Biology XI: 20 Locomotion & Movement(3 Skeletal System)

Skeletal System Skeletal System Bony framework of our body Helps in locomotion and maintaining erect posture; provides protection to internal soft organs Skeletal system = 206 bones + A few cartilages Bones are connective tissues, which are hard due to calcium salts Cartilages are connective tissues. They have a pliable matrix due to chondroitin salts. Major divisions of the skeletal system Axial Skeleton (80 bones) Skull − 22 bones Has two sets of bones − Cranial (8) and Facial (14) Skull also includes a U-shaped bone called hyoid, present at the base of the buccal cavity Ear Bones (ear ossicles) − Malleus, Incus, Stapes Skull articulates with the vertebral column via two occipital condyles. Vertebral Column − 26 vertebra Each vertebra has a central hollow portion through which the spinal cord passes. This hollow portion is called the neural canal. Functions: Protects the spinal cord; supports the head; serves as the point of attachment of the ribs and the musculature of the back First vertebra: Atlas − it articulates with the occipital condyles Formula for vertebral column in man is C7 T12 L5 S 1 Co1 Sternum − 1 Flat bone on the ventral midline of the thorax, to which the ribs are attached ventrally Ribs − 12 pairs Connects dorsally to the vertebral columnConnects ventrally to the sternum True Ribs: First 7 pairs; they connect both dorsally and ventrally to the vertebrae and the sternum respectively via the hyaline cartilage False (vertebrochondral) Ribs: 8th, 9th and 10th pairs; do not connect to the sternum directly, but connect indirectly through the seventh rib Floating Ribs: 11th and 12th pairs; do not connect ventrally Rib cage = Thoracic vertebra + Ribs + Sternum Appendicular Skeleton Limbs (each limb has 30 bones)  Knee cap − Patella Girdles (Pectoral and Pelvic)    Articulates the limbs with the axial skeleton Each girdle is composed of two halves. Pectoral girdle: Consists of clavicle (collar bone) and scapula Scapula is a triangular flat bone with a slightly elevated ridge called the spine, projecting as a flat, expanded process called acromion. Clavicle articulates with acromion. Below acromion, a depression called glenoid cavity is present. Here, humerus articulates to form the shoulder joint.    Pelvic girdle: Has 2 coxal bones formed by the fusion of ileum, ischium and pubis Acetabulum is a cavity formed at the point of fusion of these three bones where the thigh bone articulates Two halves of the pelvic girdle meet ventrally to form Pubic Symphysis (contains fibrous cartilage)