BONE

SSN Histology

The Basics

• Specialized connective tissue:

– mineralized matrix (hydroxyapatite)

• Type I Collagen; Proteoglycans; Non-collagenous Glycoproteins

• Functions:

– Mechanical support

– Calcium homeostasis

– Encloses bone marrow

CellsOsteoblasts = osteocyte progenitors; secrete ground substance for osteoid

Lab 5, Slide 30

CellsOsteocytes = mature, non-dividing bone cells; enclosed in calcified bone matrix

Cells Osteoclasts = remodeling/ resorption by using lysosomal enzymes

CellsOsteoclasts:

Limited bone resorption

Active bone resorption

Mature vs. Immature BoneMature (Lamellar)

Compact (Cortical) Spongy (Cancellous)•w/ Haversian systems •w/ trabecular appearance

Mature vs. Immature BoneImmature Bone (Woven)

•Nonlamellar•Found in fetus or following a fracture

Appositional vs. Interstitial

• Appositional = bone growth on pre-existing bone surface– Note that bone tissue only undergoes appositional

• Interstitial = bone growth via new cartilage formation within pre-existing cartilage mass– Note that it is cartilage that undergoes interstitial

• Long Bone Growth: – WIDTH --> Appositional(bone)– LENGTH --> Interstitial (cartilage)

Endochondral vs. Intramembranous

Endochondral

Intramembranous

Endochondral Ossification

Zone of Proliferation

Zone of Reserve Cartilage

Endochondral Ossification

Zone of Hypertrophy Zone of Proliferation

Endochondral Ossification

Zone of CalcificationZone of Resorption

Endochondral Ossification

Ground Bone Preparation of Bone Samples

Ground Bone Preparation of Bone Samples

Decalcified Bone Preparation of Bone Samples

Final Thoughts….• Let staining properties guide you

• Note cellularity; compare size, color, shape, relative quantity of cells

• Haversian = central to osteon

• Volkmann’s = perpendicular

• Think of bone as specialized connective tissue; always in a dynamic state

• Long bones = endochondral

• Parietal bones = intramembranous

• Mnemonic for Endochondral:

Real Players Have Cool Rides

Question 1. . .

Panel A Panel B

Questions 2 & 3. . .

Figure A Figure B

Questions 4 & 5. ..

Panel APanel B

Question 6. . .