2/6/08 The Heart Chapter 18

2/6/08 The Heart  Heart function = key factor in body function  Health Issues – Heart problems are one of the leading causes of death in the US  Primary function ♦Blood circulation ♦There must be enough force generated to send blood to every single cell  As A Pump ♦Pumps 1835 gallons of blood a day ♦Through 60,000 miles of blood vessels  What’s your heart doing right now?

2/6/08 Heart - Location  Remember those body cavities….?  Mediastinum = the cavity between the lungs ♦Holds Trachea Thymus Pericardial cavity  Inside the pericardial cavity… ♦Heart + Pericardium

2/6/08 Fig. 18-1

2/6/08 Fig. 18-1

2/6/08 Heart - Anatomy  Pericardial cavity ♦Sac enclosing the heart ♦Formed by membrane = pericardium ♦This is the lining of the pericardial cavity  Pericardium = 3 layers ♦Visceral pericardium Layer closest to the heart ♦Parietal pericardium On top of visceral ♦Fibrous pericardium Outermost layer – made up of collagen fibers Fig. 18.3

2/6/08 Heart - Anatomy  Pericardial cavity ♦Between the parietal and fibrous layers = pericardial fluid  Pericardium ♦Is like a plastic bag with fluid ♦Covers the heart, cushions it & anchors it in place Fig. 18.2

2/6/08 Pericarium  The fibrous layer of the pericardium attaches to the diaphragm  Fluid between layers prevents friction when the heart beats  Very important structure ♦Protects & anchors – therefore it helps it function  Damage to the pericardium can be serious ♦Pericarditis Inflamation of pericardium Results in bleeding into the cavity Heart becomes compressed Leads to heart failure = Cardiac Tamponada Fig. 18.2

2/6/08 Heart - Anatomy  Heart location = slightly left of midline  Triangular shape ♦Blunt cone ♦Apex = slightly rotated to left  Heart ♦Muscular structure Fig. 18.3

2/6/08 Heart - Anatomy  Heart location = slightly left of midline  Triangular shape ♦Blunt cone ♦Apex = slightly rotated to left  Heart ♦Muscular structure ♦With 4 hollow chambers Contain blood Fig. 18.3

2/6/08 Heart - Anatomy  Heart location = slightly left of midline  Triangular shape ♦Blunt cone ♦Apex = slightly rotated to left  Heart ♦Muscular structure ♦With 4 hollow chambers Contain blood ♦Valves Guide flow of blood between chambers & into blood vesses Fig. 18.3

2/6/08 Heart - Anatomy  Chambers ♦Atria ♦Ventricles  Arteries ♦Pulmonary ♦Aorta ♦Coronary  Veins ♦Pulmonary ♦Vena Cava ♦Coronary  Valves ♦Atrioventricular ♦Semilunar  Conduction Nodes (electrical) & Fibers Fig. 18.3

2/6/08 Heart - Anatomy  Chambers ♦Atria ♦Ventricles  Arteries ♦Pulmonary ♦Aorta ♦Coronary  Veins ♦Pulmonary ♦Vena Cava ♦Coronary  Valves ♦Atrioventricular ♦Semilunar  Conduction Nodes (electrical) & Fibers Fig. 18.3

2/6/08 Heart - Anatomy  Chambers ♦Atria ♦Ventricles  Arteries ♦Pulmonary ♦Aorta ♦Coronary  Veins ♦Pulmonary ♦Vena Cava ♦Coronary  Valves ♦Atrioventricular ♦Semilunar  Conduction Nodes (electrical) & Fibers Fig. 18.6

2/6/08 The Heart Chapter 18

2/6/08 Heart - Anatomy  Heart ♦Muscular structure ♦With 4 hollow chambers Contain blood ♦Valves Guide flow of blood between chambers & into blood vesses ♦Veins and arteries To take blood to & from the heart Fig. 18.3

2/6/08 Heart – Structure/Function  Heart = Fig. 18.6

2/6/08 Heart – Anatomy: Tissue Layers  There are 3 layers of tissue ♦Epicardium = visceral layer ♦Myocardium = cardiac muscle ♦Endocardium (innermost) = squamus epithelium (thin layer)  Heart walls are arranged as ridges ♦Trabeculae carnea Fig. 18.4

2/6/08 Fig Heart – Anatomy: Tissue Layers

2/6/08 Heart – Anatomy: Tissue Layers  There are 3 layers of tissue ♦Thickness of the myocardium is variable ♦It’s made of cardiac muscle – do you recall any special features of cardiac muscle? ♦Intercalated discs… ♦How does that relate to cell function? ♦Coordinated action potential for contraction Fig. 18.6

