cardiovascular system

chambers of the heart

right atrium, right ventricle, left atrium, left ventricle

blood vessels of the heart

inf & sup vena cava, pulmonary artery, pulmonary vein, aorta

valves of the heart

tricuspid valve, pulmonary valve, mitral valve, aortic valve

aorta

carries oxygenated blood from the heart (left ventricle) to the rest of the body

pulmonary artery

carries deoxygenated blood from the heart (right ventricle) to the lungs

vena cava

carries deoxygenated blood from the upper (superior) and lower (inferior) body to the heart (right atrium)

pulmonary vein

carries oxygenated blood from the lungs to the heart

tricuspid valve

valve between the right atrium and right ventricle

pulmonary valve

valve between the right ventricle and pulmonary artery

mitral valve

valve between the left atrium and left ventricle

aortic valve

valve between the left ventricle and aorta

transport of blood through the body

(deoxygenated) vena cava > right atrium > right ventricle > pulmonary artery > lungs (oxygenated) > pulmonary veins > left atrium > left ventricle > aorta (deposits oxygen around body & repeats)

function of valves in the heart

prevent the backflow of blood

systole

period of the cardiac cycle when the heart muscle contracts and blood is pumped out of the chambers

diastole

period of the cardiac cycle when the heart muscle relaxes and blood fills the chambers

sinoatrial (SA) node

initiates the electrical impulse that starts each heartbeat

why is there a delay at the atrioventricular node

to allow the atria to finish contracting before the ventricles contract

what is atrial depolarisation

the electrical activation of the atria that causes atrial contraction

what is ventricular depolarisation

the electrical activation of the ventricles that causes ventricular contraction

what is the function of the Bundle of His

to conduct electrical impulses from the AV node to the ventricles

what is the function of purkinje fibres

they rapidly distribute electrical impulses throughout the ventricles

what is the sequence of electrical conduction through the heart

SA node > AV node > Bundle of His > Purkinje fibres

what does an electrocardiogram (ECG) measure

the electrical activity of the heart

what does systolic pressure (SP) represent

the maximum arterial pressure reached during ventricular ejection

what doe the diastolic pressure (DP) represent

the minimum arterial pressure just before ventricular ejection begins

what is the pulse pressure (PP)

the difference between the systolic and diastolic pressures

what is mean arterial pressure (MAP)

the average arterial pressure during one cardiac cycle

how do you calculate MAP

DP + 1/3(PP)

why is MAP clinically important

it reflects tissue perfusion and organ blood supply

primary function of the capillaries

exchange of gases, nutrients, and waste products between blood and tissues

what is microcirculation

blood flow through vessels less than 100μm in diameter

what structures make up the microcirculation

metarterioles, capillaries, postcapillary venules

approximate diameter of capillaries

5-10μm

what controls blood flow through capillary beds

precapillary sphincters

what is the structure of capillary walls

a single layer of endothelial cells

why are capillary walls thin

to allow efficient diffusion of gases and nutrients

what are the three main types of capillaries

continuous, fenestrated, and sinusoid capillaries

what characterises continuous capillaries

a continuous endothelial lining with intercellular clefts

which type of capillary is most common

continuous capillaries

what characterises fenestrated capillaries

they contain fenestrations (pores) that increase filtration and absorption

where are fenestrated capillaries commonly found

in organs requiring high levels of filtration or absorption, such as kidneys

what characterises sinusoid capillaries

large fenestrations, incomplete basement membrane, large intercellular clefts

why are sinusoid capillaries highly permeable

their large gaps allow movement of large molecules and cells

how do lipid-soluble substances diffuse across capillaries

directly through plasma membranes

how do water-soluble substances diffuse across capillaries

through intercellular spaces or fenestrations

what is lymph

fluid collected from tissues and transported through lymphatic vessels

what are lymphatic capillaries

closed-ended vessels that collect excess tissue fluid

why are lymphatic capillaries more permeable than blood capillaries

they lack a basement membrane and tight junctions

how does lymph flow through lymphatic vessels

in one direction due to flap valves

what helps move lymph through the lymphatic system

contraction of lymphatic vessels, skeletal muscle contraction, and pressure changes

what are lymph nodes

structures along lymphatic vessels that filter lymph and contain lymphocytes

what is the function of lymph nodes

to filter lymph and support immune responses

where does the right lymphatic duct drain lymph from

the upper right side of the body

where does the thoracic duct drain lymph from

the rest of the body except the upper right quadrant

into which does lymph return to the bloodstream

the junctions of the internal jugular and subclavian veins

what is oedema

excess accumulation of fluid in tissues

which tissues are most prone to oedema

loose tissues such as subcutaneous tissue around the eyes or scrotum

why is oedema harmful to tissues

it increases diffusion distance for oxygen and nutrients and impairs waste removal

how does inflammation contribute to oedema

it increases capillary permeability, causing greater fluid loss into tissues

what is lymphoedema

oedema caused by impaired lymphatic drainage

what commonly causes lymphoedema

surgical removal or irradiation of lymph nodes