Cartilage and Bone Flashcards
1
Q
Cartilage
A
- Specialized connective tissue
- Has a semi-rigid extracellular matrix that is highly hydrated and has viscoelastic properties
- Predominantly avascular
- Has a capacity for continued interstitial and appositional growth
2
Q
Functions of Cartilage
A
- Found in areas that require soft tissue support along with flexibility
- Trachea
- Larynx
- Eustachian tube
- External ear
- Nose
- Found in areas where needed as a developmental precursor for much of the skeleton
- Bones that undergo endochondrial ossification
- Found on joint surfaces, particularly in synovial joints ⇒ articular cartilage
- Enhances movement
- Cushions surfaces transmitting mechanical stress
- Acts as a shock absorber
3
Q
Types of Cartilage
A
- Hyaline Cartilage
- Most common
- Type II collagen
- Elastic Cartilage
- Type II collagen and elastic fibers
- Fibrocartilage
- Type I collagen
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/455/125/a_image_thumb.jpg?1508014478)
4
Q
Perichondrium
A
- Dense fibrous CT that surrounds hyaline and elastic cartilage structures except within joint capsules
- Fibrocartilage has no perichondrium
- Functions in the growth and maintenance of cartilage
- Rich in Type I collagen fibers
- Houses the vascular supply to cartilage tissue
- In actively growing cartilage the perichondrium appears as a two layered structure
- Outer layer
- Fibrous
- Poor in cells
- Comprised primarily of fibroblasts and Type I collagen
- Inner layer
- Cellular
- Composed of chondroblasts and chondrogenic cells
- Outer layer
- Chondroblasts associated with the perichondrium capable of producing new cartilage matrix through appositional growth
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/455/215/a_image_thumb.jpg?1508014939)
5
Q
Chondrogenic Cells
A
- Derived from mesenchymal cells
- Can differentiate into chondroblasts
- Found within the inner cellular layer of the perichondrium
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/455/615/a_image_thumb.jpg?1508015043)
6
Q
Chondroblasts
A
- Found within the inner layer of perichondrium
- Responsible for secreting cartilage matrix at the surface of the cartilage
- When they become completely surrounded by matrix they are known as chondrocytes
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/455/750/a_image_thumb.jpg?1508015196)
7
Q
Chondrocytes
A
- Cells occupy spaces called lacunae
- With mitotic division tend to occur in groups of up to 8 cells called isogenous groups
- Active chondrocytes by LM basophillic with perinuclear clear staining area representing the golgi zone
- Mature active chondrocytes have the typical characteristics of a secretory cell
- As cell ages become heterochromatic, lipid vacuoles accumulate, increased glycogen stores.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/455/819/a_image_thumb.jpg?1508015469)
8
Q
Cartilage Extracellular Matrix
A
- Includes fibers, proteoglycans with sulfated GAGs, and adhesive glycoproteins
- Forms a semi-firm gel
- Basophillic and PAS + due to sulfated GAGs
- Territorial marix
- Directly surrounds chondrocytes
- Higher concentration of sulfated GAGs and less water
- More basophillic
- Interterritorial matrix
- Lighter staining
- GAGs more dispersed
- Fibers
- Varys depending on cartilage type
- Collagen forms ~ 50% dry weight of cartilage
- Ground substance
- Consists of sulfated GAGs for proteoglycans
- Proteoglycans bound to hyaluronan core via link proteins to form aggrecan aggregates
- Matrix is 60-80% water by weight because negatively charged GAGs attract water
- Gives cartilage its resilience and compressive resistance
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/456/207/a_image_thumb.jpg?1508015821)
9
Q
Cartilage Histogenesis
A
- Most cartilage derived from the mesoderm
- Except cartilage of the branchial arches which is dervied from neural crest ectoderm
- Cartilage cells differentiate from mesenchyme into chondroblasts
- Mesenchyme surround the developing cartilage becomes the perichondrium
10
Q
Cartilage Nutrition
A
- Most cartilage is avascular
- Except very rapidly growing cartilage which may contain cartilage canals
- House branches of the perichondrial vessels
- Except very rapidly growing cartilage which may contain cartilage canals
- Nutrients diffuse through intervening matrix
- Limits the thickness of cartilage to a few mm
11
Q
Cartilage Growth
A
-
Appositional growth
- Growth that takes place on inner surface of perichondrium along a free surface
- Produces increase in size by adding material to the periphery
- Mesenchymal cells → chondrogenic cells → chondroblasts → chondrocytes once enclosed by matrix
-
Interstitial growth
- Growth due to mitosis of chondrocytes within the matrix
- Forms isogenous groups
- Chondrocytes within an isogenous group grow and secrete matrix thus moving apart from one another
- Results from expansion from within
- Great advantage for growth
- Adaptive reason for the retention of cartilage by the growing skeleton
- Important during periods of rapid growth as part of endochondrial ossification or at articular surfaces where perichondrium absent
- Growth due to mitosis of chondrocytes within the matrix
12
Q
Cartilage Degeneration
A
- Occurs in deep areas of thick cartilage because cells cannot get nutrients from diffusion
- Chondrocytes begin to atrophy and shrink
- Cartilage may calcify
- Process important as part of normal process of endochondrial bone formation
- Also occurs as cartilage ages ⇒ osteoarthritis
- Articular surfaces can become undulated
- Loss of protective articular cartilage will affect underlying bone causing chronic inflammation
13
Q
Cartilage Regeneration
A
- Very limited ability to regenerate
- Chondrogenic ability of perichondrium limited to active growth periods before adulthood
- Intra-cartilage division of chondrocytes too slow to repair damage
- Acute injuries during adulthood results in deposition of vascularized CT which eventually loses vascularity and persist as fibrous tissue
- Cartilage suited for transplantation without marked immune response
14
Q
Hyaline Cartilage
A
- Most common type
- Glassy non-fibrous matrix composed primarily of Type II Collagen
- Found in fetal and growing skeletons prior to ossification
- Persists at growth plates of immature long bones until skeletal maturity
- Remains cartilaginous in adults in:
- Articular surfaces of bones
- Reinforces/supports areas of respiratory tract
- Forms costal-sternal border
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/457/251/a_image_thumb.jpg?1508017045)
15
Q
Articular Cartilage
A
- Found on the articular surface of bones especially in synovial joints
- Specialized form of hyaline cartilage
- Has no perichondrium
- Cells and fibers are more regularly arranged
- Vertical rows deep
- Horizontal rows near surface
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/457/810/a_image_thumb.jpg?1508017398)
16
Q
Elastic Cartilage
A
- Most cellular type of cartilage with larger cells
- Matrix more opaque than hyaline
- Contains elastic fibers and Type II Collagen
- Has perichondrium
- Less susceptible to degeneration than hyaline
- Not susceptible to calcification as with hyaline
- Found:
- Eustachian tube
- External auditory canals
- Ear
- Epiglottis
- Cuneiform cartilages of larynx
![](https://s3.amazonaws.com/brainscape-prod/system/cm/222/457/668/a_image_thumb.jpg?1508017299)