What Makes Up My Back?
The human back is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck and the shoulders. It is the surface opposite to the chest; its height is defined by the vertebral column (commonly referred to as the spine or backbone) and its breadth is supported by the ribcage and shoulders. The spinal canal runs through the spine and provides nerves to the rest of the body.
Skeletal Structure of the Back
The central feature of the human back is the vertebral column, specifically the length from the top of the thoracic vertebrae to the bottom of the lumbar vertebrae, which houses the spinal cord in its spinal canal, and which generally has some curvature that gives shape to the back. The ribcage extends from the spine at the top of the back (with the top of the ribcage corresponding to the T1 vertebra), more than halfway down the length of the back, leaving an area with less protection between the bottom of the ribcage and hips. The width of the back at the top is defined by the scapula, the broad, flat bones of the shoulders.
The Function of the Back
The intricate anatomy of the back provides support for the head and trunk of the body, strength in the trunk of the body, as well as a great deal of flexibility and movement. The upper back has the most structural support, with the ribs attached firmly to each level of the thoracic spine and very limited movement.
Muscles of the Neck and Upper Back
The two sternocleidomastoid muscles (SCMs) are superficial, strap-like muscles located in the front of the neck (one on each side). Each SCM originates at the base of the neck on the sternum (breastbone) and clavicle (collarbone) and inserts behind the ear on the mastoid process of the skull. When one SCM acts alone, it bends the neck to that side, at the same time rotating the head toward the opposite side. When both act together, they flex the neck while extending the head.
Underneath the SCMs, in the front of the neck, is a group of strap-like muscles that produce movements of the tongue during swallowing.
There are two main groups of back muscles, deep and superficial. The deep muscles are responsible for movements of the spine and for maintaining posture. The superficial muscles are responsible for movements of the scapulae (shoulder blades) and shoulders.
The deep muscles (sometimes referred to collectively as paraspinal muscles) form a thick mass on each side of the spine, extending from the base of the skull to the sacrum. This muscle mass consists of many separate, overlapping muscles of different lengths, attached to the spinous or transverse processes of different vertebrae. Each individual muscle can be thought of as a string. Pulling a string (contracting a muscle) causes one or more vertebrae to tilt or turn on the vertebra below. Working in coordination, these muscles extend (backward bend) and rotate the spine. Flexion or forward bending is accomplished by the muscles of the abdomen. The deep muscles of the back also maintain posture by holding the spine erect against gravity.
Overlying the deep muscles of the back are the superficial muscles. In the upper back, the most superficial of these is the trapezius, a large flat muscle that extends like a cape over the upper back and the back of the neck. Underneath the trapezius are the levator scapulae and rhomboid muscles. Each of these muscles has its origin (attachment of one end) on the cervical and /or thoracic spine and its insertion (attachment of the other end) on the scapula. Acting together in various combinations, these muscles produce movements of the scapulae (e.g., shrugging the shoulders, bracing the shoulders back).
The deep muscles of the neck are a continuation of the deep muscles of the back. They consist of separate, overlapping muscles of different lengths, connecting the cervical vertebrae to each other and to the base of the skull. Attached to the spinous or transverse processes, these muscles extend (backward bend), side bend, and rotate the head and neck. Another group of muscles connects the front of the cervical vertebrae to each other and the base of the skull; these muscles flex (forward bend) the head and neck.
The scalene muscles are located on the sides of the neck. There are three scalenes on each side: scalenus anterior, medius, and posterior. These muscles originate in the transverse processes of the cervical vertebrae and are inserted in the first and second ribs. When the scalenes of one side act alone, they bend and rotate the neck to that side. When both sides act together, they flex the neck slightly.
As mentioned above, the trapezius is a large, flat, superficial muscle that covers the back of the neck and extends like a cape onto the upper back. It originates on the base of the skull and the spine, down to T12; it inserts on the scapulae. The trapezius acts with other muscles to produce scapular movements (shrugging, bracing the shoulders back). However, if the scapula is kept immobile, the trapezius produces movements of the head. Contraction of one side of the trapezius tilts the head to that side; contraction of both sides together tilts the head backward.
Summary
By learning more about the anatomy of our backs, we can better understand how to prevent and treat symptoms associated with it. When back pain is present, whatever is required depends on the area affected and the symptoms present, and that is why it is important to have a team of doctors that is able to identify the root cause.
At BBC Health in Lewisville, Texas, we know how to identify, treat, or refer in the proper direction for any problems with your back and neck. As a primary care provider, we can quickly provide medical, chiropractic, and rehab treatments in order to get you well as fast as possible. If you’re suffering from foot pain, don’t delay, and contact us immediately to see how we can help.
