Hearts Anatomy and Physiology

Содержание

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Heart

Hollow, muscular organ
Mediastinum between the lungs resting on the diaphragm, tilting

Heart Hollow, muscular organ Mediastinum between the lungs resting on the diaphragm,
forward and to the left
Pumps 60mL of blood (5 L/min)
Encapsulated by pericardium

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Heart

Muscle tissue layers
- epicardium (visceral pericardium)
> thin & transparent
- myocardium (cardiac muscle

Heart Muscle tissue layers - epicardium (visceral pericardium) > thin & transparent
tissue)
> striated muscle fibers
- endocardium (smooth endothelial tissue)

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Chambers of the Heart

Right atrium
- receives unoxygenated blood from peripheral tissues through

Chambers of the Heart Right atrium - receives unoxygenated blood from peripheral
SVC and IVC
Right ventricle
- propels blood into the pulmonary artery & lungs
- low-pressure system

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Chambers of the Heart

Left atrium
- receives oxygenated blood from the 4 pulmonary

Chambers of the Heart Left atrium - receives oxygenated blood from the
veins
Left ventricle
- largest & most muscular chamber
- high pressure system
- propels blood through the aorta to the periphery

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Heart Valves

Atrioventricular valves
- Tricuspid valve (3 leaflets)
> separates RA from RV
- Bicuspid

Heart Valves Atrioventricular valves - Tricuspid valve (3 leaflets) > separates RA
valve (mitral valve)
> separates LA from LV
Semilunar valves
- Pulmonic valve
> separates RV from the pulmonary artery
- Aortic valve
> separates LV from the aorta

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Coronary Arteries

Originates from the aorta just beyond the aortic valve
Coronary blood flow

Coronary Arteries Originates from the aorta just beyond the aortic valve Coronary
to the myocardium occurs primarily during diastole
* To maintain adequate blood flow through the coronaries, mean arterial pressure (MAP) must be at least 60 mmHg

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Coronary Arteries

Left main coronary artery (LCA)
- Left anterior descending artery (LAD)
>descends toward

Coronary Arteries Left main coronary artery (LCA) - Left anterior descending artery
the anterior wall & apex of LV
> supplies LV, ventricular septum, chordae, papillary muscle & RV
- Left circumflex artery (LXA)
> descends toward the lateral wall of LV & apex
> supplies LA, lateral & posterior LV surfaces
*45% supplies SA node

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Coronary Arteries

Right main coronary artery (RCA)
- descends toward the apex of RV
-

Coronary Arteries Right main coronary artery (RCA) - descends toward the apex
supplies the RA, RV, & inferior portions of LV

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Coronary Veins

Coronary Veins

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Physiology of the Heart

Electrophysiologic properties (regulates heart rate & rhythm)
- Automaticity –

Physiology of the Heart Electrophysiologic properties (regulates heart rate & rhythm) -
ability of all cardiac cells to initiate an impulse spontaneously & repetitively
- Excitability – ability of cardiac cells to respond to stimulus by initiating an impulse (depolarization)
- Conductivity – cardiac cells transmit the electrical impulses they receive
- Contractility – cardiac cells contract in response to an impulse
- Refractoriness – cardiac cells are unable to respond to a stimulus until they’ve recovered (repolarized)

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Conduction System of the Heart

Sinoatrial node (SA node)
- pacemaker cells initiate impulses

Conduction System of the Heart Sinoatrial node (SA node) - pacemaker cells
at 60 – 100 beats/min
Atrioventricular node (AV node)
- located in the junctional area
- normal delay (allows the atria to contract completely before the ventricles are stimulated to contract)
- 40 – 60 beats/min
Bundle of His
- located in the interventricular septum
- Left and Right bundle branches
Purkinje fibers
- terminal branches that carry the impulse to RV & LV
- 20 – 40 beats/min

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Cardiac Cycle

Diastole
- relaxation and filling of the atria and ventricles
- “dub”
Systole
-

Cardiac Cycle Diastole - relaxation and filling of the atria and ventricles
contraction and emptying of the atria & ventricles
- “lubb”

