Ch. 13 Cardiovascular System Flashcards
Functions of Heart
- unidirectional flow of blood
- back flow of blood is prevented by valves within the heart
- two independent pumps that work independently but at same rate: one directs blood to lungs for gas exchange, other directs blood to body tissues for nutrient delivery
- develops blood pressure through alternate cycles of the heart wall contraction and relaxation
Location and surface
- lies in mediastinum
- two thirds of mass lies to the left of the midline
- apex: lower, pointed end by the tip of the left ventricles
- base: broader, superior portion by the atria
- surface projection is outlined shape of an organ on the surface of the body
- anterior surface: deep to the sternum and ribs
- inferior surface: rests mostly on the diaphragm
- right border: faces the right lung
- left border: faces the left lung
- outline: connect the superior right point, superior left point, inferior left point, and inferior right point
Pericardium
Fibrous pericardium: superficial tough, 1 elastic layer, composed of dense irregular connective tissue. Prevents overstretching of the heart, provide protection, and anchors the heart to the mediastinum
Serous pericardium: thinner, more delicate layer that forms a double layer around the heart and divided into parietal and visceral pericardium
Pericardial fluid: slippery secretion of pericardial cells that reduces friction between the membranes as the heart moves
Heart wall
Epicardium: external layer, composed of mesothelium and connective tissue(fibro-elastic and adipose)
Myocardium: middle layer, muscular pumping layer, 95% of the heart wall (cardiac muscle)
Endocardium: inner layer, consists of a layer of endothelium covering connective tissue, continuous with the endothelium of the blood vessels connected to the heart (tight junctions)
Endocarditis: inflammation of endothelium
Cardiac muscle characteristics
Intercalated discs, desmosomes, Gap junctions
Heart surface markings (3 major grooves/ sulci)
Coronary sulcus: encircles most of the heart seperates the atria from the ventricles
Anterior interventricular sulcus: marks the external boundary between right and left ventricles
Posterior interventricular sulcus: marks the external boundary between ventricles on the posterior surface
Characteristics and functions
- heart is the centre
- arteries carry blood away and veins carry blood back to the heart
- arteries are high in oxygen (except pulmonary arteries
- veins carry low blood in oxygen (except pulmonary veins)
- entering and leaving the heart are called great veins
Chambers of Heart
Two superior chambers
- right and left atria (weaker pumps)
- receive blood returning to the heart via the veins
Two Inferior chambers
- right and left ventricles (powerful pumps)
Pulmonary Pump
- right atrium and right ventricle, moves deoxygenated blood through the lungs (pulmonary artery)
Systemic Pump
- left atrium and left ventricle, pumps oxygenated blood to all systems (pulmonary vein)
Right Atrium (3 veins, lined by?, valve)
- receives deoxygenated blood
- superior vena cava: drains blood from parts of the body superior to the heart
- inferior vena cava: collects blood from all parts of the body inferior to the diaphragm
- coronary sinus: recieves blood fro most of the vessels draining the wall of the heart
- anterior wall had muscular ridges called pectinate
- interatrial septum (wall)
- fossa ovalis: depression on the septum, remnant of the foramen ovate (close at birth)
- blood flows from the right atrium into the right ventricle through the right atrioventricular valve (tricuspid valve)
Right Ventricle
- inner surface lined with ridges called trabecule carneae
- chordae tendineae connects the tricupsid valve to the papillary muscles
- interventricular septum seperates the two ventricles
- blood passes through pulmonary valve to lungs
Left Atrium
- forms most of the base of the heart
- receives oxygenated blood from the lungs via four pulmonary veins (two from each lung)
- blood flows from the left atrium into the left ventricle through the atrioventricular valve (bicuspid/mitral valve)
- interatrial septum seperates left and right atriums
Left Ventricle
- thickest part of the heart, forms apex
- contains trabeculae carneae and chordae tendinae
- blood passes from the left ventricles into the aorta through the arotic valve
- right and left coronary arteries branch from the ascending aorta to supply the walls of the heart
- rest passes into the arch of aorta and descending aorta
Myocardial Thickness and Function
- ventricles have thick walls as they pump blood at a higher pressure and over greater distances
- left ventricle is three times thicker than right
- both eject equal amounts of blood
Fibrous Skeleton of the Heart
- dense connective tissue embedded in the walls of the heart
- functions (4): prevent overstretching of valves, secure valves to the heart wall, point of insertion for bundles of cardiac muscle fibers, and provide electrical insulator between atria and ventricles
- right atrioventricular fibrous ring, left atrioventricular fibrous ring, pulmonary fibrous ring, aortic fibrous ring
Atrioventricular (AV valve)
- tricuspid valve between the right atrium and the right ventricle
- bicuspid between the left atrium and left ventricle
- chordea tendineae and associated papillary muscles permit flow but prevent backflow
Semilunar Valves
- two SL valves each having three semilunar cusps
- allow ejection of blood from ventricles into pulmonary trunk and aorta
- prevent backflow of blood into heart
- pulmonary valve: between pulmonary trunk and the right ventricle
- aortic valve: between arota and left ventricle
Systemic Circulation
- receives oxygenated blood from the lungs
- pumps this blood into the aorta which then continue to branch into arteries, arterioles, capillaries where nutrients, gases, wastes, ect are exchanged with surrounding cells
- venules and systemic valves return the deoxygenated blood to the right atrium
Pulmonary Circulation
- right ventricle pumps blood into the pulmonary trunk which branches into the pulmonary arteries
- this blood goes to the pulmonary capillaries where the blood becomes oxygenated
- pulmonary veins carry the oxygenated blood to the left atrium
Coronary Circulation
- needed because can not reach myocardium or heart wall
ascending aorta- coronary arteries - left:
1. anterior interventricular artery: wall of both ventricles and interventricular septum,
2. circumflex artery: wall of left atrium and ventricle - right:
1. posterior interventricular artery: left and right posterior ventricles
2. marginal artery: wall of right ventricle - anastomoses or collateral circuits for blood to reach heart tissue ex. coronary by-pass
Cardiac Conduction System
- during embryonic development about 1% of cardiac muscle fibers become autorhythmic cells; generate action potential
- act as a pacemaker setting the contractile rhythm of the heart even if heart is separated from body and nerve are cut
- form the cardiac conduction system of the heart that conduct action potentials throughout the myocardium
- to spread the action potential throughout heart
Components of Conduction System
SInoatrial node: heart’s natural pacemaker, initiates heartbeat (two atria contract at same time)
Atrioventricular node: action potential slows, provides time for atria to empty blood into ventricles
Atrioventricular bundle (bundle of His): only site where action potentials can conduct from the atria to the ventricles
Right and Left bundle branches: through interventricular septum toward the apex of the heart
Purkinje fibers: relay action potential to the contractile cells of ventricular myocardium
- can alter pace of contractions but not initiate contractions
Heart Sounds
Auscultation: listening to the heart sounds with stethoscope
Lubb: first sound is due to blood turbulence cause by closing of the AV valves
Dupp: second sound due to blood turbulence cause by closing of the semilunar valves
- sounds are best heard over the chest at areas slightly away from the actual location of the valves
