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The heart
  • a muscular double pump
  • Pulmonary circuit: takes blood to & from the lungs
  • Systemic Circuit: vessels transport blood to & from body tissues
  • Atria: receive blood from the pulmonary and systemic circuits
  • Ventricles: the pumping chambers of the heart
Locatiion & Orientation Within thorax
  • heart typically weighs 250-350 grams (less than 1 pound)
  • largest organ of the mediastinum
  • located between the lungs - 4 sides
  • Apex lies to left of midline
  • Base is the broad posterior surface
Four Corners of teh Heart
  • Superior Right: at costal cartialge of third rib & sternum
  • Inferior Right: at costal cartilage of sixth rib lateral to sternum
  • Superior Left: at costal cartilage of second rib lateral to sernum
  • Inferior left: lies in fifth intercostal space at the midclavicular line
Structure of Heart- Coverings
Pericardium: two primary layers
  • Fibrous pericardium: strong layer of dense connective tissue
  • Serous pericradium: formed from two layers- parietal & visceral pericardium
  • Heart wall = Pericardium
  • Myocardium = heart muscle
  • Endocardium: outermost layer
*Layers rub against each other there to help wtih friction
Layers of the Heart Wall
Epicardium:


  • Visceral layer of the serous pericardium


Myocardium:


  • consists of cardiac muscle

  • Muscle arranged in circular & spiral patterns


Endocardium:


  • Endothelium resting on a layer of connective tissue

  • lines the internal walls of the heart


*Top of heart contracts and goes to Apex
Heart Chambers (4 chambers)
Superior Chambers:


  • Right & Left Atria


Inferior Chambers:


  • Right & left ventricles


Internal Divisions:


