Anatomy & Physiology: The Heart

Learning Outcomes

• Describe the anatomy of the heart, including vascular supply and pericardium structure, and trace the flow of blood through the heart, identifying the major blood vessels, chambers, and heart valves.

• Explain the events of an action potential in cardiac muscle, state the importance of calcium ions to the contractile process, describe the conducting system of the heart, and identify the electrical events associated with a normal electrocardiogram.

• Explain the events of the cardiac cycle, including atrial and ventricular systole and diastole, and relate the heart sounds to specific events in the cycle.

• Define cardiac output, describe the factors that influence heart rate and stroke volume, and explain how adjustments in stroke volume and cardiac output are coordinated at different levels of physical activity.

Introduction to the Heart

The Cardiovascular System

The cardiovascular system is responsible for transporting blood throughout the body, delivering oxygen and nutrients, and removing waste products. It consists of three main components:

• Heart: The muscular organ that pumps blood.

• Blood: The fluid that carries oxygen, nutrients, and waste.

• Blood vessels: The network of arteries, veins, and capillaries through which blood flows.

The heart beats approximately 100,000 times each day, pumping about 8,000 liters of blood daily.

Anatomy of the Heart

Pulmonary and Systemic Circuits

The heart is the central organ of two major circulatory circuits:

• Pulmonary circuit: Carries blood to and from the gas exchange surfaces of the lungs.

• Systemic circuit: Carries blood to and from the rest of the body.

Each circuit begins and ends at the heart, and blood travels through these circuits in sequence.

Types of Blood Vessels

• Arteries: Carry blood away from the heart.

• Veins: Return blood to the heart.

• Capillaries (exchange vessels): Interconnect the smallest arteries and veins, allowing exchange of dissolved gases, nutrients, and wastes between blood and surrounding tissues.

Chambers of the Heart

The heart has four chambers, each with a specific function:

• Right atrium: Receives blood from the systemic circuit.

• Right ventricle: Pumps blood into the pulmonary circuit.

• Left atrium: Receives blood from the pulmonary circuit.

• Left ventricle: Pumps blood into the systemic circuit.

External Anatomy and Location of the Heart

• Great vessels connect at the base (superior aspect) of the heart.

• The pointed tip is called the apex (inferior aspect).

• The heart sits between two pleural cavities in the mediastinum.

Overview of the Cardiovascular System (Diagram)

The cardiovascular system is organized into pulmonary and systemic circuits. The pulmonary circuit includes pulmonary arteries and veins, and capillaries in the lungs. The systemic circuit includes systemic arteries and veins, and capillaries in the head, neck, trunk, and limbs.

Key Terms and Concepts

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

• Vein: A blood vessel that returns blood to the heart.

• Capillary: A microscopic blood vessel where exchange of substances occurs between blood and tissues.

• Atrium: An upper chamber of the heart that receives blood.

• Ventricle: A lower chamber of the heart that pumps blood out of the heart.

• Mediastinum: The central compartment of the thoracic cavity, containing the heart.

Example: Blood Flow Through the Heart

Blood enters the right atrium from the systemic circuit, passes to the right ventricle, and is pumped to the lungs via the pulmonary circuit. Oxygenated blood returns to the left atrium, moves to the left ventricle, and is pumped out to the body through the systemic circuit.

Additional info: These notes cover the introductory anatomy and organization of the heart, including its chambers, major vessels, and the two main circulatory circuits. Further details on heart valves, electrical conduction, cardiac cycle, and cardiac output would be included in subsequent sections of the chapter.