The Axial and Appendicular Skeletons.

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Unit Assignment 1

The Axial and Appendicular Skeletons.

The axial skeleton consists of the cranium (skill), the vertebral column (spine) and the rib cage; it is the main area of support for the body.

The appendicular skeleton consists of the appendages, or the bones of the limbs, together with the girdles that join onto the axial skeleton.

Bones in the Axial skeleton:

Cranium

Sternum

Vertebral Column

Sacrum

Llium

Bones in the Appendicular skeleton:

Ulna

Radius

Humerus

Clavicle

Scapular

Phalanges

Metacarpals

Carpals

Pubis

Femur

Patella

Tibia

Fibula

Tarsals

Metatarsals

These bones can be put into four bone type groups, there is flat, long, short, irregular and Sesamoid.

Long Bones

Long bones are cylindrical in shape, and are found in the limbs of the body, examples of long bones are;

Femur

Tibia

Humerus

Phalanges (although not great in length, these possess the cylindrical shape and so also are long bones)

Long bones primary functions are to act as levers; therefore they are essential in movement, i.e. when running, the psoas, iliacus and rectus femoris muscles pull on the femur to cause flexion of the hip, effectively pulling the leg off the ground. The rest of the quadriceps group (the vasti muscles as well as the rectus femoris) then pull on the tibia causing extension to take place at the knee joint, enabling the lower leg to ‘snap’ through. Long bones also produce blood cells, this occurs deep inside the bone.

Short Bones

Short bones are small and compact in nature, often in length and width. They are designed for strength and weight bearing, for example when performing a handstand, and include:

The bones of the wrist (carpals)

The ankle (tarsals) and calcaneum

Flat Bones

Flat bones are often protection to the internal organs of the body. Examples include;

The Sternum

The bones of the Cranium

The bones of the Pelvis

The Ribs

Flat bones also provide suitable sites for muscle attachment, with the origins of the muscles often attaching to them, in this way  the muscle contraction has a firm, immovable base against which to pull, and can therefore carry out its function efficiently. For example, a major function of the quadriceps muscle group is to pull on the tibia, causing extension at the knee. In order to raise the tibia, the muscle group must have a stable base against which it can pull, in this case, the ilium. The bone can now act as a lever and cause movement to occur. The pelvis, sternum and cranium also produce blood cells.

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Irregular Bones

Irregular bones are so named due to their complex, individual shapes and the difficulty in classifying them. They have a variety of functions which include protection. Examples:

The Vertebra (protects the spinal cord and helps to absorb shock when running and jumping)

The bones of the face.

Sesamoid Bones

Sesamoid bones have a specialized function: they ease joint movements and resist friction and compression. They are usually developed in tendons and are covered with a layer of articular cartilage as they exist where bones articulate. Although generally small in appearance, Sesamoid bones do very in size, ...

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