S KELETAL S YSTEM

S KELETAL S YSTEM Skeletal system consists of a framework of bones and a few cartilages. This system has a significant role in movement shown by the body. Imagine chewing food without jaw bones and walking around without the limb bones. Bone and cartilage are specialised connective tissues. The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts. In human beings, this system is made up of bones and a few cartilages. It is grouped into two principal divisions – the axial and the appendicular skeleton. Axial skeleton comprises bones distributed along the main axis of the body. The skull, vertebral column, sternum and ribs constitute axial skeleton. The skull (Figure . ) is composed of two sets of bones – cranial and facial, that totals to bones. Cranial bones are in number. They form the hard protective outer covering, cranium for the brain. The facial region is made up of skeletal elements which form the front part of the skull. A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull. Each middle ear contains three tiny bones – Malleus, Incus and Stapes, collectively called Ear Ossicles . The skull region articulates with the superior region of the Parietal bone Frontal bone Temporal bone Occipital bone Occipital condyle Sphenoid bone Ethmoid bone Lacrimal bone Nasal bone Zygomatic bone Maxilla Mandible Hyoid bone Figure . Diagrammatic view of human skull vertebral column with the help of two occipital condyles (dicondylic skull). Our vertebral column (Figure . ) is formed by serially arranged units called vertebrae and is dorsally placed. It extends from the base of the skull and constitutes the main framework of the trunk. Each vertebra has a central hollow portion (neural canal) through which the spinal cord passes. First vertebra is the atlas and it articulates with the occipital condyles. The vertebral column is differentiated into cervical ( ), thoracic ( ), lumbar ( ), sacral ( -fused) and coccygeal ( -fused)