The human skeletal system is made up of 206 bones and a few cartilages. It is divided in to two main categories.
A. Axial skeleton : It is present on median longitudinal axis of body e.g. skull, vertebral column, sternum, ribs etc. It comprises of 80 bones.
i. The skull - is composed of two sets of bones cranial and facial, that totals to 22 bones. Cranial bones are 8 in number.
ii. The vertebral colummn - is formed by 26 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.
iii. Sternum is a flat bone on the ventral midline of thorax.
iv. Ribs - There are 12 pairs of ribs. Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. The first 7 pairs are called True ribs, the 8th, 9th and 10th are called False ribs, and the 11th and 12th are called Floating ribs.
B. Appendicular skeleton : It is present on sides and present in appendages and associated with them. It includes the bones of the limbs and the pectoral girdles, pelvic girdles.
i. Bones of the limbs - each limb is formed of 30 bones. The bones of the hand are humerus, radius and ulna, carpals (8), metacarpals (5) and phalanges (14).
The leg is made up of Femur, tibia and fibula, tarsals (7) metatarsals (5) and phalanges (14). A cup shaped bone called patella cover the knee ventrally (knee cap).
ii. Pelvic and pectoral girdle - Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton. Each girdle is formed of two halves. Each half of pectoral girdle consists of a clavicle and a scapula. Pelvic girdle consists of two coxal bones. Each coxal bone is formed by the fusion of three bones – ilium, ischium and pubis.