Bone & Cartilage

Question 1

• Connective Tissues - function & derived from

- ECM (components)

Answer 1

• Provide struct. & metabolic support for other tissues
• derive from mesenchyme (from embryonic mesoderm)
• ECM dominant functional & mechanical component - relatively aceullar

ECM: (Stroma) - bulk of tissue non-living material (produced by cell and assembled out of cell
Composed of: ground substand (fluid + proteoglycans), fibres & crystal (additional component in bone)

-Variable vascularity (bone = extensive; cartilage = none)

Question 2

How ECM is produced

-3 types of cells that maintain ECM

Answer 2

-produced and maintained ‘remotely’ by local cell types;

• fibrocyte/fibroblast: fibrous tissues
• chondrocyte/condroblast - cartilage
• Osteocyte/osteoblast - bone
• ECM constantly turned over - most digested by specific enzymes (matrix metallopoteases - MMPs)
  
  • esp. important for bone - would become too fragile due to microfractures

Question 3

Types of connective tissues based on their ECM composition

• tendons
• cartilage - why it is stiff
• bone

Answer 3

• Tendon: regular, large bundles of type 1 collagen
  
  • long parallel arrays that provide excellent tensile strength in direction of fibres
• Cartilage: meshwork of type 2 collagen trapping massive sponge-like proteoglycans (have polar side that sucks water in - causes swelling & for them to get trapped n meshwork - is what makes cartilage stiff)
  - firm but resilient and springy
• Bone: woven collagen sheets trap hard, calcified matrix (trap a lot of inorganic minerals)
  - very hard but brittle

Question 4

3 Types of cartilage that form skeleton

-definition of Perichondrium

Answer 4

1. Hyaline Cartilage (slightly transparent)
2. Fibrocartilage (opaque white - due to type 2 collagen)
3. Elastic Cartilage (little webs of elastin throughout)

Perichondrium: fibrous membrane that covers growing and non-articular cartilage

Question 5

3 Functions of Cartilage

Answer 5

1. Provide structure or support for soft tissue
   
   • i.e. airways (hyaline), pubic synapsis (fibrocartilage)
2. Form or assist articulations
   
   • smooth surfaces where bones meet, joins bones together & shock absorbing pads
3. Precursor model for most bone growth
   
   • serves as a “rough draft”

Question 6

Types of Cartilage: Hyaline

• Characteristics
• Function
• Where found

Answer 6

*most common & weakest
-clear glassy appearance under microscope
-chondrocytes w/in lucunae scattered through ECM
-collagen mainly in submicroscopic fibrils
-surrounded by perichondrium
Function:
-provides support through flexibility & resilience
-forms most of fetal skeleton & model for most future bone growth
-allows bones in joint to move
Found in: nose, trachea, most of larynx, coastal cartilage (attached to ribs), & articulate ends of long bones>

Question 7

Types of cartilage: fibrocartilage

• Characteristics
• Function
• Where found

Answer 7

*has numerous course, readily visible fibres in ECM
-fibres arranged as irregular bundles b/w large chondrocytes that are arranged in parallel rows
-sparse amount of ground substance
-collagen fibres interwoven = extreme durability
-no perichondrium (stress would destroy it)
Function: Acts as shock absorber and resists compression
Found: intervertebral discs, pubic symphysis & menisci

Question 8

Types of Cartilage: Elastic

• Characteristics
• Function
• Where found

Answer 8

-Numerous elastic fibres in ECM
-Fresh sections appear yellow
-chondrocytes closely packed & surrounded by small amount of ECM
-elastin fibres denser & more branched - from weblike mesh around chondrocytes w/in lucunae
-surrounded by periosteum
Function: Resists deformation
Found: epiglottis (larynx - stops swallowed materials entering trachea) & external ear

Question 9

Bone;-

• structure
• features
• cells w/in

Answer 9

• Composite (elements that make up bone don’t have same properties as they do mixed together) structural tissue.
  
  • collagen = flexibility & tensile strength
  • calcium hydroxyapatite crystals = rigidity & compressive strength
• 1/3 = organic (fibres & protein)
• 2/3 = inorganic (Ca salts)
• rich blood & nerve supply
• continuous growth & remodeling due to stress
• OSTEONS (bony units) laid down by OSTEBLASTS, maintained by OSTEOCYTES, eaten away by OSTEOCLASTS

Question 10

Compact bone vs. Spongy bone

Answer 10

Compact (aka cortical): appears solid, but perforated by vascular canals (usu. forms hard outer shell)

Spongy bone (aka trabecular, medullary, cancellous): w/in interior of bone - contains spaces (lattice structure) - is v. strong yet lightweight

Question 11

Structure of Compact Bone

Answer 11

• solid & relatively dense
• made of cylindrical struct. called osteons that run parallel to bone
• contain concentric rings (lamellae) that encircle central canal
• lucunae b/w lamellae contain bone cells (osteocytes) that communicate w/ each other via blood vessels
  
  • minute passages = canaliculi

Question 12

Structure of Spongy Bone

Answer 12

• porous
• No osteons
• trabeculae composed of parallel lamellae
• between adjacent lamellae = osteocytes resting in lacunae - nutrients diffuse through canaliculi that open to surface of trabeculae (often form crisscross bars & plates of bone pieces)
  
  • provide great resistance to stresses in many directions

Question 13

2 Types of Ossification

• Origins
• What bones they produce

Answer 13

• Ossification = formation & development of bone connective tissue (Begins in embryo & continues as skeleton grows - even happens into adulthood)
  1. Intramembranous Ossification:
• develops from mesenchyme
• produces flat bones of skull, most facial bones, mandible & central portion of clavicle
  2. Endochondral ossification:
• begins w/ a hyaline cartilage model
• Produces majority of bones in body

Question 14

Regions of long bone

Answer 14

1. Diaphysis (shaft) - ossifies first
2. Ephiphysis (ends of bone) - ossifies second
3. metaphysis (between dia & epi)

*Epiphyseal Plate (aka Growth plate): where endochondral ossification continues to allow lengthening of a long bone

Question 15

TERMINOLOGY: Articulating Surface

• Condyle
• facet
• head
• trochlea

Answer 15

Condyle: Large, smooth, rounded articulate oval structure

Facet: small, flat, shallow articulating surface

Head: prominant, rounded epiphysis

Trochlea: smooth, grooved, pully-like articular process

Question 16

TERMINOLOGY: Depessions

• Alveolus
• Fossa
• Suclus

Answer 16

Alveolus: Deep pit or socket in maxillae or mandible

Fossa: flattened or shallow depression

Sulcus: Narrow groove

Question 17

TERMINOLOGY: Projections of tendon and ligament attachment

• Crest
• Epicondyle
• Line
• Process
• Ramus
• Spine
• Trochanter
• Tubercle
• Tuberosity

Answer 17

• Crest: narrow, prominent, ridgelike projection
• Epicondyle: projection adjacent to a condyle
• line: low ridge
• Process: any marked bony prominence
• Ramus: angular extension of a bone relative to the rest of the structure
• Spine: pointed, slender process
• Trochanter: massive, rough projection found only on femur
• Tubercle: small round projection
• Tuberosity: Large, round projection

Question 18

TERMINOLOGY: Openings and spaces

• Canal
• Fissure
• Foramen
• Sinus

Answer 18

• Canal: passageway through a bone
• Fissure: Narrow, slitlike opening through a bone
• Foramen: rounded passageway through a bone
• Sinus: cavity or hollow space in a bone