2/6/08 Heart – Anatomy: Cardiac muscle Fig. 18.5

2/6/08 Heart – Cellular Anatomy  Cardiac muscle is striated and contains myofibrils made up of sarcomeres like skeletal muscle  Intercalated discs ♦Cell membranes of adjacent cardiac cells are extensively intertwined (gap junctions & desmosomes) ♦Provide direct connection between cells ♦Stabilize positions of adjacent cells & maintain tissue structure ♦Action potentials can travel across an intercalated disc b/c ions and small molecules can move quickly through the gap junctions  Intercalated disc arrangement creates a direct electrical connection between 2 muscle cells Fig. 18.6

2/6/08 Heart – Cellular Anatomy Fig. 18.6

2/6/08 Heart – Anatomy: Chambers Fig. 18.6

2/6/08 Heart – General Arrangement  Heart Chambers ♦4♦4 ♦Superior =  Superior ♦Atria Right & Left  Inferior ♦Ventricles Right & Left  Atria & Ventricles are separated by the coronary sulcus Fig. 18.6

2/6/08 Heart – General Arrangement  Atria ♦Thin walled ♦3 layers are all thin ♦When the atria are deflated there is a flap of tissue (fold near the ventricle) = auricle ♦Right & left atria separated by interlateral septae  Ventricles ♦Thicker walls to withstand more pressure ♦Left ventricle pumps the highest pressure ♦Largest chamber ♦Thickest muscular wall to withstand force ♦Right and left ventricle are separated by interventricular septae Fig. 18.6

2/6/08 Heart – General Arrangement  Valves ♦Soft flaps of connective tissue separate chambers ♦Guard openings to blood vessels  Main Valves ♦Atrioventricular valves Guard the entrance to the ventricle Blood flows from the atrium → ventricle on both sides Valves direct the flow Prevent backflow into atria ♦Semilunar valves Guard vessel openings that exit from ventricle 2 valves: Pulmonary & Aortic – ½ moon-shaped folds Fig. 18.6

2/6/08 Fig. 18.8b Heart – Anatomy: Valves

2/6/08 Heart – Anatomy: Valves Fig. 18.8a

2/6/08 Heart – General Arrangement  Right Side ♦Tricuspid valve ♦= 3 flaps Fig  Left side ♦Bicuspid valve ♦ = 2 flaps ♦Mitral valve  Semilunar valves

2/6/08 Heart – Blood Vessels  Superior & Inferior Vena Cava ♦Veins ♦Enter R atrium  Pulmonary Artery ♦Exits from R ventricle  Pulmonary Veins ♦Enter left atrium  Aorta ♦Exits left atrium Fig. 18.6

2/6/08 Heart – Anatomy: Blood vessels Fig. 18.9

2/6/08 Heart – Blood Vessels  Artery ♦Leaves heart (Away from heart)  Vein ♦Toward heart  Not based on oxygenated or deoxygenated blood  Coronary Artery ♦Supplies heart muscle itself  Blood enters ATRIA ♦From the body OR from the lungs  Blood leaves via the VENTRICLES

2/6/08 Heart – Flow of Blood  The atria must contract together  Followed by the ventricles contracting  For this to happen you need voluntary control  Cardiac muscle is involuntary  Pre-set action potentials – give you a steady rate/beat  Does not have to be relayed through the brain Fig. 18.6

2/6/08 What drives blood flow  Cardiac muscle contraction ♦Involuntary  Skeletal muscle contracts only when conscious nerve impulses are sent to muscle (neuromuscular junctions)  Cardiac muscles, however… ♦Programmed control Fig. 18.6

2/6/08 Heart – Rhythm  Special cells = CONDUCTION SYSTEM ♦Nerve-like cells  Nodes and conduction fibers trigger & conduct action potential to cardiac muscle  Components of this CONDUCTION SYSTEM ♦Sinoatrial node (SA node) ♦Atrioventricular node (AV node) ♦Internodal pathways ♦AV bundles ♦Purkinje fibers Fig. 18.6

2/6/08 Heart – Conduction System  CONDUCTION SYSTEM – positions/location  SA node ♦Right atrium  Internodal pathways ♦Travel through atria, conducts left  AV node ♦Junction between atria & ventricles  AV bundles ♦Between ventricles  Purkinje fibers ♦Through ventricles Fig. 18.6

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2/6/08 Heart – Anatomy Fig. 18.7

2/6/08 Heart – Anatomy: Chambers Fig. 18.7

2/6/08 Heart – Anatomy: Chambers  Fig. 18.6

2/6/08 Heart – Anatomy: Blood Vessels  Fig. 18.6

2/6/08 Heart – Anatomy: Blood vessels Fig. 18.9

2/6/08 Heart – Anatomy: Chambers Fig. 18.9

2/6/08 Blood flow Fig. 18.1

2/6/08 Blood flow Fig. 18.1

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