Blood Vessel structure and hypertension Flashcards
What are the 3 layers of blood vessels
-tunica intima
-tunica media
-tunica adventitia
What is the structure of the tunica intima
-endothelium
-internal elastic lamina (subendothelial layer) which have proteoglycans and collagen
-squamous epithelium
What is the tunica media
-external elastic lamina (elastic fibers) which stretch and recoil during systole and diastole
-many smooth muscle cells
What does the tunica adventitia contain
-collagen and elastic fibers which anchor vessels to surrounding tissue
-vasa vasorum (oxygen and nutrients to outer layer of the vessel)
3 main types of arteries
elastic
muscular
arterioles
Elastic arteries
pressure reservoirs
contain many elastic fibers in the tunica media
receive blood directly from the heart
Muscular arteries
distributing arteries
thicker tunica media
more muscle cells
regulated blood flow to organs and tissues
arterioles
fewer muscle cells
highly responsive to changes in BP
regulate blood flow into capillaries
What are veins
drainage channels which carry blood from different parts of the body to the heart
work at lower pressure due to reduced muscle tone in tunica media
what are venules
smallest vessels in venous circulation
What is the venae cavae
venules come together to form larger veins into the greater vein
Tunica intima in arteries vs veins
Arteries - thin layer of endothelial cells/subendothelial layer/internal elastic lamina
veins - endothelial cells/subendothelial layer/lacks internal elastic lamina
tunica media in arteries vs veins
arteries - thicker, more smooth muscle/more elastic fibers/muscular arteries have more smooth muscle
veins - thinner/less elastic tissue
tunica adventitia in arteries vs veins
arteries - thinner tunica adventitia
veins - thicker tunica adventitia to provide greater structural support
What are valves
in veins
folds of tunica intima
prevent backflow of blood
important in lower extremities
What are arterioles
smaller diameter blood vessels with muscular walls
regulate blood flow and pressure
resistance vessels
Roles of the arterioles
vary diameter to prevent damage to tissue
What are capillaries
thin walled vessels which facilitate exchange of nutrients
link arteries and veins
contain endothelial cells (1 cell thick), basement membrane, collagen fibrils
5-8um diameter
why do capillaries have precapillary sphincters
regulate blood flow through contraction and dilation
types of capillaries
continuous
fenestrated
sinusoidal/discontinuous
What are continuous capillaries
-in many tissues (CNS/lymph nodes/muscle/skin)
-no opening on the walls
-continuous basement membrane
-joining of endothelial cells
-maintained by complex intercellular junction proteins
What are fenestrated capillaries
-small pore called fenestrae
-in endocrine/GIT/kidney peritubular plexus
-continuous basement membrane
-fenestrations between endothelial cells, less complex intercellular proteins
What are sinosoidal/discontinuous capillaries
-irregularly shaped endothelial cells with gaps
-in liver/bone marrow/spleen/lymph nodes
-large lumen
-discontinuous or absent basement membrane
-gaps have no diaphragm
Lamina flow/streamlined/parabolic flow
Endothelium is smooth/non-stick which allows laminar flow. Blood in the centre is faster than vessel wall
most common
What is turbulent flow
vessels branch when blood pressure is raised, flow is disrupted causing damage to the endothelium, this exposes blood to collagen and causes blood to clot
What is pulsatile flow
periodic surges of blood due to heart’s rhythmic contraction e.g. arterial blood flow
Functions of the endothelial cell
-blood vessel barrier
-regulates BP
-vasomotion (blood flow)
-produces NO (vasodilator/prevents platelet aggregation)
-immune response
-angiogenesis
-regulate blood clotting
-production of vasoactive substance
-nutrient exchange in capillaries
Transport through the endothelial cells
paracellular (tight junctions)
transcellular (diffusion/vesicular/receptor-mediated)
active transport
pinocytosis (smaller molecules ingestion)
What can dysfunction of microcirculation lead to
-CV disease
-DM
-Raynaud’s disease
benign veins
varicose veins
most common in legs
serious vein pathology
-venous insufficiency (leg swelling)
