The Skeletal System

The human skeleton is an endoskeleton of bone and cartilage.

Major Functions   Support for the soft tissues and largely

responsible for the shape of the human body. Movement: the strong rigid bones function as

levers moved by the contraction of muscles. Protection: the tough bones protect delicate

vital organs • the brain is protected by the skull • heart and lungs are protected by the rib cage • spinal cord is protected by the backbone

Axial Skeleton: skull, backbone, ribs and sternum.

Bone is made of mineral compounds of Calcium that are strong yet brittle.

Inside bone there is a network of cells, blood vessels and nerves.

Large bones are hollow, the outside (matrix) being hard while the centre (marrow) soft and fatty and rich in blood and leucocytes.

Smaller bones (like the ribs) are not hollow but have several smaller holes.

In these holes there is red bone marrow, where red blood corpuscles are made.

The Spine or Backbone is divided into different sections:

Cervical Vertebrae (Neck region) The Thoracic Vertebrae (Ribs area) The Lumbar Vertebrae (Lower back) The Sacrum (Sacral region) The Caudal region (The tail) Composed of 33 small bones in a line -

cervical (7), thoracic (12), lumbar (5), sacrum (5), coccyx (4).

The vertebrae of the sacrum and coccyx are fused.

A joint is the junction between two or more bones.

There are three major types of joints. Fused Joints: skull, sacrum, pelvis,

and coccyx. Slightly Moveable: between the

vertebrae. Synovial: freely moveable - the

movement is lubricated by synovial fluid.

Hinge: movement in one plane during flexion and extension.

Examples: bending the elbow or knee. Ball and Socket: permits movement in three

planes, i.e., in all directions. Examples: the shoulder and hip joints. Gliding: the bones move across each other, back-

and-forth and side-to-side. Examples: between the carpals of the wrist and

tarsals of the ankle. Pivot: allows a turning movement. Examples: between the first and second vertebras

when turning the head, between the ulna and the radius of the lower arm when turning the palm of the hand up or down.

Muscles are used for movement and are attached to bones via tendons.

For effective movement there are two muscles connected to each limb.

These muscles are said to be antagonistic muscles. This means that will one contracts, the other relaxes

and vice versa. The biceps and triceps are examples of antagonistic

muscles.  There are three types of muscle in the body: Striated Muscle (Voluntary muscle attached to bones

etc) Smooth Muscle (Involuntary muscle found in our

stomachs and intestines) Cardiac Muscle (Involuntary muscle only found in the

heart)

Muscle is an extremely contractile connective tissue. There are a number of different types of muscle:

Skeletal, Cardiac and Smooth. The contraction of muscle performs four important

functions:• Movement • Posture maintenance • Support the joints • Heat production

Skeletal muscle is connected to the skeleton by tendons.

It is under conscious control. Its contraction is fast and strong. Skeletal muscle tires easily.