Editing Anatomy and Physiology (section)

== Skeletal System ==

The adult skeleton has 206 bones divided into the '''axial skeleton''' (skull, vertebral column, ribs, sternum) and the '''appendicular skeleton''' (limbs, shoulder girdle, pelvic girdle).

Functions: support, protection of organs, movement through leverage with muscles, mineral storage (about 99% of body calcium is in bone), and '''hematopoiesis''' in red bone marrow.

Bone is dynamic tissue. '''Osteoblasts''' build bone, '''osteoclasts''' resorb it, and '''osteocytes''' maintain it. Remodeling is driven by mechanical stress, parathyroid hormone, calcitonin, vitamin D, and sex hormones.

Joint types include synovial (freely movable, such as the knee and shoulder), cartilaginous (slightly movable, such as intervertebral discs), and fibrous (immovable, such as skull sutures).

'''Nursing application:'''
* Immobility causes bone resorption to outpace formation, releasing calcium into the blood. Expect disuse osteoporosis, hypercalcemia, and renal calculi in immobilized patients. Weight bearing and mobilization are therapeutic, not merely comfort measures.
* Estrogen restrains osteoclast activity, so postmenopausal women lose bone rapidly. This drives fall precautions and calcium and vitamin D teaching.
* Long bones and the pelvis contain marrow, so fractures there cause substantial blood loss and carry a risk of fat embolism, which classically presents with respiratory distress, confusion, and petechiae.
* Compartment syndrome is a pressure problem inside a fascial compartment. The earliest and most reliable sign is pain out of proportion to the injury and pain on passive stretch. Pulselessness is a very late finding. Report suspected compartment syndrome immediately and do not elevate the limb above heart level or apply ice.