Bone Physiology

Question 1

What is bone?

Answer 1

Rigid form of connective tissue

Collagen fibres, GAG’s, and mineral salts

Question 2

What are osteocytes?

Answer 2

main cell found in bone, they are found in small spaces called lacunae, projections from the cell membrane spread through the caniculi to sense whats happening in the extracellular matrix

Question 3

What is an osteogenic cell?

Answer 3

a cell that develops into an osteoblast

Question 4

What is an osteoblast?

Answer 4

a cell that forms bone tissue

Question 5

How do osteocytes communicate?

Answer 5

they communicate through gap junctions

Question 6

How do osteoblasts form bone tissue?

Answer 6

They synthesize and secrete collagen and other components of the bone matrix

Question 7

Where are the end products of bone degradation absorbed into/

Answer 7

into the osteoclasts

Question 8

What do osteoclasts leave behind as they resorb bone?

Answer 8

they leave behind mitogens (growth factors) to
encourage osteoblasts to mature and lay down matrix

Question 9

Where does the nutrient artery enter from?

Answer 9

through nutrient foramens

Question 10

Where does the nutrient artery supply the bones from?

Answer 10

supplies the inner 2/3 of the bone from the endosteum

Question 11

What supplies the outer third of the bone?

Answer 11

Periosteal vessels, via attachments of muscles and tendons

Question 12

What is the endosteal side of the bone?

Answer 12

woven or cancellous bone that houses the bone marrow

Question 13

What makes up 95% of the bone matrix?

Answer 13

collagen fibres

Question 14

hydroxyapatite

Answer 14

filler between collagen fibres that provides strength

Question 15

What is cortical bone also known as?

Answer 15

compact bone

Question 16

Where does the osteocyte come from?

Answer 16

the mesenchymal stem cell line

Question 17

What is osteoid?

Answer 17

The substance that is secreted from osteoblasts before it becomes mineralised bone

Question 18

What are the two sides of bones?

Answer 18

endosteal and periosteal

Question 19

What does the endosteal side of the bone contain?

Answer 19

It houses the bone marrow and the main blood supply

Question 20

What does the periosteal side of the bone contain?

Answer 20

it is the outer bone surface that can also bring blood to the bone via soft tissue

Question 21

What is endochondral ossification?

Answer 21

ossification that begins in the primary growth plate in the centre of long bones

Question 22

What marks skeletal maturity?

Answer 22

When the growth plate closes

Question 23

What is intramembranous ossification?

Answer 23

growth occurs in the membrane rather than in a cartilaginous structure (occurs in flat bones)

Question 24

Where are collagen fibres embedded in bone?

Answer 24

They are embedded into GAG’S or glycosaminoglycans (mineral salts are also embedded)

Question 25

What makes up the majority of long bones?

Answer 25

Dense cortical bone

Question 26

What makes up the majority of irregular bones?

Answer 26

Cancellous bone

Question 27

What makes up flat bones?

Answer 27

They are thin cortical plates with small amounts of cancellous bone in-between

Question 28

What are canaliculli?

Answer 28

Small canals that connect adjacent lacunae

Question 29

What are lacunae

Answer 29

small spaces in the mineralised matrix that house osteocytes

Question 30

How do osteocytes communicate with each other?

Answer 30

Through gap junctions

Question 31

What separates bone fluid from other fluids in the body?

Answer 31

bone cell layer (made up of endosteum periosteum and haversian canals)

Question 32

What is osteoid?

Answer 32

the substance secreted by the osteoblasts

Question 33

How does osteoid become mineralised bone?

Answer 33

mixes with calcium phosphate that is also secreted from osteoblasts

Question 34

How do osteoclasts destroy the bone matrix?

Answer 34

They acidify their environment to dissolve the calcium phosphate, they also digest collagen and other matrix proteins

Question 35

What parts of the bone does the nutrient artery supply?

Answer 35

The inner 2/3 of the bone from the endosteum

Question 36

What supplies the outer 1/3 of the bone with blood?

Answer 36

Periosteal vessels

Question 37

What is apositional growth?

Answer 37

Increase in the diameter of the bone (bone becomes thicker)

Question 38

How does intamembranous growth work?

Answer 38

Osteoblasts between the membrane secrete osteoid (osteoblasts differentiate from mesenchymal cells) this then becomes woven bone, lamellar bone and the outer periosteum then forms

Question 39

How does endochondral growth work?

Answer 39

Bones begin as hyaline cartilage, Chondrocytes die leaving open spaces in the cavity of the bone Blood vessels enter the primary ossification centre, osteoblasts enter through the blood vessels and begin to produce spongy bone, which over time will become a medullary cavity

Question 40

What are perforating canals?

Answer 40

(haversian) Canals that move horizontally through the bone

Question 41

Where does the blood supply run in the endosteal side of bones?

Answer 41

Inside of a volkmanns canal