Cardiovascular system

3 layers of the heart wall

epicardium

myocardium

endocardium

epicardium

single squamous epithelium called a mesothelium

myocardium

cardiac muscle cells, muscle layer of the heart

endocardium

consists of a layer of endothelial cells in contact with the blood in the chambers of the heart

systole

contraction and ejection

aortic and pulmonary valves open

diastole

relaxation and filling

tricuspid and mitral valves open

mitral and tricupsid valves (AV valves)

prevents blood flowing back into the ventricle

aortic and pulmonary valves (semilunar)

prevents blood flowing back into the ventricles from the aorta and main pulmonary artery respectively

coronary arteries

an extensive network ensuring the oxygen supply

coronary artery disease causes angina, heart attack and heart failure

RCA vs LAD

RCA= right coronary artery- supplies RV, RA, SA and AV nodes

LAD= left anterior descending artery

ventricle

pumping chamber

high pressure

arteries

conductance vessels- wide bore, thick elastic wall, damp down pressure variations

arterioles

resistance vessels- narrow bore, thick muscular wall, control blood

capillaries

exchange vessels- narrow bore, narrow wall

venules/veins

capacitance vessels- wide bore, thin collapsible wall

atrium

receiving chamber

arteries vs veins

A= more muscular and elastic

V= thinner and more capacity

4 layers of blood vessels

tunica

intima- endothelial

media- smooth muscle/elastin

adventitia- collagen/elastin

3 types of capillaries

continuous- muscles and fat

fenestrated- kidneys and pancreas

sinusoid- liver and spleen

vascular endothelium functions

vessel tone

movement of fluid into tissue

heart beat

cardiac muscle is myogenic- generates its own action potentials spontaneously at the SA node

SA node is the pacemaker of the heart

APs are conducted from myocyte to myocyte via intercalated discs which have gap junctions

intercalated discs

specialised junctions that allow for rapid transmission of the action potential

Different heart rhythms

normal= sinus rhythm

bradycardia= slow rate

tachycardia= fast rate

cardiac output

the amount of blood pumped out by each side of the heart in 1 min

heart rate x stroke volume

ejection fraction

percentage of the blood volume that is pumped out by the ventricle, determined by contractility

parasympathetic nervous system and heart rate

decreases heart rate

reduces the force of contraction

sympathetic nervous system and heart rate

increase in heart rate

increases the rate of conduction and overall excitability

increases force of contraction

dilates coronary arteries

high blood pressure/ hypertension

chronically elevated arterial blood pressure

high blood pressure causes an increased risk for:

stroke

heart attack

aortic aneurysm

kidney disease

dementia

normal BP vs hypertension

normal= 120/80 mmHg

Hypertension= >140/90 mm

What is capillary exchange caused by

starling forces

hydrostatic (push)

oncotic (pull)

2 main circulatory circuits

pulmonary circuit

systemic circuit

physiological roles of the circulatory system

transport