1. Principles of Biology By Frank H. Osborne, Ph. D. Skeletal System

2. Types of Skeletons Exoskeleton The exoskeleton (exo- refers to the exterior of the animal) is a type of skeleton that is found on the outside of the body. This type of skeleton is common in many invertebrate animals like starfish, insects, spiders and lobsters.

3. Types of Skeletons Endoskeleton The endoskeleton (endo- refers to the interior of the animal) consists of internal bones that have muscles attached to them. It is found in the vertebrate animals like fishes, amphibians, reptiles, birds and mammals ( including humans ).

4. Bone Structure Bone consists of bone cells surrounded by a matrix of calcium phosphate. The bone tissue is hard and impervious. So the blood supply for the bone cells is located in the Haversian canal system.

6. Bone Structure Spongy bone has spaces in the bone tissue structure This gives it the appearance of a sponge. Compact bone does not have any spaces.

7. The Human Skeleton The axial skeleton consists of the skull and spinal column. It includes the vertebrae, ribs and pelvic bones.

8. The Human Skeleton The appendicular skeleton consists of the appendages that are attached to the axial skeleton. These appendages are the arms and the legs. Bones are connected to each other by ligaments, which are structures made of dense connective tissue

10. The Human Skeleton Spina bifida is a condition in which the spinal column does not connect completely. This condition confines the individual to a life in wheelchairs.

11. The End Principles of Biology Skeletal System