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 major blood vessels, chambers, and heart valves.

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

• Explain the events of the cardiac cycle, including atrial and ventricular systole and diastole, and relate 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 the transport of blood, nutrients, gases, and wastes throughout the body. It consists of the heart, blood, and blood vessels.

• Heart: The muscular organ that pumps blood.

• Blood: The fluid medium for transport.

• Blood vessels: The network through which blood circulates.

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

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 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.

Diagram: Overview of the Cardiovascular System

• Pulmonary arteries and veins connect the heart to the lungs.

• Systemic arteries and veins distribute blood to the rest of the body.

• Capillaries are present in all major organs and tissues for exchange.

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 contains four chambers, each with a specific function in the circulation of blood:

• 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.

Additional info:

• The mediastinum is the central compartment of the thoracic cavity, containing the heart, thymus, parts of the esophagus and trachea, and major blood vessels.

Summary Table: Circulatory Circuits

Key Terms

• Artery: Vessel carrying blood away from the heart.

• Vein: Vessel returning blood to the heart.

• Capillary: Smallest blood vessel for exchange.

• Atrium: Upper chamber of the heart.

• Ventricle: Lower chamber of the heart.

• Mediastinum: Central thoracic cavity compartment.

Example: Blood Flow Sequence

• Deoxygenated blood enters the right atrium from the systemic veins.

• Blood moves to the right ventricle, which pumps it to the lungs via the pulmonary arteries.

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

• Blood moves to the left ventricle, which pumps it to the body via the aorta.