Skeletal System: Facts, Function & Diseases
The adult human skeletal system consists of 206 bones, as well as a network of tendons, ligaments and cartilage that connects them. The skeletal system performs vital functions — support, movement, protection, blood cell production, calcium storage and endocrine regulation — that enable us to move through our daily lives.
Animals with internal skeletons made of bone, called vertebrates, are actually the minority, as 98 percent of all animals are invertebrates, meaning they do not have internal skeletons or backbones. Human infants are born with 300 to 350 bones, some of which fuse together as the body develops. By the time most children reach the age of 9 they have 206 bones.
The skeletons of adult males and females have some variation, primarily to accommodate childbirth. The female pelvis is flatter, more rounded and proportionally larger. A male's pelvis is about 90 degrees or less of angle, whereas a female's is 100 degrees or more.
While they become brittle when outside of the body, bones are very much alive inside the body, being fed by a network of blood vessels from the circulatory system and nerves from the nervous system.
A typical bone has a dense and tough outer layer. Next is a layer of spongy bone, which lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for blood.
Teeth are considered part of the skeletal system but they are not counted as bones. Teeth are made of dentin and enamel, which is strongest substance in your body. Teeth also play a key role in the digestive system.
The skeletal system has two distinctive parts: the axial skeleton and the appendicular skeleton.
The axial skeleton, with a total of 80 bones, consists of the vertebral column, the rib cage and the skull. The axial skeleton transmits the weight from the head, the trunk and the upper extremities down to the lower extremities at the hip joints, which help humans maintain our upright posture.
The appendicular skeleton has a total of 126 bones, and is formed by the pectoral girdles, the upper limbs, the pelvic girdle and the lower limbs. Their functions are to make walking, running and other movement possible and to protect the major organs responsible for digestion, excretion and reproduction.
Diseases of the skeletal system
X-rays, MRIs, bone density tests and arthroscopy are some of the primary diagnostic tools used to detect diseases and deformities of the skeletal system. Bone scans and bone marrow biopsies are used to diagnose cancer.
Osteoporosis is a prevalent disease of the skeletal system, particularly among the elderly, resulting in the loss of bone tissue. In osteoporosis, bone loses calcium, becomes thinner, and may disappear completely.
Also common is scoliosis, a side-to-side curve in the back or spine, often creating a pronounced "C" or "S" shape when viewed on an x-ray of the spine. This condition is typically becomes evident during adolescence.
Arthritis is a group of more than 100 inflammatory diseases that damage joints and their surrounding structures. Arthritis can attack joints, joint capsules, the surrounding tissue, or throughout the body. It usually affects the joints of the neck, shoulders, hands, lower back, hips, or knees.
While leukemia is a cancer that primarily affects the blood, the skeletal system is involved as the cancer starts in the marrow of the bone. With this type of cancer, abnormal white blood cells multiply uncontrollably, affecting the production of normal white blood cells and red blood cells.
Bone cancer is another disease of the skeletal system. It may originate in the bones or spread there from another part of the body. In the United States, bone cancer accounts for only about 1 percent of cancer cases.
Bursitis is a disorder that causes pain in the body's joints. It most commonly affects the shoulder and hip joints. It is caused by an inflammation of the bursa, small fluid-filled bags that act as lubricating surfaces for muscles to move over bones.
Rickets, the result of insufficient amounts of vitamin D, calcium and phosphorous, can result in poor bone development in children.
The skeletal system is also susceptible to breaks, strains and fractures. While bones are meant to protect the body’s vital organs, it takes about 10 to 16 pounds of pressure to break an average bone. Bones such as the skull and femur are much tougher to break.
Study of the skeletal system
Orthopedics is the medical specialty responsible for treating entire skeletal system. In the United States, orthopedic surgeons have typically completed four years of undergraduate education and four years of medical school. They then undergo residency training in orthopedic surgery. The American Board of Orthopaedic Surgery oversees the certification process for this specialty. Many go on to further specialize in specific areas, such as the spine, hand or sports injuries.
Humans have been dealing with injuries and disease from the beginning of time. Some important milestones in the history of orthopedics include:
- Hippocrates, the ancient Greek father of medicine, develops splints for fractures of the tibia.
- During the Roman era, Galen (129-199 BC) describes the skeletal system and the surrounding muscles. Medical experts of the time also develop the first artificial prostheses.
- Ambroise Pare (1510-1590), the father of French surgery, develops techniques for amputations and artificial limbs.
- Antonius Mathysen (1805-1878), a Dutch military surgeon, in 1851 invents the plaster of Paris (POP) bandage. A POP cast remains the primary method of fracture immobilization today.
- In 1895, Wilhelm Conrad Roentgen accidentally discovers an image cast from his cathode ray generator, projected far beyond the possible range of the cathode rays. He wins the Nobel Prize for Physics in 1901 for his discovery of x-rays.
- Sir Reginald Watson-Jones (1902-1972) publishes “Fractures and Joint Injuries” in 1940, which remains a standard reference for several decades.
- In 1949, H. Lowry Rush (1879-1965) uses stainless steel pins to treat long bone fractures.
Facts, Functions & Diseases:
- Circulatory System
- Digestive System
- Endocrine System
- Immune System
- Integumentary System (Skin)
- Lymphatic System
- Muscular System
- Nervous System
- Reproductive System
- Respiratory System
- Urinary System
MORE FROM LiveScience.com