Cartilage & Bone

What is cartilage?

Resilient semirigid form of connective tissue that forms parts of skeleton where more flexibility is required

What is cartilage composed of?

• Chondrocytes

• Extracellular matrix (collagen)

What are chondrocytes?

Specialized cells that produce & maintain the extracellular matrix

What is hyaline cartilage?

• Articular cartilage

• Covers ends of bones

• Provides smooth surface to decrease friction between bony surfaces

• Mainly type 2 collagen

What is elastic cartilage?

• Higher ratio of elastin:collagen fibers

• Gives more flexibility

What is fibrous cartilage?

• Unites bones in joints that have limited motion

• Mostly type 1 collagen

Name some general characteristics of cartilage.

• Avascular → limited healing ability

• Receives oxygen & nutrients through diffusion

Name some characteristics of hyaline/articular cartilage.

• Provides low friction surface

• Assists in lubrication of synovial joints

• Avascular → limited ability to heal

• Aneural (not innervated) → may not experience pain

• Found on ends of bone

• Extracellular matrix with lots of water → manage compressive forces

• Injured by SHEAR FORCES → damage ECM

• Repairs with fibrous tissue

Name some characteristics of elastic cartilage.

• Function: flexible support

• Location ex: external ear, external acoustic meatus walls, eustachian tube

Name some characteristics of fibrocartilage.

• Function: firm support with tensile strength

• Resists compression/shear forces → shock absorption

• Location ex: IV discs, pubic symphysis, TMJ disc, knee menisci

What is cortical bone?

• Compact bone

• Appears solid

• Hard outer shell

What is trabecular bone?

• Spongy bone

• Interior of bones

• Provides strength without much weight

• Contains marrow & blood vessels

What is the difference between primary vs secondary ossification centers?

• Primary = first area to become bone

  • Diaphysis

• Secondary = forms into bone later in life

  • Epiphysis

What is the diaphysis of a bone?

• Shaft of bone

• Primary ossification center

• Contains bone marrow

What is the epiphysis of a bone?

• Found at the ends of bone

• Secondary ossification center

What is the metaphysis of a bone?

• Region of diaphysis nearest the epiphysis

• Contains epiphyseal plate (growth plate)

• Where diaphysis & epiphysis meet

What is the general rule for bone vasculature?

• Generally, bone has good blood supply

• Blood supply → healing ability

What could happen if a bone is fractured?

• Potentially significant swelling

  • Clear/yellow fluid = synovial fluid

  • Blood = possible ligament/bone problem

• Swelling may lead to → compartment syndrome

What is important to know about bones with poor blood supply?

• Less healing ability

• Need to be treated with more caution

• May need more conservative tx

• Ex: scaphoid in wrist

If bone is not highly innervated, then what is?

• Periosteum (outer layer covering bones)

• When bone fx, pain is from periosteum not actual bone

What results from deficiencies in calcium/bone?

• Resorption by osteoclasts > deposition by osteoblasts

• From immobilization or bed rest

• Reduced bone density → more risk of fx

What results from deficiencies in vitamin D?

• Bone matrix does NOT calcify normally → rickets

• Vitamin D needed for absorption of Ca in intestines

• Bone deforms easily due to poor Ca absorption

What results from deficiencies in vitamin C?

• Scurvy

• Inability to produce & maintain bone matrix

• Growth restriction, poor healing of fx

• Affects the ECM