Sys Path FINAL

bone matrix consists of what 2 components?

• osteoid (organic)

• hydroxyapeptite (inorganic)

osteoblast

produces osteoid and line trabeculae

when osteoblasts are highly active, what increases in the blood?

ALP

osteocyte

osteoblast that resides in lacunae surrounded by matrix and sense bone loading

osteoclast

macrophage type cell that resorbs bone via acidic enzymes

cortical bone features:

• dense

• longitudinal osteons

• concentric lamellae around central blood vessel

trabecular bone features:

• no osteons

• lamellae parallel to surface

woven bone features:

• rapid ± reactive growth

• no lamellae or osteons

• irregular lacunae and collagen

• weak bone later replaced by lamellar bone

periosteum covers what parts of bone?

everywhere but articular surfaces plus tendon insertions

periosteum layers:

• outer fibrous

• inner cambium

where is the primary ossification center of bone?

at diaphysis and extends into metaphysis

where is the secondary ossification center of bone?

epiphysis

physis (growth plate)

band of cartilage between primary and secondary ossification centers until maturity

what are the 3 zones of the physis?

1. reserve

2. proliferative

3. hypertrophic

how does cartilage at physis become metaphyseal bone?

• as cartilage hypertrophies, matrix gets mineralized

• capillaries invade with osteoblasts, which deposit osteoid on mineralized cartilage (primary spongiosa)

• later cartilage removed (secondary spongiosa)

what species has very late physeal closure?

sheep

what 2 major factors affect deposition and resorption of bone?

1. demand for minerals

2. mechanical forces

fracture classifications:

• simple vs comminuted

• impacted (one fragment in another)

• compound (open)

• greenstick (intact periosteum with minimal fragment separation)

• avulsion (excess traction on tendon or ligament tears off piece of bone)

• microfractures (tiny fractures of trabecular or cortical bone)

• infraction (multiple microfractures together)

stress fracture

combining stress related cortical microfractures

salter harris fracture classification:

fractures of physis

fracture repair timeline:

perfect fracture realignment speeds/slows healing

slows

fracture repair complications:

• large fragments of necrotic bone interfere with healing

• infection

• excess movement and displacement can result in pseudoarthrosis (false joint)

angular limb deformity due to physis damage pathogenesis:

one side of physis is detroyed and other side keep growing and bending toward damaged side

valgus

lateral deviation of distal joint

varus

medial deviation of distal joint

causes of bone necrosis:

• trauma

• neoplasia

• inflammation

• embolism

sequestra

large fragments of necrotic bone

outcomes for necrotic bone:

• osteoclasts resorb it in areas that have blood flow

• bone can heal with some dead bone

• pyogenic infections lead to sequestra

• separates from viable tissue and forms sequestra

involucrum

granulation tissue wall that forms to wall off sequestrum

legg-calve-perthes disease

avascular necrosis of femoral head due to delayed incorporation of blood vessels into bone channels

spina bifida

failure of dorsal midline closure

what are the main causes of generalized skeletal dysplasia?

• cartilage defects

• bone matrix problems

• bone remodeling defects

achondroplasia

absence of cartilage development

chondrodysplasia

disorder of cartilage development

chondrodysplasia bulldog type:

• seen in dexter cows

• autosomal recessive

chondrodysplasia spider lamb syndrome:

• suffolk and hampshire sheep breeds

• FGF3 receptor defect

• long necks and limbs, spinal curvature, angular limb deformities

• multiple ossification centers

FGF4 defect

chondrodysplasia in corgis, pekingnese, and bassett hounds

physeal dysplasia of femoral capital physis

persistence of mutiple physes after they should close

osteopetrosis

autosomal recessive disease causing defective osteoclast numbers and/or activity

congenital hyperostosis

rare lethal disease in newborn pigs that causes periosteal new bone and soft tissue edema

craniomandibular osteopathy

bilateral bone proliferation on skull, mandibles, ± tympanic bulla

craniomandibular osteopathy signs:

• 4-7 months

• painful chewing or inability to open mouth

• fever

• atrophy of masticatory muscles

hypertrophic osteopathy

diffuse periosteal new bone formation along limbs, associated with chronic inflammatory or neoplastic lesion in thorax

benign bone cyst pathology:

• long bones

• erode cortex

• can cause fractures

• resolve with curettage, steroid, or bone graft

aneurysmal bone cyst pathology:

• ballooned periosteum

• soap bubble appearance

• resolve with excision

• can cause fractures

signs of malnutrition or starvation in bone:

• growth arrest lines

• osteoporosis

• serous atrophy of fat

where is the majority of body Ca and P stored?

hydroxyapatite

what stimulates activation of vitamin D?

