Bone, Joint, and Soft Tissue Pathology

Question 1

What is osteoid?

Answer 1

Unmineralized organic portion of bone

Question 2

What is osteoid comprised of?

Answer 2

Type I collagen

GAGs

Question 3

What is hydroxyapatite?

Answer 3

Inorganic minerals of bone

Question 4

What makes up hydroxyapatite?

Answer 4

Calcium

Phosphorus

Question 5

What does the RANKL pathway promote?

Answer 5

Osteoclast bone resorption

Question 6

What is the RANKL pathway?

Answer 6

RANK ligand osteoblasts binds to the RANK receptor on osteoclasts to activate them by releasing NF-k(kappa)B

Question 7

Where are osteoclasts typically found?

Answer 7

Cowships lacunae

Question 8

What does the Wnt pathway promote?

Answer 8

Osteoblasts bone formation

Question 9

What is osteoprotegrin?

Answer 9

Blocks the RANK ligand to decrease bone resorption

Question 10

What occurs in the Wnt pathway?

Answer 10

WNT proteins are produced by osteoprogenitor cells, WNT binds to LR5 and LR6 on osteoblasts to release beta-catenin activating OPG and inhibiting the RANKL pathway

Question 11

What is produced by osteocytes to inhibit the WNT pathway?

Answer 11

Sclerostin

Question 12

What is a dysostosis?

Answer 12

Bone abnormality in a localized place

Question 13

What is a dysplasia?

Answer 13

Bone abnormality affecting the entire skeleton

Question 14

What are common dysostosis?

Answer 14

Aplasia
Supernumerary digit
Syndactyly/craniosynosteosis

Question 15

What is aplasia?

Answer 15

Complete absence of bone or digit

Question 16

What is Syndactyly/craniosynosteosis?

Answer 16

Abnormal fusion of bones

Question 17

What is a common dysplasia?

Answer 17

Abnormal growth

Question 18

What is an important structural protein in bone?

Answer 18

Collagen type I

Question 19

What is an important enzyme in bone?

Answer 19

Carbonic anhydrase 2

Question 20

What is osteogenesis imperfecta?

Answer 20

Genetic deficiencies in synthesis of collagen type I

Question 21

What is the most common inherited disorder of CT?

Answer 21

Osteogenesis imperfecta

Question 22

Clinical presentation of osteogenesis imperfecta?

Answer 22

Too little bone
Blue sclera
Hearing loss
Small misshapen blue-yellow teeth (decrease dentin)

Question 23

What is osteopetrosis?

Answer 23

Marble bone disease; bones are brittle and break easily

Question 24

What causes osteopetrosis?

Answer 24

Impaired function of osteoclasts due to defect in carbonic anhydrase 2 (pH too high)

Question 25

What is osteopenia?

Answer 25

Bone mass 1-2.5 standard deviations from peak bone mass

Question 26

What is osteoporosis?

Answer 26

Bone mass greater that 2.5 standard deviations from peak bone mass

Question 27

What histologically unique about osteopenia/osteoporosis?

Answer 27

The bone is histologically normal it is just decreased in quantity

Question 28

What characterizes Paget disease?

Answer 28

Increased but structurally weak bone due to Cancellous bone becoming dense bone; typically polyostotic

Question 29

What are the three stages of Paget disease?

Answer 29

Osteolytic Mixed osteoclastic-osteoblastic Osteosclerotic (burnout/quiescent)

Question 30

What is the difference between rickets and osteomalacia?

Answer 30

Rickets: childhood disorder Osteomalacia: adult disorder

Question 31

What causes rickets/osteomalacia?

Answer 31

Vitamin D deficiency or abnormal metabolism

Question 32

What occurs in rickets?

Answer 32

Deposition of bone in growth plates is affected

Question 33

What causes osteomalacia?

Answer 33

Undermineralized bone formation during remodeling

Question 34

What hormone is elevated in hyperparathyroidism?

Answer 34

Parathyroid hormone

Question 35

What does increased PTH do?

Answer 35

Increases the activity of osteoclasts

Question 36

What are the clinical effects of hyperthyroidism?

Answer 36

Osteoporosis | Brown tumors

Question 37

What causes brown tumors?

Answer 37

Bone loss -> Microfractures -> hemorrhage -> macrophages | Hemosiderin in bones

Question 38

What is the general rule for bone tumors relating to age?

Answer 38

Bone tumors are more common in younger individuals but are mostly benign If an older individual has a bone tumor it is more likely to be malignant

Question 39

What is the most common primary malignant bone tumor?

Answer 39

Osteosarcoma

Question 40

What is indicative of an aggressive tumor in X-rays?

Answer 40

Codman triangle

Question 41

What is the appearance of Ewing Sarcoma when stained with H and E?

Answer 41

Nests of densely packed small round cells called Homer-Wright rosettes

Question 42

What is Ewing Sarcoma?

Answer 42

Primitive malignant primary bone tumor typically found on diaphysis of long bones and flat bones of the pelvis

Question 43

What is a synarthroses?

Answer 43

Solid joint immovable lacking space or synovial fluid

Question 44

Why is osteoarthritis a misnomer?

Answer 44

There is no inflammation that takes place in it

Question 45

What is eburnation?

Answer 45

"Polishing" of the bone head in a joint due to loss of cartilage