THE VERTEBRAL COLUMN

The vertebral column (also called the backbone, spine, or spinal column) consists of a series of 33 irregularly shaped bones, called vertebrae. These 33 bones are divided into five categories depending on where they are located in the backbone.
The first seven vertebrae are called the cervical vertebrae. Located at the top of the spinal column, these bones form a flexible framework for the neck and support the head. The first cervical vertebrae is called the atlas and the second is called the axis. The atlas' shape allows the head to nod "yes" and the axis' shape allows the head to shake "no".
The next twelve vertebrae are called the thoracic vertebrae. These bones move with the ribs to form the rear anchor of the rib cage. Thoracic vertebrae are larger than cervical vertebrae and increase in size from top to bottom.
After the thoracic vertebrae, come the lumbar vertebrae. These five bones are the largest vertebrae in the spinal column. These vertebrae support most of the body's weight and are attached to many of the back muscles.
The sacrum is a triangular bone located just below the lumbar vertebrae. It consists of four or five sacral vertebrae in a child, which become fused into a single bone after age 26. The sacrum forms the back wall of the pelvic girdle and moves with it.
The bottom of the spinal column is called the coccyx or tailbone. It consists of 3-5 bones that are fused together in an adult. Many muscles connect to the coccyx.
These bones compose the vertebral column, resulting in a total of 26 movable parts in an adult. In between the vertebrae are intervertebral discs made of fibrous cartilage that act as shock absorbers and allow the back to move. As a person ages, these discs compress and shrink, resulting in a distinct loss of height (generally between 0.5 and 2.0cm) between the ages of 50 and 55.
When looked at from the side, the spine forms four curves. These curves are called the cervical, thoracic, lumbar, and pelvic curves. The cervical curve is located at the top of the spine and is composed of cervical vertebrae. Next come the thoracic and lumbar curves composed of thoracic and lumbar vertebrae respectively. The final curve called the pelvic or sacral curve is formed by the sacrum and coccyx. These curves allow human beings to stand upright and help to maintain the balance of the upper body. The cervical and lumbar curves are not present in an infant. The cervical curves forms around the age of 3 months when an infant begins to hold its head up and the lumbar curve develops when a child begins to walk.
In addition to allowing humans to stand upright and maintain their balance, the vertebral column serves several other important functions. It helps to support the head and arms, while permitting freedom of movement. It also provides attachment for many muscles, the ribs, and some of the organs and protects the spinal cord, which controls most bodily functions.

THE STERNUM AND RIBS

The sternum is a flat, dagger shaped bone located in the middle of the chest. Along with the ribs, the sternum forms the rib cage that protects the heart, lungs, and major blood vessels from damage.
The sternum is composed of three parts:
The manubrim, also called the "handle", is located at the top of the sternum and moves slightly. It is connected to the first two ribs.
The body, also called the "blade" or the "gladiolus", is located in the middle of the sternum and connects the third to seventh ribs directly and the eighth through tenth ribs indirectly.
The xiphoid process, also called the "tip", is located on the bottom of the sternum. It is often cartilaginous (cartilage), but does become bony in later years.
These three segments of bone are usually fused in adults.
The sternum serves an important function in the body. The ribs are connected to it by the costal cartilage. Without the sternum, there would be a hole in the bone structure in the middle of your chest, right above your heart and lungs. The sternum protects this vital area and completes the circle of the rib cage.

The ribs are thin, flat, curved bones that form a protective cage around the organs in the upper body. They are comprised 24 bones arranged in 12 pairs.These bones are divided into three categories:The first seven bones are called the true ribs. These bones are connected to the spine (the backbone) in back. In the front, the true ribs are connected directly to the breastbone or sternum by a strips of cartilage called the costal cartilage.The next three pairs of bones are called false ribs. These bones are slightly shorter than the true ribs and are connected to the spine in back. However, instead of being attached directly to the sternum in front, the false ribs are attached to the lowest true rib.The last two sets of rib bones are called floating ribs. Floating ribs are smaller than both the true ribs and the false ribs. They are attached to the spine at the back, but are not connected to anything in the front.The ribs form a kind of cage the encloses the upper body. They give the chest its familiar shape.The ribs serve several important purposes. They protect the heart and lungs from injuries and shocks that might damage them. Ribs also protect parts of the stomach, spleen, and kidneys. The ribs help you to breathe. As you inhale, the muscles in between the ribs lift the rib cage up, allowing the lungs to expand. When you exhale, the rib cage moves down again, squeezing the air out of your lungs

THE SKULL

The skull is the bony framework of the head. It is comprised of the eight cranial and fourteen facial bones.

Cranial Bones
The cranial bones makeup the protective frame of bone around the brain. The cranial bones are:
The frontal forms part of the cranial cavity as well as the forehead, the brow ridges and the nasal cavity.
The left and right parietal forms much of the superior and lateral portions of the cranium.
The left and right temporal form the lateral walls of the cranium as well as housing the external ear.
The occipital forms the posterior and inferior portions of the cranium. Many neck muscles attach here as this is the point of articulation with the neck.
The sphenoid forms part of the eye orbit and helps to form the floor of the cranium.
The ethmoid forms the medial portions of the orbits and the roof of the nasal cavity.
The joints between bones of the skull are immovable and called sutures. The parietal bones are joined by the sagittal suture. Where the parietal bones meet the frontal is referred to as the coronal suture. The parietals and the occipital meet at the lambdoidal suture. The suture between the parietals and the temporal bone is referred to as the squamous suture. These sites are the common location of fontanelles or "soft spots" on a baby’s head.

Facial Bones
The facial bones makeup the upper and lower jaw and other facial structures. The facial bones are:
The mandible is the lower jawbone. It articulates with the temporal bones at the temporomandibular joints. This forms the only freely moveable joint in the head. It provides the chewing motion.
The left and right maxilla are the upper jaw bones. They form part of the nose, orbits, and roof of the mouth.
The left and right palatine form a portion of the nasal cavity and the posterior portion of the roof of the mouth.
The left and right zygomatic are the cheek bones. They form portions of the orbits as well.
The left and right nasal form the superior portion of the bridge of the nose.
The left and right lacrimal help to form the orbits.
The vomer forms part of the nasal septum (the divider between the nostrils).
The left and right inferior turbinate forms the lateral walls of the nose and increase the surface area of the nasal cavity.