Skeletal SystemBone Basics

Basics

ComponentsFunctions

– Support– Storage– Blood cell production– Protection– Leverage

Connective Tissue

4 types - Bone - Cartilage

- Hyaline- Elastic- Fibrocartilage

* function * location

Classification of Bones

Axial

Appendicular

Classification of Bones - Shape

Long Short Flat Irregular

Classification of Bone: Texture Compact Bone

Surfaces except joints Heavy stress areas Osteons parallel to

long axis– Bend with end force– Smaller force from side

can cause breaks

Classification of Bone: Texture Spongy Bone

Inner part– Less dense– Stress from many

directionsLighter weightTrabeculaeHematopoeitic tissue

– red marrow vs. yellow marrow

Microscopic Features

Osteocytes– Lacunae– Canaliculi

Osteon– Around central

canalOsteoblastsOsteoclasts

Microscopic Structure of Bone: Compact Bone

Figure 6.6a, b

Features of a long bone

• Epiphyses & Diaphysis• Epiphyseal Line

• Compact & Spongy bone• Medullary Cavity• Endosteum• Periosteum

Periosteum

Outer layerInner layerPerforating

canals

Bone Development

Bone Remodeling

6 wks after fertilization – 25 yrs Calcium

– 99% in skeleton– Role in nerve and muscle cells

18% of proteins and minerals removed and replaced a year– Remodeling– Not same rate for all bones– Important for calcium homeostasis

Injury and Repair

Fractures– Closed

(simple)– Open– Transverse– Spiral– Comminuted

As long as blood supply exists

4 months – year

Step 1– Bleeding– Clot (hematoma)

forms– Kills osteocytes– Dead bone

Step 2

Periosteum and endosteum cells divide

Migrate to fracture Localized

thickenings– Externally produces

hyaline cartilage

Step 3

Osteoblasts– Replace cartilage

Spongy bone at internal callus

Grows together Stabilizes fracture

Step 4

RemodelingDead and

spongy compact

Good as new– May be thicker

Aging

Bones thinner and weaker– Osteoblast activity declines– Osteoclast activity normal– More lost in epiphyses, vertebrae,

jawsFragile limbs, reduced height, loss of

teeth

Osteoporosis

Reduces bone mass Bone formation

– Effected by sex hormones– Decreases after menopause

More common in older women Slowed, not prevented

– Hormone replacement– Dietary changes– Exercise

Articulations

Classifications

Structure or function

Immovable– Fibrous or

cartilaginous– Suture– Gomphosis– Synchondrosis

Slightly movable– Fibrous or

cartilaginous– Syndesmosis– Symphysis

Freely movable

Synovial Wide range of motion Bones not in contact Covered with articular cartilage

– Arthritis Fibrous capsule Shock absorption

– Menisci– Fat pads

Ligaments and tendons Bursae

Movement

GlidingAngular motion

– Flexion– Extension– Hyperextension

AbductionAdductionCircumduction

Rotation

PronationSupination

Special movements

InversionDorsiflexionOppositionProtractionElevation

Classification of Synovial Joints

Gliding– Limited rotation– Clavicles, carpals,

tarsals, vertebraeHinge

– Motion in a single plane

– Elbow, knee, ankle, atlas

Pivot– Rotation only– Atlas and axis,

radius and ulna Ellipsoidal or condyloid– Oval articulation in a

depression– Motion in two planes– Radius and carpals,

phalanges and metacarpal or metatarsals

Saddle– Opposing faces nest

together

– Angular motion, no rotation

– Base of thumb

Ball-and-socket– Round head in cup-

shaped depression– Motion in most directions– Should and hip

Intervertebral Articulations

Gliding and symphyseal joints

Slipped discCondition of

discs as we age

Shoulder

Ball-and-socketMost frequently

dislocatedSeveral bursae

– BursitisRotator cuff

Elbow

Hinge joint Stronger

articulation Extremely stable

– Interlocking– Joint capsule– Reinfored with

ligaments

Hip

Ball-and-socket Articulating surface

– Fibrocartilage pad– Fat pad– Synovial membrane– Ligaments

Joint capsule Fractures

– Common in elderly– Dislocation

Knee

Hinge joint Fibrcartilage pads

– Minisci

Fat pads Burae Patella within ligament Surrounded by ligaments

– ACL