1. Skeletal System

2. Introduction
The framework of bones and cartilage that protects our organs and allows us to move is called the skeletal system.
The branch of medicine that deals with the preservation and restoration of the skeletal system, articulations (joints), and associated structures is called orthopaedics.

3. The skeletal system performs the following functions:
Support
Protection (for internal organs)
Movement
Mineral storage
Storage of blood cell-producing cells
Storage of energy

4. Types of Bones There are five principal types of bones based on shape
1. Long bones (e.g. thighs, legs, toes, arms, forearms, and fingers)
greater length than width
consist of a shaft and extremities (ends)
slightly curved for strength
consist mostly of compact bone (dense bone with few spaces) but also contain considerable amounts of spongy bone (bone with large spaces)

5. 2. Short bones (e.g. wrist, ankle bones)
Somewhat cube-shaped and nearly equal in length and width
Spongy except at the surface where there is a thin layer of compact bone

6. 3. Flat bones (e.g. cranial bones, sternum, ribs, scapulas)
Generally thin and composed of two more or less parallel plates of compact bone enclosing a layer of spongy bone
Flat bones afford considerable protection and provide extensive areas for muscle attachment

7. Irregular bones (e.g. vertebrae, and certain facial bones)
Have complex shapes and cannot be grouped into any of the other three categories
They vary in the amount of spongy and compact bone

8. 5. Sesamoid bones
Are small bones in tendons where considerable pressure develops, for instance, the wrist
Their number varies greatly from person to person
All people have at least two sesamoid bones: the patella (kneecap)

9. Divisions of the Skeletal System
The adult human skeleton consists of 206 bones grouped as the axial skeleton and the appendicular skeleton.
The axial division consists of the bones of the skull, auditory ossicles, hyoid bone, ribs, breastbone, and the backbone.
The appendicular division consists of the bones of the upper and lower extremities (limbs), plus the bones called girdles, which connect the extremities to the axial skeleton.
There are 80 bones in the axial division and 126 in the appendicular. Listed below are the divisions of the skeletal system.

10. Anatomical Position (AP)
AP is the reference position used to describe the location of anatomical parts and to describe and explain human movement.
The subject is:
standing upright with feet flat on the floor
arms at the side of the body
facing the observer
palms are facing forward (supinated)

11. Anatomical Position

12. Directional Terms
Note: the midline is an imaginary vertical line that divides the body into equal left and right sides
Superior: nearer the head
e.g. the heart is superior to the liver
Inferior: farther away from the head
e.g. the stomach is inferior to the lungs

13. Directional Terms
Anterior (ventral): nearer to or in front of the body
e.g. the sternum is anterior to the heart
Posterior (dorsal): nearer to or at the back of the body
e.g. the esophagus is posterior to the trachea

14. Directional Terms Medial: closer to the midline of the body
e.g. the ulna is on the medial side of the forearm
Lateral: farther away from the midline of the body
e.g. the ear is lateral to the nose in all individuals

15. Directional Terms
Proximal: nearer to the attachment of an extremity (limb) to
the trunk; nearer to the point of origin
e.g. the humerus is proximal to the radius
Distal: farther from the attachment of an extremity (limb) to the
trunk; farther away from the point of origin
e.g. the phalanges are distal to the carpals (wrist bones)

16. Directional Terms Superficial: on or near the surface of the body
e.g. the skin is the most superficial organ of the body
Deep: farther away from the surface of the body
e.g. the ribs are deep to the skin of the chest

17. Planes of Motion and Axes
Biomechanics is the study of human movements through the use of physics. As such, biomechanics has its own language and terminology. The language of biomechanics establishes a common reference system of standard terms. Planes and axes of motion are an important part of this language.

