Equipping People To Make Sense Of What They Are Told
The Skeletal System - Bone - a type of connective tissue made of specialised cells
and protein fibres. Bone is constantly breaking down and rebuilding itself. The point
at which two bones meet is known as a joint or an articulation which are classified
according to their structure and the types of movement they allow.
The most versatile and free moving joints are known as synovial joints. The bone
ends in a synovial joint are covered by a smooth, slightly compressible tissue called
articular cartilage, surrounding the joint is the joint capsule which is made of
connective tissue which is attached to the bone. The inner lining of the joint capsule
is called the synovial membrane which secretes viscous synovial fluid into the synovial
cavity to ensure the joint is kept well lubricated.
The range of movement of a synovial joint is determined by the shape of its articular
cartilage surfaces and how they fit together:
Types of synovial joint:
Ball & Socket - provides the widest range of movement such as the shoulder and hip
joints.
Ellipsodial - provides side to side and flexing movement with limited rotation.
Gliding - provides flat surface limited movement.
Hinge - provides to and fro movement mainly through one plane, in some cases allows
limited rotation such as the elbow joint.
Pivot - provides side to side and rotating movement.
Saddle - provides back and forth and side to side movement with limiter rotation.
Bone Marrow.
There are two types of bone marrow, red marrow and yellow marrow.
Red blood cells, platelets and most white blood cells arise in red marrow.
Some white blood cells develop in yellow marrow.
Both types of bone marrow contain numerous blood vessels and capillaries.
Red marrow is found mainly in the flat bones, such as the hip bone, breast bone,
skull, ribs, vertebrae and shoulder blades, and in the cancellous ("spongy") material
at the proximal ends of the long bones femur and humorous.
Yellow marrow is found in the hollow interior of the middle portion of long bones.
In cases of severe blood loss, the body can convert yellow marrow back to red marrow
in order to increase blood cell production.
The Skull - 29 bones make up the skull - 22 form the skull itself, three pairs are
ear bones known as ossicles plus the hyoid bone found in the neck. The skull is the
bony framework of the head. It is comprised of the eight cranial and fourteen facial
bones.
The cranial bones makeup the protective frame of bone around the brain. They are:
The frontal bone forms part of the cranial cavity as well as the forehead, the brow
ridges and the nasal cavity.
The left and right parietal bone forms much of the superior and lateral portions
of the cranium.
The left and right temporal bone form the lateral walls of the cranium as well as
housing the external ear.
The occipital bone 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 form forms part of the eye orbit and helps to form the floor of the
cranium.
The ethmoid form forms the medial portions of the orbits and the roof of the nasal
cavity.
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.
The facial bones makeup the upper and lower jaw and other facial structures. They
are:
The mandible - the lower jawbone. It articulates with the temporal bones at the temporomandibular
joints. This forms the only freely moveable joint in the head and 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.
