The heart.

Cardiovascular System Blood Heart Blood vessels Arteries - bring blood away from heart Veins – bring blood to heart Capillaries – smallest vessels where oxygen/nurtrient exchange occurs

Heart Wall Located in the mediastinum within the thoracic cavity (pericardial cavity) Protected by serous membrane called pericardium Epicardium – forms outermost layer of cardiac wall Myocardium – composed of cardiocytes Endocardium – thin layer that covers chambers of heart

Myocardium

External Anatomy of the Heart Four chambers  2 ventricles , 2 atria Atria: “receiving” chambers and return blood from veins Ventricles: “pumping” chambers and distribute blood to lungs and tissues Pulmonary circuits  directs deoxygenated blood to lungs Systemic circuit  takes oxygenated blood to the body

Carotid Brachiocephalic Subclavian Vena Cava Aorta Pulmonary Arteries Pulmonary Trunk Pulmonary Veins Left Atrium Semilunar Valves & Aortic Valve Right Atrium Bicuspid/Mitral Valve Tricuspid/AV Valve Left Ventricle Right Ventricle

https://www.youtube.com/watch?v=X_R8-S5bEYo

Coronary Circulation The heart can NEVER completely rest It needs to nourish itself Systemic circulation  coronary circulation: supplies myocardium with oxygen for muscle contraction

Left Coronary Artery Right Coronary Artery Circumflex Artery Marginal Artery Anterior IV Branch Posterior IV Branch

Coronary Circulation cont’d The arteries are circulating oxygenated blood Cardiac veins collect the deoxygenated blood from myocardium Veins merge at the coronary sinus Empties deoxygenated blood into the right atrium

How can the heart contract? Cardiac muscle tissue is “autorhythmic” Does NOT need stimulation from nerves Brain only dictates how fast the heart contracts Pacemaker  Sinoatrial node (SA node) Sets the pace by sending an electrical impulse to other nodal cells SA Node AV Node

Blood Pressure Pressure of the circulating blood against your vessel walls Systolic – when heart contracts and pushes through arteries Diastolic – measures pressure when ventricles are filling up / in between beats Normal is about 120/80 Hypertension  silent killer