The upper-middle back is also the one area of the body which a typical human under normal conditions might be unable to physically touch. The skin of the back is innervated by the dorsal cutaneous branches, as well as the lateral abdominal cutaneous branches of intercostal nerves. Movement
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. The lower back (lumbar vertebrae) allows for flexibility and movement in back bending (extension) and forward bending (flexion). It does not permit twisting. Clinical significance
Back pain
The back comprises interconnecting nerves, bones, muscles, ligaments, and tendons, all of which can be a source of pain. Back pain is the second most common type of pain in adults (the most common being headaches). By far the most common cause of back pain is muscle strain. The back muscles can usually heal themselves within a couple of weeks, but the pain can be intense and debilitating. Other common sources of back pain include disc problems, such as degenerative disc disease or a lumbar disc herniation, many types of fractures, such as spondylolisthesis or an osteoporotic fracture, or osteoarthritis.
It is composed of trapezius, latissimus dorsi, rhomboid major, rhomboid minor and levator scapulae. It is innervated by anterior rami of spinal nerves, reflecting its embryological origin outside the back. Intermediate group
The intermediate group is also known as respiratory group as it may serve a respiratory function. It is composed of serratus posterior superior and serratus posterior inferior. Like the superficial group, it is innervated by anterior rami of spinal nerves. Deep group
The deep group, also known as the intrinsic group due to its embryological origin in the back, can be further subdivided into four groups:

Spinotransversales - composed of splenius capitis and splenius cervicis. Erector spinae - composed of iliocostalis, longissismus and spinalis
Transversospinales - composed of semispinalis, multifidus and rotatores
Segmental muscles - composed of levatores costarum, interspinales and intertransversariiThe deep group is innervated by the posterior rami of spinal nerves. Organs near the back
The lungs are within the ribcage, and extend to the back of the ribcage making it possible for them to be listened into through the back. The kidneys are situated beneath the muscles in the area below the end of the ribcage, loosely connected to the peritoneum. A strike to the lower back can damage the kidneys of the person being hit. Surface of the back
The skin of the human back is thicker and has fewer nerve endings than the skin on any other part of the torso. With some notable exceptions (see, e.g. George "The Animal" Steele), it tends to have less hair than the chest on men.