Bone and Joint

Question 1

What are fibroblasts?

Answer 1

They are connective tissue cells that synthesise the synovial membrane, tendons and ligaments.

Question 2

What are chondrocytes?

Answer 2

They are connective cells that synthesises and secrets cartilage.

Question 3

What are osteocytes?

Answer 3

They are connective tissue cells that synthesise and secret bone.

Question 4

What are the three main molecules the extracellular matrix is composed of?

Answer 4

Collagens, proteoglycans and glycoproteins.

Question 5

Give 4 examples of proteoglycans.

Answer 5

Aggrecan, Verisican Decorin and Fibromodulin.

Question 6

Give an example of an glycosaminoglycan (GAG) and two proteoglycans that function as biolubricants at joints.

Answer 6

GAG = Hyaluronan

Proteoglycan = Lubricin and Aggrecan.

Question 7

What is are Bursa?

Answer 7

A bursae is a sac filled with synovial fluid that lines the synovial membrane and helps with joint movement.

Question 8

What is Bursitis?

Answer 8

Bursitis is inflammation of the bursa.

Question 9

What are the two types of synovial cells that are in the synovial fluid. What are they are what is each of their function?

Answer 9

Type A = acts as a macrophage to remove wear-and-tear debris from the synovial fluid.

Type B = has a synthetic function and synthesises hyaluronan and lubricin.

Question 10

What are the three dominant amino acids present in collagen fibrils?

Answer 10

Glycine, Proline and Hydroxyproline.

Question 11

Which three collagen types are the major structural collagens?

Answer 11

Collagen types I, II and III.

Question 12

What collagen type provides tendons their tensile strength.

Answer 12

Type I collagen.

Question 13

What is cartilage mainly composed of?

Answer 13

Type II collagen, aggrecan and hyaluronan.

Question 14

Name four members of the Matrix Metalloproteinases (MMP) family

Answer 14

Acrhetypal, Gelatinases, Matrilysins, and Furin-activated MMPs.

Question 15

What is the function of Matrix Metalloproteinases (MMPs)?

Answer 15

MMPs functions to degrade the proteins in the extracellular matric

Question 16

Name two proteins that can inactivate Matrix Metalloproteinases (MMPs)?

Answer 16

α2-macroglobulins and tissue inhibitors of metalloproteinases (TIMPs).

Question 17

Which two cytokines can activate pro-MMPs?

Answer 17

Interleukin-1 (IL1) and Tumour Necrosis Factor (TNF).

Question 18

What is Osteoarthritis?

Answer 18

Osteoarthritis is a degenerative disease that affects the joints and bones. It occurs as a result of increased ECM degradation relative to synthesis.

Question 19

What is Rheumatoid arthritis?

Answer 19

It is a disease that affects all connective tissues that results in inflammed joints. It occurs as a result of increased matrix degradation relative to synthesis.

Question 20

What is Tendinopathy (tendinitis)?

Answer 20

It is a degenerative disease that affects the joints and occurs as a result of increased matrix degradation and synthesis.

Question 21

What are the major proteins types that degraded in patients with Osteoarthritis?

Answer 21

Proteoglycans.

Question 22

What is Scelerosteosis & Van Buchem Disease?

Answer 22

It is an autosomal recessive disease characterised by increased bone growth, resistance to bone fracture and excessive height.

It is associated with reduced production of the protein ‘Sclerostin’.

Question 23

What is the Medullary cavity?

Answer 23

It is the central cavity of bones where the bone marrow is stored - it is the site of blood cell formation.

Question 24

What are the two types of bone structures?

Answer 24

Cortical bone (compact) and trabecular (spongy).

Question 25

What is the basic unit of cortical (compact) bone called?

Answer 25

The Haversian System or the ‘Osteon’.

Question 26

What hormone stimulates bone formation and how?

Answer 26

Calcitonin.

1) an increase in blood [calcium] stimulated the release of calcitonin.
2) Its release reduces calcium uptake in the kidney and stimulates calcium deposition in the bones.

Question 27

What hormone and vitamin works together to stimulate bone remodelling and calcium release, and how?

Answer 27

The Parathyroid hormone (PTH) and Vitamin D.

1) Low calcium stimulates PTH release, which activated vitamin D.
2) This promotes calcium uptake in the kidney and intestines.

Question 28

What is the main active form of Vitamin D?

Answer 28

1,25 Hydroxy Vitamin D.

Question 29

What is the difference between osteoblasts, osteocytes and osteoclasts?

Answer 29

Osteoblasts = synthesizes bone cells (e.g. osteocytes).

Osteocyte = a bone cell.

Osteoclasts = a type of bone cell that reabsorbs breaks down bone tissue.

Question 30

Which signalling pathway is essential for bone formation?

Answer 30

Wnt/beta-catenin signalling.

Question 31

How does the inhibition of the Wnt/beta-catenin signalling pathway result in reduced bone formation?

Answer 31

1) Sclerostin binds to LRP and prevents Wnt binding to its receptor.
2) As a result beta-catenin is targeted for degraded and so does not translocate to the nucleus.
3) Consequently, the target genes are not activated and osteoblast formation is reduced.

Question 32

What is Sclerostin and what is its function?

Answer 32

Sclerostin is a negative regulatory of bone formation - reduced sclerostin results in bone formation.

It functions to inhibit the Wnt/beta-catenin pathway to reduce bone formation.