T1 Phys - Topic 8 - Circulatory - Apr 2021 PDF

Module #8 – Circulatory System 1) Cardiovascular System 2) Lymphatic System Cardiovascular System Functions 1) transportation a) nutrients & wastes b) hormones 2) immunity & protection a) clotting b) disease/infection 3) regulation a) pH b) body temperature c) fluid levels p. 151 Structures 1) heart...

Module #8 – Circulatory System 1) Cardiovascular System 2) Lymphatic System Cardiovascular System Functions 1) transportation a) nutrients & wastes b) hormones 2) immunity & protection a) clotting b) disease/infection 3) regulation a) pH b) body temperature c) fluid levels p. 151 Structures 1) heart 2) blood vessels 3) blood The Heart roughly the size of your closed fist sits almost in the middle of the chest in the mediastinum 2/3rds of its mass is on the left attached to the diaphragm inferiorly functions: pump, adaptation to changes, homeostasis inferior portion is the apex superior portion is the base p. 152 Mediastinum a mass of organs and tissues that separates the lungs boundaries: superiorly: first rib inferiorly: diaphragm anteriorly: sternum (breastbone) posteriorly: vertebral column (spine) contains heart & its large vessels trachea esophagus thymus & lymph nodes connective tissue p. 153 Connective Tissues of the Heart – The Pericardium a two‐layered CT membrane that surrounds and protects the heart 1) fibrous pericardium 2) serous pericardium 1) Fibrous Pericardium most superficial tough, inelastic, dense irregular CT attaches to the diaphragm inferiorly, to the CT of the blood vessels superiorly it holds the heart in the mediastinum and allows for movement 2) Serous Pericardium thinner, deep to the fibrous forms a double layer around the heart outer layer: parietal layer of the serous pericardium fused to the fibrous pericardium inner layer: visceral layer of the serous pericardium a.k.a. epicardium attached to the heart muscle Pericardial Cavity the space between the parietal and visceral layers of the pericardium filled with pericardial fluid (a thin layer of fluid to reduce friction) p. 154 The Heart Wall 3 layers a) epicardium b) myocardium c) endocardium a) epicardium    a.k.a. visceral layer of the serous pericardium simple squamo us epithelium and CT gives the outer surface a smooth, slippery texture b) myocardium   cardiac muscle tissue site of contraction c) endocardium    endothelium overlying a thin layer of CT endothelium: the layer of simple squamous epithelium that lines the cavities of the heart, blood vessels, and lymphatic vessels provides a smooth lining for the chambers and valves of the heart p. 155 p. 156 Heart Chambers 4 chambers: 2 atria, 2 ventricles Atria 2 superior chambers receive blood from blood vessels (veins) returning to the heart Ventricles 2 inferior chambers receive blood from the atria and eject it out into blood vessels (arteries) p. 157 Septa sing.: septum a dividing wall interatrial septum: divides the 2 atria interventricular septum: divides the 2 ventricles Veins: carry blood to the heart Arteries: carry blood away from the heart p. 158 Right Atrium receives blood from three veins superior vena cava inferior vena cava coronary sinus blood passes from the right atrium through the right atrioventricular (AV) valve (a.k.a. tricuspid valve) into the right ventricle Right Ventricle receives blood from the right atrium the cusps of the right A‐V valve are connected to tendon‐like cords called chordae tendineae chordae tendineae are anchored to the ventricular wall by papillary muscles blood is ejected by the right ventricle through the pulmonary semilunar valve into the pulmonary trunk the pulmonary trunk divides into the right and left pulmonary arteries Left Atrium receives blood from the pulmonary veins (4) blood passes from the left atrium through the left atrioventricular (AV) valve (a.k.a. bicuspid valve, mitral valve) into the left ventricle Left Ventricle thickest chamber of the heart receives blood from the left atrium the cusps of the left A‐V valve are connected to tendon‐like cords called chordae tendineae chordae tendineae are anchored to the ventricular wall by papillary muscles blood is ejected by the left ventricle through the aortic semilunar valve into the aorta some of the blood in the aorta flows into coronary arteries which supply the heart with oxygen‐rich blood p. 159 p. 160 The Heart Valves Atrioventricular (a.k.a. tricuspid & bicuspid/mitral) Valves when blood flows into the atria, it increases pressure in the atria the pressure opens the AV valves allowing blood to flow into the ventricles when the ventricles contract, the increased pressure forces the AV valves closed the papillary muscles contract to prevent the valves from being forced open in the opposite direction Pulmonary & Aortic Semilunar Valves when the ventricles contract, they increase pressure in the ventricles this pressure closes the AV valves and opens the pulmonary and aortic valves blood is ejected into the arteries (pulmonary and aorta) when the ventricles relax, blood in these arteries starts to flow back toward the heart this fills the cusps of the semilunar valves and they close p. 161 p. 162 Heart Sounds ‘lub‐dup’ ‘lub’: the sound made by the blood turbulence