L19 - Cardiovascular System 2 Flashcards
What is the equation for net pressure?
net pressure = hydrostatic pressure - colloid osmotic pressure
What do Starling forces describe?
describe whether there is filtration / movement of fluid out of capillaries or absorption / movement into the capillaries
Which end of a capillary is involved in filtration / outward movement of fluid? Why?
arterial end
hydrostatic pressure is high
Which end of a capillary is involved in absorption / inward movement of fluid? Why?
venous end
hydrostatic pressure is low
Which factor results in absorption of fluid into the capillaries?
oncotic pressure which is determined by albumin inside the capillaries
What happens when hydrostatic pressure is greater than oncotic pressure?
net filtration / inward movement of fluid occurs
What happens when oncotic pressure is greater than hydrostatic pressure?
net absorption / outward movement of fluid occurs
How much fluid flows out of the capillaries and is not reabsorbed (per day)? How is this excess fluid dealt with?
3 L/day
lymphatic system recirculates this fluid
Will interstitial oncotic pressure favor filtration or absorption?
filtration
What does colloid osmotic pressure favour?
water movement into capillary
What does hydrostatic pressure favour?
water movement out of capillary
What does net movement depend on?
balance of filtration and absorption
balance changes down length of capillaries
What is bulk flow?
movement of fluid into and out of the capillaries via Starling forces
What is the route via which excess fluid takes after leaving the capillaries?
capillaries -> lymph vessels -> larger lymphatic vessels -> lymph ducts -> venous circulation
What is the role of the lymphatic system?
return fluid / proteins filtered out of the capillaries back to the circulatory system
pick up fat absorbed at small intestine and transfer it to circulatory system
serve as filter to help capture and destroy foreign pathogens
What does lymph flow depend upon?
smooth muscle contraction of larger lymphatic vessels
one-way valves which stop back-flow
external compression created by skeletal muscle contraction
Which one/s of the following conditions is likely to cause oedema? (dehydration / increase in blood protein concentration / severe malnutrition / heart failure which increases venous pressure / obstruction of lymph nodes by parasites or cancerous cells)
obstruction of lymph nodes by parasites or cancerous cells, severe malnutrition and heart failure which increases venous pressure
What is ventricular systole?
contraction of the ventricles
What is ventricular diastole?
relaxation of the ventricles
What is the conduction system of the heart?
SA node which is autorhythmic and has pacemaker cells (~70 bpm)
also AV node (50 bpm) and purkinje fibers (25-40 bpm)
What is the role of the AV node?
delays transmission of electrical signal so that ventricles have the chance to fill with blood
electrical signal cannot pass from the atria to the ventricles without passing through the AV node
How does an electrical signal pass through the heart?
SA node -> atria -> AV node -> ventricles
What is the role of the Purkinje fibres?
allow for rapid conduction and contraction of these fibres starts at apex
What are the steps of electrical conduction in the heart?
SA node depolarises -> electrical activity goes rapidly to AV node via internodal pathways -> depolarisation spreads more slowly across atria, conduction slows through AV node -> depolarisation moves rapidly through ventricular conducting system to the apex of the heart -> depolarisation wave spreads upward from the apex
