Tissue and Bone Growth

Question 1

4 types of bone

Answer 1

long, short, flat, irregular

Question 2

diaphysis

Answer 2

main shaft of long bone. the hollow space in it is called the medullary cavity- which is filled with yellow marrow

Question 3

function of diaphysis

Answer 3

• the main shaft of long bones, to provide strong support without a lot of weight

Question 4

ends of long bone, made with cancellous bone filled with marrow

Answer 4

epiphysis

Question 5

function of epiphysis

Answer 5

to provide attachments for muscles and give stability to joints

Question 6

layer of hayline cartilage that covers the articular surface of the epiphysis

Answer 6

articular cartilage

Question 7

endosteum

Answer 7

thin epithelial membrane that lines the medullary cavity in long bone

Question 8

medullary cavity

Answer 8

the hollow space in the diaphysis of long bone

Question 9

dense white fibrous membrane that covers long bone is called

Answer 9

periosteum

Question 10

function of the periosteum

Answer 10

contains cells that form and destroy cells, contains blood vessels and attaches tendons to bones

Question 11

could long bones survive without periosteum

Answer 11

no, very essential for bone broth and survival

Question 12

inner portion of short, flat and irregular bones

Answer 12

cancellous bone, with red bone marrow, covered by compact bone

Question 13

where is red bone marrow found in irregular bones

Answer 13

inside the spaces of cancellous bone

- large amounts found in flat bones: found in ribs, pelvis and skull

Question 14

group substance

Answer 14

the organic matrix secreted by bone cells–> collagen fiber, protein and polysaccharides
- this is the medium in which bone grows, nutrients diffuse and waste is excreted

Question 15

are there osteons in cancellous bone

Answer 15

no, instead is has trabeculae- needle like bony spicules

Question 16

difference between compact bone and cancellous bone

Answer 16

cancellous bone is spongy and consists of trabeculae, whereas compact has osteons

Question 17

bone reabsorbing cells

Answer 17

osteoclasts (giant cells, multinucleate)

Question 18

bone building cells

Answer 18

osteoblasts

Question 19

osteoclasts are attached to the surface by

Answer 19

integrins

Question 20

osteocyte

Answer 20

is a trapped osteoblast that is surrounded by bone matrix

Question 21

RANK ligand (released by osteoblast to recruit osteoclasts)

Answer 21

is a protein expressed by osteoblasts. it binds to the RANK receptors on osteoclasts precursors. this interaction stimulates precursor to make them become active and resorbs bone

Question 22

what triggers RANK pathway

Answer 22

parathyroid hormone (PTH) from parathyroid gland, want to release calcium from stores

Question 23

what inhibits the RANK pathway and prevents bone resorption

Answer 23

estrogen

Question 24

what hormones control blood calcium levels

Answer 24

parathyroid hormone and calcitonin

Question 25

post menopause women tend to have a

Answer 25

negative calcium balance- more output

Question 26

parathyroid (PTH)

Answer 26

released when blood Ca levels are low - bone erosion- release calcium - enhance renal reabsorption of Ca - stimulates the release of calcitriol - which increases intestinal ca absorption

Question 27

calcitriol

Answer 27

increase cal reabsorption in intestine

Question 28

where does calcitriol come from

Answer 28

vitamin D | - with release of parathyroid hormone the kidneys convert 25-hydroxycholecalciferol to calcitriol

Question 29

what lowers blood calcium levels

Answer 29

calcitonin ( different from calcitRIOL)

Question 30

what acts opposite of parathyroid

Answer 30

calcitONIN Calcitonin

Question 31

action of vitamin D on calcium regulation

Answer 31

1. increase reabsorption in the tubules of kidney | 2. increase amount of transporters in intestine ( more calcium)

Question 32

vit D stimulates

Answer 32

osteoblasts. to build more bone

Question 33

what does exercise stimulate

Answer 33

osteoblasts to secrete more collagen which makes bones stronger

Question 34

two mechanisms for bone formation

Answer 34

1. intramebranou | 2. endochondral

Question 35

intramembranous

Answer 35

does not begin with cartilage model - instead, just dense areas of mesenchymal cells differentiate and begin to lay down bone themselves - occurs within a CT membrane

Question 36

examples of intramembranous bone

Answer 36

flat bones, skull or jaw bone

Question 37

endochondrial bone development

Answer 37

mesenchymal cells migrate to site of bone, differentiate into chondrocytes--> very dense avascular mass, catalogue forms in the shape of bones - they die - then cartilage gets surrounded by periosteum, now it can develop and enlarge - osteoblasts that differentiate from inner collar of periosteum produce a hollow of bone - blood vessels enter the cartilage at the diaphysis

Question 38

which way do bones grow endochondrally?

Answer 38

ossification progress from the diaphysis towards each epiphysis--> this is how the epiphyseal plate remains/forms!! - the epiphysis plate remains until the bone is totally done growing ( it keeps getiting pushed up)

Question 39

epiphyseal plate has ___ layers

Answer 39

4: top= resting, proliferating, hypertrophy, calcification --> diaphysis

Question 40

how do bones grow in diameter?

Answer 40

osteoclasts enlarge the diameter of the medullary cavity and osteoblasts from the periosteum build new bone around the outside of the bone

Question 41

how do bones grow in length ?

Answer 41

through the action of either endochondrial formation or intramembranous development --> formed from mesenchymal stem cells which either turn into chondrocytes which differentaite into osteoblasts or differentiate right into osteoblasts right away (as in flat bones)

Question 42

what does OPG do?

Answer 42

binds to RANKL, competitive inhibitor for RANK on precursor osteoclasts (cause less osteoclasts to be made- thereby limiting bone resorption)

Question 43

how is OPG made?

Answer 43

estrogen causes osteoblasts to product TGF-B, which casues them to produce OPG

Question 44

high levels of estrogen

Answer 44

= high levels of TGF-B = high levels of OPG = low levels of bone resorption and low calcium

Question 45

low levels of estrogen

Answer 45

= low TGF-B = low OPG= high osteoclast activity = breaking down bone -> this is why post menopause women are at high risk of osteoporosis (less estrogen)

Question 46

how to treat osteoporisis

Answer 46

raloxifene, calcitonin, estrogen replacement therapy, exercise

Question 47

what expresses RANK ligand

Answer 47

osteoblasts ( its like they are telling the precursors to become mature to remodel bone!) they release RANK ligand which bind to RANK on precursor osteoclasts

Question 48

after resorption of bone...

Answer 48

osteoblasts move back into the pit and start reforming the bone, some become embedded into the matrix become osteons, while other become new lining cells

Question 49

estrogen causes what?

Answer 49

osteoblasts to secrete TGF-B, which casues them to produce OPG- which block RANK

Question 50

increasing PTH has wat effect on the kidneys?

Answer 50

tells kidney to make more calcitriol from vitamin D, which results in more Ca+ absorbed from intestines ( calcitriol makes more transporters)

Question 51

low Ca2+ casues release of ___ to stiulate ______

Answer 51

PTH, osteoclasts, kidneys to make calcitriol, intestines to absorb more Ca+

Question 52

high blood Ca+ causes release of _____ to stimulate

Answer 52

calcitonin from the thyroid, to stimulate osteoblasts to make more blood and use calcium