associated with the closing of the AV valves ‘dup’: the sound made by the blood turbulence associated with the closing of the semilunar valves Pulmonary Circulation a function of the right side of the heart deoxygenated blood returns from body tissues and enters the right atrium gets pumped into the right ventricle which ejects the blood into the pulmonary arteries these blood vessels take the deoxygenated blood to the lungs to clear the CO2 and pick up the O2 the blood (now oxygenated) returns from the lungs via the pulmonary veins and enters the left atrium Systemic Circulation a function of the left side of the heart oxygenated blood returns from the lungs and enters the left atrium blood is pumped into the left ventricle which ejects the blood into the aorta and out to body tissues tissues use the O2 and release CO2 which eventually makes its way back to the right atrium (now deoxygenated) p. 163 Coronary Circulation the heart needs its own circulation – the coronary circulation coronary arteries branch off from the aorta and encircle the heart the heart gets its blood supply between beats The Conduction System of the Heart specialized cardiac muscle cells generate their own APs – they are called autorhythmic fibres because they are self‐excitable they form structures that (1) set the rhythm of the APs that cause contraction and (2) they form a conduction system the conduction system is the pathway along which the APs progress through the heart the APs propagate through this conduction system in a specific sequence: SA node atria AV node bundle of His bundle branches Purkinje Fibres ventricles p. 164 The SA (Sinoatrial) Node in the right atrial wall it repeatedly generates APs which propagate through the atria via gap junctions causing atrial contraction and ejection of blood into the ventricles the APs travel throughout the atria and reach the AV node p. 165 The AV (Atrioventricular) Node from the AV node, the APs enter the bundle of His (a.k.a. atrioventricular bundle) the APs conduct along the right and left bundle branches which extend along the interventricular septum to the apex of the heart the Purkinje fibres very quickly conduct the APs upward through the ventricles causing ventricular contraction and ejection of blood into the arteries Electrocardiogram (ECG) as the APs move through the heart, they can be detected on the surface of the body problems can be identified based on the shape and timing of the tracing p. 166 The Cardiac Cycle all of the events associated with one heart beat systole: contraction phase diastole: relaxation phase in each cycle, the atria and ventricles alternately contract pushing blood through the chambers of the heart and out of the heart Cardiac Output the amount of blood the heart ejects each minute heart rate (HR): the number of times the heart beats in 1 minute stroke volume (SV): the amount of blood ejected from each ventricle with each beat cardiac output (CO): heart rate x stroke volume average HR: 72 bpm average SV: 70 mL average CO: ~ 5 L/min different factors will affect HR and SV – there are limits as to how high or how low they can go p. 167 Factors Affecting Heart Rate heart rate must adjust to meet blood flow demands (e.g. exercise, changes in blood volume) factors that regulate HR: 1) ANS 2) hormones/ions 3) Other 1) ANS the control centre in the __________ gets input from sensory receptors and high brain centres (e.g. limbic system and cerebral cortex) based on input, the control centre increases or decreases the frequency of APs in the SyNS and PaNS increased SyNS: increases HR increased PaNS: decrease HR 2) Hormones/Ions epinephrine/norepinephrine increase HR and contractility thyroid hormones increase HR and contractility sodium and potassium – needed for normal APs – elevated blood levels decrease HR elevated levels of calcium increase HR and contractility 3) Other Factors age sex fitness level body temperature p. 168 Factors Affecting Stroke Volume the left and right ventricles need to eject the same volume of blood three factors help to maintain equal stroke volume 1) preload 2) contractility 3) afterload 1) Preload the degree of stretch on the heart before it contracts greater stretch = stronger contraction (Frank‐Starling law) the amount of stretch is proportional to the volume of blood that fills the ventricles at the end of diastole (end diastolic volume or EDV) EDV is affected by: the duration of ventricular diastole venous return there are limits 2) Contractility the strength of contraction at any given preload factors that increase contraction strength: SyNS activation hormones (adrenaline/epinephrine) medications (e.g. digitalis) factors that decrease contraction strength decreased SyNS activation chemical imbalances medications (e.g. calcium channel blockers) 3) Afterload ejection of blood from the heart begins when ventricular pressure > vessel pressure (pulmonary trunk or aorta) when the pressure is greater in the ventricles than in the vessels, the semilunar valves open the pressure that must be overcome before a semilunar valve can open is the afterload factors that increase afterload: hypertension (high blood pressure) narrowing of arteries by atherosclerosis p. 169 Blood Vessels Arterial