5.3 - Lecture - Cartilage + Bone Flashcards
Cartilage is responsible for and confers
- structure with flexibility
- specialized to respond to repeatable stressors
- confers structural integrity in the context of intermittent forces (joints, respiratory system)
- functions as shock absorbers
- is fast growing
Bone is responsible for and characterized by
- withstanding compressive forces
- being very light but not brittle
FXNs:
A) levers for movement
B) protect organs
c) support body
D) store Calcium
Hyaline cartilage
- matrix is smooth and flexible
- haylos = greek for glassy
- comprised of cells in specialized matrix
Describe the morphology of cartilage
- mostly water ~ 70%
- Organic materials include 40-60% Type I collagen
- remainder is ground substance - adhesive glycoproteins (e.g. fibronectin) and proteoglycans
- has no dedicated blood supply (explains why so many artefacts in LM)
Describe Aggrecan
- a proteoglycan with 2 types of GAGs
1) chondroitin sulfate
2) keratan sulfate - has around ~160 GAGs total?
- aggregates of aggrecan are specific in that they bind a tremendous amount of water and some ind collagen type II fibrils to the proteoglycan aggregates
Describe how Proteogylcans and Collagen give rise to the anti-compressibilty function of Cartilage
- Proteoglycan aggregates bind to collagens to form a dense meshwork
- collagen type II has a small positive charge but the proteoglycans attached to it make it possess a large net negative charge attracting a lot of water to the proteoglycan aggregates –> which fxn to transport nutrients to chondrocytes via compressive forces
- this underlies the turgor pressure that gives cartilage its anti-compressiblity FXN
What are the 2 regions of the cartilage matrix
- Cells are organized into isogenous groups that forms two regions within the matrix
1) Territorial Region
2) Interterritorial Region
Describe the territorial region of cartilage matrix in terms of LM appearance
- interior part of the matrix (closer to chondrocytes)
- more basophilic than interterritorial region
(typical of increased binding of hematoxylin dye - because increased number of negative charge due to proteoglycen presence and large amount of water in the area)
Describe the interterritorial region of cartilage matrix in terms of LM appearance
- the outer-region, farther away from chondrocytes
- less basophilic than the territorial region
What is the function of the two regions of the cartilage matrix
- creates a local water current allowing water to bring things in/out of the spaces near chondrocytes (which are trapped in the matrix)
Describe places where Hyaline Cartilage, FibroCartilage, and Elastic Cartilage are found
1) Hyaline cartilage - most places not occupied by other two?
2) Fibrocartilage - in between vertebrae, pubic symphysis, minucus (pad-like cartilage in knee joint)
3) Elastic cartilage - in external ear, and epiglottis, Eustachian tube
Describe elastic cartilage
- composed of type II collagen + elastic fibers
- required when increased flexibility is required to return the structure to normal position after being acted on by external/internal forces
- found in: Eustachian tube, epiglottis, external ear
Describe Fibrocartilage
= type I collagen introduced into matrix of hyaline cartilage
- in the spinal cord around nucleus propulsis (also pubci symphysis and miniscus) - in this area it holds together the fluid core of the spinal cord
Describe the appearance in LM of fibrocartilage
- round cell clusters (chondrocytes) surrounded by basophilic substance (matrix near chondrocytes)
- has proteoglycans around them (consistent with cartilage - makes the basophilic stain)
- also has invasion of eosinophilic type I collagen fibers coming from CT
Synovial Joint is made up of
- articular cartilage
- joint (articular) cavity
- joint capsule
- synovial membrane
Articular cartilage is
- Type collagen + chondrocytes
- is hyaline cartilage with addition “gothic arch” style collagen from added support
Describe the synovial Membrane
- Has two layers
1) Intimal layer = 1-4 layers of cells largely composed of the two types of synoviocytes ( A and B)
2) Fibrovascular layer (subintimal) = between the intima and the joint capsule - contains the internal synovial fluid- a mixture of transulate from capillary plexus and ground substance (plasma + HA)
Describe Type A synoviocytes
- derived from monocytes (like macrophages and osteoclasts)
- are the equivalent of macrophages in this area
Describe Type B synoviocytes
- same morphology of fibroblast
- create the HA that makes up fluid of synovial cavity
Describe the cartilage repair ability and efficiency
- cartilage has a highly limited capacity for repair
- cells in perichondrium have ability to differentiate into chondrocytes but it is very very limited
- defects in cartilage are often filled by fibroblasts, which produce a dense CT –> limiting and impairing the recovery of function of cartilage in that area
The fact that cartilage is avascular and without nerves confers 4 important characteristics to the tissue:
1) lower change of transplant rejection with cadaver-base tissue
2) Poor recovery of chondrocyte after damage
3) No direct pain from cartilage damage
4) need to have diffusion from surrounding CT to be substrate for metabolic support
What are the 2 mature bone macroscopic classifications (include all common names)
1) Compact Bone = dense bone = cortical bone
2) Trabecular bone = spongy bone = cancellous bone
Describe Compact Bone
- typically outer cortical bone
- will vary in density depending on what part of bone you are observing (e.g. epiphysis vs. diaphysis)
Describe Spongy Bone
- highly organized –> confers strength without increasing weight
= a 3D latticework using rods, arches, plates to counter forces and provide maximum support of weight
