The Cardiovascular System PDF

THE CARDIOVASCULAR SYSTEM Heart & Blood Vessels The Location of the Heart http://www.bem.fi/book/06/fi/0601.gif  Near to anterior chest wall  Posterior to sternum  Base of heart lies at the 3rd costal cartilage  Apex of heart reaches the 5th intercostal...

THE CARDIOVASCULAR SYSTEM Heart & Blood Vessels The Location of the Heart http://www.bem.fi/book/06/fi/0601.gif  Near to anterior chest wall  Posterior to sternum  Base of heart lies at the 3rd costal cartilage  Apex of heart reaches the 5th intercostal space The Location of the Heart http://dic.academic.ru/pictures/enwiki/71/Gray968.png  The Heart surrounded by the pericardial sac sits in the anterior portion of the mediastinum The Heart  Measuresapproximately 12.5 cm from base to apex  The adult heart weighs about 250 – 350 grams or 8.8 – 12.3 ounces The Heart in-situ The Position of the Heart The Pericardium  Lines the pericardial cavity  A serous membrane of two parts:  The Visceral Pericardium (Epicardium)  The Parietal Pericardium Pericardium and Heart Wall The Heart Wall  Consists of three layers:  The Epicardium (visceral pericardium)  The Myocardium  Endocardium Epicardium Covers the heart Consists of a mesothelium and underlying loose areolar connective tissue Myocardium  Cardiac muscle layer with blood vessels and nerves  Consists of concentric layers of cardiac muscle tissue  Muscle arrangement facilitates efficient pumping of blood Endocardium  Lines heart chambers and valves  Lined by a simple squamous epithelium and underlying areolar tissue Superficial Anatomy of the Heart (Anterior View)  Two Auricles/Atria (upper chambers)  Two Ventricles (lower chambers)  Coronary Sulcus  Depression between atria and ventricles  Anterior Interventricular Sulcus  Depression between left and right ventricles Sulci of the Heart  The heart is a hollow structure. On the interior, it is divided into four chambers. These divisions create grooves on the surface of the heart – these are known as sulci. Coronary Sulcus  The coronary sulcus (or atrioventricular groove) runs transversely around the heart – it represents the wall dividing the atria from the ventricles. Interventricular Sulci  The anterior and posterior interventricular sulci can be found running vertically on their respective sides of the heart. They represent the wall separating the ventricles. Great Vessels of the Heart Great Vessels of the Heart  Located above the base of the heart  Superior & Inferior Vena Cavae return deoxygenated blood to the right atrium  Pulmonary Trunk leaves right ventricle bifurcates (pulmonary arteries) and goes to lungs  Pulmonary Veins return oxygenated blood to the left atrium Great Vessels of the Heart  Aorta takes blood from left ventricle to body. It is divided into ascending aorta, aortic arch and descending aorta HOW MANY STRUCTURES CAN YOU IDENTIFY? Internal Anatomy of the Heart Chambers of the Heart  The heart is Interatrial divided into left Septum and right parts by Septa  Interatrial Septum separates the upper chambers Interventricular  Interventricular septum Septum separates the lower chambers Chambers of the Heart  The upper chambers  Right Atrium – collects blood from the vena cavae  Left Atrium – collects blood from the pulmonary veins  ATRIA  The upper chambers of the heart  Hollow chambers with significantly thinner walls than the ventricles  Their walls extend outward to form a flap called an Auricle which extends to increase internal volume  The right atrium collects deoxygenated blood from the vena cavae & Coronary Sinus & then pumps it to the Right Ventricle  The left atrium collects oxygenated blood from the Pulmonary Veins & pumps it to the Left Ventricle  The Sinoatrial node is located in the right atrium ATRIA  PECTINATE MUSCLE  Muscle ridges lining the walls of atria  The wave like pattern of fibers of this muscle allows stronger contraction with minimum muscle mass Chambers of the Heart  The lower chambers  Right Ventricle – collects blood from the right atrium & pumps it to the Pulmonary trunk  Left Ventricle – collects blood from the left atrium & pumps it to the Aorta VENTRICLES The left ventricular wall is thicker to generate enough pressure to force oxygenated blood throughout the body VENTRICLES  Within the walls of ventricles are muscle ridges called Trabeculae carneae  They prevent suction as would occur in a flat surfaced membrane  The moderator band is a type of trabeculae carneae that transmits impulses from the Right Bundle Branch Valves of the Heart  Prevent Backflow of Blood Atrioventricular Valves  Separate the