SUPPORT AND MOVEMENT

       SUPPORT AND MOVEMENT

In this chapter, we study human skeleton system (skeleton) which is primarily responsible for support and movement.
Human Skeleton
Skeleton system or skeleton is defined as the framework of hard, articulated structures that provide physical support, attachment for skeleton muscles, and protection for the bodies of animals.
Skeleton are of two types which are following:
1. Endoskeleton
2. Exoskeleton
Endoskeleton:
                     Like other vertebrates, the human skeleton is on the inside of body and is called endoskeleton.
Exoskeleton:
                    The skeleton system of some invertebrates e.g. arthropods, is on the outside of body, and is called exoskeleton.
Role of Skeleton System:
                                      The big function of skeleton system is protection, support and movements. In our body, skeleton work very closely with the muscular system to help us move. Similarly, skeleton provides protection to many internal organs e.g. skull protects brain, vertebral column protects spinal cord and ribs protects most of other internal organs. Vertebral column also provides the main support to our body mass.
Bone and Cartilage:
                              Overall, the human skeleton is made of bony framework but in certain parts, this framework is supplemented by cartilage.
a. Cartilage:
                        Cartilage is dense, clear blue-white firm connective tissue. The cells of cartilage are called chondrocytes. Each chondrocyte lies in a fluid space called lacuna present in the matrix of cartilage. The matrix of cartilage contains also collagen fibers.
Blood vessels do not enter cartilage. There are three types of cartilage.
Hyaline Cartilage is strong yet flexible. It is found covering the ends of the long bones, in the nose, larynx, trachea and bronchial tubes.
Elastic Cartilage is similar in structure to hyaline cartilage. It is also quite strong but has elasticity due to a network of elastic fibers in addition to collagen fibers. It is found in epiglottis, pinna etc.
Fibrous Cartilage is very tough and less flexible due to large number of thick collagen fibers present in knitted form. It is found in intervertebral discs.
b. Bone:
                  Bone is the hardest connective tissue in body. Bone not only moves, support and protect the various parts of body but also produce red and white blood cells and store minerals. The hard outer layer of bone is called compact bone.
While the interior of bone is soft and porous. It is called spongy bone. Spongy bone consists of blood vessel and marrow.
The mature bone cells are called osteocytes.