Kinesiology - Biomechanics of the skeletal system

Functions of the skeletal system

1)Support  provides structure for the body
2) Protection  protects vital organs
3) Blood cell formation  blood cell development occurs in the bone marrow (haematopoiesis)

Long bones

Hard, dense cylindrical bones that provide strength and stability
Their length is much greater than their width
E.g.  femur

Short bones

Length, width, and depth are all similar
Provide support and stability
E.g.  wrist

Flat bones

Broad, flat plates that lack depth compared to their height and width
E.g.  scapula, skull

Irregular bones

Those with complex shapes that provide support and protection
E.g.  vertebra

Sesamoid bones

Develop within tendons due to stress
They serve as pulleys for the muscle attached to that tendon and increase ability to produce force
E.g.  patella in knee, sesamoid bones in big toe

Arthrology

Study of joints

Articulation

connection between two bones or between bones and cartilage… aka joint

Stable joints

little mobility, high stability

Mobile joints

wide range of motion, poor stability

How are joints classified

Function or ability to move

Fibrous joints

Immovable, usually have sutures and appear as one bone

Cartilaginous joints

Slightly movable
Vertebral joints are common example

Synovial joints

Freely moveable

ball-and-socket joint

Triaxial

Ball-shaped end fits into concave socket

Greatest range of motion of any joint

Synovial joint types - Condyloid

Biaxial

Oval head fits into shallow cavity

Allows forward/backward and side-to-side movement

Synovial joint types - Gliding

Nonaxial because the joints slide, not rotate

Two mostly flat bone surfaces slide across one another

Small amount of movement allowed

Synovial joint types - Hinge

Uniaxial

Concave surface fits over spool-like process

Large range of motion, but only in one plane (sagittal)

Synovial joint type - Pivot

Uniaxial

Transverse plane motion

One bone rotates around another

Radioulnar, atlanto-axial C1-C2) joint

Synovial joint type - Saddle

Biaxial

Two bones fit together as a riding saddle
Found only in the thumb
Allows all movement expect rotation

Joint stability

Ability to resist abnormal displacement.
Maximized when: closely packed, surrounded by ligaments/tendons, muscle fatigue minimal

Kyphosis

Hunchback - relaxed trapezius muscles

Lordosis

Sway back - Weak abdominals, tight lower back/hip flexors

Scoliosis

Lateral curvature - least common but most debilitating