2024 Chapter 15 The Cardiovascular System PDF

Heart & Blood Vessels Chapter 15 & 16 1 The Pulmonary and Systemic Circuits Major divisions of circulatory system Pulmonary circuit: right side of heart Carries blood to lungs for gas exchange Systemic circuit: left side of heart Suppl...

Heart & Blood Vessels Chapter 15 & 16 1 The Pulmonary and Systemic Circuits Major divisions of circulatory system Pulmonary circuit: right side of heart Carries blood to lungs for gas exchange Systemic circuit: left side of heart Supplies oxygenated blood to all tissues of the body 2 Position, Size, and Shape of the Heart Heart located in mediastinum, between lungs Base - wide, superior portion of heart Apex - tapered inferior end, tilts to the left At any age, heart is size of fist 3 The Pericardium Pericardium - double-walled sac surrounds and protects the heart Consists of two parts; Fibrous pericardium - outer wall composed of dense irregular connective tissue Prevents overstretching, provides protection and anchors the heart Serous pericardium – inner layer that forms a double layer around the heart Parietal layer – outer layer is fused to the fibrous pericardium Visceral layer (also called epicardium) – attaches to the surface of the heart 4 The Heart Wall Three layers of the heart: Epicardium Thin transparent outer layer Composed of simple squamous epithelial (mesothelium) & areolar c.t Myocardium (Cardiac muscle) Cardiac muscle spirals around heart producing wringing motion Endocardium Simple squamous epithelial tissue Smooth inner lining of heart & blood vessels 5 External Anatomy of the Heart 6 Internal Anatomy of the Heart 7 Gross Anatomy of the Heart - External 8 Gross Anatomy of the Heart - Internal 9 Blood Flow Through the Chambers 10 Coronary Circulation 11 Conduction System of the Heart Cardiac conduction system is intrinsic (does not require nervous stimulation) Nodal Tissue: muscular & nervous characteristics coordinates contraction of atria & ventricles electrical signals travel from one cell to the next through gap junctions 12 Conduction System of the Heart 1. SA (sinoatrial) node - modified cardiomyocytes (upper RA) Considered pacemaker - Initiates the heartbeat & determines heart rate Sends excitation impulse ~ 0.85 seconds (~70 beats/minute) Signal spreads across to the left atrium (blue arrows) 13 Conduction System cont’d 2. AV (atrioventricular) node - embedded in interatrial septum Slight delay before impulse reaches AV node - this allows both atria to contract at the same time 3. Signal moves along the AV bundle (Bundle of His) and branches as it travels along the interventricular septum Fibrous skeleton acts as insulator thus inhibits current from reaching ventricles by other means 14 Conduction System cont’d 4. Right and Left bundle branches Signal leaves AV node Bundle of His forks into L & R bundle branches Signal travels down toward the apex 15 Conduction System cont’d 5. Purkinje fibers Processes arising from lower end of bundle branches modified cardiomyocytes specialized for electrical conduction NOT contraction At apex turn upwards and ramify through myocardium of ventricles initiating contraction 16 Pacemaker (SA) Physiology Why does SA node fire spontaneously? 17  Electrocardiogram Composite of all action potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on skin PQ signal conduction from ST represents QRS - AV signal SA to AV node the time spreads through Atrial systole duration for the ventricular SA signal spreads begins ventricles to myocardium and through atria and contract & eject depolarizes them depolarizes them blood Ventricular repolarization immediately before diastole QT - Represents how long the ventricles remain depolarized & is equivalent to length of Time it takes for cardiomyocytes AP signal to pass through AV node before activating ventricles 18 Chapter 16: Blood Vessels and Circulation 19 Pulmonary & Systemic Circulation 20 Blood vessels Functions of blood vessels: Transport blood and its contents Carry out gas exchange Regulate blood pressure Direct blood flow Types of vessels: arteries, capillaries, and veins 21 Walls (tunics) to vessels Arteries - thick, strong walls; Veins - all 3 walls - thinner Inner Layer – endothelium Thinner walls – less tunica media (simple squamous epithelial) larger lumen Middle Layer– smooth muscle & presence of valves elastic fibers (expand & recoil Outer Layer– outer connective tissue layer 22 23 Blood Vessels 24 Arteries and arterioles Constriction/dilation of vessels impacts blood flow/pressure Vasoconstriction – blood flow from arteries to capillaries is restricted & blood pressure is increased Vasodilation – blow flow in significantly increased & blood pressure is decreased 25 Capillaries Microscopic blood vessels One layer of endothelial cells Site of nutrient and gas exchange Not all capillary beds are in use at the same time Most have a shunt to bypass the capillaries when needed The more capillaries that are open, the lower the BP Tissues with higher metabolic requirements (muscles, liver, kidney) has more capillaries 26 Capillaries https://www.youtube.com/watch?v=M-vNa3NdGmA&feature=youtu.be 27 Capillary Gas Exchange Takes place across thin capillary walls cells of the body are near a capillary Oxygen/nutrients leave while wastes/carbon dioxide enter Substances leaving and entering capillaries pass through tissue fluid 28 Capillary Gas Exchange Three processes influence capillary exchange: Blood pressure – outward force, pushes blood through the capillary and against vessel walls Diffusion – movement of substance from an area of higher concentration to an area of lower concentration Osmotic pressure – inward force caused by a difference in solute concentration on either side of a membrane 29 Veins & Venules Return blood to the heart Venules - drain blood from the capillaries & merge to form veins Vein walls are thinner (tunica media is thinner) than arterial walls and thus are can be helped by skeletal muscle to bring blood back to the heart 30 Arteries/Veins: Chapter 16 (369-386) You are responsible for knowing the principal arteries in 16.9 & 16.10e) You are responsible for knowing the principles veins in 16.12 & 16.14e) 31 Gross Anatomy of the Heart - External 32 Gross Anatomy of the Heart - Internal 33 Valve Attachments 34