heart anatomy

Heart Anatomy

Overview of the Heart

• Hollow, muscular organ

• Function: Pumps blood throughout the body

• Beats: Approximately 72 beats/min, totaling about 3 billion beats in a lifetime

• Size: Approximately the size of a fist

• Location: Mediastinum, situated between the 2nd and 5th rib, with 2/3 of its mass located to the left of the midline

Layers and Coverings of the Heart

Endocardium

• Made of squamous epithelium supported by underlying connective tissue

• Continuous with blood vessels and lines heart valves

• Function: Provides a smooth interior surface for blood flow

Myocardium

• Composed of cardiac muscle

• Features a spiral arrangement of muscle fibers

• Contains connective tissue, referred to as the "skeleton" of the heart

Epicardium (Visceral Pericardium)

• Thin outer layer of the heart

• Contains blood vessels that supply the heart

• Connects the pericardium at the apex

Pericardium: A Serous Membrane

• Function: Supports and protects the heart

• Composed of three layers:

  • Epicardium (Visceral pericardium)

  • Parietal pericardium

  • Fibrous pericardium

• Serous fluid within the pericardial space reduces friction between layers

• Inflammation can lead to increased fluid, resulting in cardiac tamponade which compresses the heart and is life-threatening

Chamber and Vessel Anatomy

Atria

• Structure: Thin-walled chambers

• Right Atria: Receives blood from inferior and superior venae cavae

• Left Atria: Receives blood from the pulmonary veins

Vessels

• Vein Definition: A vessel that transports blood to the heart

Ventricles

• Structure: Muscular walls

• Right Ventricle: Pumps blood to the lungs via pulmonary arteries

• Left Ventricle: Pumps blood to the body through the aorta (systemic pump)

• Artery Definition: A vessel that carries blood away from the heart

• Left Ventricle Thickness: Thicker wall due to the need to exert more force

Blood Flow

• Trace a drop of blood as it travels from the aorta through systemic circulation and back to the aorta.

Heart Valves: Ensuring One-Way Flow

Atrioventricular (AV) Valves

• Located between the atria and ventricles

• Function: Control the flow of blood into the ventricles

• Right AV Valve: Tricuspid

• Left AV Valve: Bicuspid (Mitral)

How AV Valves Function

• Flaps or Cusps: Open when ventricular pressure is lower than atrial pressure

• Closing Mechanism: Closes when ventricles contract, creating higher pressure than atrial pressure

• Prevention of Backflow: Achieved by chordae tendineae (fibrous strings attaching the valve to ventricular walls)

Semilunar Valves

• Resemble a half moon

• Right Valve: Pulmonic (pulmonary valve)

• Left Valve: Aortic valve

• Open when ventricles contract and pressure within ventricle exceeds vessel pressure; close when ventricle relaxes

Heart Sounds

• Sounds Identification: Lub-Dub

  • Lub: AV valve closure

  • Dub: Semilunar valve closure

• Locations for Auscultation: 2nd and 5th intercostal spaces

• Murmurs: Result from incomplete closure and backflow of blood

Coronary Vessels

• Blood supply to the heart muscle (myocardium) primarily through the coronary arteries which branch from the aorta

• Left Coronary Artery: Branches into the left anterior descending artery and circumflex artery (supplying left ventricle)

• Right Coronary Artery: Branches into the posterior descending artery (supplying right ventricle)

Shunts and Defects

• Shunting Mechanism: Diversion of blood through an interventricular hole

• Septal Defect: Left to right shunt (pressure higher in left side) or right to left shunt (due to stenosis of pulmonary artery, increasing right side pressure)

Vessel Blockage and Related Conditions

• Causes of Narrowing: Due to plaque buildup or clot formation

• Consequences: Lack of oxygen leads to ischemia (angina), potential cell death (necrosis)

• Key Biomarkers: CPK, AST, LDH, troponin

• Myocardial Infarction Treatment: Includes thrombolytics and surgical interventions