Cartilage, bone, and bone development

Question 1

Compare the three kinds of cartilage.

Describe their matrix.

State their location in the body.

Answer 1

Hyaline- most common type of cartilage

• Traits in slide
  
  • stains basophilic (blue)
  • small aggregations of chondrocytes
• Matrix:
  
  • type II Collagen
  • proteoglycans
  • hyaluronic acid
  • glycoprotein is chondronectin
• Location:
  
  • ​growth plates
  • articular cartilage
  • nasal septum
  • larynx

Elastic- very flexible!

• Traits in slide:​
  
  • large lacunae
  • stains pink
  • to see elastic fibers, use silver stain
• Matrix:
  
  • mostly elastic fibers
• Location:
  
  • ​larynx
  • ear pinna

Fibrocartilage- in special places where support/stregnth needed

• Traits in slide:
  
  • long/stringy/dense fibers
  • pink
• Matrix:
  
  • type I collagen fibers
  • NO perichondrium
• Location:
  
  • intervertebral disk
  • menisci

Question 2

List the types of collagen found in cartilage.

Answer 2

Type II- Hyaline cartilage

Type I- Fibrocartilage

(elastic- Elastic cartilage)

Question 3

Explain the healing potential of the three cartilages.

Answer 3

Minimal healing potential for all cartilage!

Hyaline cartilage-regeneration

***except Articular hyaline cartilage (aka growth plate) (because no perichondrium)

elastic cartilage-regenration

Fibrocartilage- CANNOT REGENERATE (because no perichondrium)

Question 4

Explain appositional and interstitial growth.

Answer 4

Growth of cartilage occurs in two ways…

Interstitial growth: from within the cartilage

Appositional growth: at periphery

Question 5

Be able to identify the three types of cartilage in section.

Answer 5

Question 6

List the two kinds of bone and configurations.

Answer 6

List the two kinds of bone and configurations.

Spongy bone- aka cancellous bone. found at ends of bone. comprised of trabeculae network. contains bone marrow

Compact bone- outer layer of dense bone. comprised of osteons. provides rigid support. stores calcium

Question 7

Briefly explain the relationship of PTH/calcitonin to bone and serum calcium levels.

List some target organs and cells of these two hormones.

Answer 7

PTH (parathyroid hormone): increases density and activity of osteoclasts. osteoclasts resorb bone!!! serum ca levels increase.

calcitonin: inhibits osteoclast activity. Ca in serum decreases.

Question 8

Explain the function and composition of synovial fluid.

Answer 8

Synovial Fluid

• within synovial joints
• made of hyaluronic acid and tissue fluid
• provides nutrition, lubrication, and protection at articular surfaces

Question 9

List and explain the osteogenic processes.

Give examples of bones formed by each process.

Answer 9

Osteogenic processes

Intramembranous ossification

• Location: flat bones of scull
• Mechanism:
  
  • direct conversion of mesenchymal tissue into bone

Enchondeal ossification:

• Location: all other bones
• Mechanism:
  
  • mesenchymal tissue converted into cartilage (hyaline)
  • hyaline cartilage replaced by osseus tissue at ossification centers or growth plates.

Question 10

Define primary/secondary ossification centers.

Answer 10

Primary ossification center: site of initial ossification. fetal development. on body/shaft of bone

Secondary ossification center: side of ossification arising later than primary center. in long bones= epiphysis (growth plate)

Question 11

List and explain the zones of the growth plate.

Answer 11

Zone 1: resting cartilage

Zone 2: proliferating cartilage

Zone 3: hypertrophic cartilage

Zone 4: calcified cartilage

Zone 5: ossification

Question 12

Define: perichondrium, chondroblast, chondrocyte, chondroclast, isogenous groups (nests), lacunae.

Answer 12

perichondrium: zone of condensed CT at periphery of mature cartilage zone. (kind of like a capsule surrounding cartilage).

• two layers
  
  • outer-fibrous layer. like Dense CT
  • inner-has chondrogenic cells (give rise to chondroblasts)

chondroblast: immature chondrocyte

chondrocytes: mature cells of lacunae. role in synthesis of ground substance and fibrous elements of cartilage matrix.

• only highly specialized cell in normal articular cartilage

chondroclast: mature osteoclasts. ability to absorb cartilage

isogenous groups (nests): chondrocytes are arranged in clusters of 2-4 cells.

lacunae: area where chondrocytes are. (center/emptyish space in cartilage)

Question 13

Define: mesenchymal cell, osteons, osteonal canal, communicating canal, canaliculi, concentric lamellae, interstitial lamellae, resorption space, Howship’s lacunae, ruffled border, osteoid and trabeculae.

Answer 13

mesenchymal cell: unit of embryonic CT

osteons: functional unit of bone

osteonal canal: canal in center of osteon (aka Haversian canal)

communicating canal: communicating canal between osteons (aka volkmans canal)

canaliculi: little collagenous fibers
* inside canaliculi is filopodia of osteocyte

Howship’s lacunae: indentations in bone matrix which contain osteoclasts. site of bone reasorbtion.

ruffled border:

osteoid: unmineralized organic matrix of bone. produced by osteoblasts
trabeculae: network of bony bars in spongy bone

Question 14

Cartilage- overview

Answer 14

Cartilage- overview

• Avascular form of connective tissue
  
  • no vessels or nerves
• supports soft tissues, important in bone growth
• composed of ground substance and CT fibers.

Question 15

diaphysis, epiphysis, physis, periosteum, endosteum,

Answer 15

diaphysis:

epiphysis:

physis:

periosteum: CT layer on external surface of bone. site of insertion.
endosteum: CT on inner surface of bone. Lines spongy bone. can differentiate into osteocytes.

Question 16

osteocyte, osteoblast, osteoclasts,

Answer 16

Cellular elements of bone

Osteocyte: maintain bone matrix. (“mature cells of bone”)

• originate from osteoblasts
• occupy lacunae
• communicate using filopoda
• cannot replicate

Osteoblast: matrix formation + regulate mineralization. (“immature”)

• produce type I collagen fibers
• differentiate to become osteocytes
• external to osteoid matrix

Osteoclast: digest bone (role in Ca homeostasis)

• large multinucleated cells with ruffled border
• found in indentations called Howship’s lacunae

Question 17

Bone overview

Answer 17

Bone overview

• bone is a tissue and an organ!
• Function:
  
  • support
  • shape/movement
  • calcium storage
  • maintenance of calcium HOMEOSTASIS
• Structure:
  
  • Water (9%)
  • Organic Matrix (22%) aka-osteoid
  • Inorganic Matrix (69%)
    *

Question 18

Organix Matrix vs. Inorganic Matrix of Bone

Answer 18

Organic matrix of bone

• 95% collagen (Type I)
• tensile stregnth!
• osteoid

Inorganic matrix of bone

• composed mainly of hydroxyapitite crystals within collagen fibers
  *

Question 19

Intramembranout ossification vs. Endochondral ossification

Answer 19

Osteogenic Processes

Intramembranous ossification

• occurs in flat bones of the skull
• occurs within membranes of condensed primative mesenchymal tissue

Enchondral ossification

• occurs in most bones of skeleton
• bone develops from cartilage that is replaced by ossues tissue at ossification centers

Question 20

Define: woven bone and lamellar bone

Answer 20

Woven bone: immature bone in developmental stages. collagen fibers randomly arranged.

Lamellar bone: mature bone. collagen fibers in parallel pattern. successive concentric layers around a central canal containing blood vessels and nerves.

***according to stage of maturation, bone (compact or spongy) can either be woven or lamellar!