Chapter 19 - The Heart Flashcards
Pulmonary circuit
Right side receives oxygen poor blood from body and pumps it to lungs
Blood vessels that carry blood to and from the lungs
The Heart
Is a muscular double pump with two functions pulmonary circuit systemic circuit atria ventricles
Systemic circuit
left side reveives oxygen rich blood from lungs and pumps it to body
Vessels that transport blood to and from body tissues
Atria
Receiving chambers of heart (2)
Ventricles
pumping chambers of heart (2)
Location/Orientation of Heart
Weights < 1 pounds
Thorax, posterior to sternum, superior surface of diaphragm
Specifically located in the mediastinum (region between the lungs/pleural cavities)
Oblique position
Apex (point) is left of the midline and anterior to the rest of the heart
Base is broad posterior surface
Structure of the Heart
Coverings
Coverings
Pericardium
Pericardium
3 layered sac that encloses the heart
Fibrous pericardium
Serous pericardium
Fibrous pericardium
Outer layer (dense CT)
Serous pericardium
Deeper 2 layers Parietal layer of serous pericardium visceral layer of serous pericardium (epicardium) pericardial cavity pericarditis
Parietal layer of serous pericardium
Adheres to surface of fibrous pericardium
Visceral layer of serous pericardium/epicardium
lies on the heart; is considered part of the heart wall
Pericardial cavity
Lies between the two layers, contains serous fluid
Pericarditis
Inflammation of the pericardium
Layers of the Heart Wall
Epicardium
Myocardium
Endocardium
Epicardium
Superficial layer (aka visceral layer of serous pericardium), serous membrane
Myocardium
cardiac muscle, contracts
Cells are arranged in circular/spiral networks called bundles
Endocardium
Sheet of endothelium resting on thin CT layer, lines the chambers and covers the valves
Chambers of the Heart
4 chambers: 2 atria and 2 ventricles
Atria
Blood comes into heart via atria
Walls are thinner than ventricles
Contract and push blood into ventricles simultaneously
Separated by interatrial septum (not permeable)
Ventricles
Are thicker (especially left side) Separated by interventricular septum
Right Atrium
Receives systemic oxygen poor blood via three veins: superior vena cava, inferior vena cava, and coronary sinus
Opens into right ventricle via tricuspid valve (aka right AV valve)
Right auricle (external)
Flap that projects to the left
2 portions of internal atrium
Posterior part
Anterior part
Separated by crista terminalis
Posterior part of internal atrium
has smooth walls
Anterior part of internal atrium
has pectinate muscles
Crista terminalis
C-shaped ridge important for locating sites where veins enter
Right Ventricle
Receives blood from right atrium and pumps it to lungs via pulmonary trunk then arteries
Forms most of anterior surface of heart (external)
Internal structures of Right Ventricle
Trabeculae carneae
Papillary muscles
Chordae tendineae
Trabeculae carneae
muscle ridges
Papillary muscles
cone-shaped muscles that project from wall
Chordae tendineae
Project superiorly from papillary muscles to valve flaps of tricuspid valve
Valve between right ventricle and pulmonary trunk
Pulmonary semilunar valve (aka pulmonary valve)
Left Atrium
Makes up most of base, receives oxygen rich blood from lungs via pulmonary veins (2 on right, 2 on left)
Auricle is external on anterior side
Pectinate muscles line auricle only; rest of inside is smooth
Opens into left ventricle via the mitral (bicuspid) valvue (left AV valve)
Left Ventricle
Forms apex of heart, pumps blood systemically
SImilar to right ventricle, with trabeculae carneae, papillary muscles and chordae tendineae
Sends blood to body via aortic semilunar valve (aortic valve)
Valves of the Heart
AV valves (atrioventricular) Semilunar valves
Function: to prevent backflow of blood
AV valves
Between atria and ventricles (there are 2)
Right side valve is known as tricuspid or right AV
Left side is known as bicuspid, left AV, or mitral
Semilunar valves
Both have 3 cusps
Between ventricles and vessels leaving the heart (arteries)
Right side is between right ventricle and pulmonary artery (right semilunar or pulmonary valve)
Left side is between left ventricle and aorta (called left semilunar or aortic valve)
Contraction
systole
Relaxtion
Diastole
Heartbeat
atrial contraction followed by ventricle contraction
Lub
closing of AV valves at beginning of ventricular systole
Dup
closing of semilunar valves at end of ventricular systole
Blood Flow through the Heart
SVC/IVC/Coronary sinus Right atrium Tricuspid valve Right ventricle Pulmonary semilunar valve Pulmonary trunk Lungs Pulmonary veins Left atrium Mitral Valve Left Ventricle Aortic semilunar valve Aorta Body SVC/IVC/Coronary Sinus
Fibrous Skeleton
Made of dense CT Anchors valve cusps Prevents valves from opening too far Muscle insertion for cardiac bundles Blocks spread of electrical impulses directly from atria to ventricles
Electrical COnduction
Measure by EKG
Cardiac cells have ability to contract on their own, but signal usually starts with the pacemaker (SA node)
Conduction pathway
SA node Internodal pathway AV node Atrioventricular bundle Left/Right bundle branches Purkinje fibers
SA node
sinoatrial
Considered the pacemakes, beats 70-80 bpm
Located in superior/posterior wall of right atrium
Produces signal that spreads electrical impulse across both atria
Valves are open
Internodal Pathway
Some impulses spread through this area on the way to AV node
AV node
atrioventricular
Located at inferior aspect of interatrial septum
Delays impulse so that atria contract first and ventricles finish filling
Atrioventricular bundle
Located in interventricular septum (top)
Left/Right bundle branches
Branches from atrioventricular bundle, take signal to apex of hearth
Purkinje fibers
Approach apex and turn into ventricular walls, located in between endocardium and myocardium
Are special cells (Purkinje myocytes) that maximize signal conduction
Vagus nerves
Act on parasympathetic innervation to SA and AV nodes, also coronary vessels
Blood Supply to/from the Heart
Blood inside chambers doesn’t supply heart muscle itself
Right and left coronary arteries branch off of aorta to serve heart
Left coronary artery branches into anterior interventricular artery and circumflex artery - supplies left atrium and ventricles
Right conronary artery branches into marginal artery and posterior interventricular artery - supplies right atrium and almost all of right ventricle
Cardiac veins return deoxygenated blood (coronary sinuse is largest
Heart Disorders
Coronary Artery Diseases
Heart Failure (weakening of the heart)
Conduction system disorders
Coronary Artery Diseases (CAD)
Atherosclerosis Arteriosclerosis Coronary Artery Disease Myocardial Infarction (Silent) Ischemia
Atherosclerosis
Fatty deposits accumulate in body’s arteries
Arteriosclerosis
Hardening/loss of elasticity of the arteries for any reason
Coronary Artery Disease
Arteries supplying the heart are blocked or narrowed (consequence of atherosclerosis)
Angina pectoris
chest pain due to low oxygen supply to heart muscles
Myocardial infarction (MI)
Heart attack; complete or prolonged coronary artery blockage (cardiac muscle cells die due to lack of oxygen)
(Silent) Ischemia
Heart blood flow is interrupted, but there is no pain involved
Heart Failure
Congestive heart failure
Weakening of the heart
Congestive heart failure
Heart enlarges and pumping efficiency decreases
Conduction system disorders
Arrhythmia
Arrhythmia
Variation from normal rhythm of heartbeat
Fibrilation
Fibrilation
Atrial or ventricular fibrillation
Conduction system is disturbed
