

Answer 18

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

Question 19

Varicose veins

Answer 19

Valves don’t work as well, so blood flows backwards, you get bulging and swelling of veins

Question 20

Chronic venous insufficiency

Answer 20

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