Block 2 Flashcards
What are two benign bone forming lesions?
Osteoid osteoma and osteoblasoma
Osteosarcoma
Malignant mesenchymal tumor, most common sarcoma of bone - mets in lungs, poorly delineated
What is the mean age of those diagnosed with osteosarcoma?
Male > Female
15 (peaks again in 50s)
Atypical mitoses are indicative of ______________.
Malignancy
What is the most common benign tumor of bone?
Osteochondroma
Where does osteochondroma occur?
Metaphysis of long bones
What causes multiple chondromatosis?
Point mutations in IDH1 or IDH12
What are the 4 main functions of bone?
- Infrastructure
- House bone marrow
- Specialized CT
- Reservoir of Ca and phosphate
What is the term for the inorganic material of bone matrix?
Hydroxyapatite - Ca, phosphate
What is the term for the organic material of bone matrix?
Osteoid (Type 1 Collagen)
What is cartilage made up of?
Water and Type II collagen
No mineral, neuronal, or vascular structures
Osteoblasts are specialized __________ and function to ______ bone.
fibroblasts
build
Bone formation is completed by __________-mediated deposition of Ca within the osteoid.
Osteocalcin
Osteocytes function to ________ bone, they occupy ___________, and they have cytoplamsic process that join those of other osteocytes via ____________.
- Maintain bone (long lived, most numerous cells in bone)
- Lacunae
- Gap junctions
Osteoclasts function to ____________ bone matrix and they reside in ____________. They are multinuclear since they develop from __________________.
- Destroy/remodel bone matrix
- Howship’s lacunae (hollow matrix areas)
- Fused macrophages
Osteoclasts are inhibited by ___________ and activated by _____.
- Calcitonin
2. PTH
How do osteoclasts break down bone matrix?
They attach to ECM via their ruffled border.
They release cathepsin-K and H+ into the microenvironment created
Paget’s Disesase
Lose bone mass - extensively multinucleated osteoclasts
Osteoblasts mainly reside in the ___________.
Periosteum
Osteoclasts reside attached to the bony matrix on the ______________.
Endosteal side
What microscopic differences are observed between compact/cortical bone and spongy/trabecular bone?
None.
Osteon
cylinder w/ concentric lamellae
Lamellae have _______ that contain osteocyte that communicate via ______________.
Lacunae
Canaliculi
Haversian canal
BV, nerves, and lymph run through
Intramembranous bone development
Osteoblasts deposit osteoid onto mesoderm
Endochondral ossification
Osteoblasts deposit osteoid onto cartilage base.
What processes use endochondral ossification?
Long bones in embryo and repair after fracture
At the diaphysis and epiphyses osteoblasts invade _______________ and secrete osteoid.
calcified cartilage
How do bones get long?
- Somatomedin induces cells to proliferate
- Get large and hollow out cartilage (zone of hypertrophy)
- Zone of calcification - becomes basophilic (blue)
- Zone of ossification - eosinophilic (red)
What happens in the zone of calcification?
Collagen X replaces collagen II –> Osteoblasts can secrete osteoid
What happens in the zone of ossification?
Deposition of collagen I
Bone Repair
- Macrophages remove debris
- Chondroblasts secrete hyaline cartilage
- Osteoblasts replace with bony callus
- Primary (woven) bone is deposited then replaced by lamellar bone
What are three methods of bone tissue engineering?
- Bone morphogenic proteins (BMP-2 and BMP-7)
- Adult stem cells (MSC) - Osteoblasts
- GFs or cells or both are implanted w/i biodegradable sponges made of collagen 1
Osteopetrosis
Dense, heavy bone - osteoclasts lack ruffled border
Osteoporosis
Fragile - hollow bone - osteoclasts outpace osteogenesis - deviation from bone mineral density mean with age
Osteoclast production: Stromal cells in BM are induced by PTH to secrete which 3 things?
- M-CSF - macrophage proliferation
- RANK-L - macrophage diff into osteoclasts
- OPG - osteoprotegerin antagonizes RANK-L??
What allows osteoclasts to attach to bone?
Alpha5-beta3 integrin
Osteoblasts are inhibited by ______ and induced by ____.
Leptin
BMP
Osteoclasts are inhibited by ________ and ___________ and induced by _________.
- Calcitonin and osteoprotegerin
2. RANK-L
Spikes of PTH favor __________ formation while constant PTH favors ____________ formation.
Osteoblast
Osteoclast
What are three types of anti-resorptive drugs?
- SERMs
- Bisphosphonates
- Calcitonin
What are other types of bone saving drugs?
- Osteoprotegerin, inhibit alpha5-beta3, anabolic agents, CBFA-1 master gene
Pathogenesis for most soft tissue tumors is ________.
Unknown
40% of sarcomas occur in the ______.
Thigh
15% of sarcomas arise in _______ – incidence _________ with age.
Children
Increases
What is the most common soft tissue tumor of adulthood?
Lipoma
What is the most common soft sarcoma of childhood and adolescence?
Rhabdomyosarcoma
