Cartilage and Bone Flashcards
What is the origin of cartilage?
What are the functions of cartilage?
Describe the general features of cartilage tissue.
Origin: mesenchyme during the 5th week of development
Function:
- Bear mechanical stress without distortion
- Shock absorption
- Development of the fetal skeleton and growing bones
General Features:
- Avascular, nutrition by diffusion
- Two types of growth: appositional (from surface) and interstitial (from inside)
- Poor regeneration, fibrous scar
What are the main components of cartilage?
Describe them with regard to location, RER and Golgi, growth, and function
Three main: perichondrium, cells, and extracellular matrix
Perichondrium: dense irregular connective tissue covering the cartilage in a capsule, allows passage of blood, lymphatic vessels, and nerves
Chrondroblast Cells:
-found close to surface
-derived from mesenchymal cells
-secreting cartilage matrix
-abundant RER and Golgi,
-responsible for appositional growth (on surface)
Chondrocyte Cells:
- chondroblasts that have been embedded in cartilage matrix
- lacunae: spaces in matrix occupied by chondrocytes
- produce and maintain extracellular matrix, responsible for interstitial growth
- isogenous groups:dividing chondrocytes in clusters of cells
Extracellular Matrix: composed of collagen, glycosaminoglycans, proteoglycans, and multiadhesive glycoproteins. Like 60-70% is water.
- Mostly type II collagen in thin fibrils providing mechanical stability and strength
- glucosaminoglycans and proteoglycans: hyaline cartilage is mostly hyaluronic acid, chondroitin sulfate, and keratin sulfate (sulfates link to core)
- Multiadhesive glycoproteins: linking collagen and proteoglycans and attaching chondrocytes to matrix
What is the name for the matrix surrounding the lacunae? What is prevalent in this region?
What is the name for the matrix between the lacunae?
How can you tell the difference between the two on slides?
territorial matrix: surrounding lacunae, contains few collagen fibers and is richer in GAGs
interterritorial matrix: the matrix in between lacunae
Typically the territorial matrix stains more intensely with basic dyes like hematoxylin because of the GAGs, but these differences are not obvious on slides…this was a trap
Describe the three types of cartilage.
What type(s) of connective tissue is involved?
Where is it found?
Are its molecular components visible in light microscopy?
Hyaline cartilage: main type
- type II collagen fibers
- GAGs, and proteoglycans
- has perichondrium made of dense irregular connective tissue (except in articular cartilages and epiphyseal plates)
- chondrocytes often in isogenous groups
- widely distributed: embryonic skeleton, articular surfaces, epiphyseal plates, costal cartilage, respiratory system
Elastic cartilage:
- type II collagen fibers + elastic fibers (visible in light microscope)
- GAGs and proteoglycans
- has perichondrium made of dense irregular connective tissue
- chondrocytes in large distended lacunae
- found in ear and epiglottis
Fibrocartilage: hybrid of hyaline and dense irregular connective tissue
- type II collagen + type I collagen (bundles bb): visible in light microscope
- GAGs and proteoglycans
- no perichondrium
- found in intervertebral discs, pubic cartilage, and sternoclavicular joints and TMJ
What is the name for malignant proliferation of cartilage?
What population does this effect?
Where is this the most common?
Describe the histological presentation.
Chondrosarcoma: cancer with malignant proliferation of cartilage
Effects a wide age range and a mild male predominance
Common in pelvis, proximal femur, and proximal humerus but can occur at any cartilage
Malignant cells with abundant cartilaginous matrix
What characteristics make bone a connective tissue and what characteristics distinguish bone from other connective tissue?
Compare and contrast vascularization of bone and cartilage.
Connective tissue (formed by collagen fibers, ground substance, and cells) characterized by a mineralized extracellular matrix.
Because of the mineralization, diffusion through tissue is limited. Bone, unlike cartilage, is vascular with blood and lymphatic vessels.
Describe the bone in the outer shell.
Describe the bone inside the outer shell extending into the marrow cavity.
What is in the marrow cavity?
Describe the layers of connective tissue covering the external and internal surface of bone.
The outer shell is formed of compact (cortical) bone.
On the inner side of compact bone there is spongy (trabecular) bone that forms a series of spicules and trabeculae
Bone marrow cavity is full of reticular (hematopoietic) connective tissue or fat
The surface of bone is covered with a layer of connective tissue. Periosteum covers the external surface and is made of of dense irregular tissue. In growing bone this has two layers: an external fibrous layer and an internal osteogenic layer containing osteoprogenitor cells. The internal surface of bone is lined with endosteum which also contains osteoprogenitor cells.
Describe the two components of the bone matrix.
Organic matrix:
- collagen type I bundles, GAGs , proteoglycans, and multiadhesive proteins
- very little ground substance
Inorganic matrix:
- mostly calcium phosphate in the form of hydroxyapatite crystals
- also calcium carbonate, Mg, Na, K, etc…