System arteries carry blood away from the heart large elastic arteries divide into medium‐sized muscular arteries which branch out into the different regions of the body muscular arteries divide into smaller arteries which divide into smaller arterioles (a.k.a. the resistance vessels) as arterioles enter the tissue, they divide/branch out into capillaries (a.k.a. the exchange vessels) capillaries exchange substances (gases, nutrients, wastes) between the blood and the tissues p. 170 p. 171 Venous System carry blood to the heart capillaries within tissues ‘reunite’ to form venules venules merge to form progressively larger veins veins merge into the vena cavae p. 172 p. 173 Blood Vessel Walls BVs (except capillaries) have the same 3‐layered arrangement surrounding the lumen tunica intima tunica media tunica externa Tunica Intima/Interna inner layer simple squamous epithelium (called endothelium) and a CT basement membrane Tunica Media middle layer contains elastic fibres and smooth muscle Tunica Externa (a.k.a. tunica adventitia) outer layer contains elastic and collagen fibres supports BVs and anchors them to surrounding structures p. 174 Vasoconstriction a decrease in lumen size Vasodilation an increase in lumen size p. 175 Blood Vessel Function Arteries stretch to accommodate blood flow (especially under pressure (i.e. when the ventricles contract)) recoil which helps force the blood forward Arterioles blood flow regulation they have a substantial ability to constrict or dilate the vessel they therefore have a significant effect on blood pressure Capillaries microcirculation found near almost every cell in the body walls are a single layer of endothelium and a basement membrane nutrient and waste exchange p. 176 Venules blood flow from capillaries to veins Veins little smooth muscle and less elastic CT not designed to withstand high pressure need help moving blood have one‐way valves to prevent backflow transport blood to the heart (venous return) p. 177 Blood fluid (55%) and cells (45%) 38oC, pH 7.4 male blood volume: 5‐6 L, female blood volume: 4‐5 L Functions transportation (nutrients, wastes, heat, hormones) regulation (pH, body temperature, fluid levels) protection (vs blood loss, foreign invaders) Blood Components Plasma the fluid matrix of blood contains dissolved substances (including nutrients, wastes, hormones) Plasma Proteins albumin: transport protein globulins: some are transport proteins, some are involved in the immune response fibrinogen: essential in blood clotting Blood Cells red blood cells (RBCs) (a.k.a. erythrocytes) white blood cells (WBCs) (a.k.a. leukocytes) platelets (a.k.a. thrombocytes) Erythrocytes (a.k.a. red blood cells (RBCs)) contain hemoglobin an oxygen carrying protein a pigment that gives blood its red colour live for ~ 120 days hemopoiesis (or hematopoiesis): the formation of RBCs hematocrit: the % of blood volume occupied by RBCs anemia: lower than normal hematocrit polycythemia: higher than normal hematocrit p. 178 Leukocytes (a.k.a. white blood cells (WBCs)) functions fight off foreign invaders phagocytosis immune responses 1) granular a) neutrophils (a.k.a. polymorphonuclears): most common, function in phagocytosis (esp. bacteria) b) eosinophils: function in allergic reactions, parasitic infections c) basophils: function in stress and allergic responses 2) agranular a) lymphocytes i. B lymphocytes ii. T lymphocytes iii. natural killer cells b) monocytes leukocytosis: increased WBC count leukopenia: decreased WBC count Leukocytes granular neutrophils eiosinophils agranular basophils B‐cells lymphocytes T‐cells monocytes NK cells Platelets help stop bleeding/contain substances to promote clotting live 5‐9 days p. 179 p. 180 Blood Pressure blood flows from areas of high pressure to areas of low pressure ventricular contraction generates blood pressure (the pressure on the walls of the blood vessel) systolic BP: the highest arterial pressure during ventricular systole diastolic BP: the lowest arterial pressure during ventricular diastole pressure falls progressively with distance from the left ventricle mean arterial pressure (MAP): the average blood pressure in the arteries blood pressure is affected by: cardiac output (CO)  CO =  MAP blood volume significant  in blood volume =  in BP vascular resistance lumen size ( lumen size =  BP) blood viscosity ( viscosity =  BP) total vessel length ( vessel length =  BP) p. 181 p. 182 Lymphatic & Immune Systems Lymphatic System Functions drainage of excess interstitial fluid transportation of lipids (from the digestive system) protection/immune responses Structures lymph (the fluid of the system) lymphatic vessels (to transport the fluid) structure and organs that contain lymph tissue red bone marrow (where various blood cells develop) Lymph plasma and solutes filter freely from blood capillaries into interstitial space some is re‐absorbed into the blood excess filtered fluid (~3 L/day) drains into lymphatic system (capillaries) the few proteins that leak out of the blood capillaries must return to circulation via the lymphatics p. 183 Lymphatic Flow capillaries  lymphatic vessels  trunks  ducts Lymphatic Capillaries begin in the spaces between cells closed at one end high