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Anatomy & Physiology
Anatomy of the Cardiovascular System
Heart songhttp://www.youtube.com/watch?v=q0s-
1MC1hcE
Location of the heartIn mediastinum
behind the sternum between 2nd & 6th ribs. Shifted to left.
Posteriorly between 5th to 8th thoracic vertebrae
Apex (lowest point) lies on diaphragm
PericardiumSac covering the heart
Fibrous pericardium – tough, inelastic
Serous pericardium- 2 layersParietal layer- lines fibrous
pericardiumVisceral layer (epicardium)-
adheres to outside of heart; space between parietal & visceral layer contain small amount of fluid
Function of pericardiumProvides protection against friction
Layers of the heartEpicardium (also the serous pericardium)Myocardium-thick contractile layer of muscle
cellsEndocardium-cover trabeculae (muscular
projections); specialized folds of endocardium make up the major valves of heart
Chambers of heart
Atria: upper chambers
Ventricles: lower chambers
Chambers are separated by an extension of heart wall, septum
Atria
Receive blood from veins
Send blood to ventricles
Thin myocardial wall
Auricle: earlike flap protruding from each atrium
Ventricles
Receive blood from the atria
Pump blood out of heart into arteries
Thicker myocardium
Myocardium of left ventricle thicker than right ventricle
Heart valves
Permit flow of blood in one directionAtrioventricular valves
Semilunar valves
Atrioventricular valves
Made of flaps of endocardium
Flaps anchored to papillary muscle by chordae tendineae
Rt AV valve: tricuspid valve
Lt AV valve: mitral (bicuspid) valve
Semilunar valves
Consists of half moon shaped flaps
Pulmonary semilunar valve: at the entrance to the pulmonary artery
Aortic semilunar valve: at the entrance to aorta
Flow of blood through the heart
Heart videohttp://www.youtube.com/watch?
v=DAXa4eR1s0M
Blood supply to heart Blood supplied thru the right & left coronary arteries
Coronary arteries are first branches off aorta
After blood has passed thru capillary beds, enters cardiac veins then thru common channel, coronary sinus, then into rt atrium
Conduction system of heartSinoatrial node (pacemaker): in rt atrium
near opening of superior vena cavaAtrioventricular node: in rt atrium along
lower part of interatrial septumAtrioventricular bundle: originate in AV
node & extend by 2 branches thru the 2 sides of the interventricular septum
Purkinje fibers: extension of AV bundle out to the lateral walls of the ventricles & papillary muscles
Conduction System
Blood vesselsArteries: carry blood away from heartArterioles: small arteries
Veins: Carry blood toward heartVenules: small veins
Capillaries: microscopic blood vessels that carry blood from arterioles to venules
3 layers of blood vessels
Tunica adventitia: outer layer, fibrous connective tissue
Tunica media: layer of smooth muscle & elastic connective tissue
Tunica intima: made of smooth endothelium
Blood Vessel StructureType of vessel
Tunica intima
Tunica media
Tunica adventitia
artery Smooth lining
Thicker than in veins
Thinner than tunica media
vein Smooth lining with valves
Thinner than in arteries
Thicker than tunica media
capillary Makes up entire wall: very thin
absent absent
Functions of capillaries
Transport materials to and from cells
Capillaries so numerous & so small that blood flows at its slowest rate in capillaries
Functions of arteries
Function as “distributors”
Arterioles also function as resistance vessels
Smooth muscle cells on arterioles act as precapillary sphincters where a capillary originates
Functions of veinsReturn blood to heartAct as reservoir vesselsAbility to stretch by veins called capacitance thus veins are capacitance vessels
Circulatory routes
Systemic circulation: blood flow from heart to all parts of body (except lungs)
Pulmonary circulation: blood flow from heart to lungs
ArteriesEnd-arteries: most of the arteries, they diverge into capillaries
A few arteries open into branches of other arteries; this communication is an arterial anastomosis
Incidence of arterial anastomosis increases as distance from the heart increases
AortaMajor artery that
serves as trunk of the entire systemic arterial system
First few cm conducts blood up away from lt ventricle-ascending aorta
Then turns 180 degrees-aortic arch
Then downward from arch-descending aorta
Veins
Large veins that return blood to heart in systemic circulation are superior & inferior vena cava