perichondrium consists of chondroblasts and chondrocytes

type II collagen

aggrecan proteoglycan

epiphyseal plates

can calcify

glassy

synovial (articular) joints

costal cartilage of rib cage

hyaline chondrogenesis usually takes place by appositional growth (cell on top of cell on top of cell)

this does not happen at synovial joints (the only exception for hyaline cartilage joints) because the chondroblasts would be work down by the constant activity of these joints

this is bad because there can be no regeneration of cartilage at these joints

horizontal growth

capsular matrix around isogenous group

territorial matrix around capsular matrix

interterritorial matrix between isogenous groups

death of chondrocytes

decreased joint space -> erosion down to subchondral bone

signs:

heberdens nodes: osteophyte growth at DIP

bouchards nodes: osteophyte growth at PIP

flexiable and elastic

perichondrium consists of chondroblasts and chondrocytes

does NOT calcify

collagen type 2 and aggrecan

on epiglottis and larynx

marfans syndrome (walker "thumb" and steinberg "wrist" test)

no perichondrium

can calcify

made of chondrocytes and fibroblasts

type 1 and 2 collagen

shock absorber

intervertebral discs

Structure:

Endosteum - Inner lining of compact & spongy bone

Periosteum - Outer sheath of dense connective tissue (2 layers)

cylindrical concentric lamellae running vertically housing a canal within which blood vessels and nerves pass

volkmann's canals run horizontally but still carry vessels and nerves

¨Synthesize bone matrix proteins & collagen-I  (osteoid)

where do osteoclasts originate from?

how are they activated?

macrophages

they are non-dividing and are NOT mesynchemal

the tiny pits and divits they cause in bone can be called howship's lacuna

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the precursor cell has a receptor which requires complexing with an RANK ligand (secreted by stromal cells and some osteoblasts) to become an osteoclast

osteoprotegrin (OPG) receptors are free floating and can bind RANK ligands so they are no longer available to bind to progenitor cell receptors.  this is how bone destruction is prevented

it is a crystallized form of Calcium Apatite and can serve as a space filler in bone

it can be degraded by H+ ions

intramembranous ossification - the fusion of flat bones as in the skull bones

endochondral ossification - arises from mesenchymal stem cells which turn into progenitor cells, then osteoblasts, spicules, trabeculae, woven bone, then lamellar bone

Growth process:

Fractors regulating bone remodeling

actions of PTH and calcitonin

growth hormone

estrogen

PTH (parathyroid hormone) raises blood Ca2+ by stimulating osteoclasts, stimulates insteinal absorption of calcium, and inhibits kidney excretion

calcitonin inhibits PTH

growth hormone (GH) or somatotropin stimulate osteoprogenitor cells

IL-1, IL-6, TNF, and M-CSF promote osteoclast activity.  estrogen inhibits them and therefore inhibits osteoclast activity.  this is why osteoporosis can begin during menopause

Bone Repair

FractureàTear of blood vesselsàBlood collectionàBlood clot

Epimysium

à Attachment & cushioning

Perimysium

àPasses contractive force to periphery

Endomysium

àHold muscle components together transmit contractive force houses blood vessels & nerves

what is Myasthenia Gravis

an autoimmune disorder

eyelids droop and there is a weakening of the limbs (cranial nerves are most effected)

the patient has few ACh receptors, therefore, the action potential signal is not propogated very well. in order to strengthen the signal, an inhibitor of ACh esterases (the enzyme that clears ACh) can be introduced to increased the amount of ACh that is being delivered to muscle cells

àIntercalated Disks (gap junctions)

slightly more frequent in the lower extremeties

more often benign

chromosomal abnormalites

lipoma, usually well encapsulated.

