Visibly Human Health and Disease in the Human Body

The Musculoskeletal System

Bones, muscles, ligaments, tendons and cartilage comprise the musculoskeletal system. Together, these tissues perform several important tasks that include support, movement, protection and storage.

Bone

Bone is a living and dynamic tissue. It is composed of an organic phase that gives bone flexibility, while its inorganic phase gives bone its rigidity. After dental enamel, bone is the second hardest tissue in the body. The adult human skeleton consists of 206 bones that provide support of soft tissue and organs, and acts as a protective armor for the vital internal organs. Bones are the main storehouse of minerals in the body, particularly calcium and phosphorus. The soft fatty tissue (marrow) within them produces red blood cells and stores fat.

Muscle

Muscle of the human body comes in three forms: skeletal, smooth and cardiac. Skeletal muscles account for the majority of muscle mass in the body, and are composed of specialized cells called myofibers that contain myosin and actin proteins that work in tandem to contract and relax, thereby creating movement. Muscles are responsible for all movement, from the blink of an eye to feats of endurance such as running an Olympic marathon. There are more than 600 muscles in the body, which together make up 35 to 45 percent of the body’s weight.

Cartilage, Ligaments and Tendons

Chondrocytes (a mature cartilage cell) form three different types of cartilage within the human body: elastic, hyaline, and fibrous. All cartilage is flexible and spongy, and is composed of various concentrations of collagen proteins, elastin and proteoglycins. Hyaline cartilage lines the surface of joints and along with synovial fluid acts as a shock absorber, allowing smooth and fluid movement of the joints. Among other places, fibrous and elastic cartilage can be found in the ears and the tip of the nose.

Ligaments are dense fibrous bands of cartilaginous tissue that hold bones together at various joint surfaces. Ligaments not only increase the stability of joints, but also permit greater flexibility for biomechanical activity, such as throwing a baseball or kicking a soccer ball.

Tendons are strong flexible straps of connective tissue that are similar to ligaments in that they are composed primarily of collagen fibrils. Tendons however, attach muscle to bone and serve as pulley to permit proper muscle flexion, extension, abduction, adduction and rotation.

Lateral view of dissected head and neck . This dissection highlights the muscles of the head and neck. The sternocleidomastoid rotates and flexes the head. It is the long strip of muscle obliquely oriented along the neck. The temporalis, masseter, and the orbicularis oris are important muscles of mastication. The temporalis is the flat wide muscle on the side of the head. The masseter is the thick muscle of the mandible and the orbicularis oris surrounds the mouth. AFIP 502981

Human skull This skull was prepared using the Beauchene method of anatomical preparation. Named after the 18th century French doctor, the technique separates the bones at their joint surfaces so they can be viewed in anatomical relation to one another. This skull shows the 22 bones separated and held in anatomical position. Not shown are the six ear ossicles (three per side). MM4256

Hands The hand has many ligaments, muscles, and tendons that allow for a wide range of motion. The three dissected hands on display show deep muscle tissue (left), superficial muscles of the palmar surface (middle), and innervation of the hand by the ulnar, median, and palmar nerves (right). AFIP 30979

Wax model of head mounted on a book M-550-10713