Circulation -PPT PDF

CIRCULATION  The Circulatory System Three Major Elements – Heart, Blood Vessels, & Blood  Circulation Schematic Left Side of Heart Pulmonary Vein Aorta A V...

CIRCULATION  The Circulatory System Three Major Elements – Heart, Blood Vessels, & Blood  Circulation Schematic Left Side of Heart Pulmonary Vein Aorta A V Aortic Valve Mitral Valve Lungs Tissues Tricuspid Valve Pulmonary Valve V A Pulmonary Artery Right Side of Heart Sup. & Inf. Vena Cava The Closed Circulatory System Humans have a closed circulatory system, typical of all vertebrates, in which blood is confined to vessels and is distinct from the interstitial fluid. Functions of the Circulation 1. Supply of nutrients to the tissues 2. Removal of waste products of tissue metabolism 3. Controls blood flow to skin and regulate heat loss to the environment 4. Aids in body’s defense mechanism by delivering antibodies, platelets and leucocytes to affected areas of the body  Blood Distribution Largest portion of blood at rest is in systemic veins and venules Blood reservoir Venoconstricti on reduces volume of SYSTEMIC AND PULMONARY CIRCULATION Pulmonary circulation The flow of blood between the heart and lungs. Low pressure system Systemic circulation The flow of blood between the heart 6 Types of blood vessels Arteries Elastic (conducting) arteries Muscular arteries Arterioles Capillaries reunite to form Venules merge into Veins converge and convey blood back to the heart Large elastic arteries or conducting arteries Pressure reservoirs Recoil of elastic fibers propels the blood. Muscular or distributing arteries Constrict or dilate to  PHYSIOLOGICAL CLASSIFICATION OF BLOOD VESSELS Windkessel vessels Resistance vessels  Exchange vessels Capacitance vessels.  Windkessel Vessels aorta and large arteries have more elastic elements in their wall higher compliance during systole, their wall stretches during diastole, their wall recoils back recoiling effect is called Windkessel effect  Aorta, pulmonary artery & their branches Pressure reservoir Arterial walls are able to expand and recoil because of the pressure of elastic fibers in  Resistance Vessels Arterioles, Metarterioles and pre- capillary sphincters (main site of Peripheral Resistance) thick muscle coat and less elastic fiber in their wall. Small arteries (10-300mm) that offer resistance to blood flow towards the capillaries. Regulates blood flow and blood pressure maximum resistance to flow is Arterioles Less elastic & highly muscular Myogenic control Metarterioles & Precapillary sphincter  Exchange Vessels Capillaries which allow easy exchange of gases and nutritive substances (thin wall and sluggish flow) favor exchange of gases and nutrients along the capillary wall. 50,000 millions At rest only 25% are patent Total cross sectional area of capillary bed if fully patent is 4000 times that of aorta Does not have smooth muscles Not controlled by either nervous or metabolic factors  Exchange Vessels – Continuous Capillaries eg brain Exchange Vessels – Fenestrated capillaries eg GIT, Kidney Exchange Vessels – Sinusoidal capillaries eg Liver Capillary beds: Microcirculation  Capacitance Vessels Veins can accommodate larger amount of blood without increasing much pressure in them. large and small veins - capacitance vessels.  Capacitance Vessels – Venules and veins Capillaries unite and form venules Venules converge and form veins Veins – No elastic layers – Large lumen  Special features of veins Valves Prevent backflow Most abundant in legs (where blood has to travel against gravity) Muscular contraction Aids the return of blood to heart in conjunction with valves 24 Sympathetic Tone Exercise helps circulation (because muscles contract and squeeze blood back to the heart)  Varicose Veins most common manifestations are : 1. Aching and edema 2. Their appearance through the skin is unsightly. 3. Tortuous veins. Shunt vessels or Thoroughfare vessels ARTERIOVENOUS ANASTOMOSIS Bypass capillaries Connect metarterioles with venules Skin of nose, Lips, ear lobe, Mucus membrane of GI & nose Erectile tissue of sex organ, Tongue  END ARTERIES 1.Central artery of retina 2. Arteries of spleen, liver, kidneys and metaphyses of long bones 3. Central branches of cerebral cortex