All About Bone
What is bone?
Bone is living tissue that makes up the body's skeleton. There are three types
of bone tissue:
- compact tissue - the harder, outer tissue of bones
- cancellous tissue - the sponge-like tissue inside bones
- subchondral tissue - the smooth tissue at the ends of bones, which
is covered with another type of tissue called cartilage
Together, compact and cancellous tissues are called the periosteum. Beneath
the hard outer shell of the periosteum blood and lymphatic vessels run through
tunnels and canals to carry nourishment to the bone. Muscles, ligaments, and
tendons may attach to the periosteum.
Bones are classified by their shape as long, short, flat, and irregular --
primarily, they are referred to as long or short.
There are 206 bones in the human skeleton, not including teeth and sesamoid
bones (small bones found within cartilage):
- 80 axial bones, which include the head, facial, hyoid, auditory,
trunk, ribs, and sternum.
- 126 appendicular bones, which include arms, shoulders, wrists, hands,
legs, hips, ankles, and feet.
What are the functions of bone?
Bone provides shape and support for the body, as well as protection for some
organs. Bone also serves as a storage site for minerals and provides the medium
-- marrow -- for the development and storage of blood cells.
What are the different types of bone cells?
Types of bone cells include:
- osteoblast - found within the bone, its function is to form the tissue
and minerals that give bone its strength.
- osteoclast - a very large cell formed in bone marrow, its function
is to absorb and remove unwanted tissue.
- osteocyte - found within the bone, its function is to help maintain
bone as living tissue.
Fat cells and hematopoietic cells are found within the bone marrow. Hematopoietic
cells produce blood cells.
Because of the complexities of a bone's function -- from providing strength
and support for the body, to serving as a site for development and storage of
blood cells -- Many disorders and diseases can affect bone.
|
