CCIV: BST

mesoderm; notochord and neural tube

somites form from ________ on either side of the _________ and ________

sclerotome

ventromedial portion of the somite

dermomytome

dorsolateral portion of somites

vertebrae and ribs

the sclerotome (ventromedial of the somite) forms the ?

myoblasts and dermis

the deromyotome (dorsolateral of the somite) forms the?

late week 4 to early week 5

when do limb buds begin to elongate?

myogenic cells (myoblasts)

originate from somite and migrate into limb buds

cylindrical myotubes containing myofilaments (muscle fibers)

what do myoblasts fuse into?

weeks 4-8

when do the hands and feet develop?

end of week 6

when are hand plates visible and are forming digital rays?

digital rays

by the end of week 6, hand plates are visible and form ?

week 7

when do toe buds form?

apoptosis

the loose mesenchyme between digits must undergo _________ to create separate digits by the end of week 8

week 8

by when must loose mesenchyme (webbing between digits) must undergo apoptosis to create separate digits ?

week 7

when does osteogenesis of long bones begin?

week 12

by when are ossification centers present in all long bones?

weeks 7-8

what week ? (hand plate present with elongated digits, but webbing still present, toes are starting to form)

intramembranous

bone formation in which mesenchymal cells differentiate directly into osteoblasts between two membrane sheaths and osteoblasts secrete osteoid

intramembranous

what type of bone formation for flat bones?

endochondral

bone formation in which mesenchymal cells condense and differentiate into chondrification centers in the late 5th week; cartilage models of bones form; by week 8 primary ossification centers form within cartilage models

late week 5

when do mesenchymal cells condense and differentiate into chondrification centers for endochondral bone formation?

week 8

when do primary ossification centers begin to form within cartilage models in endochondral bone formation

endochondral

which type of bone formation for long, short, and irregular bones?

syndactyly

failure of webbing to degenerate creating fused digits

syndactyly

polydactyly

supernumerary digits

cleft hand (foot)

failure of the digit rays to form and becomes only 2-3 opposing parts

cleft hand

congenital talipes (clubfoot)

•  clubfoot; many different types 

• uncertain etiology - sometimes hereditary but often environmental factors 

• multifocal inheritance pattern

talipes equinovarus

most common type of congenital talipes with foot turned medially and inverted

congenital talipes (clubfoot)

amelia

complete absence of limb from suppression of limb bud development in the early 4th week

meromelia

partial absence of a limb from arrest or disturbance of growth during the 5th week

• Genetic factors (trisomy 18)

• Mutant genes = skeletal dysplasias (achondroplasia), bradydactyly, or osteogenesis imperfecta

• Environmental factors (thalidomide)

• Vascular disruption and ischemia

what are common causes of limb defects (4)

long

what type of bone: humerus, radius, ulna, metacarpals, phalanges, femur, fibula, tibia

short

what type of bone: tarsal, carpals

irregular

what type of bone: vertebrae, sacrum

flat

what type of bone: cranial, sternum, scapula, ribs

sesamoid

what type of bone: patella

pivot

what type of joint: neck (C1-C2)

hinge

what type of joint: elbow

saddle

what type of joint: thumb

ball and socket

what type of joint: hip

condylar

what type of joint: wrist

plane

what type of joint: between tarsal bones of foot

hyaline cartilage

elastic cartilage

fibrocartilage

smooth muscle

skeletal muscle

adipose tissue

dense fibrous tissue

loose fibrous tissue

eburnation

the result of long term bone-on-bone movement making the surface smooth and glistening (ivory-like)

DJD/osteoarthritis

DJD/osteoarthritis

• older patients, obese, athletes

• bone components within joint are in contact after wear and tear → damaged articular cartilage and underlying bone

