Definition of Axial and Appendicular Skeleton
The axial skeleton (shown in red above) forms the central axis of the body. It consists of the skull, the
vertebral column, the ribs and the sternum or breastbone. The axial skeleton contains 80 bones and
is fused
The appendicular skeleton (shown above in blue) is composed of 126 bones in the human body. The
word appendicular is the adjective of the noun appendage, which itself means a part that is joined to
something larger. Functionally it is involved in locomotion (lower limbs) of the axial skeleton and
manipulation of objects in the environment (upper limbs). The appendicular skeleton is unfused.
Functions of the Skeletal System

Protection – The skeleton protects vital organs from damage by encasing them within hard
bones. The cranium encases the brain, while the vertebral, or spinal, column protects the
delicate spinal nerves, which control all bodily functions by allowing all body parts to
communicate with the brain. The bony thorax, comprised of the ribs and sternum, provides
protection to the heart and lungs.

Shape- The structure of the bones give the underlying shape to the body. Shape develops
over the growth of an individual and the skeletal system will determine if they are tall or
short, wide or narrow and other factors, such as the size of hands and feet.

Support - The skeleton provides support to the body and holds internal organs in their place.
The vertebral column allows for standing erect while cavities, or hollow spaces, of the
skeleton are designed to hold organs within them. For example, the skull holds the brai, the
chest cavity holds the lungs and the heart while the abdominal cavity holds gastrointestinal
organs. Additionally the lower appendages, or feet, are strong and thick to support the
weight of the entire skeleton, while the foot possesses an arch to enable this kind of
support.

Movement - The skeletal bones attach to each other by ligaments and further attach to
muscles by tendons. The muscular and skeletal system work together to carry out bodily
movement, and thus are jointly called the musculoskeletal system. When muscles contract,
bones are pulled along to produce a movement allowing people to walk or run. The shape of
the skeletal system also has a role in movement. The many small bones of the foot allow for
adaptation to all sorts of terrain, while the small bones in the hands allow for precise and
detailed movement.

Blood cell production and mineral storage - The spongy tissue inside long bones, such as the
femur, or thigh bone, have two types of marrow responsible for blood cell production. On
average, 2.6 million red blood cells are produced each second by the bone marrow. Red
bone marrow gives rise to blood cells while yellow bone marrow stores fat, which turns into
red bone marrow in case of severe red blood cell depletion or anemia. Skeletal bones also
function as a storage "bank" for minerals, such as calcium and phosphorus. These minerals
are necessary for vital body functions, such as nerve transmission and metabolism.