DIVISIONS OF SKELETON
The human skeleton can be divided into two main parts; the first part is the axial skeleton and second part is the appendicular skeleton.
The axial skeleton consists of the skull, thevertebral column, and the thorax.
SKULL.— The skull is the bony structure in the head. It supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible
Cranial Bones.—The cranium is formed by eight major bones, most of which are in pairs.
The frontal bone forms the forehead and the nasal cavity.
The parietal bones form the roof of the skull.The temporal bones help form the sides and base of the skull and also house the auditory and hearing organs.
The occipital bone forms part of the base and back of the skull, and contains a large hole called the foramen magnum
The sphenoid bone is situated on the base of the skull
The ethmoid bone is located in front of the sphenoid
Facial Bones.— : 13 immovable bones and a movable lower jawbone
The maxillary bones form the upper jaw, the anterior roof of the mouth, the floors of the orbits, and the sides and floor of the nasal cavity
The lower jawbone is called the mandible
VERTEBRAL (SPINAL) COLUMN
The vertebral column consists of 24 movable or true vertebrae; the sacrum; and the coccyx or tail bone. The bodies of the vertebrae are separated from each other by intervertebral discs
The spinal column is divided into five regions in the following order:
Cervical (neck), seven vertebrae
Thoracic (chest) twelve vertebrae that articulate with the ribs
Lumbar five lumbar vertebrae located in the small of the back, these vertebrae are the larger and stronger segments of the vertebral column
Sacrum is the triangular bone immediately below the lumbar vertebrae. It is composed of five fused vertebrae The sacrum is connected on each side with the hip bone and with the coccyx to form the posterior wall of the pelvis.
Coccyx is the tailbone. It have four fused vertebrae
The skeleton of the thorax includes 12 ribs on each side articulates posteriorly with the thoracic vertebrae and the sternum in the front upper half of the chest wall.
ribs 1 to 7 are connected to the sternum' by their costal cartilages and are called true ribs
ribs 8 to 10 are termed false ribs. They join the costal cartilage immediately above.by means of their costal cartilages.
ribs 11 and 12, which are free, are known as floating ribs.