In biology, a skeleton is a rigid framework that provides protection and structure in many types of animal, particularly those of the phylum Chordata and of the superphylum Ecdysozoa. Exoskeletons are external, as is typical of many invertebrates; they enclose the soft tissues and organs of the body. Exoskeletons may undergo periodic moulting as the animal grows. Endoskeletons are internal, as is typical of many vertebrates; they are usually surrounded by skin and musculature, though they often enclose vital organs. Endoskeletons are attachment points for musculature and act as leverage for movement, and in many animals contain marrow, which produces blood cells. Skeletons may or may not be mineralized - human skeletons are calcified, while shark skeletons are cartilaginous - and may be jointed for flexibility and motility or rigid for structural strength.

The average adult human skeleton has around 206 bones. These bones meet at joints, the majority of which are freely movable. The skeleton also contains cartilage for elasticity. Ligaments are strong strips of fibrous connective tissue that hold bones together at joints, thereby stabilizing the skeleton during movement.

The Human skull

main: Human skull The human skull shapes the head and face, protects the brain, and houses and protects special sense organs for taste, smell, hearing, vision, and balance. It is constructed from 22 bones, 21 of which are locked together by immovable joints, to form a structure of great strength.

The bony framework of the head is called the skull, and it is subdivided into 2 parts, namely:

Cranial bones

The eight bones of the cranium support, surround and protect the brain within the cranial cavity. They form the roof, sides, and back of the cranium, as well as the cranial floor on which the brain rests. The frontal bones and the parietal bones form the roof and sides of the cranium. Two in the temporal bone, the external auditory meatus, directs sounds into the inner part of the ear that is encased within, and which contains three small, linked bones called ossicles. The occipital bones forms the posterior part of the cranium and much of the cranial floor. The occipital bone has a large opening, the foramen magnum, through which the brain connects to the spinal cord. The occipital condyles articulate with the atlas (first cervical vertebra), enabling nodding movements of the head. The ethmoid bone forms part of the cranial floor, the medial walls of the orbits, and the upper parts of the nasal septum, which divides the nasal cavity vertical into left and right sides, The sphenoid bone, which is shaped like a bat's wings, acts as a keystone by articulating with and holding together, all the other cranial bones.