Back regions (regiones dorsales) are the topographic areas of the posterior trunk delineated for clinical examination and layered anatomical study. There are five primary regions, each defined by distinct bony or muscular landmarks.
Topography5 main back regions (paired and unpaired)
Bony landmarkScapula spans from the 2nd to 7th ribs
Muscular reliefErector spinae muscle forms the lumbar groove
ClassificationMuscles are divided into superficial (above the fascia) and deep (below it)
Topographic Division of the Back
To systematize anatomical structures, the posterior trunk is divided into five key areas. Some lie strictly along the midline, while others are symmetrically paired laterally.
Vertebral region (regio vertebralis). An unpaired area located centrally on the back. Its borders correspond precisely to the contours of the vertebral column.
Scapular region (regio scapularis). A paired region located symmetrically on the right and left sides. Its boundaries are defined by the contours of the scapula. Important topographic markers here are the angles of the scapula: the superior angle projects at the level of the 2nd rib, and the inferior angle reaches the 7th rib. Visually, the bone contours and muscle bulges (specifically, the erector spinae) are well-defined in this zone.
Infrascapular region (regio infrascapularis). Also a paired region, located immediately inferior to the scapula, representing the lower posterior part of the thorax.
Lumbar region (regio lumbalis). Represented by right and left halves. Superiorly, it is clearly bounded by the 12th rib line, and inferiorly it extends to the iliac crest. A characteristic surface feature here is the lumbar groove, which runs along the lateral margin of the erector spinae muscle.
Sacral region (regio sacralis). The lowest unpaired region of the back, shaped by the underlying contours of the sacrum.
External Examination and Palpation
Back examination relies on several reliable visual and palpable markers that allow clinicians or students to quickly orient themselves.
Directly along the posterior midline, the spinous processes of the vertebrae are easily palpable.
Lateral to the midline, a prominent muscular ridge stands out — the contours of the erector spinae muscle.
In the upper trunk segment, the primary visual landmarks are the overall outlines of the scapulae and, specifically, the spine of the scapula.
In the lower back, the baseline skeletal reference point is the iliac crest.
Organization Principles of Back Muscles
The entire muscular mass of the posterior trunk (mm. dorsi) is functionally and topographically divided into two major categories separated by fascia:
Superficial muscles. These lie superficial to the fascial layer. Their biomechanical role involves moving and stabilizing the upper limb.
Deep muscles. These are the true back muscles. They lie deep to the fascia and are responsible for posture and all movements of the vertebral column itself.
Mnemonic
To easily remember the projection of the scapula, recall the numbers 2 and 7: Superior angle — 2nd rib, Inferior angle — 7th rib.
Frequently asked questions
Which specific muscles comprise the superficial back muscle group?
The superficial back muscles lie superficial to the fascia and move the upper extremity. They include:
Semispinalis muscle — participates in extension, rotation, and stabilization.
Multifidus muscles (mm. multifidi) — deep muscles innervated by medial branches.
Rotator muscles (mm. rotatores) — the deepest back muscles (long and short) that rotate vertebrae and contribute to proprioception.
What is the name of the fascia that separates the superficial and deep back muscles?
The fascia separating these muscle groups is called the thoracolumbar fascia (fascia thoracolumbalis). Superficial muscles lie superficial to this fascia, whereas the deep (true) back muscles lie deep to it. The thoracolumbar fascia is a dense connective tissue fibrous sheet enclosing the deep back muscles. It divides into posterior (superficial) and anterior (deep) layers, forming a fibrous sheath for the deep muscles in the lumbar region.
What bony landmarks determine the boundaries of the scapular region?
The key landmarks are the angles of the scapula: the superior angle lies at the level of the 2nd rib, and the inferior angle projects at the level of the 7th rib.
What delineates the lumbar region superiorly and inferiorly?
The superior boundary of the lumbar region follows the line of the 12th rib, while the inferior boundary is marked by the iliac crest.
How do deep back muscles fundamentally differ from superficial ones?
Deep (true) muscles lie beneath the fascia and move the vertebral column. Superficial muscles lie superficial to the fascia and act primarily on the upper limb.
Go deeper
Anatomy and functions of superficial back muscles
Deep (true) back muscles: topography and biomechanics