Human Movement Systems:

Skeletal System

Objectives

• After this presentation, the participant will be able to explain the basic structure and function of:

– Skeletal System Organization

– Types of bones

– Bone remodeling

– Joints (including stability vs. mobility)

– Connective Tissue

– Role of Exercise

The Skeletal System

Provides:

– Structure

– Protection of vital organs

– Levers for movement

– Storage for mineral

Bones form junctions that

are connected by

muscles and connective

tissue known as joints. Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Vertebral Column

Series of irregularly shaped

bones called vertebrae.

Houses the spinal cord.

– Cervical spine has 7 (concave curve) vertebrae.

– Thoracic spine has 12 (convex curve).

– Lumbar spine has 5 (concave curve).

– Sacrum is fused triangle attached to pelvis.

– Coccyx is tail bone.

Divisions of the Skeletal System

Axial skeleton:

• Skull

• Rib cage

• Vertebral column

Appendicular skeleton:

• Upper and lower extremities

• Shoulder and pelvic girdles

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Types of Bones

Long bones: Long

cylindrical shaft and irregular

or widened ends

Epiphysis: End of long bone

Diaphysis: Shaft of long bone;

Epiphyseal plate: growth plate

Periosteum: Hard membrane

Medullary cavity: marrow

Articular cartilage: Covers

articular surfaces of bones

Types of bone tissue

Types of bone tissue:

Compact Bone (a.k.a.

cortical bone)

– Dense bone found primarily in

shaft of long bones.

Cancellous Bone (a.k.a.

spongy or trabecular bone)

– Found at end of long bones and

in irregularly shaped bones.

– Less dense, more flexible

– Prone to effects of osteoporosis

– Site of red blood cell production

•

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Irregular bones:

• Unique shape

and function

Copyright © 2012 Wolters Kluwer

Health | Lippincott Williams & Wilkins

Types of bones

Copyright © 2012 Wolters Kluwer

Health | Lippincott Williams & Wilkins

Flat bones:

• Thin, protective

Short bones:

• Similar in length and

width and appear

somewhat cubical in

shape

Copyright © 2012 Wolters Kluwer Health | Lippincott

Williams & Wilkins

Bone Markings

Depressions:

• Flattened or

indented portions

of the bone

• Common

depressions:

• Fossa

• Sulcus

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

Processes:

• Projections protruding from the bone to which muscles, tendons, and ligaments attach

• Common processes:

• Condyle

• Epicondyle

• Tubercle

• Trochanter

Bone Growth & Remodeling

Bones under go remodeling throughout life cycle:

Osteoblasts build up new bone tissue.

Osteoclasts chew up old bone tissue.

Remodeling is the constant process building up and

breaking down of these cells.

In children, osteoblasts are more active; as we age,

osteoclasts become more active.

Bone Growth & Remodeling

Wolff’s Law: Bone will adapt to the loads under which it is

placed.

– Sensitive to direction and amount of force.

Importance of weight bearing exercise:

– Exercise that forces the body to work against gravity appear to

stimulate bone growth the best:

– Running, lifting weights, calisthenics are weight bearing

– Swimming and cycling are not, so less bone stimulation than land

training.

Kyphosis of the upper back

due to osteoporotic

fractures of the thoracic

vertebrae.

Dowager’s Hump

Osteoporosis Fracture

Aging and Bone Density

Race:

Caucasian

Asian

Diet:

Low Calcium Low Vitamin D

Medication:

Corticosteroids

Size:

Small Frame

Low weight

Hormones

Menopause

Premature menopause

Amenorrhea

Hyperthyroidism Low testosterone in men

Advanced Age

Smoking

Inactivity

Alcohol & Caffeine

Osteoporosis

Low Bone Density Risk Factors

Joints

One bone that articulates with another bone.

Joint motion is referred to as arthrokinematics.

Typical joint motions seen in the human articular system include:

• Roll: Rolling on joint surface on another such as femoral condyles rolling over the tibial condyles during a squat

• Slide: Sliding of a joint surface across another such as tibial condyles moving (sliding) across the femoral condyles during a knee extension

• Spin: Rotation of one joint surface on another such as head of the radius rotating on the end of the humerus during pronation and supination of the forearm

Classifications of Joints

Synovial joints:

– Produce synovial fluid

– Have a joint cavity and fibrous connective tissue

– Example: Knee

Non-synovial joints:

– No joint cavity and fibrous connective tissue

– Little or no movement

– Example: Sutures of the skull

16

Connective Tissue anatomy

Connective tissue —serves to connect, support, and anchor various body parts. Characterized by poor vascularity and do not repair or adapt as easily as other tissues in the body

– Fascia —a sheet or band of fibrous tissue that lies deep to the skin or forms an attachment for muscles and organs

– Tendon —when a muscle contracts to produce movement, it pulls on a tendon, which attaches the muscle to the bone

– Ligaments —supportive structures found at joints that connect bones to other bones

– Cartilage —serves as padding between the bones at a joint and functions to provide cushioning and the smooth gliding of joint movement

Connective Tissue

Davis’s Law - Soft tissue models

along the lines of stress.

– If muscle is in a constant shortened state

(such as when you sit all day), your

connective tissue remodels to adapt to the

shorter length, resulting in:

• Relative flexibility (seeking the path of least

resistance)

• Poor neuromuscular efficiency (altered

length-tension relationship, and force-

couple relationships.

• Synergistic Dominance (muscles other than

prime movers help too much)

Myofascial Release

Myofascial release applies pressure to tight, restricted areas of fascia and

underlying muscle in an attempt to relieve tension and improve flexibility

– It is thought that sustained pressure to a tight area can inhibit tension in a

muscle by stimulating the GTO to bring about autogenic inhibition.

– Trigger points can be diminished through the application of pressure followed by

static stretching of the tight area.

In the fitness setting, a foam roller is used, allowing the exerciser to control

his or her own intensity and duration of pressure.

Summary

Structure & function of the skeletal system

Bone growth and remodeling

Joints

Connective Tissue

Role of Exercise