Bone & Cartilage Flashcards
- Connective Tissues - function & derived from
- ECM (components)
- 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)
How ECM is produced
-3 types of cells that maintain ECM
-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
Types of connective tissues based on their ECM composition
- tendons
- cartilage - why it is stiff
- bone
- 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
3 Types of cartilage that form skeleton
-definition of Perichondrium
- Hyaline Cartilage (slightly transparent)
- Fibrocartilage (opaque white - due to type 2 collagen)
- Elastic Cartilage (little webs of elastin throughout)
Perichondrium: fibrous membrane that covers growing and non-articular cartilage
3 Functions of Cartilage
- Provide structure or support for soft tissue
- i.e. airways (hyaline), pubic synapsis (fibrocartilage)
- Form or assist articulations
- smooth surfaces where bones meet, joins bones together & shock absorbing pads
- Precursor model for most bone growth
- serves as a “rough draft”
Types of Cartilage: Hyaline
- Characteristics
- Function
- Where found
*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>
Types of cartilage: fibrocartilage
- Characteristics
- Function
- Where found
*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
Types of Cartilage: Elastic
- Characteristics
- Function
- Where found
-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
Bone;-
- structure
- features
- cells w/in
- 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
Compact bone vs. Spongy bone
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
Structure of Compact Bone
- 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
Structure of Spongy Bone
- 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
2 Types of Ossification
- Origins
- What bones they produce
- 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
Regions of long bone
- Diaphysis (shaft) - ossifies first
- Ephiphysis (ends of bone) - ossifies second
- metaphysis (between dia & epi)
*Epiphyseal Plate (aka Growth plate): where endochondral ossification continues to allow lengthening of a long bone
TERMINOLOGY: Articulating Surface
- Condyle
- facet
- head
- trochlea
Condyle: Large, smooth, rounded articulate oval structure
Facet: small, flat, shallow articulating surface
Head: prominant, rounded epiphysis
Trochlea: smooth, grooved, pully-like articular process
