bones Flashcards by denzie hurst

COMPONENTS of the Bone

CELLS
Osteoblasts
Lay down osteoid
PTH, Vit C, Vit D
Osteocytes
PTH, Vit D, Calcitonin
Osteoclasts
Howship’s lacunae (microscopic bone concavities due to bone resoprtion)
PTH, Vit D, Calcitonin, PG2, etc.
MATRIX!!! (first thing)
Collagen
Glycoproteins
Mineral
Calcium hydroxyapatite
Non-mineralized matrix may be called “osteoid”

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3 areas of the bone

epiphysis (end),
metaphisis (inbetween)
diaphysis (middle part of bone (longest part/ shaft

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epiphysis

covered by cartlidge- form joint with other bone joint

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diaphysis

lenthg and strenghs- center in mostly hollow and bone marrow

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metaphysis

blood supply comes in and gives it to other areas

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epiphyseal growth plate

the way the long bones growth- lay down the cartiledge (first) that gets converted to the bone
endocontral osification

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first step

lay down collagen (osteoite)and sprinkle calcium

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osteoid

first step in bone formation where it is just collagen before calcium has been sprinkled

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what lays down ca

osteoblast make osteoids

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mature osteoblasts

osteocytes (function depends on hormones and vit c, d

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osteoclasts

remodeling bone- eat away part of the bone so that osteoblaste replace it

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is bone fixed

no-

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Achondroplasia

Defect of endochondral ossification
Causes dwarfism
Growth of the long bones is retarded: Short legs, short arms but normal trunk
Autosomal dominant
lack of endocartiocarcitofication- short bones are made by different process so are ok

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Osteogenesis Imperfecta(defective bone formation)

Basic problem: Mutations in gene encoding collagen I (which is the principal component of osteoid).
Autosomal recessive or dominant

Age of presentation depends upon the extent of gene defects
Some born with multiple fractures, others develop symptoms in childhood , puberty or later.

Other defects
Blue sclerae (eye whites)
Think skin
Thin dental enamel

weak bones- not enough collagen

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Osteopetrosis

don’t need to know

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Osteomyelitis

Bacterial infection of bone
Causes
Pyogenic cocci: Staph aureus.
Mixed flora ( drug addicts)
TB
Usually presents as acute infection which may progress to chronic
Starts with hematogenous deposit of Staph in metaphysis
PMN’s attracted, forming pus
Pus spreads into epiphysis, and through compact bone under periosteum
Sequestra: devitalized bone fragments cut off from blood supply
Involucrum: reactive bone formed to wall off infection
can go to diaphysis area (mostly hollow) can take over it
becomes necrotic- sequestral

Osteoporosis(thin bones)

enough calcium and collagen just less so prone to breaks
Bone is normal but thinned out (less than normal tissue density)
Absolute reduction of total bone mass
1/3 of women > 65 years are affected
Causes
Primary – disease of elderly
Secondary
Hormonal problems ( thyroid,  cortisol,  estrogen)
Dietary (calcium, vitamin C)
Immobilization
Drugs (anticonvulsants, heparin)
Pathogenesis
Loss of bone matrix !!!and mineral
After age 30y, bone loss exceeds formation
After menopause in women, bone loss accelerates 5-fold ( due to loss of estrogen)

Osteoporosis(thin bones)- pathlogy

Pathology
Thin, brittle, prone to fracture
Type I (postmenopause)
Trabecular bone 			(vertebrae, wrist)
Type 2 (old age)
Cortical &amp; trabecular bone of long bones (e.g., neck of femur)

Osteoporosis(thin bones)

Clinical Features
Vertebral fractures (crush Injury)
Back pain,  kyphosis
Fracture of neck of femur
Incapacitation
> 1 Million/year in USA

Osteomalacia soft bones

Bone is abnormal (i.e., normal tissue present but not calcified)
Inadequate mineralization of organic matrix
Caused by disturbance of vit. D or PO4 metabolism
Called “rickets”!!!! (word in kids) in young people
Causes
Vitamin D deficiency
Inadequate intake
Inadequate exposure to sunlight
Intestinal malabsorption
Hypophosphatemia
Malabsorption
Excess loss of PO4

enough collagen but not of anything else
enough osteoites
not enough calcium -no sprinkling

