Anatomy of the Heart
Anatomy of the Heart
Lesson Objectives
Describe the location of the heart.
Name the three layers and the covering of the heart.
Explain the function of the heart as two separate pumps.
Identify the four chambers and great vessels of the heart.
Explain the functions of the four heart valves.
Describe the physiological basis of the heart sounds.
Describe blood flow through the heart.
List the vessels that supply blood to the heart.
Identify the major components of the heart's conduction system.
Function, Location, and Size of the Heart
Heart:
Hollow, muscular organ that functions to pump and force blood through the blood vessels, providing essential nutrients and oxygen to every cell in the body.
Location:
The heart is located in the thoracic cavity within the lower mediastinum, positioned between the two lungs and posterior to the sternum.
Size:
The adult heart is approximately the size of a closed fist and weighs less than 1 lb.
Layers and Covering of the Heart
Endocardium:
The innermost layer of the heart.
Myocardium:
The middle layer, composed of cardiac muscle tissue.
Epicardium:
The thin, outermost layer that also contributes to the formation of the pericardium, the protective sac around the heart.
Pericardium:
Supports the heart and is composed of three layers.
The Heart's Function as Two Pumps
Double Pump System:
The heart acts as two separate pumps, one for pulmonary circulation and one for systemic circulation.
Pulmonary Circulation:
Involves the right side of the heart, which pumps deoxygenated blood to the lungs via the pulmonary artery.
Blood receives oxygen in the pulmonary capillaries and returns to the left atrium through the pulmonary veins.
Systemic Circulation:
Involves the left side of the heart, which pumps oxygenated blood to all tissues of the body through the aorta.
The Heart’s Chambers and Great Vessels
Chambers of the Heart:
Right Atrium: Receives deoxygenated blood from the body via the superior and inferior venae cavae.
Right Ventricle: Pumps deoxygenated blood to the lungs.
Left Atrium: Receives oxygenated blood from the lungs.
Left Ventricle: Pumps oxygenated blood to the body.
Great Vessels of the Heart:
Superior and Inferior Venae Cavae: Return deoxygenated blood to the right atrium.
Pulmonary Trunk: Divides into pulmonary arteries that carry blood to the lungs.
Four Pulmonary Veins: Return oxygenated blood to the left atrium.
Aorta: Carries oxygenated blood from the left ventricle to the body.
Heart Valves
Atrioventricular Valves:
Tricuspid Valve: Located between the right atrium and right ventricle.
Bicuspid Valve (Mitral Valve): Located between the left atrium and left ventricle.
Chordae Tendineae: Fibrous cords that support the atrioventricular valves.
Semilunar Valves:
Pulmonic Valve: Controls blood flow from the right ventricle into the pulmonary trunk.
Aortic Valve: Controls blood flow from the left ventricle into the aorta.
Heart Sounds
Commonly described as lubb-dupp, lubb-dupp:
S1: First heart sound, known as "lubb"; corresponds to the closure of the atrioventricular valves.
S2: Second heart sound, known as "dupp"; corresponds to the closure of the semilunar valves.
Murmurs: Abnormal heart sounds that may indicate valvular problems.
S3 and S4: Extra heart sounds caused by vibrations; their presence can indicate heart conditions, with S3 and S4 giving a "gallop rhythm".
Pathway of Blood Flow Through the Heart
Right Atrium
Tricuspid Valve
Right Ventricle
Pulmonic Semilunar Valve
Pulmonary Trunk
Pulmonary Arteries
Pulmonary Capillaries
Four Pulmonary Veins
Left Atrium
Bicuspid Valve (Mitral Valve)
Left Ventricle
Aortic Semilunar Valve
Aorta
Blood Supply to the Myocardium
Supplied by the Coronary Arteries:
Right Coronary Artery: Nourishes the right side of the heart.
Left Coronary Artery: Supplies blood to the left side of the heart.
Characteristics of Coronary Blood Flow:
Can increase based on the heart’s metabolic demands.
Greatest during myocardial relaxation, allowing efficient oxygen delivery.
Coronary arteries can form anastomoses, which are multiple connections between the arteries that provide redundancy in blood supply.
Cardiac Enzymes and Leaky Cells
When myocardial cells die, they leak enzymes into the bloodstream, leading to:
Plasma elevations of cardiac enzymes.
Troponin levels in the blood serve as a diagnostic tool for detecting heart attacks.
Cardiac Conduction System
Parts of the Cardiac Conduction System:
Sinoatrial Node: Acts as the natural pacemaker of the heart, generating electrical signals.
Atrial Conducting Fibers: Transmit impulses from the sinoatrial node to the atria.
Atrioventricular Node: Acts as a gatekeeper, delaying the conduction to the ventricles.
His-Purkinje Fibers: Conduct impulses throughout the ventricles, allowing for coordinated contraction.
Automaticity and Rhythmicity:
Automaticity: The ability of cardiac pacemaker cells to generate their own electrical signals independent of external stimuli.
Rhythmicity: The rhythmic firing of cardiac impulses at regular intervals.
Electrocardiogram (ECG)
P-wave: Represents the depolarization impulse occurring in the atria.
QRS Complex: Represents the depolarization impulse occurring in the ventricles.
T-wave: Represents the repolarization impulse occurring in the ventricles.
Summary of ECG Intervals
P-R Interval: Time taken for the impulse to travel from the atria to the ventricles.
S-T Interval: Represents the time when the ventricles are depolarized.
Note: This guide was created based on the content provided from the transcript for comprehensive understanding of heart anatomy and physiology.