1. Function of the skeletal system:
Support and protection of body organs.
Form the hard core of all segments that provide shape and form for body structures.
Lever action and its many articulations provide mobility.
Acts as store for inorganic cells.
Blood cell transformation.
Sound transmission

2. Reference Planes and Axes for Body Motion
The plane is an imaginary surface on which the movement takes place.
The axis is an imaginary straight line around which ( axial, angular,…) movements take place. (Axes = plural of axis).

3. Types of reference planes:
Planes defined with reference to earth’s surface such as horizontal and vertical planes.
Planes defined with reference to the body itself. These planes are used in kinesiological analysis.
There are three kinesiological planes each perpendicular to each of the other two. There are likewise three axes of motion, each perpendicular to the plane in which the movement occurs
The planes are called cardinal planes if it divides the body into equal halves and they intersect at the center of gravity of the body.

4. Sagittal Plane ( antero – posterior or median) is an imaginary vertical plane passing through the body from front to back dividing it into right and left halves (e.g. flexion – extension of the neck).
Frontal (lateral or coronal) plane is an imaginary vertical plane passing through the body from side to side dividing it into anterior and posterior halves ( e.g. bending of the neck).
Horizontal (transverse) plane: is an imaginary horizontal plane dividing the body into upper and lower halves (e.g. rotation of the neck from side to side).

5. N.B.: Kinesiologic planes remain the same
When movements occur in a plane parallel to any of the cardinal planes, these planes are called parallel planes ( e.g. movements of the upper and lower limbs).
When movements occur in any plane which is not perpendicular to any of the cardinal or parallel planes these planes are called diagonal planes ( e.g. raising the arm between straight forward and straight sideward.
N.B.: Kinesiologic planes remain the same
regardless of the position of the body
with reference to the earth.

6. Types of Axes:
Sagittal axis: it is an imaginary antero-posterior transverse axis passing horizontally from front to back and is perpendicular to the frontal plane.
Frontal axis: it is an imaginary transverse axis passing from side to side and is perpendicular to the sagittal plane.
Longitudinal axis: it is an imaginary vertical axis and is perpendicular to the transverse plane.

7. Sagittal axis Frontal Plane
Frontal Axis Sagittal Plane
Longitudinal Horizontal
Vertical Transverse