The Skeletal System 1.framework A. Components B.Functions 2.protection 3.storage 4.blood cell formation C.Changes with age.

The Skeletal System

1. framework

A. Components

B. Functions

2. protection

3. storage

4. blood cell formation

C. Changes with age

The Skeletal System

C. Types of bone

1. Short, long, flat, irregular

2. Long bone structure

a. diaphysis

b. epiphysis

c. medullary cavity

d. compact bone

e. spongy bone

f. periosteum

g. endosteum

The Skeletal System

D. Compact bone structure

1. Bone cells

a. osteogenitor cells

b. osteoblasts

c. osteocytes

d. osteoclasts

osteoprogenitor osteoblast osteocyte osteoclast

The Skeletal System

D. Compact bone structure

2. Haversian system (osteon)

a. central canal

b. lamellae

c. lacunae

d. canaliculi

lamella

lacuna Haversian canal

osteon

Volkmann’s canal

The Skeletal System

D. Compact bone structure

3. Bone matrix

a. ground substance (25%)

b. collagen (25%)

c. mineral salts (50%) = hydroxyapatite primarily

d. functions

The Skeletal System

E. Bone formation

1. Endochondral ossification

2. Intramembranous ossication

F. Bone resorption

G. Bone remodeling

1. Resist mechanical stress

2. Remove worn/heavily deposited bone

3. Participate in calcium homeostasis

The Skeletal System

G. Bone remodeling – parathyroid hormone (PTH)

CONTROLLED CONDITIONNormocalcemia

(blood calcium = 9.5-10.5mg%)A stress or stimulus causes a decrease in

blood calcium

RECEPTORChief cells of parathythyroid glands

recognize hypocalcemia(blood calcium <9.5 mg%

CONTROL CENTER

Chief cells secrete PTH

EFFECTORS

Increased osteoclast activityDecreased osteoblast activity

Increased urine phosphate outputDecreased urine calcium output

RETURN TO HOMEOSTASISIncreased bone breakdown results in increased calcium release to blood –

Return to normocalcemia

negative feedback

The Skeletal System

G. Bone remodeling – calcitonin (CT)

CONTROLLED CONDITIONNormocalcemia

(blood calcium = 9.5-10.5mg%)A stress or stimulus causes a increase in

blood calcium

RECEPTORParafollicular cells of thyroid gland

recognize hypercalcemia(blood calcium >10.5 mg%

CONTROL CENTER

Parafollicular cells secrete CT

EFFECTORS

Decreased osteoclast activityIncreased osteoblast activity

Increased urine calcium output

RETURN TO HOMEOSTASISIncreased bone formation results in

increased calcium deposition in bone --Return to normocalcemia

negative feedback

The Skeletal System

H. Cartilage

1. chondrocytes

2. matrix type determines function

a. hyaline c. elasticb. fibrocartilage

3. avascular and aneural

The Skeletal System

I. Synovial joints

1. Components

a. articulating bones

b. articular (joint) capsule

c. articular cartilage

d. synovial membrane

e. synovial fluid

f. ligaments

2. Movements allowed

J. Other joint types

medullary cavity

compact bone

spongy bone

fibrous capsule

synovial membrane

periosteum

synovial membrane

joint cavity

articular cartilage

tendon sheath

tendon

The Skeletal System

K. Age-related changes

1. Loss of calcium from bone matrix

2. Collagen fiber replacement slows with age

3. Results in ration change, leading to brittle bones

4. Articular cartilages wear thin and aren’t replaced

5. Fibrocartilage changes result in disc problems

The Skeletal System

L. Age-related dysfunctions

1. Bursitis

a. What is a bursa?

b. Where are they found?

c. What causes bursitis?

d. How is it treated?

The Skeletal System

L. Age-related dysfunctions

2. Arthritis

a. To what does the term ‘arthritis’ refer?

b. What parts of a synovial joint are involved?

c. What is the response of the joint?

d. Three main types

i. osteoarthritis

ii. rheumatoid arthritis

iii. gouty arthritis

The Skeletal System

L. Age-related dysfunctions

2. Arthritis

d. Three main types

i. osteoarthritis (degenerative joint disease)

1) 90% of people >40 years old have it

2) articular cartilages degenerate

3) bony spurs develop

4) most common locations

5) possible causes

The Skeletal System

L. Age-related dysfunctions

2. Arthritis

d. Three main types

ii. rheumatoid arthritis

1) not necessarily old age disease

2) bilateral effects

3) initial insult is inflammation of synovial membrane

4) scarring occurs with growth of a pannus

5) causes

6) what can be done

The Skeletal System

L. Age-related dysfunctions

2. Arthritis

d. Three main types

iii. gouty osteoarthritis

1) excessive blood uric acid sodium urate crystal precipitation

2) inflammatory response usually begins in great toe

3) tends to be chronic

4) can lead to tophus formation

5) causes

6) what can be done

The Skeletal System

L. Age-related dysfunctions

3. Osteoporosis

a. Bone remodeling gone bad?

b. Women vs. men

c. Vertebrae most affected

d. Suspected factors

i. calcium

ii. vitamin D

iii. estrogen

iv. lack of exercise

normal osteoporotic

normal osteoporotic

The Skeletal System

L. Age-related dysfunctions

3. Osteoporosis

e. treatments

i. estrogen replacement therapy

ii. calcitonin therapy

iii. exercise

4. Tumors of bone

end

The Skeletal System

M. Take home messages

1. Healthy bone is in balance between formation (osteogenesis) and resorption (osteolysis)

2. Synovial joints allow free movement

3. Bursitis and arthritis are inflammatory problems that limit movement

4. Osteoporosis is a direct result of decreased sex steroids that affects us all