Bone

Question 1

What are the functions of the bone?

Answer 1

1. Protect other organs
2. produce hematopoietic cells, store minerals,
3. Provide structure and support the body

Question 2

Describe the weight of bone and flexibilty

Answer 2

they are lightweight, but strong yet have internal flexibility because of spongy bones (spicules with spaces between)

Question 3

Trabecular Bone

Answer 3

** cancellous/spongy bone

large surface area; bone marrow

Question 4

Cortical bone

Answer 4

** Compact bone
more dense than the tubercular bone

Question 5

Label all the letters

Answer 5

T- Trabecular
C - Cortical bone
E – epiphysis
D -diaphysis
M – metaphysis
P – physis = growth plate
AC – articular cartilage

Question 6

Label each line

Answer 6

Question 7

What is the structural organization of bone tissue

Answer 7

Lamellar bone
Woven bone

Question 8

Lamellar Bone

Answer 8

strong mature, forms slowly

collagen fibers in matrix arranged in layers (lamellae) resulting in strong mature bone (osteoid)

organized into osteons (Haversian systems) in mature cortical and trabecular bone

Question 9

Woven bone

Answer 9

weak immature, produced quickly

disorganized arrangement of collagen fibers

present at sites of rapid bone formation (e.g. fracture repair, inflammation, neoplasia)
◦ E. g. periosteal new bone or reactive bone

Question 10

Osteon

Answer 10

functional unit of lamellar bone located in circles around the central canal (Haversian) and in the interstitial bone between the circles of bone

Question 11

India ink has been used to

Answer 11

Demonstrate the canaliculi and lacunae

Question 12

Where are haversian canal seen

Answer 12

at the center of each osteon `

Question 13

Where is Osteon found?

Answer 13

Osteons are in mature bone = lamellar; not woven bone Located in cortex, trabeculae of bones

Question 14

What are the cellular elements of bone tissue

Answer 14

Osteoblasts
Osteocytes
Bone lining
Osteoclasts

Question 15

Where are osteoblast, osteocytes and bone linning cells derived from?

Answer 15

Derived from osteoprogenitor cells

Question 16

Osteoclasts origin

Answer 16

Monocytic origin

Question 17

Osteoblast

Answer 17

Produce osteoids and initiate its mineralization.

Secrete type 1 collagen

Positioned external to osteoid matrix

Differentiate to become osteocytes

Some osteoblasts (ob) become surrounded by osteoid and embedded in the bone (osteocytes)

Question 18

Osteocytes

Answer 18

Most abundant cells

Reside in lacunae surrounded by mineralized

matrix (long filipods to increase their cell area)

Regulate exchange of Ca2+ and other ions between the bones

Fluid and ECF under influence of parathyroid hormone`

Question 19

Osteoclasts

Answer 19

Bone resorption

Reside in shallow pits (Howship’s lacunae)

Acid demineralizes bone and enhances activity of acid hydrolases released from osteoclasts (extracellular digestion)

Question 20

What stimulates osteoclast activity

Answer 20

PTH

Question 21

Label this image

Answer 21

Osteoblasts are rounded, form a single row of cells along trabeculae.

Osteocytes are thinner and located within lacunae embedded in bone.

Osteoclasts are multinucleated cells located along trabeculae and will resorb bone under stimulation of cytokines secreted by osteoblasts or inflammatory cells

Question 22

System hormones affecting bone

Answer 22

Parathyroid hormone (PTH)– promotes bone resorption

1,25-dihydroxyvitamin D3 – required for normal bone growth and mineralization; also stimulates bone resorption

Calcitonin – inhibits bone resorption

Glucocorticoids – inhibit formation and stimulate resorption

Estrogen – inhibits bone resorption Insulin, growth hormone, androgens and thyroid hormones are also involved in bone metabolism

Question 23

Osteoid Organic components contain (bone matrix)

Answer 23

Type I collagen – main component of osteoid (~90%)

Osteonectin – involved in mineralization

Osteocalcin – vitamin K-dependent; also involved in mineralization

Proteoglycans – less abundant than in cartilage matrix

Growth factors – e. g. BMPs, IGFs, TGFs, FGFs

Question 24

How does bone formation occur?

Answer 24

Endochondral bone formation is preceded by hyaline cartilage. It occurs when cartilage differentiates, matures, mineralizes, die and is scaffold that osteoblast resides on

Question 25

What produces osteoids

Answer 25

Osteoblasts

Question 26

What zone are osteoid produced and bone produced?

Answer 26

Zone of primary spongisosa and is gradually mineralized into mature lamella bone

Question 27

Matrix mineralization

Answer 27

In bone, osteonectin and osteocalcin absorb to type 1 collagen and bind Ca2+

Osteoid is not mineralized immediately after depostion - failure to mineralize bone produce rickets = osteomalacia (can result in soft bone fracture)

Question 28

Intramembranous ossification

Answer 28

↑WIDTH; adult

Bone formed from mesenchymal tissue in periosteum

Occurs in flat bones of skull and pelvis and on
all periosteal surfaces throughout life

Responsible for the growth of bones in width

NO cartilage needed first

Question 29

Endochondral ossification

Answer 29

↑LENGTH; young

Bone formed from hyaline cartilage precursors in PHYSES

Most bones develop by this method (appendicular, axial and base of skull)

At physes responsible for growth of bones in length

Hyaline cartilage precedes and is scaffold

Question 30

Bone blood supply

Answer 30

Blood enters the marrow cavity of bones through nutrient, metaphyseal and epiphyseal arteries.

In young animals, the cortex is supplied mainly from the endosteal surface and exits via periosteal veins (i. e. blood flows centrifugally).

With age, the cortex becomes increasingly dependent on periosteal arteries.