Cardiovascular System: Anatomy and Physiology of the Heart

Cardiovascular System

Introduction

The cardiovascular system is responsible for the transport of blood, nutrients, gases, and wastes throughout the body. The heart is the central organ of this system, functioning as a pump to maintain circulation.

Objectives

• Understand basic cardiac anatomy

• Compare skeletal muscle and cardiac muscle

• Correlate electrical activity with ECG

• Describe the cardiac cycle

• Explain cardiac output and its regulation

Basic Cardiac Anatomy

Location of the Heart

The heart is located in the mediastinum, the central compartment of the thoracic cavity. It lies between the lungs and is protected by the rib cage.

• Positioned between the 2nd rib and the 5th intercostal space

• Sits on the superior surface of the diaphragm

• Two-thirds of the heart is to the left of the midsternal line

• Located anterior to the vertebral column and posterior to the sternum

Orientation of the Heart

• The heart's apex points downward, forward, and to the left

• The base is directed upward, backward, and to the right

• The location of the apical impulse can be palpated in the 5th intercostal space at the midclavicular line

Visual Representation

• Transverse section shows the heart in the mediastinum, flanked by the lungs and above the diaphragm

• Anterior view highlights the heart's position relative to the sternum, ribs, and diaphragm

Key Terms

• Mediastinum: The central compartment of the thoracic cavity, containing the heart, thymus, parts of the esophagus and trachea, and major vessels.

• Diaphragm: The muscular partition separating the thoracic and abdominal cavities, supporting the heart from below.

• Apical Impulse: The point of maximal impulse (PMI) where the heartbeat can be felt most strongly, typically at the 5th intercostal space.

Summary Table: Heart Location and Orientation

Feature	Description
Mediastinum	Central thoracic cavity, between lungs
Rib Landmarks	Between 2nd rib and 5th intercostal space
Diaphragm	Heart rests on superior surface
Midsternal Line	Two-thirds of heart to left
Anterior/Posterior	Anterior to vertebral column, posterior to sternum

Clinical Relevance

• Knowledge of heart location is essential for physical examination, imaging, and emergency procedures such as pericardiocentesis.

• Abnormalities in heart position (e.g., dextrocardia) can affect clinical findings and management.

Example

During a physical exam, the physician palpates the apical impulse at the 5th intercostal space, midclavicular line, to assess heart size and position.

Additional info: Further details on cardiac muscle structure, ECG correlation, cardiac cycle, and cardiac output will be covered in subsequent sections.