The Skeleton

The skeleton or skeletal system is the biological system providing support in living organisms. An internal skeletal system consists of rigid structures within the body, moved by the muscular system. If the structures are mineralized or ossified, as they are in humans and other mammals, they are referred to as bones. Cartilage is another common component of skeletal systems, supporting and supplementing the skeleton. The human ear and nose are shaped by cartilage.

The human skeleton is made of bones, some of them joined together, supported and supplemented by a structure of ligaments, tendons, muscles, and cartilage.

The skeleton changes composition over a lifespan. Early in gestation, a fetus has no hard skeleton - bones form gradually during nine months in the womb. When a baby is born it has more bones than it will as an adult. On average, an adult human has 206 bones in their skeleton (the number can vary slightly from individual to individual), but a baby is born with approximately 270. The difference comes from a number of small bones that fuse together during growth. These include the bones in the skull and the spine. The sacrum (the bone at the base of the spine) consists of six bones which are separated at birth but fuse together into a solid structure in later years.

There are 6 bones (three on each side) in the middle ear that articulate only with themselves, and one bone, the hyoid bone, which does not touch any other bones in the body.

The longest bone in the body is the femur and the smallest is the stapes bone in the middle ear.

Function

The skeleton functions not only as the support for the body but also in haematopoiesis, the manufacture of blood cells that takes place in bone marrow. It is also necessary for protection of vital organs and is needed by the muscles for movement.

Gender differences

There are small differences between the male and female human skeletons. Men tend to have slightly thicker and longer limb bones while women tend to have larger pelvic bones in relation to body size.

Organization

One way to group the bones of the human skeleton is to divide them into two groups, namely the axial skeleton and the appendicular skeleton. The axial skeleton consists of bones in the midline and includes all the bones of the head and neck, the vertebrae, ribs and sternum. The appendicular skeleton consists of the clavicles, scapulae, bones of the upper limb, bones of the pelvis and bones of the lower limb.

The bones of the human skeleton are structurally and in many taxonomies organized as those of the:
· skull

· middle ear

· throat

· shoulder girdle

· thorax

· vertebra

· arms

· hands

· pelvis

· legs

· feet

Diseases

The skeleton can be affected by many diseases that compromise physical mobility and strength. Skeletal diseases range from minor to extremely debilitating. Bone cancer and bone tumors are extremely serious and are sometimes treated by radical surgery such as amputation of the affected limb. Various forms of arthritis attack the skeleton resulting in severe pain and debility. Osteoporosis can increase the likelihood of fractures and broken bones, especially among post-menopausal women and the elderly.

The Skeleton Inside You (Let's-Read-and-Find-Out Science 2) Author: Philip Balestrino Description Your skeleton helps you leap, somersault, and touch your toes -- without it, you would be as floppy as a beanbag! There are over 200 bones living and growing inside you that make up your skeleton. There are also ligaments and joints that hold your bones together, and cartilage in your bendable parts like your ears and your nose...

The Anatomy and Biology of the Human Skeleton Author: D. Gentry Steele

Inside Your Outside: All About the Human Body (Cat in the Hat's Learning Library) Author: Tish Rabe Description The Cat in the Hat takes Sally and Dick for a ride through the human body where they visit the right and left sides of the brain, meet the Feletons from far off Fadin (when they stand in the sun you can see through their skin), scuba dive through the blood system, follow food and water through the digestive tract, and a whole lot more!

Scholastic Reader Level 2: Skeletons Author: Lily Wood Description It's easy to bone up on Skeletons with the relaunch of thIs Scholastic Science Reader--now with a new cover, photographs, and interior design.With brand new covers, updated photographs, and new interior designs, this series brings simple and fun information to beginning readers...

The Human Bone Manual Author: Tim D. White Description Building on the success of their previous book, White and Folkens' The Human Bone Manual is intended for use outisde the laboratory and classroom, by professional forensic scientists, anthropologists and researchers...

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