Heart Anatomy Identification

Overview

The heart is a muscular organ responsible for pumping blood throughout the body. Understanding its anatomy is essential for tracing blood flow, identifying oxygenated and deoxygenated blood, and recognizing the function of each structure. The following notes cover external and internal heart structures, their functions, and their roles in circulation.

External Structures of the Heart

Sheep Heart – External

• Parietal Pericardium: The outermost layer of the pericardium; protects the heart and anchors it within the thoracic cavity.

• Epicardium (Visceral Pericardium): The innermost layer of the pericardium; forms the outer surface of the heart and provides protection.

Sheep Heart – External Anterior

• Anterior Interventricular Sulcus: Groove on the anterior surface marking the boundary between the right and left ventricles; contains coronary blood vessels.

• Right Atrium: Receives deoxygenated blood from the body via the vena cava.

• Right Ventricle: Pumps deoxygenated blood to the lungs via the pulmonary trunk.

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

• Left Ventricle: Pumps oxygenated blood to the body via the aorta.

• Coronary Blood Vessels: Supply oxygen and nutrients to the heart muscle itself.

• Pulmonary Trunk: Carries deoxygenated blood from the right ventricle to the lungs.

• Aorta: Largest artery; carries oxygenated blood from the left ventricle to the systemic circulation.

• Brachiocephalic Trunk: First major branch of the aorta; supplies blood to the right arm and head.

Sheep Heart – External Posterior

• Posterior Interventricular Sulcus: Groove on the posterior surface marking the boundary between the ventricles; contains coronary vessels.

• Right Atrium: As above.

• Right Ventricle: As above.

• Left Atrium: As above.

• Left Ventricle: As above.

• Coronary Sinus: Collects deoxygenated blood from the heart muscle and empties into the right atrium.

• Vena Cava (Superior and Inferior): Large veins returning deoxygenated blood from the body to the right atrium.

• Pulmonary Veins: Carry oxygenated blood from the lungs to the left atrium.

Internal Structures of the Heart

Sheep Heart – Internal (Dissected)

• Endocardium: Inner lining of the heart chambers; provides a smooth surface for blood flow.

• Tricuspid Valve: Valve between the right atrium and right ventricle; prevents backflow of blood.

• Chordae Tendineae: Tendinous cords anchoring the AV valves to papillary muscles; prevent valve prolapse.

• Papillary Muscle: Muscles in ventricles that contract to tighten chordae tendineae during ventricular contraction.

• Moderator Band: Muscular band in the right ventricle; part of the conduction system.

• Pulmonary Semilunar Valve: Valve between right ventricle and pulmonary trunk; prevents backflow into ventricle.

• Aortic Semilunar Valve: Valve between left ventricle and aorta; prevents backflow into ventricle.

• Bicuspid (Mitral) Valve: Valve between left atrium and left ventricle; prevents backflow of blood.

• Openings to Coronary Arteries: Allow blood to flow from the aorta into the coronary circulation.

Additional Heart Structures (Model Hearts and PAL)

• Left Pulmonary Artery: Carries deoxygenated blood from the pulmonary trunk to the left lung.

• Right Pulmonary Artery: Carries deoxygenated blood from the pulmonary trunk to the right lung.

• Left Pulmonary Vein: Returns oxygenated blood from the left lung to the left atrium.

• Right Pulmonary Vein: Returns oxygenated blood from the right lung to the left atrium.

• Ligamentum Arteriosum: Remnant of the fetal ductus arteriosus; connects the pulmonary trunk to the aorta.

• Left Common Carotid Artery: Branch of the aorta; supplies blood to the left side of the head and neck.

• Left Subclavian Artery: Branch of the aorta; supplies blood to the left arm.

• Superior Vena Cava: Returns deoxygenated blood from the upper body to the right atrium.

• Inferior Vena Cava: Returns deoxygenated blood from the lower body to the right atrium.

Blood Flow Through the Heart

Tracing Blood Flow

Blood flows through the heart in a specific sequence, passing through chambers, valves, and vessels. It is important to identify the type of blood (oxygenated or deoxygenated) in each structure.

• Deoxygenated blood enters the right atrium via the superior and inferior vena cava.

• Passes through the tricuspid valve into the right ventricle.

• Pumped through the pulmonary semilunar valve into the pulmonary trunk and pulmonary arteries to the lungs.

• Oxygenated blood returns via the pulmonary veins to the left atrium.

• Passes through the bicuspid (mitral) valve into the left ventricle.

• Pumped through the aortic semilunar valve into the aorta and systemic circulation.

Blood Oxygenation Table

Heart Valves

Types and Functions

• Atrioventricular (AV) Valves: Tricuspid (right) and bicuspid/mitral (left); prevent backflow from ventricles to atria.

• Semilunar Valves: Pulmonary (right) and aortic (left); prevent backflow from arteries to ventricles.

Summary Table: Major Heart Structures and Functions

Example: Tracing Blood Through the Heart

Deoxygenated blood enters the right atrium, passes through the tricuspid valve to the right ventricle, then through the pulmonary semilunar valve to the pulmonary trunk and arteries. After oxygenation in the lungs, blood returns via pulmonary veins to the left atrium, passes through the bicuspid valve to the left ventricle, and is pumped through the aortic semilunar valve into the aorta for systemic distribution.

Key Terms

• Pericardium: Double-layered membrane surrounding the heart.

• Epicardium: Outer layer of heart wall.

• Endocardium: Inner layer of heart wall.

• Atria: Upper chambers of the heart.

• Ventricles: Lower chambers of the heart.

• Valves: Structures ensuring one-way blood flow.

• Coronary Circulation: Blood supply to heart muscle.

Additional info:

• Some structures may not be visible in all heart specimens, but knowledge of their function and location is required.

• Blood flow tracing is a fundamental skill for understanding cardiac physiology and pathology.