Human Anatomy - Kotsan I. Y. 2009

Muscles and Fascia of the Trunk
Regions of the Thorax

The following regions are distinguished on the Thorax.

The presternal region (regio presternalis) is bounded by the margins of the Sternum.

The infraclavicular region (regio infraclavicularis) appears as a slight depression just below the clavicle. It includes a small triangular fossa—the deltopectoral triangle—which continues into the deltopectoral sulcus.

The mammary region (regio mammaris), or breast region, corresponds to the Base of the mammary gland and is typically bounded superiorly by the 3rd rib, inferiorly by the 6th rib, medially by the parasternal line, and laterally by the anterior axillary line.

The inframammary region (regio inframammaria) lies immediately below the preceding region and is bounded superiorly by the 6th rib, inferiorly by the costal margin, medially by the edge of the sternum, and laterally by the midaxillary line.

The axillary region (regio axillaris) is bounded anteriorly by the inferior border of the pectoralis major Muscle, posteriorly by the inferior border of the latissimus dorsi muscle, medially by a line connecting the edges of these two Muscles on the chest wall, and laterally by a line connecting their edges on the Medial surface of the arm. When the upper limb is abducted, the axillary fossa (fossa axillaris) becomes clearly visible within this region.

The following vertical lines can be identified on the chest wall.

The anterior median line (linea mediana anterior) represents the surface contour of the median plane on the anterior body surface.

The sternal line (linea sternalis) runs along the lateral border of the sternum.

The parasternal line (linea parasternalis) runs midway between the sternal margin and the midclavicular line.

The midclavicular line (linea medioclavicularis) runs vertically through the midpoint of the clavicle.

The mamillary line (linea mamillaris) passes through the nipple and typically coincides with the midclavicular line.

The anterior axillary line (linea axillaris anterior) runs along the anterior fold of the axilla.

The midaxillary line (linea axillaris media) is located midway between the anterior and posterior axillary lines.

The posterior axillary line (linea axillaris posterior) runs along the posterior fold of the axilla.

The posterior median line (linea mediana posterior) runs along the spinous processes of the vertebrae.



Last update: 08/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.