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Cardiac Muscle Contraction

Release of large amounts of Calcium ions from the sarcoplasmic

Cardiac Muscle Contraction Release of large amounts of Calcium ions from the
reticulum of myocardial cells
Ca ions diffuse into the myofibril sarcomere (basic contractile unit of the myocardial cell)
Ca ions promote interaction of actin & myosin protein filaments causing the filaments to link & overlap (cross-bridges or linkages)
Sliding of protein filaments shortens sarcomere producing contraction

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Mechanical Properties of the Heart

Cardiac output
- volume of blood (liters) ejected by

Mechanical Properties of the Heart Cardiac output - volume of blood (liters)
the heart each minute
- 4 – 7 L/min
- heart rate x stroke volume
Heart rate
- number of times the ventricles contract each minute
- 60 – 100 beats/min
- controlled by the ANS via the vagus nerve
Stroke volume
- amount of blood ejected by the LV during each systole

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Mechanical Properties of the Heart

Preload
- degree of myocardial stretch at the end

Mechanical Properties of the Heart Preload - degree of myocardial stretch at
of diastole & just before contraction
- determined by the amount of blood returning to the heart from the venous ® & pulmonary system (L) – LVED
*Starling’s law – the more the heart is filled during diastole, the more forcefully it contracts

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Mechanical Properties of the Heart

Afterload
- pressure or resistance that the ventricles must

Mechanical Properties of the Heart Afterload - pressure or resistance that the
overcome to eject blood through the semilunar valves & into the peripheral blood vessels
- directly proportional to the BP & diameter of blood vessels
Impedance (peripheral component of afterload)
- pressure that the heart must overcome to open the aortic valve
- depends on aortic compliance, blood viscosity & arteriolar constriction

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Mechanical Properties of the Heart

Myocardial contractility
- force of cardiac contraction independent of

Mechanical Properties of the Heart Myocardial contractility - force of cardiac contraction
preload
- increased by sympathetic nervous stimulation, calcium release & positive inotropic drugs
- decreased by hypoxemia & acidemia

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Vascular System

Provide conduits for blood to travel from the heart to nourish

Vascular System Provide conduits for blood to travel from the heart to
the body
Carry cellular wastes to the excretory organs
Allow lymphatic flow to drain tissue fluid back to the circulation
Return blood to the heart for recirculation

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Arterial System

Delivers blood to various tissues for nourishment
Transport of cellular wastes
Contribute to

Arterial System Delivers blood to various tissues for nourishment Transport of cellular
thermal regulation

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Arterial System

Blood pressure
- force of blood exerted against the vessel walls
= CO

Arterial System Blood pressure - force of blood exerted against the vessel
x peripheral vascular resistance
- regulated by:
> autonomic nervous system (ANS)
> kidneys (renin-angiotensin-aldosterone)
> endocrine system (catecholamines, kinins, serotonin, histamine)

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Blood Pressure

Systolic:
- amount of pressure/force generated by LV to distribute blood

Blood Pressure Systolic: - amount of pressure/force generated by LV to distribute
into the aorta w/ each contraction of the heart
- 90 – 135 mmHg (120)
- affected by CO and arterial distention
Diastolic:
- amount of pressure/force sustained by the arteries during the relaxation phase of the heart
- ability of the heart to rest while filling with blood
- affected by peripheral vascular resistance
- 60 – 85 mmHg (80)

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Regulation of BP

Autonomic Nervous System
- Baroreceptors (arch of aorta & origin of

Regulation of BP Autonomic Nervous System - Baroreceptors (arch of aorta &
internal carotid arteries)
> stimulated when arterial walls are stretched by increased BP
> inhibit vasomotor center (pons & medulla or brainstem)
- Chemoreceptors (bifurcation of carotid arteries & aortic arch)
> sensitive to hypoxemia, hypercapnia

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Venous System

Series of veins located adjacent to arterial system
Veins collect blood from

Venous System Series of veins located adjacent to arterial system Veins collect
the capillaries & terminal arterioles
Acts as reservoir for blood
Low-pressure, collapsible system that work against effects of gravity
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