Lecture 8 - Vertebrate Cartilage And Bone Flashcards
List the 3 categories of cartilage
- Hyaline Cartilage
- Elastic Cartilage
- Fibrocartilage
List some of the functions of cartilage
Compressible, Resists distortion, Absorbs shock in joints, Reduces friction in movable joints, Necessary for endochondral bone growth, Involved in bone fracture repair
Note: Cartilage doesn’t Turn into Bone during that transition, it just gets replaced by bone.
What are cartilage cells called?
Describe the extracellular matrix environment of cartilage cells
Two Types of Cartilage Cells:
- Chondroblasts - Form Cartilage Material
- Chondrocytes - Maintain Cartilage material
ECM:
- Mostly Type II Collagen fibers, (Although type I in fibrocartilage)
- Amorphous mix of Hyaluronan (Hyaluronic acid), chondroitin, keratin, heparin, and glycosaminogens.
Describe the environment of the perichondrium (connective tissue outside of the cell, but not at a joint).
- 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.
Describe the characteristics of cartilage pertaining to it’s vascularity (or lack thereof)
It’s avascular. That means it’s slow to heal. Nutrients and oxygen are derived from blood vessels that surround the cartilage and must diffuse through the matrix to the cells.
Describe Hyaline Cartilage Characteristics (Part I)
Most common type of avascular cartilage(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 (Occurs by adding more material to the outside of existing material), and Interstitial (Growth that occurs by inserting additional material into the existing substance)
Describe Hyaline Cartilage Characteristics (Part 2)
Mostly a support cartilage, and associated with highly movable joints: The articular cartilage covering the ends of long bones does not possess a perichondrium: Meaning 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.
- This will become significant when we consider the development of bone.
Review the diagram on Slide 12 of Lecture 8
Do It
Describe the characteristics of bone tissue
Bone tissue is based on a canalicular system. This system allows blood vessels, oxygen and nutrients to be dispersed throughout the matrix of the bone.
- Volkmann canals extend from the exterior of the bone to the bone matrix and are oriented perpendicular to the surface.
- Haversian canals extend from the Volkmann canals and run parallel to the long axis of the bone.
- Canaliculi are tiny canals that interconnect the lacunae with each other and with the Haversian canals. Haversian canals contain cytoplasmic extensions of the osteocytes contained within the lacunae.
- Bone is highly vascular and is found in close proximity to capillaries.
Memorize the diagram of compact bone (Slide 18)
What are the 7 components of compact bone?
A. Fibrous Periosteum B. Osteogenic Periosteum [Haversian System/Osteon] C-F C. Lacuna D. Lamellae E. Canaliculus F. Haversian Canal G. Volkman Canal
List the three main categories of bones
- Woven bone: Occurs during bone development and bone repair
- Compact bone: Also called lamellar bone
- Spongy bone: Also called trabecular or cancellous bone
Describe 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 Trabecular (Spongy) Bone
Has a 3-D lattice of branching, bony spicules intertwined to form trabeculae surrounding the bone marrow spaces in the long bones and flat bones.
Describe membrane bone formation up until compact bone is laid on top of spongy bone.
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).
Describe characteristics of membrane bone formation
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.
