Circulatory System A general tour

Exchange of materials Animal cells exchange material across their cell membrane  Fuel for energy  Nutrients  Oxygen  Waste (urea, CO 2 ) If you are a 1-cell organism, this is easy!  Diffusion If you are multicellular, it becomes more difficult

Overcoming limitations of diffusion O2O2 CHO aa CH CO 2 NH 3 aa O2O2 CH aa CO 2 NH 3 O2O2 aa CH aa CHO O2O2 Diffusion is not adequate for moving material across more than 1-cell barrier So … set up a “highway” system to transport materials!

In circulation … What needs to be transported?  Nutrients & fuels From digestive system  Respiratory gases O 2 & CO 2 from & to gas exchange systems: lungs/gills  Intracellular waste Waste products from cells  Water, salts, nitrogenous wastes (urea)  Protective agents Immune defenses  White blood cells & antibodies Blood clotting agents  Regulatory molecules hormones

Circulatory systems All animals have:  Circulatory fluid = “blood”  Tubes = blood vessels  Muscular pump = heart openclosed hemolymphblood

Vertebrate cardiovascular system Chambered heart  Atria = receive blood  Ventricles = pump out blood Blood vessels  Arteries = carry blood away from heart Arterioles  Veins = return blood to heart Venules  Capillaries = thin wall, exchange/diffusion with cells Capillary beds = networks of capillaries

Blood vessels arteries arterioles capillaries venules veins

Arteries: built for high pressure pump Thick walls  Provide strength for high pressure pumping of blood ( mm Hg) Narrow diameter/lumen Elasticity  Elastic recoil helps maintain blood pressure even when heart relaxes Middle layer = elastin Outer layer = collagen No valves No exchange with cells

Veins: built for low pressure flow Thinner walls Wider diameter/lumen  Blood travels back to heart at low velocity & pressure  Lower pressure (<10 mm Hg) Distant from heart  Blood must flow by skeletal muscle contractions when we move  Squeeze blood through veins Valves  In larger veins, one-way valves allow blood to flow only toward the heart No exchange with cells

Capillaries: built for exchange Very thin walls  Lack 2 outer walls  Only endothelium Enhances exchange across capillary Diffusion  Exchange occurs between blood & cells No valves Some capillaries have pores  Fenestrations  Allows plasma & certain other cells/molecules to “leak” into tissue

Controlling blood flow to tissues sphincters opensphincters closed Why? Blood flow in capillaries controlled by pre- capillary sphincters  Supply varies as blood is needed  After a meal, blood supply to digestive tract increases  During strenuous exercise, blood is diverted from digestive tract to skeletal muscles Capillaries in brain, heart, kidneys & liver usually filled to capacity

Exchange across capillary walls Arteriole Blood flow Venule Lymphatic capillary Interstitial fluid Fluid & solutes flows out of capillaries to tissues due to blood pressure “bulk flow” Interstitial fluid flows back into capillaries due to osmosis  plasma proteins  osmotic pressure in capillary BP > OPBP < OP 15% fluid returns via lymph 85% fluid returns to capillaries What about edema? Capillary

Lymphatic system Parallel circulatory system  Transports white blood cells Defends against infection  Collects interstitial fluid & returns to blood Maintains volume & protein concentration of blood Drains into circulatory system near junction of vena cava & right atrium

Lymphatic system Production & transport of WBCs Traps foreign invaders lymph node lymph vessels (intertwined amongst blood vessels)

Mammalian circulation What do blue vs. red areas represent? pulmonary systemic

Mammalian heart Coronary arteries to neck & head & arms Arteries that supply blood specifically to the heart

Coronary arteries bypass surgery

Heart valves 4 valves in the heart  Flaps of connective tissue  Prevent backflow Atrioventricular (AV) valves  Between atrium & ventricle  Keeps blood from flowing back into atria when ventricles contract  Tricuspid & bicuspid/mitral valves Semilunar valves  Between ventricle & artery  Prevents backflow from arteries into ventricles while they are relaxing  Aortic & pulmonary valves

Left Ventricle Left Atrium Right Atrium Right Ventricle Tricuspid valve Pulmonary Vein AortaPulmonary Artery Vena Cava Aortic valve Mitral valve Pulmonary valve Septum

Our circulatory system is a double circulatory system. Lungs Body cells the right side of the system deals with deoxygenated blood. the left side of the system deals with oxygenated blood.

lungs head & arms liver digestive system kidneys legs pulmonary vein aorta pulmonary artery main vein LeftRight

What about blood? There are 4 main components to blood:  Erythrocytes Red blood cells  Oxygen transport  Leukocytes White blood cells  Non-specific immunity Lymphocytes  Specific immunity  Platelets Blood clotting  Plasma Fluid medium

Red blood cells contain hemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it. can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries. a biconcave disc that is round and flat without a nucleus

White blood cells there are many different types and all contain a big nucleus. the two main ones are the lymphocytes and the macrophages. some lymphocytes fight disease by making antibodies to destroy invaders by dissolving them. other lymphocytes make antitoxins to break down poisons. macrophages ‘eat’ and digest micro- organisms.

Platelets Platelets are bits of cell broken off larger cells. Platelets produce tiny fibrinogen fibres to form a net. This net traps other blood cells to form a blood clot.

Blood clotting Damaged cells release chemical signals called clotting factors Clotting factors convert prothrombin (zymogen) into thrombin Thrombin converts fibrinogen into fibrin Clotting factors cause platelets to become sticky, resulting in a clot at the injury site Stops blood flow & helps prevent pathogens from entering

Plasma Also contains:  Carbon dioxide  Glucose  Amino acids  Proteins  Minerals  Vitamins  Antibodies  Hormones  Waste (like urea)  Heat A straw- coloured liquid that carries the cells and the platelets which help blood clot.

Atherosclerosis Hardening & narrowing of the arteries  Due to deposit of plaque  High blood pressure damages artery wall Causes chronic inflammation  Accumulation of lipids, cholesterol, debris & calcium  Fatty deposits (atheromas) reduce diameter of lumen (stenosis) and elasticity of the artery  May lead to the formation of clots & blockages in the artery  Major cause of heart attacks, strokes, and peripheral vascular disease

Atherosclerosis Risk factors for coronary heart disease  Lack of exercise  Diet  Obesity  Genetics  Gender Males at greater risk due to low estrogen levels  Smoking Nicotine causes vasoconstriction Increases blood pressure  Age

Bloody well ask some questions, already!