Osteomalacia and Rickets

lowAbsorption of calcium + PO4 in intestines leads to increase in Urinary PO4 loss leads to increase Bone resorption
Loss of minerals  leads bone softening
 compensatory new bone formation (without mineralization) called osteoid

Children: New bone formation is affected in children
Growth retardation
Including delayed dentition
Deformities
Bow legs
Pigeon breast
Rachitic rosary (enlarged costochondral junction – excess osteoid)
Adults and Children
Fractures
Muscle spasms (tetany)

Fractures

Disruption of bony continuity from mechanical stress
Simple – one fracture line; bone not exposed to environment
Compound – one fracture line; bone exposed to environment
Comminuted – several fragments
Complete – Cortex to cortex
Incomplete – part way through bone (also called “greenstick”)
CLOSED fractures are when skin is not broken

simple

one fracture line; bone not exposed to environment

compound

– one fracture line; bone exposed to environment

Comminuted

several fragments

Complete

Cortex to cortex

Incomplete

– part way through bone (also called “greenstick”)

Cause of fracture?

Traumatic – obvious physical cause Pathologic – Fracture through pre-existing disease in bone (e.g., tumour, osteoporosis)- don't need a lot of force to break

Fracture Healing

Hematoma fills and surrounds injured area Clotted blood seals off farcture site Clot organizes to soft tissue pro-callus Conversion to new formed fibrocartilaginous callus by one week) Replacement by bony provisional callus – this creates spindle-shaped splint maximum at 2-3 weeks Callus strengthened by widening of bone spicuels Remodeling (final stage)with osteoclastic and osteoblastic activity get a callus- healy of the fracture

fracture treatment

``` Treatment Immobilization of Fracture Reconstruction of any gap Debridement (removal of necrotic tissue) Immobilization (pins +/or plates) Factors that delay healing Nutrition Vitamins C & D, Calcium, PO4 Infection Foreign Bodies Failure of immobilization  leads to Fibrous non-union leads to  Pseudoarthrosis (false joint) ```

Bone Tumors

know osteosarcoma | seen in younger men and not good tumor

osteosarcoma

``` Most Common Metaphysis of long bones of extremities (50% in Knee) Young persons (rare in adults) Rx: surgery & chemotherapy 5 year survival: 30% ```

Osteoarthritis

``` Degenerative joint disease Wear and tear of the articular cartilage Cartilage shows Softening Surface defects Irregular thinning -> fibrillation & vertical clefts Denuded bone -> eburnation (polished bone) Bone degeneration ->  bone cysts Spicules of new bone (osteophytes) ``` affects the joint without the cartilidge there is rubbing which may lead to broken down bones try to regrown = sclerotic bone

3 main

thinkening of the bone thinned cartelidge bone defect broken down fragments of cartiledge

osteophytes

new bones forming

Clinical Features | osteoarthristis

Clinical Features Weight-bearing (hip, knees, spine) and small joints of hands are affected Pain & stiffness (in morning especially) (lasting 15 - 20 min)  Mobility & deformity Crepitus (grating on movement can hear about it) Swelling & warmth (2º Inflammation) Heberden’s nodes: osteophytes ( bony spicules)- bumpy on hands ULNAR DRIFT IS NOT SEEN

Heberden’s nodes

osteoarthritis

Rheumatoid Arthritis

Chronic systemic disease of unknown etiology Systemic autoimmune disease affecting synovial joints Chronic symmetric inflammation Affects women more (M:F::1:4) Affects 1% of population Synovitis – exudation of fluid & inflammatory cells into joint Ingrowth of vessels & synovial cells->  granulation tissue (pannus) Pannus secretes lytic enzymes & inflammatory mediators -> destruction of cartilage & erosion of bone Joints immobilized Intra-articular space obliterated ->  ankylosis ``` Insidious onset Systemic disease with fever, malaise, anemia etc. Symmetrical involvement of small joints Hand: PIP, MP Wrist Elbow & ankle also common May be juvenile or adult 10% of adults  severe disability 50% of children  severe disability ``` ``` Complications Joint deformities Contractures E.g., ULNAR DRIFT Subcutaneous nodules Fibrinoid necrosis surrounded by macrophages and lymphocytes Lungs  Interstitial & pleural fibrosis Eyes, heart, vasculature ```