(4) Cartilage + Bone

Lecture 4

What are the 3 components that make up sketal system?

Bones, Cartilages, Joints

Where are the 9 locations of cartilage in body?

1. External Ear

2. Nose

3. Articular Cartilage

4. Costal Cartilage

5. Larynx

6. Air tubes of the respiratory system

7. Discs Between Vertebrae

8. Pubic Symphysis

9. Articular discs with certain movable joints

What tissue is the perichondrium?

Dense irregular connective tissue

What is the location of the perichondrium?

Surrounds a cartilaginous structure in the skeleton

What is a chondrocyte?

Cells in cartilage

Where is the chondrocyte abundant in?

Extracellular Matrix

Where is the chondroblast found?

In growing cartilage

What are chondroblasts?

Cells that secrete the matrix + produce the matrix (like lacunae)

What is lacuna/lacunae?

A matrix where chondrocyte in each cartilage tissue is located

What does the matrix in lacunae have?

Contains fibers & jelly like ground substance of complex sugar molecules that attract and hold water

What are the 6 functions of the bones?

Support, movement, protection, mineral storage, blood cell formation and energy storage, energy metabolism

What is the articular cartilage?

Covers the ends of most bones at movable joints

What are costal cartilages?

Connects the ribs to the sternum (breastbone)

What is the function of periochondrium?

Acts like a girdle to resist outward expansion when the cartilage is subjected to pressure. It ufnctions in growth and repair of cartilage.

How are bones supported?

Provide a framework to support bodyweight

How does collagen help make the bones stronger?

Contributes flexibility and tensile strength
Allow bone to resist stretching and twisting

Where is collagen abundant in?

Bone tissue

What is hydroxyapatite?

Mineral salts (calcium phosphate) that are tiny crystals that are inside and around collagen fibrils in ECM

How does hydroxyapatite create bone strength?

The crystals/minerals salts pack tightly and provide bone with hardness to resist compression

What are osteoblasts?

Cells that actively produce and secrete the organic components of the bone matrix

What are the organic components of the bone matrix?

Ground substance + Collagen Fibers

What is the function of osteocytes?

Keep bone matrix healthy

Where are osteocytes from?

Former osteoblasts trapped in osteoid

What happens if osteocytes die?

The bone matrix is resorbed

What is the role of osteoclasts?

cells break down bone matrix / reabsorption of the bone

Where are osteoblasts from?

White blood cells

What is the mechanism of osteoclasts?

HCL → dissolves minerals
Enzymes → digest organics

What is osteon

Main unit of compact bone

Long cylinder, aligned with bone axis

Made of concentric rings (tree trunk)

Function: resist compression → weight bearing

What is lamella

Each ring/tube in the osteon

Collagen + crystals aligned in 1 direction

Alternating directions = stops cracks and twisting

What is interstitial lamellae?

Old osteons between new ones

Filled gaps from bone remodeling

What is Central Canal?

Middle of each osteon

Lined with endosteum (osteogenic)

Holds blood vessels + nerves

What is perforating canal?

Right angle to central canal

Links blood and nerve supply to periosteum → central canal → marrow cavity

What is canaliculi?

Tiny channels connecting lacunae → central canal

Osteocyte arms reach through to pass nutrients

Gap junctions = cell to cell nutrient sharing

Spongy Bone

Each trabecular contains several layer so lamellae and osteocytes

Too small to contain osteons or vessels of its own

Osteocytes receive nutrients from capillaries in the endosteum surrounding the trabecula via connections through canaliculi

Compact Bone

Riddles with passageways for blood vessels and nerves