The average human body contains 206 major
bones. At birth this number is greater but many fuse together as you approach adulthood.
These major bones can be divided in to six broad categories…

Long bones are relatively long and slender and are located in the arm and forearm, thigh and leg, palms, soles, fingers, and toes.
The femur (a long bone of the leg) is the largest and heaviest bone in the body.

Flat bones have thin, roughly parallel surfaces. They form the roof of the skull, the sternum, the ribs, and the scapula
(shoulder blade). They provide protection from underlying soft tissues and offer an extensive surface area for the attachment of skeletal muscles.

These are small, flat, irregularly shaped bones between flat bones of the skull. There are individual variations in the number, shape, and position of the sutural bones. Their borders are like pieces of a puzzle, and they range in size from a grain of sand to a quarter.

Irregular bones have complex shapes with short, flat, notched, or ridged surfaces.
The spinal vertebrae, the bones of the pelvis, and several skull bones are irregular bones.

Short bones are small and boxy.
Examples of short bones include the carpal bones (wrists) and tarsal bones (ankles). Short bones usually have relatively equal dimensions.
(length x width x height)

These bones are generally small, flat, and shaped somewhat like a sesame seed.
They develop inside tendons and are most commonly located near joints at the knees, the hands, and the feet.
Individuals typically vary in the location and abundance of sesamoid bones other than the patellae or kneecap. This variation accounts for disparities in the total number of bones in the skeleton.

1. Support
The skeletal system provides structural support for the entire body.
2. Storage of Minerals & Lipids
What kinds?
3. Blood Cell Production
Red blood cells, white blood cells, and other blood elements are produced in red marrow, which fills the internal cavities of many bones.

1. Protection
Many soft tissues and organs are surrounded by skeletal elements.
2. Leverage
Many bones are able to change the magnitude and direction of the forces generated by skeletal muscles.

Diaphysis is the extended tubular shaft.
Epiphysis is found at the end of the diaphysis.
The diaphysis is connected to each epiphysis at a narrow zone known as the metaphysis.
The wall of the diaphysis consists of a layer of compact bone, or dense bone. This forms a sturdy protective layer that surrounds a central space called the marrow cavity.

1. The matrix of the bone is very dense and contains deposits of calcium salts.
2. The matrix contains bone cells, or osteocytes.
3. Canaliculi are narrow passages through the matrix that form a branching network for the exchange of nutrients, waste products, and gases.

The calcium salts form calcium phosphate crystals within the bone. These are very hard, but relatively inflexible and quite brittle. They can withstand compression, but are likely to shatter when exposed to bending, twisting, or sudden impacts.
Also found in the matrix are collagen fibers. By contrast, these are very strong when subjected to tension or pull. They can easily tolerate twisting and bending, but offer little resistance to compression.

1. Mature bone cells that account for most of the cell population.
1. Produce new bone matrix in a process called osteogenesis.
1. Remove and recycle bone matrix
2. They maintain the protein 2. They make and release and mineral content of the the proteins and other surrounding matrix.
organic components of the matrix.
3. Osteocytes participate in 3. Bones contains a small the repair of damaged number of Osteoprogenitor dissolve the matrix
3. This releases the stored minerals and bone.
Cells that divide to produce osteoblasts. They is called osteolysis. are important in bone repair.
2. Acids and proteindigesting enzymes secreted by osteoclasts

1. The bones (the arrow is pointing to) of your fingers are:


A. Storage of Mineral and Lipids
B. Blood Cell Production
C. Temperature Regulation
D. Protection



A. Make and release the proteins
B.
Remove and recycle bone matrix
C.
Participate in the repair of damaged bone.
D. Undergo osteogenesis.