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 osteoprogenitorosteoblastosteocyteosteoclast

The Skeletal System D.Compact bone structure 2.Haversian system (osteon) a.central canal b.lamellae c.lacunae d.canaliculi lamella lacunaHaversian 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 CONDITION Normocalcemia (blood calcium = mg%) A stress or stimulus causes a decrease in blood calcium RECEPTOR Chief cells of parathythyroid glands recognize hypocalcemia (blood calcium <9.5 mg% CONTROL CENTER Chief cells secrete PTH EFFECTORS Increased osteoclast activity Decreased osteoblast activity Increased urine phosphate output Decreased urine calcium output RETURN TO HOMEOSTASIS Increased bone breakdown results in increased calcium release to blood – Return to normocalcemia negative feedback

The Skeletal System G.Bone remodeling – calcitonin (CT) CONTROLLED CONDITION Normocalcemia (blood calcium = mg%) A stress or stimulus causes a increase in blood calcium RECEPTOR Parafollicular cells of thyroid gland recognize hypercalcemia (blood calcium >10.5 mg% CONTROL CENTER Parafollicular cells secrete CT EFFECTORS Decreased osteoclast activity Increased osteoblast activity Increased urine calcium output RETURN TO HOMEOSTASIS Increased 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 normalosteoporoticnormalosteoporotic

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