Ch 7 Cartilage

Question 1

What is cartilage?

Answer 1

• avascular connective tissue
• composed of cells called chondrocytes
• to grow bones
• made up of glycoaminoglycans, type II collagen, hyaluronic acid

Question 2

3 types of cartilage

Answer 2

1. hyaline
2. elastic
3. fibrocartilage

Question 3

Hyaline

Answer 3

• complex, living tissue
• homogenous, amorphous
• appears glassy
• low friction surface, lubrication in synovial, distributes applied forces in underlying bone
• chondrocyte-filled lacunae
• composed of:
  
  • type II collagen fibrils
  • hyaluronic acids
  • proteoglycans
  • noncollagenous proteins
    - glycoproteins

Question 4

3 major classes of molecules:

1. Collagen
2. Proteoglycans
3. Noncollageonous proteins

Answer 4

1. Types II, XI, IX, X, VI:
   
   • bulk of fibril, regulates fibril size, facilitates fibril interaction w/ proteoglycan, organizes fibrils into 3D hexonal lattice, attached chondrocytes to matrix framework
2. 3 types of glycosaminoglycan:
   
   • hyaluronic acid, chondroitin sulfate, keratin sulfate.
   • joined to form proteoglycan monomer
3. anchorin CII, tenascin, fibronectin = help anchor chondrocytes to matrix
   
   • have clinical values as markers of cartilage turnover and degeneration

Question 5

definition and location of epiphyseal growth plate(epiphyseal disc)

Answer 5

• during dev’t when cart is replaced by bone, remaining cart serves as a growth site. Functional as long as bone grow in length.
• in articular cart, rib cages, trachea, bronchi, larynx, nose.

Question 6

Chondrocytes:

• isogenous groups
• Active
• Older

Answer 6

• specialized cells that produce and maintain the extracellular matrix and become dispersed.
• clusters recently divided
• cytoplasmic basophilia, many rER, large Golgi ap, secretory granules, vesicles, intermediate filaments, microtubules, actin microfilaments
• less active, small Golgi, sites of lipid droplets and glycogen stores

Question 7

-What is perichondrium?

Answer 7

• dense conn tiss that surrounds hyaline cartilage and glands and many organs
• a source of new carti cells
• divided into inner cellular layer and outer fibrous layer
• exemptions to the rule that hyaline cart is surrounded by peri:
• where carti forms a free surface(articular joints)
• direct contact with bone (nasal/costal, sites of bone formation)
• interstitial growth

Question 8

Elastic Carti

Answer 8

• presence of elastin, elastic fibers interconnected In carti matrix
• in external ear, external acoustic meatus, Eustachian tubes, epiglottis of larynx
• surrounded by perichondrium
• doesn’t calcify at aging.

Question 9

Fibrocarti

Answer 9

• combo of dense regular conn tiss and hyaline carti
• chondrocytes disperse among collagen fibers, singly, in rows, in isogenous groups
• less matrix material
• no surrounding perichondrium
• in intervertebral disks, symphysis pubis, sternoclavicular and tempormandibular, knee joints, where tendons attach to bone
  
  • acts as shock absorber
  • deg of which forces occur is = amt of carti matrix material present

Question 10

Blastema

Answer 10

• aggregate of mesenchymal or ectomesenchymal cells marks the site of hyaline carti formation
• chondroblasts = secrete matrix -> chondrocytes = surrounded by matrix

Question 11

2 kinds of growth:

1. Appositional
2. Interstitual

Answer 11

1. forms new carti at surface of an existing carti
   
   • from inner peri, resemble fibroblasts in form/func, producing type I collagen of peri.
   • cyto process disappears ->nucleus rounded -> cyto increases amt -> chondroblast -> secretes type II -> carti mass ^ -> new fibroblast ^
2. Forms new carti within existing carti:
   
   • arise from division of chondro w/in their lacunae
   • daughter cells occupy same lacunae -> new matrix secreted -> partition forms -> each daughter/lac -> further secretion -> more cells apart

Question 12

Why does carti have limited ability for repair?

Answer 12

• avascularity
• immobility of chondrocytes
• limited ability of mature cells to proliferate

Question 13

Calcification

Answer 13

• occurs in:
  
  • articular cart in contact w/ bone tiss in growing adult bones, but not on surface portion
  • carti about to be replaced by bone (endochondral ossification)
  • aging process
• calcium phosphate crystals become embedded in matrix bcoz diffusion is stopped in matrix and chondrocytes swell and die.

*chondroclast: digestion of calcified carti that’s replaced by bone