Lecture Notes Animal Circulation o Function transport of materials throughout the body through direct interaction Circulation and circulatory system with most other organ systems o Services Gas exchange transport gases exchanged for respiration CO2 and O2 Nutrients pick up nutrients absorbed by digestive system to be distributed Wastes products to removed by excretory system Hormones communication and control throughout the body Body defense inflammatory and immune systems o Types Primitive No circulation Protozoa cnidarian flatworms Each cell has access to the outside Simple circulation nematodes use pseudo coelom Advanced Open circulation blood is not completely enclosed in vessels throughout Closed circulation blood is contained entirely in vessels in a circuit to from circuit to from the heart o Arthropod Mollusca o Blood empties into sinuses which surround major organs o Hemolymph not in tubes the heart o Annelids chordates o More efficient because a high blood pressure is maintained o Keeps flowing o Maintains heat Evolution of vertebrate closed circulation o Single circulation Fish heart has 2 chambers 1 atrium 1 ventricle Goes through 2 capillary beds per pass through heart o Double circulation separation of circulation to gas exchange surfaces from circulation to rest of body Goes through 1 capillary bed per pass through heart Amphibia heart has 3 chambers 2 atria 1 ventricle Blood mixes in ventricle Limits the level of metabolic activity Reptiles beginning of separation of pulmonary and systemic circulation Transition from 3 to 4 chambers with the appearance of a septum between ventricle 3 5 chambers 2 atria 1 5 ventricles Birds mammals full separation of systemic and pulmonary 4 chambered heart 2 atria 2 ventricles Evolved separately Blood must go through the lungs before it can go to the body each half of the heart is involved in one part of total circulation The heart o Atrioventricular valves Between each atrium and ventricle are valves to permit 1 way flow of blood from atrium into the ventricle Left mitral valve Right tricuspid valves o Semilunar valves Between each ventricle and blood vessels carrying blood away Thub AV valves snap shut after atrial contractions Lub semilunar valves snap shut after ventricle contraction Blood vessels multilayered tube lumen endothelium smooth muscles connective from heart o Heartbeat tissue epithelium o Artery Thicker walls more muscle Blood away from heart o Vein Thinner walls less muscle Valves Blood back to heart o Capillaries only endothelium 1 cell thick Between arteries and veins All exchanges through endothelial cells Bigger than 8 micrometers so blood cells can go through Exchanges involve diffusion active transport and or endo exocytosis through endothelial cells o Functional problem Closed circulation under a lot of pressure through entire circuit Lots of water loss because of hydrostatic pressure 3L day About 85 of fluid lost from capillaries are recovered by osmotic recovery Remaining 15 must be returned by lymphatic system Lymphatic system o Lymph vessels like veins with valves o Lymph capillaries like blood capillaries but closed ended tubes o Lymph excess fluid collected from intercellular spaces of tissues o Lacteal in small intestine lymph vessel in each villus Involved in absorption processing of lipids o Peyer s patches colonies of lymphatic cells in walls of intestine for immune surveillance of digestive organs o Lymph nodes filter lymph as it progresses through vessels towards upper torso of body major immune surveillance posts remove bacteria fungi debris o Thoracic duct o Lymph vessels collect and eventually return lymph to blood circulation o Pathologies of failure of lymphatic return Elephantiasis parasitic roundworms lodge in lymph nodes and plug up lymph system Leads to accumulation of lymph in areas normally drained by lymphatic Cancer metastasis spread of cancer because lymph nodes do not recognize system and filter them out Human circulation o Pulmonary circuit right atrium atrioventricular tricuspid right ventricle semilunar valves pulmonary artery lungs pulmonary vein o Systemic circuit left atrium atrioventricular mitral valve left ventricle semilunar valve aorta system vena cavae superior and inferior Pumping of the heart o Cardiac muscle o Contractions are intrinsic and rhythmic contract without outside stimulation and have periodic spontaneous contractions o Isolated cardiac cells twitch rhythmically o Intercalated discs connect groups of cells electrically o Pacemakers control centers of specialized cells Sino atrial node SA node primary pacemaker in the right atrium Specialized cells generate an electrical contraction signal that propagates through the rest of the heart Both atria contract Atrio ventricular node AV node secondary pacemaker located between the atria and ventricles Receives signal from AV node and passes it on to the ventricles through the bundle of His Both ventricles contract o Coordination of heartbeat AV and SA nodes make the heart an efficient pump Pathology fibrillation uncoordinated contractions in ventricles produce ripples over structure and not a coordinated pumping contraction can be fatal o Control of heartbeat Nervous system regulates rate and force of heart contractions Most connections to the SA node Stimulate or inhibit pacemaker Ex Vagus nerve causes a decrease in heart beat Others speed up the node Pacemakers also sensitive to hormones and drugs in blood epinephrine caffeine nicotine Microcirculation routing of blood flow o Nervous system can also control where blood goes in the body o Microcirculation when a series of sphincter muscles at the ends of arteries connecting to capillary beds are contracted or relaxed regulating how much blood flows through the capillaries o Examples Blushing blood to face and neck Thermoregulation keep heat in body core Second wind phenomenon aerobic exercise circulation shift associated with metabolic shift in muscles from aerobic anaerobic Spleen extra reserve of about cup blood if needed Need to keep the brain heart and kidneys supplied with blood Fetal circulation and shift at birth placental mammals only o Fetal circulation Circulation in fetus is different from post birth baby or adult Lungs are collapsed no gas exchange and little blood circulation through lungs Gas circulation through placenta systemic Blood flow bypasses pulmonary circulation Foramen ovale hole between the 2 atria o Blood from systemic circulation
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