Chapter 6 Bone Tissue

A. Functions/Extracellular Matrix

1. Bone

Rigid

Support/protect/storage/lever/blood

Collagen/Ca & P crystals: hydroxyapatite = concrete

Inorganic matrix:

Hydroxyapatite

Scaffolding for

the skeleton

2. Cartilage

Tough yet smooth/resilient

Bone growth model/joints/support

Collagen/proteoglycan-↑H2O: absorbs shock

Cartilage proteoglycan, monomer structure.

3. Tendon (MuscleTBone); ligaments (BoneLBone)

Attachment sites

Collagen: tough/ropelike

B. Features of Bone

1. Long – limbs

2. Short (broad) – wrist/ankle

3. Flat (thin) - skull/ribs/sternum

4. Irregular – vertebrae/facial

C. Structure of Long Bone

1. Diaphysis: central shaft

2. Epiphysis: bone ends

3. Articular cartilage: covers ends at joints

4. Epiphyseal plate

Growth plate

Bone model cartilage between end & shaft

Epiphyseal line when bone growth stops

5. Medullary cavity

Contains marrow - soft tissue

Red: blood forming cells (↑children vs ↓adults)

Yellow: fat tissue: w/age yellow replaces red

6. Periosteum (outer)/Endosteum (thin inner):

CT w/bld vessels, nerve cells & osteoblasts-bone-

forming cells (growth, repair)

D. Two Types

1. Compact Bone: Long bone diaphysis & surfaces (all)

• Haversian Systems: (Osteons)

A. Lamellae: extracellular matrix

B. Osteocytes: bone cells

C. Lacunae: spaces containing bone cells

D. Canaliculi: canals connecting osteocytes

E. Central canal contains BVs

lamella

2. Cancellous Bone (spongy):

Long bone epiphysis & centers (all)

Trabeculae: plates of bone w/spaces

E. Bone Ossification (formation)

1. Cell types

a. Osteoblast: bone forming cell

b. Osteocyte: mature bone cell

c. Osteoclast: bone eating (remodeling cell)

Intramembranous (membrane bones) Endochondral (cartilage bones)

no cartilage starts with cartilage

numerous small blood vessels avascular

many flat bones (skull) long bones and flat bones

Two Methods of Ossification in Fetal Bone Formation

2. Intramembranous Ossification (upper fetal skull):

Osteoblasts in CT form spongy, then compact bone

3. Endochondral Ossification (fetal skull base & rest):

a. Fetal cartilage model

b. Primary ossification/

diaphysis

c. Secondary ossification/

epiphysis

d. Bone matures

(epiphysial line forms)

The hyaline cartilage model

F. Bone Growth:

Periosteum ↑diameter; Epiphyseal plate

↑length

G. Remodel: (osteoclast/osteoblast)

Hormones, diet

H. Repair:

1. Clot

2. Callus network (repair area)

3. Osteoblasts form cancellous first

(cast needed for support)

4. Remodel w/both

Incomplete Multiple Right Open/bone

fragments Angle protrudes (Review p. 120

for Chp test)

I. Calcium Homeostasis

• Osteoblast (Ca to bone) = osteoclast (to Bld)

• Parathyroid gland regulates ↓ Bld Ca levels

• Parathyroid Hormone:

• ↑ Osteoclast activity (Ca from bone to bld)

• Kidney reabsorb Ca from urine

• Kidney = ↑ Vit. D = ↑ Ca from SI

• Thyroid gland regulates ↑ Bld Ca levels

• Calcitonin Hormone: ↓ Osteoclast activity

J. Effects of Aging:

Osteoblast less active than osteoclast

Bone loss after age 35 (esp. post-menopause) =

osteoporosis: bone reabsorption ↑ than formation

Production of articular cartilage/synovial fluid slows

Prevent w/physical activity, Ca & Vit. D supplements

Normal

cancellous bone

Osteoporotic

cancellous bone