S KELETAL S YSTEM · Part 2

regions starting from the skull. The number of cervical vertebrae are seven in almost all mammals including human beings. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back. Sternum is a flat bone on the ventral midline of thorax. There are pairs of ribs. Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. It has two articulation surfaces on its dorsal end and is hence called bicephalic. First seven pairs of ribs are called true ribs. Dorsally, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage. The th , th and th pairs of ribs do not articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called vertebrochondral (false) ribs. Last pairs ( th and th ) of ribs are not connected ventrally and are therefore, called floating ribs. Thoracic vertebrae, ribs and sternum together form the rib cage (Figure . ). The bones of the limbs alongwith their girdles constitute the appendicular skeleton. Each limb is made of bones. The bones of the hand (fore limb) are Cervical vertebra Intervertebral disc Sacrum Coccyx Thoracic vertebra Lumbar vertebra Figure . Vertebral column (right lateral view) Figure . Ribs and rib cage Figure . Right pectoral girdle and upper arm. (frontal view) humerus, radius and ulna, carpals (wrist bones – in number), metacarpals (palm bones – in number) and phalanges (digits – in number) (Figure . ). Femur (thigh bone – the longest bone), tibia and fibula, tarsals (ankle bones – in number), metatarsals ( in number) and phalanges (digits – in number) are the bones of the legs (hind limb) (Figure . ). A cup shaped bone called patella cover the knee ventrally (knee cap). Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton.