Cardiovascular System Notes

Cardiovascular System Homeostasis & Haemodynamics Functions Rapid connective transport of nutrients and waste products Transport of hormones Temperature regulation Reproduction Pump Endocardium - inner layer Myocardium - muscle layer [cardiac (striated) muscle] Pericardium - fibrous sack Annulus fibrosus - insulator Atria Thin walled, venous blood, primer pumps [top up filing of ventricles], produce ANP [atrial natriuretic peptide] increasing secretions of sodium Valves 4 valves, in annulus fibrosis, prevent backflow, closure of valves = heart sounds, endocarditis = valve infection Ventricles Eject blood into arterial systems; left thicker than right to generate higher pressures, left ventricular contraction produces the 'apex' beat ? midclavicular line, 5th intercostals space Cardiac auscultation 1st heart sound = closure of tricuspid mitral valves 2nd heart sound = closure of aortic and pulmonary valves, physiological splitting 'dubba' Endocarditis Valve infection 4-50% mortality Poor dental hygiene/dental procedures Antibiotic prophylaxis Systole - phase of contraction Diastole - phase of relaxation Stroke volume - amount of blood pumped by each beat ~ 80ml Cardiac Output [Q] = heart rate X stroke volume rest ~ 5L/min The volume of blood ejected from the heart per minute Blood vessels Lumen - contains blood Tunica intima - helps maintain blood fluidity, loss of endothelium causes blood to clot Tunica media - contains collagen for strength, elastin for stretching and smooth muscle to control diameter Tunica adventitia - sticks to the BV surrounding tissues Circulation of blood Pulmonary - low resistance, low pressure Systemic - high resistance, high pressure Large elastic arteries Collagen and elastin in tunica media allows BV to stretch and = Muscular arteries Brachia and radial arteries Tunica media rich in smooth muscle Distribution vessels Structure prevents kinking of vessels at joints Arterioles Microscopic diameter<100um Resistance vessels Extensive amounts of smooth muscle in tunica media Sympathetic nervous system Capillaries Diameter ~ 7um Single layer of endothelium upon BM Exchange vessels Production of tissue fluid Venules Drain blood away from capillaries Diameter upto 50um Veins Valves prevent backflow of blood 2/3 of blood volume found here Sympathetic nervous system Venoconstrict Haemodynamics The flow (Q) through a tube is directly proportional to the pressure gradient ( P) and inversely proportional to the resistance (R) of the vessels Mean arterial pressure - central venous pressue = cardiac output X total peripheral resistance Poiseille's Law R = resistance i = fluid viscosity l = length of tube r = radius of tube Tubes in series Flow through each tube must be the same Total resistance is the sum of all individual resistance Pressure will drop along the sequence Flow patterns LAMINAR Blood at the wall flows slower than at the centre Quiet 

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