atria from the ventricles  Prevent backflow of blood from the ventricle into atria  Are anchored to the inner walls of the ventricles by Chordae tendineae  Chordae tendineae are tendons that attach the ends of the AV valves to mounds of muscles called Papillary Muscle  The Tricuspid valve separates the right atrium and ventricle  The Bicuspid/Mitral valve separates the left atrium and ventricle Atrioventricular Valves - Tricuspid & Bicuspid/Mitral Valves The Tricuspid valve has three leaflets while the Bicuspid valve has two leaflets  Semilunar valves Semilunar Valves  prevent backflow of blood from the great vessels to ventricles  Pulmonary Semilunar Valve separates the Right Ventricle from the pulmonary trunk  Aortic Semilunar Valve separates the Left ventricle from the Ascending aorta  Each of theses valve has three cusps  http://antranik.org/function-of-the-atrioventricular-and- semilunar-valves-and-fibrous-skeleton/ HOW MANY STRUCTURES CAN YOU IDENTIFY?  The Pulmonary Circuit transports deoxygenated blood from the right side of the heart to the lungs to be oxygenated and then back to the heart The Systemic Circuit transports oxygenated blood from the left side of the heart to the entire body and deoxygenated blood from the body to the heart http://mcb.berkeley.edu/courses/mcb135e/Difficult%20Slides/Fetal%20Circulation%201.jpg Pathway of Blood Through the Heart Coronary Circulation  Supplies blood to the muscle tissue of the heart.  Includes an extensive network of coronary blood vessels Coronary Arteries  The left and right coronary arteries originate at the base of the ascending aorta, at the aortic sinuses. Coronary Arteries Right Coronary Artery  Coronary Arteries Right Coronary Artery  Supplies blood to: Right atrium Portions of both ventricles Portions of the conducting system of the heart (SA & AV nodes) Coronary Arteries Marginal Arteries  Extend from the right coronary artery over the surface of the right ventricle Coronary Arteries Posterior Interventricular Artery  Arises from right coronary artery  Runs along posterior interventricular sulcus  Supplies blood to:  Interventricular septum  Adjacent portions of ventricles Posterior Interventricular Artery Posterior Interventricular Artery Coronary Arteries Left Coronary Artery  Gives rise to:  Circumflex artery  Anterior Interventricular Artery  Supplies blood to:  Left ventricle  Left atrium  Interventricular septum Coronary Arteries Circumflex Artery  Meets and fuses with small branches of right coronary artery Coronary Arteries Anterior Interventricular Artery  Forms anastomoses with the posterior interventricular artery  Coronary Circulation Cardiac Veins Cardiac Veins Great Cardiac Vein Cardiac Veins Great Cardiac Vein  Drains blood from areas supplied by the anterior interventricular artery  Empties into the Coronary Sinus which empties into the right atrium near the base of the inferior vena cava  Cardiac Veins Anterior Cardiac Vein  Drains anterior surface of right ventricle  Empty into right atrium Anterior Cardiac Vein Cardiac Veins Posterior Cardiac Vein  Drains area served by circumflex artery  Empties into Great Cardiac Vein Cardiac Veins Middle Cardiac Vein  Drain area supplied by posterior interventricular artery  Empty into coronary sinus Cardiac Veins Small Cardiac Vein  Receives blood from posterior surfaces of the right atrium and ventricle  Empties into Coronary Sinus Heart Review Video  https://youtu.be/X9ZZ6tcx ArI The Conducting System of the Heart The Conducting System of the Heart  Generates and distributes impulses to the contractile cells of the heart The Conducting System of the Heart  Consists of the:  Sinoatrial Node (SA node) Bundle of His  Atrioventricular node (AV node)  Conducting Cells  Internodal pathways  AV Bundle (Bundle of His)  Bundle Branches  Purkinje Fibres Purkinje Fibres Conducting System of the Heart Cell membranes of the SA and AV nodes cannot maintain a stable resting potential (-90 mV) Membrane drifts toward threshold (-75mV) after repolarisation: Pre-potential Rates of Spontaneous Depolarisation SA node: 80 – 100 per minute AV node: 40 – 60 per minute Therefore, SA node sets heart rate Pathway of Impulses through the Heart 1. Generation of action potential at SA Node 2. Impulse transmitted to AV node via internodal pathways (Elapsed time 50 msec) Pathway of Impulses through the Heart (cont’d)  100msec delay at the AV node.  