characteristic adiocytes will be present

round cell and pleomorphic liposarcomas are aggressive.  you can tell it is a sarcoma and not a lipoma by the presence of lipoblasts

myxoid has an intermediate agressive nature

"reactive pseudosarcoma"

rapidily growing, appear on forearm often, sometimes following trauma

plump immature fibroblasts with a

"tissue culture growth" appearance

rare and malignant tumors often of the retroperitoneum, knee, thigh, distal peritoneum

radiation induced sarcomas

FISH FLESH (HERRINGBONE) type pattern is characteristic

a lesion, small and slow growing

SUPERFISCIAL

on palm: dupuytren contracture

also can be found on penis and plantar surface

composed of mature appear, but poorly defined fibroblasts; often myofibroblasts

DEEP

more rapidly growing, can be infiltrative

there are associations with mutations of the APC and beta-catenin genes

seen in Gardners Syndome (aka, FAP, famililial adenomatous polyposis)

(benign fibrous histiocytoma)

a slow growing nodule that can be infiltrative despite being benign

MAJOR CHARACTERISTIC: spindle cells in storiform (pin wheel) pattern

malignant counterpart to this would be a "malignant fibrohistiocytoma"

rhabdomyosarcoma.  often characterized by a t(2;13) where PAX3 is on chr. 2 and controls skeletal cell differentiation upsteam (this likely gets deregulated when it becomes juxtaposed to FKHR)

dx cell is the RHABDOMYOBLAST: tapdole cells, eccentric eosinophilic granular cytoplasm

variants include:

embryonal

alveolar (worst prognosis)

pleomorphic

MHF, the most common sarcoma seen in adults.  broken down into many subtypes, not just MHF.

Have pin-wheel appearance, sometimes bizarre appearing, multinucleated giant cells, IHC often needed for precise classifiication

frequent in lower extremities

a subtype of rhabdo which usually affects adolescents and carries the worst prognosis

found in the deep muscles of the extremities, it histologically takes on a crude appears of pulmonary alveloi

t(X;18)

Biphasic: two differentiaton layers

• epithelial: cuboidal to columnar and form glands
• spindle cells: arranged in dense, cellular fasciicles around the epithelial cells

denervation of muscles.  when the neural input is lost, its is likely that the muscles will begin to atropy and the fibers will take on a triangular, angulated shape, become disorganized

neighboring unaffected nerve axons are capable of extending their branches to the denervated fibers to reinnervate them.  The fibers will take on the metabolic features characteristic to that nerve, thereby losing that checkerboard appearance that is typically seen with a large mixtures of red and white fibers

and infantile disease associated with chr. 5

most common form is Wernig-Hoffman disease; limp baby; death by age 3

low muscles nervous stimulation leads to weak muscle tone all over

• variations in fiber diameter
• degeneration, phagocytosis, necrosis of fibers
• evidence of some muscle cell regeneration
• later stages, muscles replaced by fat and connective tissue

since the diaphragm is a muscle, it is usually central to the ultimate cause of mortality

selectivity to type I fibers

grip mytonia (cannot relax, have a sustained grip)

balding, cataracts, increased serum CPK

an ion-channel myopathy

they have a dramatic hypermetabolic state with tachycardia, tachypenea, muscles spasms, hyperpryexia

inflammatory disease of skin and skeletal muscle; capillaries are attacked by Abs and complement and lead to ischmia

symmetric weakness of proximal muscles first, slow onset with myalgia

later extramusclar involvement may include lung disease, vasculitis, and myocarditis

25% of patient have underlying cancer

Juvenile Dermatomyositis - also have GI symptoms, calcinosis is observed in 1/3 of cases

grottons scales, heliotrope rash on eyelids

POLYmyositis is same without skin involvement

like dermatomyositis but with no skin involvement

the inflammation is found in the endomysium

there is NO perifasicular atrophy or evidence of vascular damage

cell-mediated injury of myocytes

skeletal muscle inflammation involving DISTAL muscles first and can be assymetric (in this was it is different from D/P)

rimmed vacuoles w/n myocytes are observed

unlike D/P, immunosupressives will not work as a therapy