Anatomy & Physiology Study Notes: Structure and Function of the Heart

Cardiovascular System: The Heart

Overview of the Heart

The heart is a muscular organ responsible for pumping blood throughout the body via the pulmonary and systemic circuits. Understanding its structure and function is essential for studying human anatomy and physiology.

• Location: The heart is located in the thoracic cavity, between the lungs, in a region called the mediastinum.

• Size: The average adult heart is about the size of a closed fist, typically weighing between 250-350 grams.

• Base and Apex: The base of the heart is the broad, superior portion where major blood vessels attach. The apex is the pointed, inferior tip that angles to the left and rests on the diaphragm.

• Function: The heart pumps blood to the lungs for oxygenation (pulmonary circuit) and to the rest of the body (systemic circuit).

Pericardium and Pericardial Cavity

The heart is enclosed in a protective sac called the pericardium, which consists of several layers and a cavity that reduces friction during heartbeats.

• Layers of the Pericardium:

  • Fibrous Pericardium: The tough, outer layer that anchors the heart and prevents overfilling.

  • Serous Pericardium: A double-layered membrane consisting of:

    • Parietal Layer: Lines the internal surface of the fibrous pericardium.

    • Visceral Layer (Epicardium): Covers the heart surface.

• Pericardial Cavity: The space between the parietal and visceral layers, filled with serous fluid to reduce friction as the heart beats.

• Purpose: Protects the heart, anchors it within the thorax, and prevents excessive movement.

Layers of the Heart Wall

The heart wall is composed of three distinct layers, each with specialized functions.

• Epicardium: The outermost layer, also known as the visceral pericardium; provides protection and contains blood vessels that nourish the heart.

• Myocardium: The thick, muscular middle layer responsible for the heart's contractile force.

• Endocardium: The innermost layer lining the heart chambers and valves; provides a smooth surface for blood flow.

Chambers and Valves of the Heart

The heart contains four chambers and four main valves that regulate blood flow and prevent backflow.

• Chambers:

  • Right Atrium: Receives deoxygenated blood from the body.

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

  • Left Atrium: Receives oxygenated blood from the lungs.

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

• Valves:

  • Atrioventricular (AV) Valves:

    • Tricuspid Valve: Between right atrium and right ventricle.

    • Bicuspid (Mitral) Valve: Between left atrium and left ventricle.

  • Semilunar Valves:

    • Pulmonary Valve: Between right ventricle and pulmonary artery.

    • Aortic Valve: Between left ventricle and aorta.

Septum of the Heart

The septum is a wall that divides the right and left sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.

• Location: The septum runs vertically through the center of the heart.

• Types:

  • Interatrial Septum: Separates the right and left atria.

  • Interventricular Septum: Separates the right and left ventricles.

Summary Table: Heart Structure and Function

Component	Location	Function
Pericardium	Surrounds heart	Protection, reduces friction
Epicardium	Outer heart wall	Protection, contains vessels
Myocardium	Middle heart wall	Contraction, pumping
Endocardium	Inner heart wall	Lines chambers, smooth flow
Right Atrium	Upper right chamber	Receives deoxygenated blood
Left Atrium	Upper left chamber	Receives oxygenated blood
Right Ventricle	Lower right chamber	Pumps blood to lungs
Left Ventricle	Lower left chamber	Pumps blood to body
Septum	Center of heart	Separates right/left sides

Example: The left ventricle has the thickest myocardium because it must generate enough force to pump blood throughout the entire body.

Additional info: Academic context and definitions have been expanded for clarity and completeness.