Surface Marking of Anatomical Structures in the Thoracic Region

Lung Borders and Fissures with Anatomical Variations

The surface marking of the lungs is essential for accurate clinical examination and diagnosis. The lungs are enclosed within the thoracic cavity and are divided into lobes by fissures. The positioning of these structures can vary among individuals.

Surface Marking of the Lung Borders

The borders of the lungs are defined as the anterior, posterior, and inferior margins:

• Anterior Border: Extends from the sternoclavicular joint down to the xiphoid process.
• Inferior Border: Located at the level of the sixth rib at the mid-clavicular line, the eighth rib at the mid-axillary line, and the tenth rib posteriorly.
• Posterior Border: Runs parallel to the vertebral column.

Lung Fissures and Variations

The right lung has two fissures (oblique and horizontal), while the left lung has one (oblique).

• Oblique Fissure: Present in both lungs, running from the level of the third thoracic vertebra down to the sixth rib.
• Horizontal Fissure: Found in the right lung, extending from the fourth rib along the sternum to meet the oblique fissure at the mid-axillary line.

Anatomical Variations

Individual variations in lung fissures and borders occur due to genetic and developmental factors:

• Accessory fissures may exist, creating additional lobulations.
• The horizontal fissure may be absent or incomplete in some individuals.
• Congenital anomalies such as lung hypoplasia can affect surface markings.

Clinical Significance

Understanding lung surface anatomy is crucial for procedures like auscultation, percussion, and imaging techniques.