• femoral heads, knee bones, humeral heads

• eburnation, surface pitting/distortion, subchondral cysts, osteophytes

avascular necrosis

• trauma, infection, alcoholism, steroid use, sickle cell disease

• almost always femoral heads

• cartilage over the infarct separates from underlying bone

• buckling, distortion, minimal eburnation

avascular necrosis

crescent-sign on x-ray

avascular necrosis

osteophytes

overgrowth on periphery of bony joint components, result of DJD

loose bodies

detached osteophytes from injury, wear and tear

gout

transient attacks of acute arthritis initiated by crystallization of urate within and around joints

primary

gout from overproduction/reduced excretion of uric acid from diet or enzyme deficits (90%)

secondary

gout from overproduction/reduced excretion of uric acid from renal disease or neoplasm (10%)

gout

• synovium thickened, fibrotic, and forms pannus which destroys the underlying cartilage

• tophi = aggregations of urate crystals

• chalky white substance grossly

• needle-shaped crystals with birefringent light

gout

gout

false (chalky substance will not be present in formalin-fixed tissue so MUST use alcohol)

T/F: gout can be placed in formalin

true (formalin will not dissolve but DECAL WILL)

T/F: pseudogout can be placed in formalin

pseudogout (chondrocalcinosis)

• calcium pyrophosphate (CPP) crystals

• more common

• commonly affects knees

• mimics tophi with no destruction of underlying bone

• chalky white substance grossly

• oval/block-shaped crystals

aneurysmal bone cyst

• first 2 decades of life

• multiple blood-filled spaces separated by thin, tan-white septa and covered with a thin layer of bone

• treated by curettage (or en bloc in certain situations)

aneurysmal bone cyst

osteomyelitis

• inflammation of the bone/bone marrow which leads to infection

• injury site, surgical site, ulcer

• bone softening, instability, abscesses

• loss of blood supply → distal degeneration

• can spread into vasculature and cause sepsis/death

• wet/dry ulcers, gangrene, eschars, skin sloughing, mummification

osteomyelitis

incidental ribs (multiple myeloma is most important dx!)

what specimen is often received for thoracic outlet syndrome?

• assess if there is osteomyelitis present

• check margin viability

• determine if PVD is present

why would we gross a specimen for osteomyelitis

wrist

where are ganglion cysts most commonly found?

synovial cyst

herniation of the synovium through a joint capsule

baker’s cyst

cyst in the popliteal synovium

morton’s neuroma

compression neuropathy in the foot

osteoma

• sessile, bosselated, round/oval tumors growing from subperiosteal cortex

• usually bones of the face/skull

• slow growing, often incidental

gardner’s syndrome

multiple osteomas present

osteoma

osteoma

osteoid osteoma

• < 2 cm

• appendicular skeleton, posterior spine, talus

• severe nocturnal pain relieved by aspirin

• severe underlying reaction of bone

• treated by radioablation (not usually received in surg path)

osteoblastoma

• > 2 cm

• spine

• dull achy pain that is not responsive to aspirin

• no bony reaction

• excised

giant cell tumor

• uncommon, benign but locally aggressive

• 20-40 years old

• most common in knee and arise from epiphysis

• destroys overlying cortex producing a large bulging ST mass with a thin shell of reactive bone

  • large red-brown masses with cystic degeneration

giant cell tumor

multinucleated osteoclast-like giant cells with a background of mononuclear cells with nuclei identical to giant cells

giant cell tumor

osteochondroma

• benign, most common bone neoplasm

• late teens, early adults

• endochondral origin - metaphysis near growth plate

• hyaline cartilage-capped tumor with “bony stalk”

• most common in knee

osteochondroma

osteochondroma

chondroma

• benign neoplasm of hyaline cartilage

• incidental and asymptomatic

• 20-50 years

chondroma

well-circumscribed lucencies, with focal opacities if calcified

enchondroma

chondroma within the medullary cavity

chondroma

“scalloping” from nodules pushing into endosteum

maffucci syndrome

endochondrmatosis associated with ST hemangiomas which can become large and cause deformities

chondroblastoma

• very rare bone tume (<1%)

• teens, male > female

• benign but aggressive

• “chicken wire” pattern of calcifications on histo

bone currettage

typical specimen received for chondroblastoma

chondroblastoma

well-defined lucency with scattered calcs