1. OVERVIEW
1.1. functions
1.1.1. cells: chondrocytes
1.1.1.1. located in lacunae
1.1.1.2. synthesize and maintain the ECM components
1.1.2. bear mechanical stresses without permanent distortion
1.1.3. cushioning and sliding regions
1.1.4. shock absorber
1.2. ECM
1.2.1. high concentrations of GAGs and proteoglycans
1.2.2. interact with collagen and elastin
1.2.2.1. type II collagen
1.3. blood and nerves
1.3.1. lack of vascular supplies → diffusion
1.3.2. lack of nerves
2. HYALINE CARTILAGE
2.1. overview
2.1.1. most common
2.1.2. homogenous and semitransparent
2.1.3. located
2.1.3.1. movable joints
2.1.3.2. larger respiratory passages (nose, larynx, trachea, bronchi)
2.1.3.3. ventral ends of ribs
2.1.3.4. epiphyseal plates of long bones
2.1.4. embryo: temporary skeleton
2.2. matrix
2.2.1. type II collagen
2.2.2. aggrecan
2.2.2.1. structure: GAG side chains of chondroitin sulfate and keratan sulfate
2.2.2.1.1. water bound → 60-80% weight
2.2.2.2. most abundant
2.2.3. chondronectin → adherence of chondrocytes to the ECM
2.2.4. territorial matrix
2.2.4.1. GAGs > collagen
2.2.4.2. surrounding the chondrocytes
2.3. chondrocytes
2.3.1. chondroblasts
2.3.1.1. periphery: elliptic shape
2.3.1.2. deeper: round → isogenous aggregates (groups of up to 8 cells)
2.3.2. chondrocytes
2.3.2.1. collagens
2.3.2.2. ECM components
2.3.3. accelerated by many hormones and growth factors
2.3.3.1. somatotropin → insulin-like GFs (somatomedins) → cells of hyaline cartilages
2.4. perichondrium
2.4.1. dense connective tissue → growth and maintenance of cartilage
2.4.1.1. outer: collagen type I
2.4.1.2. inner: mesenchymal stem cells → chondroblasts
2.4.2. all hyaline cartilages (\ articular cartilages)
3. ELASTIC CARTILAGE
3.1. ~ hyaline cartilage
3.1.1. abundant network of elastic fibers → yellowish color
3.1.2. more flexible
3.2. located
3.2.1. auricle of the ear
3.2.2. wall of the external auditory canals
3.2.3. Eustachian tubes
3.2.4. epiglottis
3.2.5. upper respiratory tract
3.3. perichondrium ~ that of hyaline cartilage
4. FIBROCARTILAGE
4.1. mingling
4.1.1. hyaline cartilage
4.1.2. dense connective tissue
4.2. located
4.2.1. intervetebral discs
4.2.2. attachments of certain ligaments
4.2.3. pubic symphysis
4.3. structure
4.3.1. chondrocytes: isogenous aggregates
4.3.1.1. collagen type II
4.3.1.2. ECM: spare
4.3.2. fibroblasts
4.3.2.1. seperate hyaline matrix from chondrocytes
4.3.2.2. collagen type I
4.3.3. no perichondrium
5. CARTILAGE FORMATION, GROWTH, AND REPAIR
5.1. formation (chondrogenesis)
5.1.1. origin: embryonic mesenchyme
5.1.2. differentiation: from center outward
5.1.2.1. superficial mesenchyme → perichondrium
5.2. growth
5.2.1. interstitial growth
5.2.1.1. mitotic division of pre-existing chondrocytes
5.2.1.2. cartilaginous regions of long bones
5.2.2. appositional growth
5.2.2.1. chondroblast differentiation from progenitor cells
5.2.2.2. important during postnatal development
5.3. repair
5.3.1. slow and incomplete (\ young children)
5.3.2. a scar of dense connective tissue
5.3.2.1. avascularity
5.3.2.2. low metabolic rate