Blood vessels structure, function and pathology Flashcards
Describe the layers surrounding the blood vessels
Surrounding the lumen is :
Tunica intima - internal elastic lamina, endothelial cells, BM, supporting CT
Tunica media - smooth muscle + elastin, external elastic lamina
Tunica adventitia - connective tissue - collagen anchors vessels to nearby organs contains sympathetic nerves and capillaries that supply blood to the vessel wall
Adaptations of arteries
Large tunica media for strength
Small lumen diameter
Elastin in smooth muscle ; allows elastic recoil , forcing blood along
Describe the 3 layers of the heart
Endocardium = (equivalent of tunica intima) ; a sample squamous epithelium lined by a thin band of relatively loose CT
Myocardium= (Equivalent of tunica media) ; contains cardiac muscle supplied by coronary vessels (vasa vasorum)
Epicardium = (equivalent of tunica adventitia) ; connective tissue bordered by a simple squamous epithelium (Called the visceral pericardium) which forms the inner lining of the pericardial sac
When does turbulent blood flow occur and why is it bad?
Occurs where vessels branch and blood pressure is raised
Eventually damages endothelium of small and large blood vessels
Blood exposed to collagen= increased chance of blood clot
What is atherosclerosis
Fatty deposits int he tunica intima
Hardens walls and narrows the lumen
Ischaemia is the consequence
What is the difference between thrombus and embolism
A thrombus is a blood clot that forms within a blood vessel. If a thrombus breaks free and travels through the bloodstream, it has become an embolus. Doctors may refer to a thrombus that has become an embolus as a thromboembolism
What is atheroma?
Type of atherosclerosis occurring in large and medium sized arteries
Initially damages tunica intima but later affects tunica media
Worsens with age
What are the risk factors for atheroma
Use the mnemonic ATHEROMA
Arterial hypertension Tobacco Hereditary Endocrine (diabetes, hypothyroidism, post menopausal oestrogen deficiency) Reduced physical activity Obesity Male gender Age
Describe the 4 stages of atheroma formation
1) fatty streak - blood lipids enter intima through damaged endothelium ; phagocytosis of lipid to make fatty streak
2) lipid plaque (smooth yellow and raised) ; lipid/cytokines released by macrophages ; myofibroblasts stimulated to secrete collagen ; early damage to elastic lamina and media
3) fibrolipid plaque (hard and white) occurs when collagen covers plaque surface ; media thins as muscle fibres are replaced by collagen
4) complicated atheroma (has features of all the above 3) ; lipids inside intima become calcified; thinning of media leads to weakness and inelasticity; ulceration of plaque surface exposes collagen leading to clot
Complications of atheroma
thrombosis/aneurysm (ballooning of wall)
Expansion of intima -> reduction of size of lumen -> reduced blood flow & hence oxygenation of tissue: ischaemia
Coronary arteries -> angina
Leg arteries -> intermittent claudication
Mesenteric arteries -> ischaemic colitis
Brain arteries -> ischaemic stroke
Severe ischaemia can cause infarction
Describe the patholgy post atheroma formation in arterioles
Hypertrophy of walls due to hypertension
Artertiosclerosis due to hypertension
No longer can effectively control blood flow by altering their diameter
what is the difference between arteriosclerosis and atherosclerosis?
atherosclerosis is a type of arteriosclerosis that occurs in medium/large arteries; arteriosclerosis is the general term referring to fatty deposits in any vessels; atherosclerosis is specific to arteriosclerosis caused by high cholesterol/alcohol intake
