Bone Tissue

Question 1

cartilage and bone are both what kinds of tissue?

Answer 1

connective tissue

Question 2

is bone vascular or avascular?

Answer 2

VASCULAR

Question 3

what are some major functions of the bone?

Answer 3

structure of body, storage and release of calcium and phosphate ions and blood cell formation (hematopoiesis).

Question 4

What is bone composed of?

Answer 4

inorganic salts (65-70%, main component): Calcium hydroxyapatite.
ground substance (30-35%) organic component: PG and type 1 collagen (which makes up 90% of GS).

Question 5

What are two types of bone?

Answer 5

1. lamellar: mature bone, it is compact outside of bones and cancellous or spongy trabeculae inside the bones, forms a meshwork.
2. Woven: only in fetus and during bone repair.

Question 6

Define epiphysis, metaphysis and diaphysis

Answer 6

epiphysis: end part of long bone
metaphysis: growing part of long bone located between epiphysis and diaphysis
diaphysis: shaft or central part of long bone.

Question 7

what layer in bone is similar to the perichondrium found in cartilage?

Answer 7

periosteum, immature cells are also found here just like in cartilage but now are called osetoblasts.

Question 8

What is the formation of compact bone?

Answer 8

organized into osteons or haversian systems

Question 9

What is the mature cell type in bone?

Answer 9

osteocytes.

Question 10

connective tissue is attached to bone by what kind of fibres?

Answer 10

Sharpeys

Question 11

Haversian canal or central canal runs in what direction? and is located where?

Answer 11

runs in vertical direction and runs up through center of osteon in compact bone.

Question 12

What are volkmanns canals? which way do they run?

Answer 12

they run perpendicular (90 degrees) to haversian canals.

Question 13

what are the layers called that surround the osteons? what is between these layers? these cells are embedded in what?

Answer 13

lamallae.
osteocytes.
lacunae (same as chondrocytes)

Question 14

tiny lines radiating from ostecytes between layers of lamallae are? what do they carry?

Answer 14

canniculi (which also join to central canal).

O2, nutrients and waste NO blood.

Question 15

what is the formation of spongy bone?

Answer 15

NO osteons, osteocytes are dispersed throughout the matrix.

Question 16

what is the main type of collagen in bone?

Answer 16

TYPE 1

Question 17

osteocytes are mature or immature? located in which type of bone?

Answer 17

mature (in lacunae) located in both spongy/compact. synthesize and secrete matrix. have long cytoplasmic processes in cannaliculi. trapped in matrix until they die.

Question 18

function of osteoblasts?

Answer 18

synthesize/secrete osteoid (organic matrix becomes mineralized). can mature to osteocytes (would then be trapped in matrix for life) or go back to osteoprogenitors.

Question 19

function of osteoclasts?

Answer 19

multinucleate, involved in resorption and remodeling (breaksdown bone).

Question 20

What are osteoprogenitors?

Answer 20

in periosteum, divide and proliferate.

Question 21

do osteocytes have high active protein synthesis?

Answer 21

NO, therefore little RER, condensed chromatin. once mature not alot of synthesis occurs.

Question 22

cytoplasmic processes from different osteocytes can touch and have what type of junction?

Answer 22

GAP, can pass nutrients, O2, etc.

Question 23

are osteoblasts highly active?

Answer 23

YES, therefore lots of RER, high protein synthesis, lots of euchromatin. on surface of developing bone, cuboidal.

Question 24

which enzyme is used by osteoblasts to lay down mineralized matrix?

Answer 24

alkaline phosphatase.

Question 25

What is the organic part of bone? the matrix where osteocytes are located have what type of matrix?

Answer 25

periosteum= made up of collagen type 1+PGs
mineralized (has calcium, mature tissue).
as the organic component matures, it becomes mineralized.

Question 26

osteoblasts are what kind of cell type?

Answer 26

polarized. active face faces maturing tissue (mineralized matrix)

Question 27

osteoblasts synthesize what cell type?

Answer 27

collagen.

Question 28

What kind of enzyme is alkaline phosphatase?

Answer 28

ecto enzyme, sits on PM and mineralizes matrix.

Question 29

osteoblasts lay down bone in what direction?

Answer 29

growing outward into mineralized matrix

Question 30

osteoclasts breakdown bone for what purpose? it responds to calcitonin by doing what? responds to parahormone by doing what?

Answer 30

in response to low Ca, it releases Ca from bone. 
inhibiting resorption (decreases osteoclasts activity, decreases blood Ca, hormone in thyroid gland)
stimulating resorption (stimulates activity of osteoclasts, increases blood calcium, hormone in parathyroid gland).

Question 31

osteoclasts sit in what type of lacunae? and have what kind of unique membrane? and what unique zones?

Answer 31

Howships

ruffled membrane and has sealing zones to prevent destroying of other tissues.

Question 32

what protein helps form the sealing zone?

Answer 32

actin filament, interacts with integrin to seal off space and makes sealing zone.

Question 33

How does bone resorption occur?

Answer 33

lysosomes from golgi release enzymes and H+ which increases acidification causing breakdown of calcium phosphate, products are then taken up by cell and taken to the blood.

Question 34

Howships lacunae also called?

Answer 34

clear zone (rich in actin, no organelles).

Question 35

Two types of bone formation are?

Answer 35

1. endochondral (main one in long bone): forms from cartilage matrix
2. intramembranous (in short/irregular bones during development).