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The Heart
Muscular double pump with 2 functions
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Pulmonary Circuit
Right side receives oxygen poor blood from body and pumps into lungs
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Systemic Circuit
Left side receives oxygen rich blood from lungs and pumps it to body
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Atria
2 receiving chambers of the heart
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Ventricles
2 pumping chambers of the heart
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Location/Orientation
- Weighs< 1 pound
- Thorax, psterior to sternum, superior surface of diaphragm
- In mediastinum
- Oblique position
- Apex= left of mdpnt. and anterior to rest of heart
- Base is broad posterior surface
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Pericardium
- 3 layered sac that encloses the heart
- Fibrous pericardium- outer layer (dense CT)
- Serous preicardium- deeper 2 layers
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Parietal Layer of Serous
Adheres to surface of fibrouf pericardium
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Visceral Layer of Serous
Lies on the heart; is considered part of heart wall
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Pericardial Cavity
Lies between the 2 layers, contains serous fluid
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Pericarditis
Inflammation of the pericardium
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Epicardium
- Superficial layer of heart
- Serous membrane
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Myocardium
- Cariac Muscle contract
- Cells arranged in circular/spiral networks called bundles
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Endocarium
Sheet of endothelium resting on thin CT layer, lines chamber and makes up valves
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Atria Chambers
- 2
- Blooda comes into heart via atria
- Walls thinner than ventricles
- Contract and push blood into ventricles simaltaneously
- Separated by interatrial septum
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Ventricle Chambers
- 2
- Are thicker (especially left side)
- Separatd by interventricular septum
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Right Atrium
- Receives systemic oxygen poor blood via three veins, superior/inferior vena cava, and coronary sinus
- Opens right ventricle via tricuspid valve
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Right Auricle
Flap that protects to the left
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2 Portions of internal atrium
- Posterior= has smooth walls
- Anterior= has pectinate muscles
- Separated by crista terminals= C-shaped ridge, important fro locating where veins enter
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Right Ventricle
- Receives blood from R atrium and pumps it to lungs via pulmonary trunk
- Forms most of anterior surface of heart
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Internal Structures of R ventricle
Trabeculae carneae- muscle ridges
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Papillary muscles
Cone shaped muscles that project from wall
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Chordae Tendineae
Project superiorly from papillary muscles to valve flaps of tricuspid valve
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Pulmonary Semilunar Valve
Valve between right ventricle and pulmonary trunk
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Left Atrium
- Makes up most of base
- Receive oxygen rich blood via pulm. veins
- Auricle is external on anterior side
- Pectinate muscles line auricle only; rest of inside is smooth
- Opens into left ventricle via teh mitral valve
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Left Ventricle
- Forms apex of heart, pumps blood systemically
- Simlilar to right ventricle, with trabeculae carneae, papillary muscles and chordae tendineae
- Sends blood to body via aortic semilunar valve
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Valves of Heart
To prevent backflow
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AV valves- Atrioventricular
- Between atria ventricles
- Right side= tricuspid
- Left side= bicuspid
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Semilunar Valves- both have 3 cusps
- Between ventricle and vessels leaving the heart
- R side between R ventricle and pulm. artery
- L side between L ventricle and aorta
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Contraction/Realxation
- Contraction = systole
- Relaxation= diastole
- Heartbeat= Atrial contraction then ventricle contraction
- Lub-Dub made by closing valves
- Lub= AV in beginning
- Dup= semilunar valves at end
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Fibrous Skeleton
- Made of dense CT
- Anchors valve cucps
- Prevents valves from opening too far
- Muscle insertion for cardiac bundles
- Blocks spread of electrical impulses from atria to ventricles
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Electrical Conduction
Measured by EKG- electrocardiogram
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SA node
- Considered pacemaker, 70-80 bpm
- Located in superior/posterior wall of right atrium
- Signal that spreads electric impulses across both atria
- Valves are open
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Internodal Pathway
Some impulses spread through this area ont the way tot he AV node
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AV node
- Located at inferior aspect of interatrial septum
- Delays impulse so that atria contract first and ventricles finish filing
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AV bundle
- Bundle of His
- Located in interventricular septum
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Left/Right bundle branches
Branches from atrioventricular bundle, take signal to apex of heart
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Purkinje Fibers
- Approach apex and turn into ventricular walls, located in between endocardium and myocardium
- Are special cells that maximize signal conduction
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Vagus Nerve
Acts on parasympathetic innervation to SA and AV nodes
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Sympathetic System
Affects SA and AV nodes via cervical/upper thoracic spinal nerves
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Atherosclerosis
Fatty deposits accumulate in body's arteries
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Arteriosclerosis
Hardening/loss of elasticity of the arteries fro any reason
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Coronary Artery Disease
Arteries supplying the heart are blocked or narrowed, chest pain
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Myocardial Infarction
Heart Attack; complete pr prolonged coronary artery blockage
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Ischemia
Heart blood flow is interrupted, but there is no pain involved
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Heart Failure
- Weakening of the heart
- Congestive heart failure- heart enlarges and pumping efficiency decreases
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Conduction System Disorders
- Arrythmia- variation from normal rhythm of heartbeat
- Fibrillation- conduction system disturbed
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