Cardiovascular Module Introduction PDF

Introduction to the Cardiovascular Module  How the module is structured sessions3 First introduction to cardiovascular system, the – anatomy & development of the heart important physiology of the cardiovascular...

Introduction to the Cardiovascular Module  How the module is structured sessions3 First introduction to cardiovascular system, the – anatomy & development of the heart important physiology of the cardiovascular system final sessions more clinically focussed group work throughout case studies  Formative assessments formative assessments 2 7week – ECG quiz8 week – 14week – Sample summative questions at end of module Recommended text books  Cardiovascular Module The broad aim of this module is that you should understand the structure and function of the human cardiovascular system, how its condition is assessed, and how cardiovascular function is altered in common diseases  Components of the cardiovascular system Distribution system – vessels & blood Pump – the heart Exchange mechanism - capillaries  Blood 2 , metabolic substrates, CO2Transports O and waste products around the body There is exchange of these substances between the blood and cells of the body  Blood Exchange occurs by diffusion Substances diffuse between the blood and the surrounding tissue The function of the cardiovascular system is to provide adequate conditions for diffusion to each tissue of the body  Where does diffusion take place? Capillaries are the site for diffusion between blood and the tissues Capillaries are composed of a single layer of endothelial cells surrounded by basal lamina  Diffusion 2 and CO2 Some substances eg O are lipophilic and diffuse through the lipid bilayer Others molecules such as glucose, amino acids and lactate are hydrophilic and diffuse through small pores in the capillaries All molecules will move down their concentration gradient  What factors affect diffusion :rate of diffusion depends on area – ’diffusion ‘resistance – concentration gradient –  Area area for exchange between capillaries and tissues is generally very large – it depends on capillary a tissue which is more metabolically active will have more capillaries  Diffusion resistance resistance to diffusion depends on nature of the molecule– eg lipophilic or hydrophilic, size nature of the barrier– eg pore size and number of pores for hydrophilic substances path length– depends on capillary density path is shortest in the most active tissues diffusion resistance is mostly low  Concentration Gradient rate of diffusion is dependent on the concentration gradient the greater the concentration gradient the greater the– rate of diffusion diffusion – the concentration which matters is between capillary blood and tissues for exchange to continue the concentration gradient between the capillary blood and tissues must be maintained  Concentration Gradient a substance which is used by the tissues will have a lower concentration in capillary blood than arterial blood arterial venous capillar end end y blood how much lower depends on flow rate tissues use the substance– rate of blood flow through the–capillary bed  Supply and Demand blood flow must match the tissues’ metabolic needs – higher the rate of metabolism the greater the and nutrients2 the demand for O – increases in metabolism must be met by increases in blood flow – the rate of blood flow is known as the perfusion rate  Blood flow to different tissues Brain needs high, constant flow 1.g-1ml.min- 0.5– Heart muscle needs high flow which increases during exercise 1.g-1ml.min-3.6 to 0.9– Kidneys need high, constant flow 1.g-1ml.min- 1.0– Blood flow to skeletal muscle can be very high during exercise and gut blood flow is high after a meal  Blood flow to different tissues Tissue Min. flow l.min-1 Max. flow l.min-1 brain 0.75 0.75 heart 0.3 1.2 kidneys 1.2 1.2 gut 1.4 2.4 1.0 16.0 muscle 0.2 2.5 skin 0.2 0.2 5.0 24.5 other  Regulating blood flow If a pump is just connected to a network of vessels blood will only flow to the parts that are easiest to perfuse The brain is harder to perfuse due to gravity To regulate blood flow you need to add resistance to the system – Reduce the ease with which some regions are perfused in order to direct blood flow to the more difficult to perfuse regions Arterioles are the resistance vessels  The pump pulmonar Heart is two pumps in y series circulation The left heart pumps Lungs blood around the Right Left systemic circulation heart heart The right heart pumps systemic blood around the pulmonary circulation circulatio n A B  The Circulation Heart pumps blood to arteries heart Arteries supply arterioles Arterioles supply capillaries veins arteries Capillaries drain into venules Venules drain into veins venules arterioles Veins return blood to the heart capillaries