Skeletal System KIN 202-M1

Structure and Function

The 3 mechanical functions of bone

1. Weight bearing

2. protection of internal organs

3. linkages and sites for muscle attachment

The 3 physiological functions of bone

1. storage of essential minerals

2. productions of blood cells

3. immune function

What force is acting on the bone?

Compression

What force is acting on the bone?

Tension

What force is acting on the bone?

Torsion

What force is acting on the bone?

Bending

What force is acting on the bone?

Shear

Living bone is made up of how much water?

~25%

2/3 of the remaining weight in bones

inorganic crystals

The 2 inorganic crystals that make up 2/3 of weight in bones

calcium and phosphorus

The remaining 1/3 of weight in bones

organic collagen fibers

The 3 types of bone cells

1. osteocytes

2. osteoblasts

3. osteoclasts

Bone is what type of material

composite material

What is a composite material

material made up of 2 or more materials

Bone is a lot like what?

Fiberglass

What is fiberglass?

Glass fibers cured in an epoxy resin

Collagen

Tough and flexible

Calcium

Rigidity and stiff

The optimal make-up of bone

2/3 calcium

1/3 collagen

Osteoblast function

Osteogenic (bone building)

Osteoclast function

bone degrader, breaks down bone mineral

Osteoclasts are derived from what?

monocytes (WBC)

Osteocytes function

mature bone cells that are trapped in bone matrix

Osteocytes were once what and can become them again?

Osteoblasts

The 2 types of bone

spongy and compact

2 other names for spongy bone

cancellous and trabecular

How much more deformable than compact bone is spongy bone?

10-15x

Another name for compact bone

cortical

T or F: compact bone is much stronger than spongy bone

T

The significance of bone architecture

efficient strength-to-weight ratio

withstands large forces and are relatively light

Compact bone protects what?

cartilage

Where does compact bone transfer forces?

to spongy bone

T or F: spongy bone absorbs forces

T

The 3 types of bone shape

1. flat

2. short

3. long

Flat bone function and make-up

Protection

lots of compact bone

Short bone function and make-up

weight bearing, absorbs ground reaction forces

less compact, lots of spongy

long bone function and make-up

weight bearing, muscle attachment

rigid links between joints

The 3 basic parts of a vertebrae

1. body

2. arch

3. spinous processes

Vertebral body function

weight bearing; cushions compressive forces

vertebral arch function

protects spinal cord

spinous processes function

provides leverages to attached ligaments and muscles; resists bending and twisting

hollow shafts functions (architecture of long bones)

resists bending, resists twisting

architecture of long bones

expanded ends with spongy bone: absorption of energy with compact, large contact area between bones

bone changes with “____”

training

training definition

mechanical loading of bone

training

ground reaction forces, forces from muscular contraction

detraining definition

absence of mechanical forces

detraining

bed rest, casting, spaceflight, hindlimb suspension of animals

bone mass in dominant limb of tennis players and carpenters are around _____ than non-dominant

30% greater

muscle mass accounts for what?

more than half of difference in bone mass between race or gender

weight bearing activity

4 hours of walking or standing restores bone loss from 20 hours of bed rest

Wolff’s Law

1892, the infrastructure of tissues adapted to the internal demands placed upon it

Wolff’s law example

bone forms in areas of stress and is reabsorbed in areas of non-stress

Basset and Becker

1982, bone acts as piezoelectric crystal

____ occur slowly in contrast to ____ with detraining, therefor exercise must be ____ and ____ to maximize benefits on bone

initial positive changes, rapid negative changes, regular, maintained

remodeling cycle of bone

3-5 months, 3-4 cycle required to maintain new steady state

stress fractures

particularly prevalent in young amenorrhoeic female athletes, 3-5%

what age do you reach peak bone mass?

30