NPB Module 2: Musculoskeletal System

Definition: Cartilage

Connective tissue that protects and supports other tissues

What is in cartilage?

Cells, extracellular matrix, and ground substances

Cartilage does Not have

Nerves, Blood supply, Lymphatic vessels

Definition: Proteoglycan

attracts water to provide resistance to compression

#1

GAG Chain

#2

Core Protein

What is this structure called?

Proteoglycan

Purpose of Proteoglycans

the collagen network holds the swollen gel in so the tissue pushes back when compressed

Extracellular matrix (ECM)

produced by the cells within a tissue

Cartilage Cell Differentiation: Mesenchymal Stem Cells

found in the perichondrium and differentiates into chondroblasts during growth/repair

Definition: perichondrium

a dense, irregular layer of connective tissue that surrounds most of the body's hyaline and elastic cartilage

Cartilage Cell Differentiation: Chondroblast

found in growing cartilage and produce most of the matrix

Cartilage Cell Differentiation: Chondrocyte

mature and less metabolic activity, no blood supply and maintain the matrix

1

Perichondrium

2

Chondroblasts

3

Chondrocytes

1

Chondrocytes

2

Fibroblasts

3

Chondroblasts

what is this image showing?

Cartilage cells differ by location and morphology

what are chondrocytes embedded in?

the matrix

What is cartilage surrounded by?

Perichondrium

1

Perichondrium

2

Cartilage

Two layers of Perichondrium: Outer

fibrous, collagen-rich; Protective

Two layers of Perichondrium: Inner

Chondrogenic precursors, blood vessles; nutrition and repair

Cartilage Growth: Appositional Growth

Mitosis and differentiation of chondrogenic cells into chondroblasts

• inner perichondrium

Cartilage Growth: Interstitial Growth

mitosis of chondrocytes and deposit new matrix

what growth is this?

Interstitial Growth

What growth is this?

Appositional Growth

What Cartilage is this

Hyaline

What Cartilage is this

Elastic

What Cartilage is this

Fibrocartilage

Hyaline Cartilage

• most common

• found in joints

Elastic Cartilage

• yellowish

• found where both elasticity and rigidity are needed (outer ear)

• contains type II collagen and elastin

Fibro cartilage

• Resists tension and compression

• Type I collagen fibers

• shock absorbers

Hyaline cartilage found in:

Shoulder joint

Elastic cartilage found in:

External ear

Fibrous cartilage found in:

intervertebral disc (in between spine)

why does joint cartilage heal so poorly?

• No blood supply

• No perichondrium

• Few and slow chondrocytes

Vertebrate skeleton functions

• support

• protection of organs

• blood cell production in marrow

1

Epiphysis

2

Diaphysis

3

Metaphysis

1

Medullary cavity

2

Compact bone

1

Compact Bone (cortical)

2

Trabecular bone (cancellous bone)

Cortical (compact) bone

• Very dense

• 80-90% of the total bone mass

• Protects the trabecular bone and the bone marrow

• repaired slowly

Trabecular (spongy, cancellous)

• network inside bone

• 10-20% of total bone mass

• Provides internal support

• Remodeled very quickly

Red marrow

• blood-forming (hematopoietic)

• at birth all available spaces are filled with red marrow

Yellow marrow

• Contains adipocytes

• Not blood forming (can covert back to red marrow after severe blood loss)

• Converts to yellow with age

1

yellow marrow

2

red marrow

Osteoclasts ____ bone

resorb

Osteoblasts form ____ or ____

• woven bone

• Lamellar bone

Woven Bone

• Formed quickly

• distributed randomly

• once mature it is more mineralized than lamellar bone

• weaker and temporary

Lamellar bone

• organized

• formed slowly

• stronger

1

Lamellar bone

2

Woven bone

Growth plates: child

open growth plates

Growth plates: Adult

Epiphyseal lines

1

Osteoclast (resorb bone)

2

Bone lining cells

3

Osteocyte

4

Osteoblast (build bone)