Cells of the AV node have a smaller diameter than SA node cells, therefore transmit impulses slower  Atrial contraction begins Pathway of Impulses through the Heart (cont’d) 3. Impulsetransmitted to AV bundle (Bundle of His) (Elapsed time150ms) Pathway of Impulses through the Heart (cont’d) Impulse passes through ventricular myocardium; atrial contraction completed ventricular contraction begins (Elapsed time 225 msec) The Cardiac Cycle Blood Vessels Structure and Major Types Types of Blood Vessels  Arteries – transport blood away from the heart  Veins – transport blood to the heart  Capillaries – vessels of exchange between the blood and tissues Structure of Vessel Walls  There are three distinct layers in the walls of arteries and veins:  Tunica Intima  Tunica Media  Tunica Externa Structure of Vessel Walls Tunica Intima (Tunica Interna)  Innermost layer  Consists of an endothelial lining and underlying connective tissue with elastic fibres  In arteries the outer margin of the tunica intima contains a thick layer of elastic fibres called the Internal Elastic Membrane Structure of Vessel Walls Tunica Intima Structure of Vessel Walls Tunica Media The middle layer Consists of concentric sheets of smooth muscle in a loose connective tissue framework This layer is thicker in arteries than in veins Collagen fibres bind this layer to the tunica intima and externa External Elastic Membrane surrounds this layer in arteries The Tunica Media changes the diameter of the blood vessel  Structure of Vessel Walls Tunica Media Note the location of the External Elastic Membrane (Lamina) Artery Vein  Structure of Vessel Walls Tunica Externa/Tunica Adventitia Outermost layer Connective tissue sheath Stabilizes and anchors vessel to adjacent tissues Thicker in veins than in arteries In arteries it consists of collagen fibres with scattered elastic fibre bands In veins it consists of bundles of elastic fibres and smooth muscle cells  Structure of Vessel Walls Tunica Externa/Tunica Adventitia Comparison of a Typical Artery and Vein  Artery  Vein  Usually rounded, with  Usually flattened or relatively thick wall collapsed, with relatively thin wall  Tunica Intima usually rippled, due to vessel  Tunica Intima often constriction; internal smooth; internal elastic elastic membrane present membrane absent Comparison of a Typical Artery and Vein Artery Vein Tunica Media is thick, Tunica Media is thin, dominated by smooth dominated by smooth muscle and elastic fibres muscle and collagen fibres External Elastic Membrane present External Elastic Membrane absent Tunica Externa of collagen and elastic fibres Tunica Externa of collagen and elastic fibres and No Valves smooth muscle cells Valves line lumen Veins Showing Valves Which of these is the Artery? Types of Arteries  Elastic  Muscular  Arterioles  Peripheral capillaries Elastic Arteries  Up to 2.5 cm lumen diameter  Large vessel  Close to the heart  Tunica media of mostly elastic fibres, few smooth muscle fibres – Elastic Rebound  Eg. Aorta, Pulmonary trunk, Common Carotid, Subclavian Muscular Arteries  Medium sized  0.4 cm – 0.5 mm lumen diameter  Distributes blood to skeletal muscle and internal organs  Thick tunica media, much thicker than in elastic arteries  Eg. External carotid, brachial, mesenteric, femoral  Arterioles  30 µm or less lumen diameter  Poorly defined tunica externa and tunica media reduced to 2 layers in larger arterioles  Small arterioles have scattered smooth muscle  Diameter changes under sympathetic nervous stimulation and hormonal control  Low oxygen levels cause dilation Capillaries  8 µm average diameter  Posses an endothelial layer with basal lamina Types of Capillaries Continuous Capillaries  The endothelium is a complete lining  A cross-section of large continuous capillaries cuts through several endothelial cells  In small continuous capillaries a single endothelial cell may completely encircle the lumen  Located in all tissues except epithelia and cartilage Types of Capillaries Fenestrated Capillaries  Contain windows or pores that penetrate the endothelial lining  Permit rapid exchange of water and solutes as large as small peptides  Eg. Choroid plexus of the brain and blood vessels in the hypothalamus, small intestine and filtration slits of the kidneys Venous System  Venules  Medium-Sized Veins  Large Veins Venules  Average diameter 20 µm  Collects blood from capillary beds  Valves present  No tunica media in venules smaller than 50 µm  Medium –Sized Veins  2 – 9 mm lumen diameter  Thin tunica media with few smooth muscle cells  Thick tunica externa of longitudinal bundles of elastic and collagen fibers  Valves present Large Veins  All tunica layers present  Tunica externa very thick; elastic and collagen fibres  Eg. Superior and inferior vena cava