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42 bone. The face consists of fourteen bones including the maxilla (upper jaw), mandible (lower jaw) and two zygomatics (cheek-bones). The bones of the skull form one large cavity, called the cranial cavity, and some smaller ones: the oral cavity, the nasal cavity and two orbits holding the eyeballs. The bones of the trunk include the spinal column, the ribs and the breast‑ bone. The vertebral column forms the central axis of the body. It contains the spinal marrow or spinal cord. The spine consists of 32–34 small bones termed the vertebrae. The vertebrae are grouped under the names cervical, thoracic, lumbar, sacral and coccygeal according to the region in which they lie. The cervical vertebrae, seven in number, are the smallest ones. Twelve thoracic ver‑ tebrae have large bodies. Together with 12 pairs of ribs and the breastbone they form the chest (thorax). The lumbar vertebrae, 5 in number, are the strongest and the largest vertebrae in the spinal column. They have oval bodies. The sacrum consists of 5 fused vertebrae. The coccyx is formed by 2–5 vertebrae. The upper and lower limbs are constructed after a common type. Each extremity includes a girdle, which connects it to the trunk. The upper limb is attached to the trunk by the shoulder girdle, which con‑ sists of the collar-bone (or clavicle) in front and the shoulder-blade (or scapula) behind. The upper arm has one bone – the humerus; the forearm contains the radius and the elbow bone (or ulna). In the frame‑ work of the hand and wrist we have twenty-seven bones: 8 carpals, 5 metacarpals and 14 phalanges. The lower limb is attached to the trunk by the pelvic girdle. The adult pelvis is composed of three pairs of fused bones: the ilium, ischium and pubis. The thigh has only one bone – the femur, the leg includes two bones: the shin-bone (tibia) and fbula; and the foot is sub‑ Figure 1. The skeleton