Sem 2 - Musculoskeletal

Question 1

In the formation of bone, osteoblasts secrete?

Answer 1

osteoid

Question 2

The intermediary tissue that is involved in the healing of fractures that forms in and around the fracture site is called

Answer 2

callus

Question 3

A 42-year-old footballer experiences an ache in his left knee when walking. An x-ray reveals early osteoarthritis. The chondrocytes of the articular cartilage in his left knee are likely to have been responding to the abnormal stresses in the joint by producing?

a) inflammatory cytokines
b) scar tissue
c) proteoglycan rich matrix
d) osteoid

Answer 3

inflammatory cytokines

Question 4

A 76-year-old woman suffers a fall and fractures the neck of her left femur. X-rays show a generalised reduction in bone density. A DXA scan of the spine and left hip reports a T-score of -2. Current evidence suggests that this is most likely to have resulted from which one of the following?

Answer 4

excessive osteoclast activty

Question 5

What are the components of synovium?

Answer 5

macrophage-like cells
fibroblast-like cells
blood vessels and lymphatics

Question 6

From what is synovial fluid derived?

Answer 6

Synovial fluid is a filtrate of plasma fluid from the many capillaries of the synovium, enriched with lubricating substances such as hyaluronic acid.

Question 7

What are the components of hyaline cartilage?

Answer 7

chrondocytes and ECM

Question 8

What makes up the extracellular matrix of hyaline cartilage? (5)

Answer 8

Type II collagen 
hyaluronic acid produced by chondrocytes
proteoglycans such as aggrecan
glycosaminoglycans such as chondroitin sulfate
water

Question 9

Name the main contents of the Haversian canals that can be seen in the section.

Answer 9

The Haversian canals contain blood vessels and supportive connective tissue. They also contain lymphatics and nerves

Question 10

What structures radiate from each lacuna to allow communication between cytoplasmic processes of the osteocytes and for the circulation of extracellular fluid and metabolites?

Answer 10

The canaliculi link the lacunae and are filled with tissue fluid and the cytoplasmic processes of osteocytes. The osteocytes maintain the structural integrity of the bone

Question 11

What 2 main ‘tissues’ are contained within the medullary cavity?

Answer 11

Bone marrow contains variable proportions of haemopoietic tissue and adipose tissue depending on how active it is.

When adipose tissue predominates in the marrow cavity, the marrow macroscopically appears yellow (rather than red) and it is referred to as yellow marrow.

Question 12

2 main types of ossification?

Answer 12

endochondral and intramembranous

Question 13

From which cells, and where, do the osteoblasts and chrondrocytes that form the callus come?

Answer 13

These cells are derived from osteoprogenitor (stem cells) in the periosteum.

Question 14

Of which one of the following basic pathological processes is osteoarthritis an example?

Answer 14

degenerative change

Question 15

A 46-year-old woman presented to her general practitioner complaining of a 6 month history of increasing stiffness, swelling and pain in the small joints of her hands and wrists that was making it increasingly difficult to do household chores, not to mention her professional kickboxing career. More recently she had noted that she felt slightly feverish and lethargic. On physical examination she appeared pale, and the proximal interphalangeal joints of both hands were warm and swollen. The distal interphalangeal joints were unaffected. X-rays of affected joints revealed soft tissue swelling, joint effusions and juxta-articular osteopaenia.

Blood tests revealed an elevated ESR, CRP and a normochromic normocytic anaemia.

Answer 15

rheumatoid arthrits

Question 16

In rheumatoid arthritis, cartilage of affected joints is destroyed and the joint surfaces can ultimately become joined by fibrous tissue and even bone. Explain how, incorporating the role of relevant cytokines and other molecules.

Answer 16

The specified terms were pannus, fibrous or fibrosis, bone or bony, and cytokine.

Cytokines produced by T cells, such as interferon gamma and IL-17, promote the production of further inflammatory cytokines, growth factors and other molecules such as IL-1, IL-6, TNF, TGF-beta and matrix metalloproteinases by synoviocytes and macrophages. Cartilage is degraded by metalloproteinases and immune mechanisms. Fibroblasts proliferate in response to TGF-beta and pannus (granulation tissue) grows into the joint, eroding the cartilage and resulting in the formation of fibrous tissue. This unites the bone ends, now devoid of cartilage, resulting in fibrous ankylosis, and the scar tissue may ultimately become ossified.

Question 17

Explain from first principles the likely pathogenesis of the fever, anaemia and elevated CRP and ESR in the above patient.

Answer 17

This is a chronic inflammatory disease process. Cells involved in the inflammatory process, particularly macrophages, release cytokines such as IL-1, IL-6 and TNF.

These increase the local production of of prostaglandins in the hypothalamus which raise the body temperature set point. Mechanisms to increase heat production such as increased skeletal muscle tone and shivering and reduce heat loss via sympathetic activation causing vasoconstriction are activated, leading to an elevation in temperature.

The above cytokines also stimulate the liver to increase the production of acute phase reactants. These include fibrinogen, hepcidin, serum amyloid associated protein and C reactive protein.

The anaemia is probably an anaemia of chronic disease. Hepcidin inhibits the use of iron from iron stores and insufficient haemoglobin is made. C reactive protein is another acute phase reactant produced in the liver in excess in inflammatory processes.

Erythrocyte sedimentation rate (ESR) refers to the height of red blood cells (RBCs) in a tube at the end of an hour after they have settled as a result of gravity. In acute phase responses, fibrinogen produced in excess by the liver and immunoglobulins cause RBCs to clump together. The clumped RBCs fall faster thus the height in the tube is greater after an hour.

Question 18

Amyloid deposition may occur in patients with rheumatoid arthritis. The amyloid frequently deposits in multiple organs rather than just one. What is the name of the precursor protein of amyloid in rheumatoid arthritis and what is its origin? Name four (4) other diseases in which this type of amyloid can occur.

Answer 18

The amyloid in rheumatoid arthritis is derived from serum amyloid associated (SAA) protein, an acute phase protein produced in excess by the liver in inflammatory states. Prolonged excess occurs in chronic inflammatory disease states. Other diseases in which this type of amyloid can occur include tuberculosis, inflammatory bowel disease, bronchiectasis, chronic osteomyelitis (and in association with certain malignancies).