18. Planes of Motion
A plane of motion can be defined as the two dimensional space cut by a moving body or the plane along which movements occur. There are generally three planes used to describe segmental and body movements in physical activity. These are:
Sagittal plane
a vertical plane that cuts the body into right and left sides
Frontal plane
vertical plane that cuts the body into anterior (front) and posterior (back) parts
Transverse plane
horizontal plane that cuts the body into superior and inferior parts

19. Anatomical Planes

20. Anatomical Axes
An axis is the point about which rotation of a body or of a body segment occurs. There are three axes of rotation. Each axis is associated with a plane of motion and the axis is perpendicular to that plane.
Horizontal axis (…think East and West)
passes through the body from side to side
perpendicular to the sagittal plane
Antereoposterior axis (axis)
passes through the body from front to back
perpendicular to the frontal plane
Longitudinal axis (…think North and South pole)
passes through the body from top to bottom
perpendicular to the transverse plane

21. Planes & Movements
Movements in the sagittal plane around a horizontal axis
(e.g. front roll, back roll, cycling, running)
Flexion
flexion at a joint results in a decrease of the angle between the two segments that meet at that joint
Extension
extension at a joint results in an increase of the angle between the two segments that meet at that joint
if the movement occurs beyond the extended position, the action is called hyperextension

22. Examples of flexion and extension
shoulder flexion and extension
elbow flexion and extension
wrist flexion and extension
fingers flexion and extension
hip flexion and extension
knee flexion and extension
ankle dorsi flexion and plantar flexion
tilt of pelvis under
Dorsi flexion: bringing the toes toward the shin
Plantar flexion: pointing the toes away from the shin (toward the floor)

23. Planes & Movements
Movements in the frontal plane around a antereoposterior axis
(e.g. cartwheel, jumping jacks, galloping)
Abduction
occurs when a body part is moved away from the midline of the body
e.g. shoulder, hip, fingers
Adduction
occurs when a body part is moved toward the midline of the body
remember “add to your midline”

24. Movements & Planes Inversion
Turning the sole of the foot inward at the ankle (so the sole of the foot faces toward the midline)
Eversion
turning the sole of the foot outward at the ankle (so the sole of the foot faces away from the midline)
Elevation
raising a part to a superior position
e.g. raising your shoulders toward your ears; closing your jaw
Depression
lowering a part to an inferior position
e.g. lowering your shoulders to normal or lower than normal position; lowering your jaw to an open position

25. More… Protraction Sticking jaw out (pouting) Retraction
Bringing jaw back to anatomical position
Lateral bending
bending of the spinal column in the frontal plane to the left or right
e.g. bending side to side at the waist

26. And More… Movements in the transverse plane around a longitudinal axis
(e.g. twist, pirouette)
Rotation
the movement of a bone around its own axis; this is also known as a pivot
e.g. the head, neck, and trunk can pivot around the longitudinal axis
Internal (medial) rotation
Rotation towards the midline
E.g. turning forearn in towards body
External (lateral) rotation
Rotation away from midline
E.g. turning forearm away from body

27. More…
Pronation
rotation of the forearm and hand to the palms down position
Supination
rotation of the forearm and hand to the palms up position (remember holding a cup of “soup”)
Protraction
Shoulder rounding (hunching shoulders)
Retraction
Bringing shoulders back to anatomical position, or squeezing shoulder blades together at back

28. Special movements Circumduction
a combination of abduction, adduction, flexion and extension
this action describes a circle
e.g. moving the shoulder in a circle (swimming, windmill throw in baseball); can also be done at the hip joint
Opposition
Bringing thumb towards fingers
Reposition
Returning thumb back to anatomical position

29. Skeletal Surface Markings
The surfaces of bones have various structural features adapted to specific functions. These features are called surface markings. Long bones that bear a great deal of weight have large, rounded ends that can form sturdy joints, for example. Other bones have depressions that receive the rounded ends.

30. Depressions and Openings
Foramen
an opening through which blood vessels, nerves, or ligaments pass
Example:
Meatus
a tubelike passageway running within a bone
Paranasal sinus
an air-filled cavity within a bone connected to the nasal cavity
Fossa
a depression in or on a bone

31. Processes that form Joints
Condyle
a large, rounded articular prominence
Example:
Head
a rounded articular projection supported on the constricted portion (neck) of a bone
Facet
a smooth, flat surface

32. Processes to which tendons, ligaments and other connective tissues attach
Tuberosity
a large, rounded, usually roughened process
Example:
Spinous process
a sharp, slender projection
Trochanter
a large, blunt projection found only on the femur
Crest
a prominent border or ridge