CONCEPTUAL LIFE SCIENCE
SKELETAL SYSTEM
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 of the
invertebrate animals like starfish, insects, spiders and lobsters.
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.
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. Spongy bone has spaces in the bone tissue structure. This
gives it the appearance of a sponge. Compact bone does not have any spaces.
THE HUMAN SKELETON
Axial skeleton
The axial skeleton consists of the skull and the spinal column. It includes the
vertebrae, ribs and pelvic bones.
Appendicular 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.
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