permeability cells forming the endothelium overlap to allow fluid in but not back out pressure drives interstitial fluid into the capillaries p. 184 Lymphatic Vessels capillaries merge into larger vessels (lymphatic vessels) lots of one‐way valves at regular intervals, lymph passes through lymph nodes Lymph Nodes clusters of lymphocytes (B cells and T cells) surrounded by a dense CT capsule bean shaped ~ 600 nodes located along the lymphatic vessels of the body (often in groups, superficial and deep) function: lymph filtration (lymph flows in, foreign substances are trapped and destroyed) p. 185 Lymphatic Trunks larger lymphatic vessels merge into trunks Lymphatic Ducts 1) thoracic duct (which drains the) left side of the head & neck left side of the chest entire body below the ribs it drains into the left subclavian vein 2) right lymphatic duct (which drains the) right side of the head & neck right side of the chest it drains into the right subclavian vein p. 186 p. 187 Lymphatic Flow Lymphatic Flow  blood capillaries (blood)  interstitial spaces (interstitial fluid)  lymphatic capillaries (lymph)  lymphatic vessels (lymph)  lymphatic ducts (lymph)  subclavian veins (blood) maintained by: 1) skeletal muscle pump 2) diaphragmatic breathing/respiratory pump 3) smooth muscle contraction (in the vessel walls – minimal contribution) Lymphatic Organs Red Marrow produces B cells and immature T cells (a.k.a. pre‐T cells) Thymus located in the mediastinum produces mature T cells from pre‐T cells large at birth, significantly atrophied by maturity p. 188 Spleen large mass of lymphatic tissue between the stomach and the diaphragm filters blood (similar to the process in a lymph node) removes ruptured, worn out, defective RBCs stores platelets and monocytes p. 189 The Immune System non‐specific defences specific defences (immunity) Non‐Specific Defences rapid responses don’t recognize specific invaders but react in the same way to all invaders no memory component First Line skin: tightly packed keratinized cells, shedding mucous membranes: mucous traps microbes, cilia sweeps them out body fluids sweat: flushes the skin tears: wash the eye saliva: washes the teeth and mucous membranes urine: regular flow reduces microbial growth gastric juice: stomach acid destroys many bacteria defecation: removes microbes vomiting: removes microbes Second Line antimicrobial proteins: discourage microbial growth natural killer (NK) cells: recognizes and kills microbes phagocytes (fixed and wandering): eat microbes fixed: histiocytes (CT), Kupffer cells (liver), alveolar macrophages (lung), microglia (CNS) inflammation: a non‐specific response to tissue damage designed to remove microbes etc., prevent their spread, and prepare the site for repair fever: intensifies antimicrobial protein activity, inhibits microbial growth, speeds up repair p. 190 Specific Defences (a.k.a. Immunity) antigen: substances that are recognized as foreign and elicit an immune response In specific responses, antigens/invaders are… identified killed remembered specific responses are slower (than non‐specific) 2 types: 1) cell‐mediated 2) antibody‐mediated Cell‐Mediated Immune Responses effective against fungi, parasites, viruses, some cancer cells, foreign tissue when an invader is recognized, T‐cells: activate enlarge proliferate differentiate (into:) helper T cells (trigger proliferation, perform other immune functions) cytotoxic T cells: migrate to the site and destroy the invader memory T cells: remain after the response, they don’t attack but with future infections (same invader), they make for a faster and stronger response Antibody‐Mediated Immune Responses effective against antigens in body fluids, extracellular pathogens (e.g. bacteria) when an invader is recognized, B‐cells: activate enlarge differentiate (into:) plasma cells which secrete antibodies memory B cells: remain after the response, they don’t attack but with future infections (same invader), they make for a faster and stronger response antibodies a.k.a. immunoglobulins proteins produced by plasma cells in response to an antigen they neutralize, inhibit, or destroy the antigen 5 classes of antibodies: p. 191 IgG most common in blood/lymph/intestines protect against bacteria, viruses they cross the placenta to confer immunity to the newborn found in sweat/tears/saliva/mucous/breast milk/GI levels decrease during stress IgA IgM found in blood/lymph part of blood transfusion reactions IgE found in blood involved in allergic/hypersensitivity reactions, protects against parasitic worms found in blood help activate B cells IgD p. 192 Aging and the Immune System increased susceptibility to infections and malignancies responses to vaccines is decreased more autoantibodies are produced lower level of immune function T cells and B cells are less responsive Exercise and the Immune System the effect of exercise on the immune system seems to be dependent on the type and intensity of the exercise more research has been conducted on endurance exercise than on resistance training in general, exercise generates a positive adaptation in immune system function post‐exercise massage seems to have a positive effect, both physiologically and psychologically p. 193