2 The Cardiovascular System A closed system of the heart and blood vesselsThe heart pumps bloodBlood vessels allow blood to circulate to all parts of the bodyThe function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products
3 Closed system?What does it mean to be a “closed system?”
4 The Heart Location: About the size of your fist In the thorax Between the lungsPointed apex directed toward left hipAbout the size of your fistLess than 1 lb.
6 The Heart: CoveringsPericardium – tissue like sac surrounding the heartA double membrane made of:A. Visceral pericardium – thin layer of tissue that hugs the heartB. Parietal pericardium – fibrous outer layer to protect heartFluid fills the space between the layers of pericardium and allows the heart to beat without friction
7 The Heart: Heart Wall 3 layers of heart tissue Epicardium Outside layer of connective tissueMyocardiumMiddle layer made mostly of cardiac muscleThis is the layer that actually contractsEndocardiumThin inner layer that lines heart chambers
13 The Heart: ValvesEach of the hearts 4 chambers has its own valveValves allow blood to flow in only one directionA. Atrioventricular (AV) valves – located between atria and ventricles1. Bicuspid or mitral valve (left side) – made of two flaps of endocardium2. Tricuspid valve (right side) – made of three flapsB. Semilunar valves – located at the base of two large arteries leaving the ventricles3. Pulmonary semilunar valve – made of 3 leaflets4. Aortic semilunar valve – made of 3 leaflets
14 How they work…AV valves are open when the heart is relaxed and blood is passively filling into the ventriclesHeld in place by tendon-like cordsAs the ventricles contract, they press on the blood in their chambers which closes the AV flapsThis prevents backflow into the atriaThe semilunar valves then open during ventricle contraction
16 So, does the heart need its own blood for nutrients and oxygen? We know that the heart pumps blood, but does the heart need blood for itself too?YES! Of course it doesBUT….Blood in the heart chambers DOES NOT nourish the myocardium (heart muscle cells)So where does the heart get blood?
17 Cardiac CirculationThe heart has its own nourishing circulatory systemThe blood supply that oxygenates and nourishes the heart is provided by:Coronary arteriesCardiac veinsWaste products in the blood are then emptied into the right atrium via the coronary sinus
18 The Heart: Conduction System Intrinsic Conduction System - Heart muscle cells contract, without action potentials, in a regular, continuous way1. Sinoatrial node (SA): group of myocytes in the right atirum that conduct AP’sAlso called the “Pacemaker” – generator of heart rhythm2. Atrioventricular node (AV) – myocytes located at the junction between the atria and ventricle
20 The Heart: Conduction System 3. Bundle of His - a collection of heart muscle cells that transmits AP’s from the AV node to the bundle branches4. Bundle branches – long muscle fibers that travel down the inner ventricular walls5. Purkinje fibers – muscle fibers located on the lower ventricular walls that allow the ventricles to contract
22 Electrocardiograms (EKG/ECG) An interpretation of the electrical activity of the heart captured and recorded by skin electrodesThree formations:P wave: impulse across SA node (P)QRS complex: spread of impulse down AV node (Q), towards Bundle of His (R), down bundle branches, and around ventricles in Purkinje fibers (S)T wave: end of electrical activity in ventricles