Osteochondrogenesis/Joint Components Flashcards
What are the two types of bone histogenesis?
Intromembranous and endochondral bone formation
What is bone remodeling?
The combination of bone formation and resorption
Is remodeling faster in primary or secondary bone?
Primary Bone
What is the relationship of Ca and bone?
Bone stores Ca used to buffer the levels of Calcium present in the blood.
Describe the mineral and H2O content of old osteons.
Highest mineral concentration and lowest H2O content
Describe the process of osteoclast activity.
Erosion tunnel and 2 weeks later, apoptosis
Describe the process of new bone being laid down
Osteoblasts –> cementing substance (forms cementing/reversal line) –> blasts get caught, become cytes.
Name flat bones.
Skull, facial bones, mandible, clavicle, pelvis
What type of tissue houses intramembranous bone formation?
Highly vascular mesenchymal tissue
List a few signalling factors involved in intramembranous bone formation.
Wnt, hedgehog, FGF, TGF-beta
What forms a primary ossification center?
Condensed mesenchymal cells, which differentiate into osteoblasts
What do the osteoblasts in intramembranous bone formation secrete?
Osteoid collagen
Whats another term for the bone formed with osteoid collagen?
Woven Bone
Collagen secretion eventually causes osteoblasts to…
become caught in the matrix, becoming osteocytes. These unite to form trabeculae.
How is spongy bone made?
Fusion of bony trabeculae, followed by invasion of blood vessels, and mesenchymal differentiation into bone marrow.
What does mesenchymal tissue that doesn’t undergo ossification become?
Periosteum and Endosteum
Woven bone is eventually converted into _______ ____ in the outer layers.
Lamellar Bone
Endochondral bone formation is used to make ____ _____ using _______ _________ as a scaffold.
Long Bones. Hyaline Cartilage.
What are the two stages of endochondral bone development?
Development of primary ossification center, development of secondary ossification centers.
Where does the primary center of ossification occur?
The midriff of the diaphysis
What does vascularization do to the perichondrium?
Converts chondrogenic cells to osteoprogenitor cells (which form osteoblasts)
After osteoprogenitor cell development, perichondrium converts to….
Periosteum
First region of bone generated by osteoprogenitors is…
Subperiosteal bone collar
How do chondrocytes respond to the development of the subperiosteal bone collar?
Become hypertrophic, secrete collagen X, and VEGF
How does the cartilage matrix respond to the development of the subperiosteal bone collar?
Calcification, Inhibited nutrient diffusion, and eventual death of hypertrophies chondrocytes. Lacunae merge forming marrow cavity.
Osteoclasts act on the bone collar to allow….
Periosteal buds (vessels, osteoprogenitors, mesenchymal cells) to enter the cavity. Cartilage in the cavity is now calcified.
What is the calcified cartilage-calcified bone complex?
Bone matrix (osteoid) calcified on the surface of calcified cartilage.
How does calcified cartilage stain?
Basophilic
How does calcified bone stain?
Acidophillic
How is the primitive marrow cavity enlarged?
Osteoclasts resorb calcified cartilage-calcified bone complex, allowing for eventual bone formation spreading to epiphysis.
Where/When do secondary centers of ossification develop?
Epiphyses when diaphyseal ossification is well established
How do secondary ossification centers develop?
Basically the same as primary ossification centers…Osteoprogenitors invade, make matrix, replace certilage
When initial bone formation is complete, what two sites can cartilage be found? How does this change at approx. age 20?
Initially cartilage at articular surfaces and epiphyseal plates. After bone growth is done, just on articular surfaces.
Describe the action occurring in an epiphyseal plate.
Addition of new cartilage. Replacement with bone at epiphyseal end.
Describe the cells of the Zone of Reserve
Small, randomly arranged, inactive chondrocytes
Describe the cells of the Zone of Proliferation
Rapid mitotic divisions, rows of isogenous cells
Describe the cells of the Zone of Cell Hypertrophy and Maturation.
Enlarged Chondrocytes
Describe the cells of the Zone of Calcification.
Cartilage Matricies Calcifies, Dead Chondrocytes
Describe the cells of the Zone of Ossification
Bone made on calcified cartilage, followed by resorption of the bone/cartilage complex.
List the zones of the epiphyseal plate.
Reserve, Proliferation, Cell Hypertrophy & Maturation, Calcification, Ossification
Epiphysis enlarges by _________ growth and _______ replacement.
Cartilage. Bone.
Hypertrophic chondrocytes secrete what two substances.
Type X Collagen and VEGF
Describe the process of post-fracture bone repair.
Blood Clotting –> Osteoprogenitor Proliferation –> Callus Formation –> Fibrous Connective Tissue/Cartilage –> Woven Bone/Bony Callus –> Secondary Bone Formation
Hairline fractures heal via what type of bone formation?
Intramembranous
What are synarthroses? Example?
Immoveable joints. First rib to sternum, skull bone connections
What are amphiarthroses? Example?
Slightly Moveable Joints. IV Discs
What are diarthroses?
Synovial Joints (Maximum Movement).
What cell type make the external (fibrous) capsular layer of diarthroses?
Dense Connective Tissue
What cell type forms the lining of the internal (synovial) capsular layer of diarthroses?
Squamous to cuboidal cells on internal surface
What are type A cells of the synovial membrane?
A – Phagocytic (with well developed Golgi and many lysosomes)
What are type B cells of the synovial membrane?
B – Probably synovial fluid secretors, well developed rER
What is osteopetrosis?
Abnormal osteoclast function, leading to mostly woven, not lamellar bone. No marrow cavity development.
What is Albers-Schonberg disease?
Deficiency in carbonic anhydrase II makes it so not enough H+ can accumulate to activate lysosomal anzymes.
What is osteoporosis?
Loss of bone mass. May be caused by increase in speed of breakdown or slowdown of formation of bone.
Rheumatoid arthritis is the product of what type of reaction?
Inflammatory
What type of cells are activated in Rheumatoid Arthritis?
CD4 T Cells
CD4 T Cells produce what to stimulate macrophage activity?
IL-15
What inflammatory cytokines are involved in rheumatoid arthritis?
TNF-alpha, IL-1, IL-6, metalloproteases
