The musculoskeletal system consists of bones, joints, ligaments, muscles, and tendons. The skeleton gives shape to the body, provides physical support and protection for the organs, stores minerals, is responsible for blood cell formation, and provides sites for muscle attachment. The action of muscles holds the skeleton upright and creates physical movement of the body. First figure depicts the bones of the skeleton. Next figures illustrate the major muscles of the body. Any disease or disorder of this system greatly affects activities of daily living.


FIGURE. Skeleton (anterior view)

The skeletal system consists of bones formed from osseous tissue that provide structure and function to the overall body. Also included in the skeletal system is the cartilage that forms the joints between bones and the ligaments that hold bones together at the joints. Bones can be subdivided into long bones (arms, legs, hands, and feet), short bones (wrist, ankles, and knee caps), flat bones (ribs, sternum, shoulder blades, hip bones, and cranial bones), and irregular bones (vertebrae and facial bones).

Anterior view of muscles

FIGURE. Anterior view of muscles

The adult skeletal system has two divisions: the axial skeletal system and the appendicular skeletal system. The axial skeleton is the center portion of the body and includes the bones of the skull, hyoid bone, bones of the middle ear, vertebral column, and rib cage. The appendicular skeleton is composed of the bones of the appendages or limbs and includes the bones of the arms and legs, the shoulders, and the pelvic girdle.

Posterior view of muscles

FIGURE. Posterior view of muscles

There are two types of bone: compact and spongy. Compact bone is the dense, hard tissue found in the shafts of long bones. Yellow marrow, which is composed of fat, is stored in these bones. Spongy bone, or cancellous bone, is less dense and is found at the ends of long bones and in the other bones of the body.

The muscular system holds the body upright and moves the skeletal system. Muscles have specialized cells for contraction wherein they shorten and pull a bone to produce movement. Muscle movement creates heat that helps to regulate body temperature.

There are three types of muscles:

  1. Skeletal muscle is also called voluntary muscle because it is attached to the skeleton and its movement is consciously controlled. The cells of this type of muscle are elongated and have the ability to stretch and return to their previous shape.
  2. Smooth muscle is also called involuntary or visceral muscle because it is found in the walls of organs and its function is not consciously controlled. This type of muscle has shorter cells with tapered ends and cannot stretch as much as skeletal muscle.
  3. Cardiac muscle is found only in the heart. This muscle is a combination of skeletal and smooth muscle. It is involuntarily controlled but has the ability to contract.