-superficial thrombophlebitis (red/tender/swollen)
-venous aneurysms (abdominal/pelvic regions)
-venous malformation
Pathologies of arteries/arterioles
-atherosclerosis (fatty deposits in tunica intima harden walls and narrow lumen)
-arteriolosclerosis (wall thickening and hardening affecting small arteries and arterioles, risk: hypertension/DM)
-aneurysms (abdominal bulge)
-peripheral artery disease
-Reynaud’s disease (spasms in fingers/toes)
-arteritis (inflammation of arterial walls)
-vasculitis (inflammation of artery and arterioles)
-artery embolism (blood clot lodges in embolism)
-thrombus (solid mass)
hypertension
persistent elevation of blood pressure levels in the arteries
damage to structure of blood vessels (small muscular and arterioles)
asymptomatic
classification for hypertension
normal: <120/<80 mmHg
Pre-hypertension: 120-129/<80-89 mmHg
stage 1: 130-139/80-89 mmHg
stage 2: >=140/>=90 mmHg
urgency/emergency: >180/>120mmHg
Risk factors
-age
-family history
-obesity
-sedentary lifestyle
-unhealthy (low potassium high sodium)
-excessive alcohol consumption
-smoking
-chronic conditions (diabetes/kidney disease)
Hypertension classification
primary (essential/idiopathic 90%)
secondary (underlying conditions 10%)
malignant - dramatic rise over a short time
benign - stable elevation of blood pressure over several years
What is secondary hypertension
caused by an external factor
renal disease (parenchymal/vascular)
-renal artery stenosis (reduced renal blood flow, RAAS activation, vasoconstriction, Na and H20 retention/hypertension
-acute kidney disorders (decreased urine formation/increased retention of Na/H20)
-chronic kidney disorders
-tumours (adrenal adenocarcinoma/pheochromocytoma)
-CV disorders (coarctation of aorta)
-obstructive sleep apnoea
-drugs (cocaine/amphetamines/licorice/oral contraceptives)
-hyperthyroidism/Cushing’s syndrome/adrenal hyperplasia/hyperaldosteronism
complications of hypertension
-coronary artery disease (atherosclerosis)
-left ventricular hypertrophy (heart remodelling/hypertrophy)
-angina (pain)
-heart failure (heart weakens)
What is an atheroma
Feature of atherosclerosis
affects large and medium arteries (not arterioles)
in systemic (high pressure systems) only
initially affects tunica intima then tunica media
4 features of atheroma
-fatty streak (barely visible)
-lipid plaque (smooth/yellow/raised)
-fibrolipid plaque (hard)
-complicated atheroma
Complications of atheroma
-stenosis
-predispose to thrombosis and embolism
-intima expansion/reduction to lumen size/reduce blood flow
-leg arteries
-mesenteric arteries - ischaemic colitis
-heart attack/stroke
What is thromboembolism
acute rupture of an unstable atheromatous plaque, forming acute artery occulusion (thrombosis) and detaching (embolus)
What can thromboembolism lead to
DVT
pulmonary embolism
stroke
What is aortic dissection
70% due to hypertension
blood enters media causing a split in the vessel wall (unusual in atherosclerotic arteries)
rupture into adventitia causing haemorrhage into surrounding areas of the pericardium
What is an aneurysm
abnormal, permanent focal dilation of an artery
atrophy of media
muscle and elastic fibers replaced by collagen (no recoil)
Types of aneurysms
-saccular/berry (sac/pouch like due to arterial wall weakness)
-fusiform (gradual/symmetrical dilation/fusiform shape)
Pathologies of arterioles
-Hyaline arteriolosclerosis (hyalin within arteriolar wall)
-hyperplastic arteriolosclerosis (concentric thickening of the arteriolar wall)
-vasospasms
-microangiopathy/arterioloar dysfunction
-ischaemia
-atherosclerosis
-inflammation
What does hypertension result in
rupture (intracerebral haemorrhage due to microaneurysm - Charcot-Bouchard aneurysm)
microinfarcts due to thrombolytic events (hypertensive lacunae)
vascular dementia due to white matter loss
Kidney victim
hypertensive nephropathy due to chronic high blood pressure
kidney villian
disrupt electrolyte balance
leading to reactivation of the RAAS system
How does hypertension cause eye damage
hypertensive retinopathy - renal arterioles
primary benign hypertension: silver wiring/arteriovenous nipping
malignant hypertension - flame haemorrhages/cotton wool spots/papilledema
