Surface Landmarks of Thorax

Topic Overview

Introduction

The thorax (chest) forms the upper part of the trunk and houses vital organs such as the heart, lungs, and great vessels. It is bounded by the thoracic cage, which provides protection and supports respiration. The diaphragm separates it from the abdomen.

Bony Landmarks

1. Suprasternal or Jugular Notch

• Felt above the superior border of the manubrium, between the sternal ends of the clavicles.

• Lies at the level of the lower border of the body of the 2nd thoracic vertebra (T2).

• The trachea can be palpated here.

2. Sternal Angle (Angle of Louis)

• Felt as a transverse ridge about 5 cm below the suprasternal notch.

• Corresponds to the manubriosternal joint.

• Lies at the level of the 2nd costal cartilage anteriorly and the disc between T4 and T5 vertebrae posteriorly.

Clinical and Anatomical Importance:

• Rib Counting: The 2nd costal cartilage marks the start point for counting ribs.

• Division of Mediastinum: Separates the superior and inferior mediastinum.

• Major Structures at this Level:

  • End of ascending aorta and beginning of arch of aorta.

  • Beginning of descending thoracic aorta.

  • Tracheal bifurcation into right and left main bronchi.

  • Azygos vein arches over the root of the right lung to open into the superior vena cava.

  • Pulmonary trunk bifurcates into right and left pulmonary arteries.

  • Thoracic duct crosses from right to left side.

  • Marks the upper border of the heart and site of cardiac plexuses.

3. Xiphisternal Joint

• Formed between the xiphoid process and body of sternum.

• Lies opposite the T9 vertebra.

• The costal margins (7th–10th costal cartilages) form the subcostal angle at this point.

• This area overlies the upper part of the liver, diaphragm, and inferior border of the heart.

Summary of Key Levels