Bone Tissue

Question 1

General characteristics of bone

Answer 1

Major Ca storage area

Dynamic tissue

Vascularized and innervated

Question 2

Composition of bone

Answer 2

Cells
Fibers
Amorphous goround substance

67% hydroxyapatite

25% collagen

5% others

Question 3

Structure of bone

Answer 3

Cortex/compact bone

Medullary/spongy bone

Spongy made of spicules and trabeculaer

Question 4

Periosteum general

Answer 4

Connective tissue covering outer cortical surface of bone

Contains the blood vessels, nerves, and tissues

Sharpey’s fibers (collagen) pass from periosteum into the cortical bone

Tendons do the same thing

Question 5

Periosteum more specific

Answer 5

Fibrous layer (fibroblasts/cytes)

Osteogenic layer (osteogenic cells)

Highly vascularized

Question 6

Cells of bone tissue

Answer 6

Osteogenic cells (bone liining cells)…line the meduallry spaces and endosteum

Osteoblasts - from BLCs or chondroblasts…deposit osteoid

Osteocytes - trapped within mineralized osteoid…cannot divide or secrete while trapped

Osteoclasts - multinucleated from monocyte fusion…bone remodeling

Question 7

Osteoblasts and importance

Answer 7

Secrete osteoid (type 1 collagen fibers) that that give strenght

Also chondrotin sulface which is primary ground substance

Also control mineralization of matrix

Non-dividing

Question 8

Osteobalsts produce

Answer 8

Type 1 collagen and proteoglycans

RANKL

Osteocalcin for bone mineralization

Osteopontin to mediate formation of the sealing zone

Bone sialoprotein to mediate binding of osteoblasts to ECM via integrins

Question 9

INactive osteoblasts become

Answer 9

BLCs

Question 10

Osteoblast morphology

Answer 10

Roughly cuboidal but become columnar when highly active

When inactive, become more squamous

Question 11

Osteoblasts to osteocytes

Answer 11

Specific genes

Also control osteocalcin that is only found in osteocytes

Occurs when trapped in ECM

Question 12

Osteocytes structure

Answer 12

Reside in lacunae and have processes that extend out that lie in the canaliculi

Question 13

Osteoclasts basic

Answer 13

Large, multinucleated

Resorb bone

Form Howships lacunae(subosteoclastic ocmpartment)

Question 14

Osteoclasts structure and importantce of sealing zone

Answer 14

Smooth outer surface

Ruffled inner surface

Sealing zone compartmetnalzizes working area from surrounding bone

Sealing zone has accumulation of actin filaments that attach to osteopontin molecules in minneralized bone surface via integrins

Question 15

Osteocalst activation

Answer 15

After activation, integrins concentrate on podosomes that contact the matrix

Degradation starts when inegrin-actin-osteopontin complex orgazies the sealing zone

Question 16

Osteoblast/osteoclast regulation

Answer 16

Monocyte becomes macrophage

Osteoblast RANKL binds to RANK and commits to osteoclastogenesis…osteoprotegerin inhibits this

Resting osteoclasts uncouple

Osteoclasts are mature when sealing zone formed

Question 17

PTH and calcitonin

Answer 17

PTH - increases blood calcium

Calcitonin - oppostie

Question 18

Osteocyte communication

Answer 18

Sit in lacunae…processes extend out in canaliculi to form gap junctions

Question 19

Compact bone structure

Answer 19

Cricular lamella of bone forms an osteon

Haversian canal in the middle of it with BV, lymph, nerve

Volkmann’s run laterally

Interstial lamella in between osteons

Question 20

Ligament structure

Answer 20

Low cellularity with less ground substance and tons of fibers

More or less avascular

Question 21

Ligament attachment

Answer 21

Fibrocytes…later of fibrocartilage…chondrocytes…osteocytes…BVs