Heart Anatomy Review

HEART ANATOMY

LOCATION

  • Thoracic Cavity: The heart is located in the thoracic cavity.

    • Superior Surface: Known as the base, where great vessels attach.

    • Major Attachments:

      • Superior vena cava

      • Inferior vena cava

      • Aorta

      • Pulmonary trunk

    • Inferior Tip: Known as the apex.

FUNCTION

  • MOVE BLOOD: The heart functions primarily to move blood throughout the body, organized into two circuits:

    • Pulmonary Circuit:

    • Pathway: Between the heart and lungs.

    • Oxygenation Process: Oxygenation of blood occurs here.

    • Systemic Circuit:

    • Pathway: Between the heart and the rest of the body.

    • Oxygen Delivery: Oxygen is delivered to bodily tissues.

STRUCTURE

  • Four Chambers: Each side of the heart has one atrium and one ventricle.

    • No Physical Connection: There is no direct physical connection between the left and right sides of the heart.

    • Function of Atria:

    • Right Atrium: Receives deoxygenated blood from body.

    • Left Atrium: Receives oxygenated blood from lungs.

    • Atrial Contraction: Contracts to push blood into the ventricles.

    • Function of Ventricles:

    • Right Ventricle: Pumps blood to the lungs.

    • Left Ventricle: Pumps blood to the rest of the body.

HEART VALVES

Atrioventricular Valves

  • Function: Prevent blood from flowing back into the atria when the ventricles contract.

  • Structure: Includes the mitral valve and tricuspid valve.

  • Mechanism of Action:

    1. Filling Phase: Blood returns to the heart, filling the atria and increasing pressure, forcing the atrioventricular valves open.

    2. Pressure Equilibrium: As ventricles fill, valves remain open.

    3. Atrial Contraction: The atria contract to push additional blood into the ventricles; atrial pressure is greater than ventricular pressure.

Closing Phase of Atrioventricular Valves

  • Heart Sound: The first heart sound (S1) is heard; mitral sound occurs slightly before the tricuspid sound.

    1. Ventricular Contraction: Ventricles contract, forcing blood against the atrioventricular valve cusps.

    2. Valve Closure: Valves close to prevent backflow.

    3. Role of Papillary Muscles: Papillary muscles contract, tightening the chordae tendineae to prevent the valve flaps from everting into the atria.

  • Blood Flow Direction: Clear distinction between open and closed states based on pressure differences between atria and ventricles.

Semilunar Valves

  • Purpose: Prevents backflow from arteries into ventricles. Located at the base of the aorta and pulmonary trunk.

  • Mechanism of Action:

    1. Opening Phase: As ventricles contract, pressure rises, pushing blood against the semilunar valves, forcing them open.

    2. Closing Phase: As ventricles relax, pressure falls, causing blood to flow back from arteries into valve cusps, closing them.

  • Heart Sound: The second heart sound (S2) is heard, with the aortic sound slightly preceding the pulmonary sound.

HEART SOUNDS

  • Overview: Heard during the cardiac cycle, including S1, S2, S3, and S4 sounds.

AUSCULTATION POSITIONS

  • Auscultation Position for Heart Valves:

    • Aortic valve

    • Pulmonary valve

    • Tricuspid valve

    • Mitral valve

HEART STRUCTURE OVERVIEW

  • Human Heart: With visible epicardium and fat.

  • Sheep Heart: Similar structural anatomy with an anterior view that highlights the epicardium.

  • Epicardium: A layer that covers the heart muscle and is superficial to epicardial fat.

BLOOD SUPPLY TO THE HEART

Coronary Arteries

  • Right Coronary Artery: Supplies the right side of the heart and the sinoatrial (SA) and atrioventricular (AV) nodes, crucial for regulating heart rhythm.

  • Left Coronary Artery: Supplies blood to the left side of the heart; includes major branches:

    • LAD Artery: The largest coronary artery.

Posterior Descending Artery (PDA)

  • Function: Supplies blood to lower and posterior heart portions plus part of the interventricular septum.

  • Circulatory Dominance:

    • Right-Dominant Circulation: 80% of people, where PDA is supplied by the right main coronary artery.

    • Left-Dominant Circulation: 10% of people, where PDA may be supplied by the LAD or circumflex artery.

    • Codominant Circulation: 20% of people, where PDA is supplied by both LAD/circumflex artery and right coronary artery.

HEART CONSTRUCTIONS AND VIEWS

  • Anatomical Views:

    • Description of a sheep heart, showing structures such as intraventricular sulcus, apex, various atria, ventricles, and major blood vessels with noted severance points for observational purposes.

  • Arterial vs. Venous Structures:

    • Arteries: Transport blood away; thicker walls, smaller lumens, rounded appearance.

    • Veins: Transport blood towards the heart; thinner walls, larger lumens, flattened appearance.

SUMMARY OF STRUCTURES

Right Side of the Heart

  • Main Components:

    • Superior vena cava

    • Inferior vena cava

    • Right atrium

    • Right ventricle

    • Tricuspid valve

    • Chordae tendineae

    • Papillary muscles

    • Pulmonary trunk

Left Side of the Heart

  • Main Components:

    • Pulmonary veins

    • Left atrium

    • Aorta

    • Mitral valve

    • Chordae tendineae

    • Papillary muscles

    • Left ventricle