Bone cells and Bone Remodelling BSM

Question 1

The ECM of a bone i c….. and it contains organic substances such as ground substnace and protein fibres and also inorganic substances like c…..h

Answer 1

calcified
calcium hydroxyapatite

Question 2

Cells in bone

Answer 2

Osteoblasts and Osteoclasts - which are formed by the stem cells called osteoprogenitor / osteogenic cells
Osteoclasts - derived from monocytes

Question 3

What are osteoprogenitor cells/ osteogenic cells derived from

Answer 3

Osteoprogenitor/Osteogenic cells
- derived from the mesenchyme
- are stem cells so can differentiate into other cells such as the osteoblast
-

Question 4

Location of endosteum and periosteum

Answer 4

Trabecula of cancellous bone = lined by endosteum, endosteum lines all the marrow spaces
. Periosteum = outer layer of compact bone
. Both endosteum and periosteum have cellular layers where the osteogenic cells reside & when needed they can differentiate into osteoblasts

Question 5

Osteoblasts facts

Answer 5

. fibroblast equivalent in bone tissue - synthesize all the ECM proteins like collagen - Type 1
. Adhesie glycoproteins like osteocalcin and osteonectin which are important for bone mineralisation since they bind avidly to Ca2+

Question 6

What is the name of the bone matrix that is synthesied by osteoblasts

Answer 6

OSTEOID - bone matrix which has not calcified yet

Question 7

What inorganic substance is needed for the osteoid to undergo mineralisation?

Answer 7

The osteoid undergoes mineralisation when inorganic components like Calcium Hydroxyapatite get added to it leading to the formation of the calcified bone matrix

Question 8

What type of strength do the organic and inorganic part give to the bone matrix

Answer 8

Bone matrix
Organic Part - tensile strength
Inorganic part - compressional strength

Question 9

What does M-CSF stand for and what type of cell produces this?

What does RANKL stand for?

Answer 9

Osteoblasts = synthesize all the proteins for the ECM - so basically the osteoid
Osteoblasts = also regulate the process of mineralisation
by producing M-CSF and RANK
Macrophage - Colony Stimulating Factor
RANK - Receptor Activator of Nuclear Factor Kappa Beta Ligand

Question 10

List the fate of an osteoblast

Answer 10

• Can undergo apoptosis when job is done
• Some remian as bone lining cells
• Whilst synthesising the osteoid, some get trapped in the matrix being formed, these trapped cells differentiate to form osteocytes

Question 11

Osteocytes
. Location and a visible feature

Answer 11

. Osteocytes = more mature cells not as active as osteoblasts
. Sit inside lacunae which are spaces in the bone matrix that house the cells
. Osteocytes have cytoplasmic extensions that are in spaces called canaliculi

Question 12

What does lamellated mean in the context of bones?

Answer 12

Lamellated = mature bone
. Has layers and layers of matrix, osteocytes sit in lacunae trapped between these layers
Between cells = calcified bone matrix which does not allow diffusion -> canaliculi have some extracellular fluid that allows exchange to happen with the cells
The cytoplasmic processes have GAP Junctions (which help connect the cells so they can communicate) - allowing the movement of ions

Question 13

Osteoblasts = s… bone matrix
Osteoclasts = m….. bone matrix

Answer 13

1. Synthesize
2. Maintain

Question 14

Bone = dynamic structure so both synthesis of bone and resorption of bone happens

Answer 14

Synthesizes of bone matrix = osteoblasts
Resorption of bone matrix = by osteoclasts

Question 15

Osteoclasts
. What are they dervied from
. Appearance
. Function
. Which cells is resonsible for regulating osteoclasts and how
. Osteoprotegnerin - what it does

Answer 15

. Monocytes
. Multi-nucleated giant cells
. Bone resorbtion
. Osteoblasts
. Osteoblasts produce Macrophage-CSF and RANK ligand and these guide the formation and proliferation of osteoclasts ->
. M-CSF- bind to the osteoclast precursor cells and increase mature osteoclast formation
. RANK ligand - bind to RANK receptor on the osteoclast precursor cells
Another cytokine is Osteoprotegnerin which binds to the same receptor and stops the RANK Ligand from binding to those cells & thus inhibits pre-osteoclasts from becoming mature osteoclasts - therefore also called Osteoclastogenesis Inhibitory Factor

Question 16

Osteoclast info read

Answer 16

Osteoclast = ruffled border makes contact with the bone forming a circumferential seal -> this attachement is mediated by adhesive glycoproteins; the integrins on the osteoclast bind to vitronectin on the surface of bone.