Chapter 18 Part A: The Cardiovascular System

18.1 Heart Anatomy

This section introduces the structure and function of the heart as a central organ in the cardiovascular system, focusing on its anatomical features and the circuits it supports.

Pulmonary and Systemic Circuits

Overview of Heart as a Double Pump

• The heart is a muscular organ that acts as a transport system, consisting of two side-by-side pumps.

• Right side of the heart receives oxygen-poor blood from body tissues and pumps it to the lungs via the pulmonary circuit to eliminate CO2 and pick up O2.

• Left side receives oxygenated blood from the lungs and pumps it to body tissues via the systemic circuit.

Key Terms:

• Pulmonary circuit: Pathway of blood from the right side of the heart to the lungs and back to the left side of the heart.

• Systemic circuit: Pathway of blood from the left side of the heart to the body tissues and back to the right side of the heart.

Heart Chambers and Their Functions

• Receiving chambers of the heart:

  • Right atrium: Receives blood returning from the systemic circuit (body tissues).

  • Left atrium: Receives blood returning from the pulmonary circuit (lungs).

• Pumping chambers of the heart:

  • Right ventricle: Pumps blood through the pulmonary circuit (to the lungs).

  • Left ventricle: Pumps blood through the systemic circuit (to the body).

Diagram: Systemic and Pulmonary Circuits

The heart is depicted as a double pump, with blue arrows indicating oxygen-poor blood flow (right side, pulmonary circuit) and red arrows indicating oxygen-rich blood flow (left side, systemic circuit). The pulmonary arteries carry deoxygenated blood to the lungs, while the pulmonary veins return oxygenated blood to the heart. The aorta distributes oxygenated blood to the body.

Size, Location, and Orientation of the Heart

Physical Characteristics and Position

• Approximately the size of a fist; weighs less than 1 pound.

• Located in the mediastinum, the central compartment of the thoracic cavity, between the second rib and fifth intercostal space.

• Sits on the superior surface of the diaphragm.

• About two-thirds of the heart lies to the left of the midsternal line.

• Positioned anterior to the vertebral column and posterior to the sternum.

• The base (posterior surface) leans toward the right shoulder; the apex points toward the left hip.

• The apical impulse (point of maximal impulse) can be palpated between the fifth and sixth ribs, just below the left nipple.

Example: During a physical examination, a healthcare provider may feel for the apical impulse to assess heart size and position.

Additional info: The mediastinum also contains other vital structures such as the trachea, esophagus, and major blood vessels, but the heart is the largest organ within this space.