• direct: PTH, low P

• indirect: low Ca

phosphatonins

reduce P

calcitonin

reduces serum Ca

osteopenia

increased radiolucency of bone that can be due to many factors

causes of osteoporosis:

• aging

• disuse

• starvation (serous atrophy)

• pure Ca deficiency

• copper deficiency (reduced collagen crosslinking)

• steroids

• GI malabsorption

radiographs only show osteoporosis when ______% of bone calcium is lost

30-50

osteoporosis lesions:

• loss of trabeculae

• remaining trabeculae become thick

• enlarged medulla

• thin cortices

• growth arrest line

• serous atrophy

rickets

defective bone mineralization in young animals

osteomalacia

defective bone mineralization in adult animals

phosphorus deficiency signs:

• pica

rickets signs:

• lameness

• angular limb deformities

• swollen joints

• segmentally thickened physes

• enlarged costochondral junctions

fibrous osteodystrophy

excess bone resorption and replacement by excess fibrous tissue due to persistent increases in PTH

what can cause fibrous osteodystrophy?

• primary hyperparathyroidism

• secondary hyperparathyroidism

• renal secondary hyperparathyroidism (reduced P excretion and loss of Ca)

• nutritional secondary hyperparathyroidism (high P:Ca diet)

nutritional secondary hyperparathyroidism signs:

• soft bones

• bilateral skull enlargement

vitamin C deficiency pathogenesis:

reduced collagen production and crosslinking (scurvy)

vitamin A toxicity pathology:

• narrowing or destruction of physes

• osteoporosis

• exostoses (bony outgrowths) in chronic exposure

• teratogenic

osteomyelitis

inflammation of medulla

exostosis

nodular, benign, bony growth projecting from bone’s surface

enostosis

bony growth within medullary cavity

what are the 3 routes of bacterial entry for osteomyelitis?

1. hematogenous

2. local extension

3. implantation

outcomes of bone infection:

• resolution

• abscess

• sequestration

what bacteria can cause osteomyelitis?

• pasteurella multocida and bordetella bronchiseptica in pigs (atrophic rhinitis)

• actinomyces bovis (lumpy jaw)

actinomyces bovis bone pathology:

• pyogranulomatous inflammation

• bone enlargement with honeycomb appearance

• sulfur granules

fungal osteomyelitis pathology:

• pyogranulomatous inflammation

what fungi can cause fungal osteomyelitis?

• coccidioides immitis

• blastomycosis

• cryptococcus spp

metaphyseal osteopathy signs:

• large breed puppies

• fever

• pain

• lameness

• double physis sign parallel to physis

panosteitis

a non-inflammatory condition that affects long bones large breed dogs

panosteitis signs:

• shifting lameness

• increased medullary density starting at nutrient foramen and spreading outward

primary bone tumors are common in ____

dogs

osteoma

benign tumor that is smooth, hard, dense and well differentiated that is common in large animals

ossifying fibroma

benign tumor that is hard, slow-growing and well differentiated that is common in horses

fibrous dysplasia

replacement of bone by fibrous tissue and disorganized osteoid matrix

osteosarcoma pathology:

• production of osteoids

what is the most common primary tumor of the appendicular skeleton in cats and dogs?

osteosarcoma

osteochondroma presentation in dogs:

• benign tumor that arises near physis or articular cartilage or bones formed by endochondral ossification

• have cartilage cap

osteochondroma presentation in cats:

• arises in periosteum

• affects flat bones

• not connected to underlying marrow

multilobular tumor of bone

slow growing, aggressive cartilage tumor that occurs mostly on skull

chondrosarcoma

malignant tumor that produces chondroids and can invade and cross link joints

giant cell tumor of bone appearance:

• expansile osteolytic mass usually in long bones

• benign

• soap bubble appearance

fibrous joints

united by fibrous tissue

kinds of fibrous joints:

• sutures

• syndesmosis

• gomphosis

sutures are on the _____ only

skull

syndesmosis

bones connected by ligament

gomphosis

connect teeth to jaw by periodontal ligament

kind of cartilaginous joints:

• synchondrosis

• symphysis

synchondrosis

temporary joint at physis

nucleus pulposis

gelatinous central part of intervertebral disc

annulus fibrosis

fibrocartilage outer part of intervertebral disc

synovial joint components:

• articular hyaline cartilage

• joint capsule

• synovial fluid

articular joint capsule is continuous with…

periosteum of adjacent bones

synovial membrane is lined by _________

synoviocytes

type A synoviocytes:

• macrophage lineage

• phagocytic

• long lifespan