EK

Heart Anatomy

Instructor Information

  • Name: Brady Little, DVM, MSc

  • Subject: Heart Anatomy

Objectives of Study

  • Analyze, describe, and apply knowledge of the following topics:

    • Position/orientation of the heart within the canine thorax

    • Surface features of the heart

    • Internal features of the heart

    • Normal blood flow covering pulmonary and systemic circulation

    • Blood supply to the heart muscle

    • Sounds of cardiac auscultation

Heart Anatomy Overview

Orientation of the Heart

  • Base: Oriented dorsocranially

  • Apex: Points ventrocaudally and to the left

    • Located at the 5th IC (Intercostal) space

Heart Positioning

Ventricles within the Thorax

  • Right Ventricle: Positioned cranially, adjacent to the sternum

  • Left Ventricle: Positioned more laterally to the left

  • Septum: Also crucial in dividing the ventricles

Views of the Heart

Dorsoventral View

  • Left View (Auricular Surface)

    • Key Structures:

      1. Left auricle

      2. Pulmonary trunk

      3. Right ventricle

      4. Left ventricle

      5. Right auricle

Right View (Atrial Surface)

  • Key Structures:

    1. Right atrium

    2. Caudal vena cava

    3. Aorta

    4. Cranial vena cava

Surface Topography

Coronary Groove

  • Function:

    • Separates atria and ventricles

    • Contains coronary vessels

    • Often surrounded by fat

Interventricular Grooves

  • Types:

    1. Paraconal interventricular groove

    2. Subsinuosal interventricular groove

Internal Features of the Heart

Right Side of the Heart

Structures:

  1. Cusp of right atrioventricular valve (Tricuspid)

  2. Chordae tendineae

  3. Papillary muscles

  4. Pulmonary valve

  5. Right auricle

  6. Right ventricle

Atrioventricular Valves

  • Components:

    • Right AV (Tricuspid) valve

    • Left AV (Mitral) valve

    • Aortic valve

    • Pulmonary valve

  • Function:

    • Prevent backflow during systole

    • Operate via papillary muscles and chordae tendineae

Circulatory Systems Overview

Two Separate Circuits

  1. Pulmonary Circulation:

  • Gas exchange in lungs

  1. Systemic Circulation:

  • Gas exchange in body cells

Blood Flow Pathway

  • Right Atrium: Receives deoxygenated blood

    • From cranial and caudal vena cava

  • Right Ventricle: Pumps blood to lungs via pulmonary trunk

  • Left Atrium: Receives oxygenated blood from the lungs via pulmonary veins

  • Left Ventricle: Pumps blood into systemic circulation through the aorta

Valves and Their Functions

  • Pulmonary Semilunar Valve: Prevents backflow during diastole

  • Aortic Semilunar Valve: Prevents backflow into the left ventricle

  • Right AV Valve: Separates right atrium and ventricle

  • Left AV Valve: Separates left atrium and ventricle

Cardiac Auscultation

Points of Maximum Intensity (PMI)

  • Left Side Sounds:

    • "P" = Pulmonary valve sound (3rd IC space)

    • "A" = Aortic valve sound (4th IC space)

    • "M" = Mitral sound (5th IC space)

  • Right Side Sounds:

    • "T" = Tricuspid sound (4th IC space)

Normal Heart Sounds

  • Sound caused by blood stopping at closed valves:

    • S1: Closure of AV valves

    • S2: Closure of semilunar valves

Cardiac Cycle

  • First Heart Sound (S1): Closure of atrioventricular valves

  • Second Heart Sound (S2): Closure of semilunar valves

  • Blood Flow:

    • Through open valves is silent in normal dogs and cats

Abnormal Heart Sounds

  • Not normally heard in smaller animals, but can occur during certain conditions such as:

    • Left and Right Ventricular filling during diastole

    • Left and Right Atrial contraction before ventricular contraction

  • Associated conditions:

    • Hypertrophic cardiomyopathy in small animals