ITHACA COLLEGE PHYSICAL THERAPY
Pathology for Physical Therapists (PTBS 40300) Spring 2008
Objectives: Connective Tissue-Specialized (cartilage & bone)
This outline should be used to supplement the review module.

Cartilage:

1. Describe the general features of cartilage and the particular features of cells, fibers, and ground substgancesthat make cartilage a specialized connective tissue.

2. Describe the specific characteristics (eg. type of collagen, cells, and ground substance) for each of the three types of cartilage (hyaline cartilage, fibro cartilage, and elastic cartilage).

3. Describe the distinctive features of appositional vs interstitial growth of hyaline cartilage, and also what limits cartilage growth, and the likelihood of cartilage repair after injury.

Bone:

1. Describe the general features of bone and the particular features (eg. type of collagen, cells, and ground substance) that make bone a specialized connective tissue.

2. Describe the fibrous coverings of bone and how they relate to tendon attachments.

3. Describe the differences between compact bone and cancellous bone.

4. Describe the internal morphology of compact bone.

5. Describe the location, morphology, and major function for each of the three principle types of bone cells (osteoblasts, osteocytes, osteoclasts).

6. Describe how nutrients reach bone tissue.

7. Outline the two mechanisms (membranous vs endochondral) of bone ossification.

8. Describe how mature bone remodels.

SPECIALIZED CONNECTIVE TISSUE-CARTILAGE

I. General Features

A. principle cell = chondrocytes
B. principle collagen = Type II
C. major ground substance GAGs = keratin, chondroiton sulfates

II. Common Elements of all types of cartilage

A. Cells = chondrocytes

• large round nucleus
  
• one or more nucleoli
  
• organelles of active secretory cell
  
• membranous surface processes
  
• cells reside in lacuna = hole or space surrounding ground substance
  
• somewhat active, but don't get alot of repair
  

B. Fibers

• type II collagen
  
• optically like ground substance
  
• extracellular area appears diffuse
  

C. Ground Substance

• high in keratin and chondroitin
  
• observed as a bluish purple matrix
  
• dark ring observed around the lacuna
  

III. Types of Cartilage:

A. hyaline cartilage

B. elastic cartilage

C. fibrocartilage

IV. Hyaline Cartilage (diagram)

A. Features:

• most common/abundant type of cartilage
• white to tranlucent glassy in gross specimens

B. Locations:

• articular surfaces of synovial joints
  
• trachea and larynx
  
• ventral ends of ribs

C. Types of Hyaline Cartilage Growth

1. Interstitial = cells in lacunae grow and proliferated within the lacuna, they get trapped together ( (known as isogenous group = collection of chrondrocytes in lacuna)

2. Appositional - cells from inner edge of perichondrium will produce cartilage (however, this does not happen often)

V. Elastic Cartilage

A. Features:

• additional meshwork of elastic fibers, dense and branching, obscures ground substance
• yellowish color when fresh
• resilient

B. Locations

• larynx
• epiglottis
• pinna of ear

VI. Fibrocartilage

A. Features:

• cross between dense connective tissue and hyaline cartilage
• intergrade form of tissue
• bundles of collagen type I
• decreased ground substance
• chondrocytes in parallel columns
• ** no perichondrium **

B. Locations:

• intervertebral disks
• ligament and tendon to bone attachment sites
• pubic symphysis
• intro-articular menisci
  

 

SPECIALIZED CONNECTIVE TISSUE-BONE

I. General Features

A. Function:

• support framework
• rigid lever
• protection
• source of minerals (i. e. maintain Ca+ levels)

B. Components of bone; (diagram)

• Cortical (compact )= dense bone that surrounds the perimeter (outer shell)
• Cancellous bone = spongy trabecular bone (coarse)
• Marrow = fills in open space within a bone
  • Red = blood precursor cells (hematopoietic)
    
  • Yellow = fat
    

C. Nutrients to bone via:

• internal network of large arteries
  
• external piercing of the periosteum
  

D. Bone Coverings

• Periosteum - two layers.
  
  • outer = more fibrous
    
  • inner = more cellular
    
    
• Endosteum - one layer of c.t.; covers inner surface of bone
  
• Sharpey's Fibers - anchors tendons into periosteum and into the bone

II. Bone as Specialized Connective Tissue

A. Cells

• Osteoblasts = matrix formation
  
• Osteocytes = mature, active bone cells, live in lacuna
  
• Osteoclasts = remodelling bone cells, work by chewing up old bone
  

B. Fibers

• collagen type I fiber
  
• parallel arrangement
  
• form layers called lamella
  
• each layer has collagen fibers oriented perpendicular to next layer
  

C. Ground Substance

1. Organic molecules

• proteoglycans: keratin, chondroiton, hyaluronic acid
  
• glycoproteins: osteocalcin - binds calcium to collagen
  

2. Inorganic - mineralized molecules

• calcium and phosphate (hydroxyapatite) are linked to collagen
  
• citrate, carbonate, magnesium make a hydration shell
  
• (these materials can leech out to end up with a rubbery bone)
  

D. Compact Bone (diagram)

1. Lamellae = sheets of bone

a. get lamellae rings = osteons or Haversian System in middle of osteon = haversian canal = where blood vessels are located


b. also have intersitial lamellae = fills in between osteons


c. circumferential lamellae on inner and outter aspents of compact bone transition into cancellous bone

E. Vascular Channels

1. Haversian Channels - run along the length of bone

2. Volkman channels - run at right angles to long bone

Periosteal blood vessels will run into a bone from side via Volkman channels which branch into
Haversian Channels to provide nutrients to cortical layer

F. Canaliculi - very small contacts from one bone cell to another in bone tissue

• allow cells to contact one another with gap junction
• trasmit hormonal messages & move ions back and forth betweent cells
  

III. Bone remodeling

A. Wolfe's Law - shape of bone is altered by mechanical forces

B. Bone Remodelling

1. Osteoclasts - reabsorb = turned on by bone disuse have ruffeled border & hydrolytic enzmes, therefore, lots of lysosomes
2. Osteoblasts - secretes new bone with disuse of bone
3. Activity of basts and clasts regulated by hormonal control:

a. parathyroid hormone - increases calcicum absorption:
b. calcitonin - decreases calcicum absorption

IV. Bone Formation - two basic types:

A. Cartilaginous model (endochondral) ossification for long bone formation (elongation continues from prenatal period through adolescence via the growth plate).

B. Membranous ossification for flat bone fromation.