MSK

Question 1

What kind of tissue includes bone and cartilage?

Answer 1

Connective / mesenchymal tissue

Question 2

Why is the non-living intercellular matrix secreted by living bone/cartilage cells relevant to injury/healing?

Answer 2

Tissue is avascular in nature, meaning that it is slow to heal

Question 3

What are 2 kinds of mature bone tissue?

Answer 3

1. Compact bone
2. Cancellous (spongy) bone

Question 4

What is the membrane that covers bone?

Answer 4

Periosteum

Question 5

Why is the vascular nature of periosteum relevant to bone injury?

Answer 5

Fractures result in bleeding

Question 6

Endosteum is a membrane that lines which 3 structures?

Answer 6

1. Spaces of spongy bone
2. Marrow cavities
3. Haversian canals of compact bone

Question 7

What is the term for the heads of long bones?

Answer 7

Epiphyses

Question 8

What is the term for the shaft of long bones?

Answer 8

Diaphysis

Question 9

What is the term for the widening part of the bone between the shaft and the epiphyseal plate?

Answer 9

Metaphysis

Question 10

In children, a fracture can affect growth/development if which structure is involved?

Answer 10

Epiphyseal plate

Question 11

Why may myeloid cancers affect bone homeostasis?

Answer 11

Osteoblasts and osteoclasts originate in bone marrow

Question 12

What is the unit of bone tissue?

Answer 12

Osteon

Question 13

What is the term for the “rings” seen in bone tissue?

Answer 13

Concentric lamellae

Question 14

What is the term for the space in the centre of an osteon where a blood vessel runs through?

Answer 14

Haversian canal

Question 15

What is the length of time of the adult cycle of bone remodelling?

Answer 15

4 months

Question 16

What is the name for the undifferentiated stem cells of osseous tissue?

Answer 16

Osteoprogenitor cells

Question 17

What is the name for bone building cells that synthesize and secrete organic (protein) matrix of bone?

Answer 17

Osteoblasts

Question 18

What is the name of mature bone cells that maintain bone matrix and release calcium into blood?

Answer 18

Osteocytes

Question 19

What is the name for bone cells that resorb bone matrix and release calcium & phosphate from bone?

Answer 19

Osteoclasts

Question 20

How do osteoclasts work to resorb bone?

Answer 20

Remove both protein and mineral components creating a tunnel-like space in the osteon

Question 21

What is the approximate composition of new bone?

Answer 21

60% mineral
20-25% organic (collagen)
20% water

Question 22

What cell lineage are osteoclasts derived from?

Answer 22

Monocyte/macrophage precursors

Question 23

What are 3 functions of osteoblasts?

Answer 23

1. Deposition of organic matrix (osteoid) on wall of canal created by osteoclasts
2. Deposition of bone lamellae
3. Release RANK-L to induce osteoclast activity

Question 24

What produces RANK ligand, and what is its function?

Answer 24

Produced by osteoblasts

Binds to RANK receptor on osteoclasts, causing osteoclast differentiation and proliferation

Question 25

What produces osteoprotegerin (OPG), and what is its function?

Answer 25

Produced by osteoblasts

Destroys RANK receptors and acts as an antagonist for RANK-L

Question 26

How are bisphosphonates released, and what is their function?

Answer 26

Released during bone resorption, concentrated under osteoclasts

Inhibit osteoclast activity, promote osteoclast apoptosis, modulate signaling from osteoblasts to osteoclasts

Question 27

What 3 hormones promote osteoblast secretion of OPG to inhibit osteoclasts?

Answer 27

1. Growth hormone
2. Thyroid hormone
3. Sex hormones

Question 28

What are 3 functions of vitamin D and parathyroid hormone?

Answer 28

Stimulate osteoblasts to:
1. Produce RANK-L and IL-6 (activate osteoclasts)

2. Produce M-CSF (increase osteoclast differentiation
3. Decrease secretion of OPG

Question 29

What are 4 functions of calcitonin, and in what population does it have a major role in?

Answer 29

1. Binds directly to osteoclast receptors to inhibit their activity
2. Increases renal elimination of Ca and PO4

Plays a major role in children’s growth/development

Question 30

What are 3 functions of parathyroid hormone, and in what population does it have a major role?

Answer 30

1. Increases release of Ca and PO4 from bone
2. Increases conservation of Ca and elimination of PO4 by kidney
3. Increases intestinal reabsorption of Ca via vitamin D (calcitriol)

Plays a major role in adults

Question 31

What are 2 functions of activated vitamin D (cholecalciferol)?

Answer 31

1. Increases absorption of Ca from intestine
2. Inhibits actions of PTH

Question 32

What are the different forms that vitamin D is converted into?

Answer 32

Vitamin D > cholecalciferol (hormone) > calcidol (inactive) > calcitriol (very active)

Question 33

What may paradoxically happen if a person with hypocalcemia takes exogenous vitamin D?

Answer 33

It would cause bone resorption as vitamin D only regulates blood calcium. Blood calcium must be sufficient for vitamin D to promote bone mineralization

Question 34

What are 3 clinically relevant ways that causes osteoclast upregulation and activation?

Answer 34

1. Inflammation
2. Immune activation
3. Corticosteroid treatment

Question 35

What microscopic features of osseous tissue help long bones withstand lateral stress without fracturing?

Answer 35

Concentric lamellae (as in a tree)