  • Interventricular septa

  • Interatrial septa


External Markings


  • Coronory Sulcus

  • Anterior interventricular sulcus

  • Posterior interventricular sulcus


*Coronary Sinus come from back of heart*

*Heart has it''s own blood supply for mycardium*

*pulmonary carries blood away from heart*

*arterys: take blood away*
*Veins: take blood in*
Right Atrium
  • Forms right border of heart
  • Recieves blood from systemic circuit
Pectinate muscles:
  • Ridges inside anterior of right atrium
Crista Terminalis:
  • landmark used to locate veins entering right atrium
Fossa Ovalis:
  • Depression in interatrial septum
  • Remnant of foramen ovale
Right Ventricle
Contains: Tricuspid Valve or AV Valve
  • Recieve blood from right atrium through the tricuspid valve
  • Pumps blood into pulmonary circuit via: pulmonary trunk
  • Internal walls of right ventricle: trabeculae carnae, papillary muscles (smooth muscle), chordae tendineae
Left Atrium
  • Makes up heart's posterior surface
  • Recieves oxygen-rich blood from lungs
  • Open's into the left ventricle through: Mitral Valve: (left atrioventricular valve)
Left Ventricle
Contains: Mitral Valve, Bicuspid Valve, or Left AV (all the same meaning)
  • Forms Apex of heart
  • Internal walls of left ventricle: trabeculae carneae, papillary muscles (smooth muscle), chordae tendinae
  • Pumps blood through systemic circuit via
  • Aortic semilunar valve (aortic valve) --> Pulmonary trunk --> Right & left Pulmonary arteries
Structure of the Heart Wall
Walls differ in thickeness:
  • Atria: thin walls
  • Ventricles: thick walls
  • Systemic Circuit: longer then pulmonary circuit, offers great resistance to blood flow
  • Left Ventricle is three times thicker than right because:
  • it exerts more pumping force
  • Flattens right ventricle into a cresecent shape
Pathway of Blood through the Heart
  • Begins with oxygen poor blood in the superios & inferior vena cava
  • Goes through pulmonary & systemic circuits
  • Atria & venticles contract together
1. Superior Vena Cava, Inferior Vena Cava, Cornoary Sinus
2. Right Atrium
3. Tricuspid Valve
4. Right Ventricle
5. Pulmonary semilunar valve
6. Pulmonary trunk
7. Lungs
8. Pulmonary veins
9. Left atrium
10. Mitral Valve (bicuspid)
11. Left Ventricle
12. Aortic Semilunar Valve
13. Aorta
14. To the Body
15. Then from body back to beginning
Blood Supply to Heart
Functional Blood Supple:
  • Coronary arteries
Arise from the Aorta:
  • Located in the coronary sulcus
  • main branches: left & right coronary arteries
HeartBeat
  • 70 to 80 beats per minute at rest
  • CARDIAC CYCLE: time of one complete heartbeat
Contraction phase is called systole:
  • forces blood either into another chamber or into a blood vessel
  • helps measure BP av= 120/80
Relaxation pahse is termed diastole:
  • chamber fills with blood
Systole & Diastole also refer to: stage of heartbeat when ventricles contract & expand
Heart Valves: Valve Structure
Each valve composed of:
  • Endocardium with connective tissue core
  • Atrioventricular (AV) valves: between atria & ventricles
  • Aortic & pulmonary valves: at junction of ventricles & great arteries
Fibrous Skeleton
Surrounds all four valves
  • composed of dense connective tissue
Function:
  • anchors valve cusps
  • prevents overdialtion of valve openings
  • main point of insertion for cardiac muscle
  • blocks direct spread of electrical impulses
Heart Sounds
Four normal heart sounds: lubb-dupp
  • Lubb due to turbulance of blood from closing of AV Valves (long, booming sound)
  • Pause
  • Dupp due to turbulance of blood from closing of semilunar valves (short, sharp sounds)
  • Longer Pause
  • Sounds are not heard exactly over valves (surface projection)
Heart Sounds: each valve sounds
  • pulmonary valve: superior left corner
  • Aortic valve: superior right corner
  • Mitral (bicuspid) valve: at the apex
  • Tricuspid valve: inferior right corner
For males: nipples in fourth intercostal
Cardiac Muscle Tissue
Forms a thick layer called myocardium
  • striated like skeletal muscle
  • contractions pump blood through heart into blood vessels
  • contracts by sliding filament mechanism
Cardiac Muscle Cells:
  • Short
  • Branching
  • Have one or two nuclei
  • Not fused colonies like skeletal muscle
Cells join at intercalated discs
  • Complec junctions
  • form cellular netowrks
Cells are seperated by delicate endomysium
  • binds adjacent cardiac fibers
  • contains blood vessels and nerves
Conducting System
Cardiac muscle tissue has intrinsic ability to:
  • generate & conduct impulses
  • signal these cells to contract rhythmically
Conducting system:
  • a series of specialized cardiac muscle cells
  • Sinoatrial (SA) node sets the inherent rate of contraction (pacemaker- fastest part of heart)
  • iniates 70-80 times/min
Conducting System Continued:
  • Impulse travels to both Atria, stimulating atrial systole
  • Via an internodal conduction pathway through an opening in the fibrous skeletion to the atrioventricular (AV) node between the right AV valve and the coronoary sinus
  • Delay at the AV node
  • From the AV node to the atrioventricular (AV) bundle (Bundle of His)
  • into the interventricular septum & then divides into one right and two left bundle branches
  • To conduction fibers called Purkinje fibers in the heart apex
  • purkinje fibers are larger then other cardaic muscle fibers
  • muscle impluse conduction alon the purkinje fibers i extremely rapid, consistent with large size of the cells.
  • The impluse spreads immediately throughtout the ventricular myocardium and the ventricles contract.
  • Fastest part of the heart sets the rhythm
  • If the SA node is damdaged, then the rhythm is set by the atria, the next fastest part of the heart
  • If the AV node is blocked, then the ventricles will beat at a slow rate (40 beats/min) & independently of the atria
Conducting System numbered
1. Sinoatrial (SA) node (pacemaker)
2. Internodal pathway
3. Atrioventricular (AV) Node
4. Atrioventricular (AV) Bundle (Bundel of His)
5. Bundle Branches
6. Purkinje Fibers (Causes contraction)

  • Pacemaker is in right ventricle
  • Atria and ventricles contract at once
  • No nervous system for heart ot beat
  • There are parasympathetic response: increased heart rate
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