Lecture 8 Flashcards
List 3 major classes of cartilage
Hyaline cartilage Elastic cartilage Fibrocartilage
List functions and location of cartilage
• Compressible • Resists distortion • Absorbs shock in joints • Reduces friction in movable joints • Necessary for endochondral bone growth • Involved in bone fracture repair
Describe general histology of hyaline cartilage including matrix and cell types involved
• Cells: - Chondroblasts (cartilage-forming cells) - Chondrocytes (cartilage-maintenance cells) • Extracellular matrix: • Collagen fibers: - Mostly type II collagen (type I in fibrocartilage) • Amorphous ground substance - Hyaluronan (hyaluronic acid) - Chondroitin sulfate, keratan sulfate, heparin sulfate - Glycosaminoglycans • Perichondrium: - Outer fibrous layer surrounding a mass of cartilage: • Contains fibroblasts - Inner chondrogenic layer: • Gives rise to chondroblasts, which become chondrocytes. • The chondrocyte is involved in the production of the collagen and proteoglycans in the matrix. • Avascular - Slow to heal - Nutrients and oxygen are derived from blood vessels that surround the cartilage and must diffuse through the matrix to the cells.
Hyaline cartilage characteristics
Most common type of cartilage • Avascular (cells depend on diffusion through matrix for oxygen and nutrients) • Contains type II collagen fibers • Surrounded by perichondrium • Translucent, bluish gray to white • Solid but flexible • Chondrocytes are often found in cell groups (resulting from cell division). • Growth patterns: - Appositional (Growth that occurs by adding more material to the outside of existing material) - Interstitial (Growth that occurs by inserting additional material into the existing substance) • Mostly a support cartilage • Associated with highly movable joints: - The articular cartilage covering the ends of long bones does not possess a perichondrium: - It cannot be repaired or replaced if it is damaged. - It deteriorates due to aging or pathological processes. • Cartilage tends to develop in regions of low oxygen; bone, however, tends to develop in regions of higher oxygen.
Distinguish between 2 major components of bone matrix
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List the 3 major categories of bone
Bone tissue is classified based on the arrangement of the matrix: • Woven bone: - Occurs during bone development and bone repair • Compact bone: - Also called lamellar bone • Spongy bone: - Also called trabecular or cancellous bone
Describe the general histology of compact bone
• Lacks cavities and forms a dense plate on the outside of long bones or flat bones. • Consists of concentric (Haversian) lamellae which encircle a central blood vessel (and associated nerves) forming an osteon, or Haversian system. • Osteocytes are found between the lamellae located in lacunae and are connected to each other and the Haversian canal via canaliculi. • Volkmann’s canals run perpendicular to the Haversian canals and connect the Haversian canals to each other and to the surface of the bone.
Describe membrane bone formation
• Bone is laid down in a fibrous (collagen) connective tissue matrix. • Osteoblasts use the collagen fibers as a framework to deposit bone matrix. • Bone formed within the original mesenchyme has a spongy texture: • = spongy bone (diplöe) • Periosteum may form on either side of the spongy bone. • Periosteum will lay down layers of compact bone on top of the spongy bone (appositional growth). • Membrane bone formation is generally found in those bones that form the walls of cavities such as the bones of the cranial vault. • Membrane bones do not form complex articulations and surfaces for tendons and ligaments. • Membrane bones can grow appositionally both in thickness and diameter.
Describe endochondral bone formation
(Look at powerpoint slides) Steps in endochondral bone formation: • Primary ossification center occurs in future diaphysis of cartilage model. • Chondrocytes become hypertrophic. • Chondrocytes secrete vascular endothelial growth factor. • Blood vessels break through perichondrium, bringing in osteoprogenitor cells. • Hypertrophic cartilage cells undergo apoptosis, leaving behind thin strands of calcified matrix. • Osteoblasts use calcified strands as substrates for deposition of osteoid. • Osteoid is calcified.
Identify the Arrows
Top= PC = Perichondrium
Bottom=HC=Hyaline Cartilage
Identify the Arrow
Vascular Bundle
Identify the arrows
Top = DEB= Developing Endochondral Bone
Bone= PB= Periosteal bone
