Blood Vessels Flashcards
Basic Structure of blood vessel
> Tunica Interna/Intima (innermost layer)
- direct contact with blood
- epithelial lining, supportive connective tissue (sometimes with elastic fibres)
Tunica Media (Middle layer)
- smooth muscle and varying connective tissue
Tunica externa/adventicia (outermost layer)
- connective tissue sheath for protection
- anchoring system to maintain position
Describe the common structure and role of an artery
- Blood from heart to body
> Round + relatively thick wall (4mm diameter, 1mm wall) - little resistance to blood flow
> Either elastic (big arteries) or muscular (more common)
TUNICA INTERNA - rippled (with internal elastic membrane)
- elastic fibres allow to change size to cope with pressure
TUNICA MEDIA - thick smooth muscle (muscular type has more)
- external elastic membrane
TUNICA EXTERNA - collagen + elastic fibres to cope with pressure
> Able to - cope with high pressure changes + even them out
- propel blood with expand + recoil
- vasodilate/constrict - ANS + hormone stimulation
Name the 5 main types of blood vessels
> Arteries (4mm diameter) Aorta = 2.5cm > Arterioles (30micrometer diameter) > Capillaries (8micrometer diameter) > Venules (20micrometer diameter) > Veins (5mm diameter)
Describe the common structure and role of arterioles
> Smallest branch of arteries (30micrometers diameter)
carry blood at reduced pressure - less collagen + elastin - more smooth muscle
Sphincters direct blood flow to capillaries
resistance vessels - controls blood flow of arteries + distributes blood
Describe the common structure + role of capillaries
> smallest vessels (8micrometers in diameter - RBC)
single layer thin walls - just tunica interna
Permeate all active tissues - for exchange
work in networks to reduce blood pressure so blood = slower moving - maximise exchange
guarded by pre-capillary sphincters to direct blood flow
Describe the common structure + role of venules
> Smallest branches of veins (20nanometers diameter)
allows blood from capillaries into venous system
nearer capillary may lack tunica media+externa
same function as veins
Describe the structure + role of veins
Regulate blood return to heart
> Flattened with thin walls (5mm diameter) - Can’t cope with high pressure
> Smooth tunica interna - no exchange
> Thin Tunica media - smooth muscle + collagen
> Tunica Externa - collagen, elastic fibres + smooth muscle cells
> Valves to stop backflow + skeletal muscle pump to aid return
> Capacitance vessels - large diameter/ little smooth muscle in walls - can act as reservoir for blood
Describe the process of venous return
> Pressure is very low (little resistance) - can’t oppose gravity
Valves on interna prevent backflow
Muscular Pump - Muscles apply pressure in movement - pushes blood up
Respiratory pump - pressure drop in thorax - drawing blood up
How is blood pressure calculated + what is normal/pre-high/high
Blood pressure= Cardiac output x Peripheral resistance
> affected by:
1. Cardiac Output
2. Peripheral resistance
3. Blood volume
> detected by baroreceptors - communicate with adrenal gland to control smooth muscle in vessel walls
> Normal = 120/80 or lower
> Pre high = 121-139/81-89 (either)
> High = 140/90 or higher
* Systolic/Diastolic = contracting/relaxing
What is hypotension
Hypotension = low blood pressure - only an issue if symptomatic (exhaustion/light headed)
What is hypertension
- risk factors
- lifestyle factors
- symptoms
Hypertension
> BP greater than 140/90 mmHg
- Primary = 80-95% of people
: no medical cause
- Secondary - specific medical cause - kidney disease
- 5-20% of people
> Risk factors: Genetics/Environment/Age/Gender/Race/Pathology
> Lifestyle factors:
Smoking/high fat+salt diet/obesity/stress/sedentary lifestyle/ excess alcohol
> Symptoms: usually require 180/110 - damage is done
headaches/SoB/chest pain/nose bleeds/disturbed vision
How is hypertension treated + what are the consequences if untreated
> Managing
- lifestyle changes
- Meds: ACE inhibitors (affect adrenal gland)
: Beta blockers - affect smooth muscle
: Ca2+ channel blockers - affect smooth muscle
: Diuretics: dilute blood
> If untreated:
- damages tunica interna
- stroke
- arteriosclerosis
- heart attack/failure
- kidney failure
Name the pathologies of arterial walls
- Arteriosclerosis - hardening + loss of elasticity of large/medium artery walls
- Arteriolosclerosis - hardening + loss of elasticity of arteriole walls
- Atherosclerosis - hardening of artery due to deposition of plaque
- slow, inflammatory disease
Describe process of atherosclerosis
> LDL cholesterol accumulates in artery wall
endothelial cells express adhesion molecules + recruit inflammatory cells
macrophages ingest LDL to form foam cells
these accumulate = fatty streaks
body surrounds these in capsule to slow growth (this is when it becomes a plaque)
Plaque grows + expands into interior layer
interior layer stretches to maintain lumen size
Inner layer then reaches full size - lumen becomes restricted (calcification of plaque reduces its elasticity)
Tunica interna becomes damaged by high blood pressure - blood clot forms (thrombus in place, embolus if dislodged)
What can atherosclerosis lead to
- blockage in heart - felt as angina
- blockage in brain - mini-stroke
- blockage in legs - intermittent claudication - feels like cramp
*Exercise can dislodge thrombus and cause embolus so be careful in prescription
