MSK/CT/Skin

Question 1

How are osteocytes connected?

Answer 1

Through gap junctions. Osteocytes send cytoplasmic projections through canaliculi to communicate with other osterocytes in other lacuni. This gap junctions exchange nutrients and waste products, along with sending signals to one another.

Question 2

What are the exocrine gland types, plus examples, plus mxn of exocrine function?

Answer 2

Merocrine: e.g. salivary glands, eccrine sweat glands, apocrine glands (originally thought to be apocrine). Cells secrete via exocytosis.
Apocrine: e.g. mammary glands. Cells secret via membrane-bound vesicles.
Holocrine: e.g. sebaceous glands, Meibomian glands (sebacious gland at rim of eye at tarsal plate). Cell lysis releases entire contents of cytoplasm & cell membrane.

Question 3

What are causes of an elevated creatinine kinase (CK)?

Answer 3

An underlying myopathy. Common causes are hypothyroidism, muscular dystrophies, inflammatory muscle diseases, and medications such as HMG-CoA reductase inhibitors.

Hypothyroid myopathy presents with myalgia, proximal muscle weakness and cramping. Myoedema is a characteristic finding that happens secondary to slow reabsorption of calcium by the sarcoplasmic reticulum.

Question 4

What is the function of fibrillin-1?

Answer 4

Forms microfibrils by surrounding elastin. Microfibrils are abundant in blood vessels (e.g. aortic media), periosteum and the suspensory ligaments of the lens. Marfan syndrome is an inherited defect in the fibrillin-1 gene.

Question 5

What is CREST syndrome?

Answer 5

Calcinosis, Raynaud’s phenomenon, esophageal dysmotility, sclerodactyly (thickening and tightening of the skin over the fingers or toes), telangiectasias. It is a localized variant of systemic sclerosis. Pulmonary hypertension is a common complication of systemic sclerosis.

Question 6

What is acanthosis?

Answer 6

Thickening of the stratum spinosum. Can happen due to prolonged antigen exposure in eczema (helps forma a raised scaly plaque along with hyperkeratosis).

Question 7

What is hyperkeratosis?

Answer 7

Thickening of the stratum corneum. This produces a scaly plaque.

Question 8

What is spongiosis?

Answer 8

An accumulation of edema fluid in the intercellular spaces of the epidermis. Seen in acute allergic contact dermatitis.

Question 9

What is the embryonic origin of melanocytes?

Answer 9

Neural crest cells

Question 10

What is Rhus dermatitis?

Answer 10

Allergic rashes produced by the oil urushiol, which is contained in various plants, most notably those of the Toxicodendron genus: the Chinese lacquer tree, poison ivy, poison oak, and poison sumac. It is contact dermatitis (Type IV hypersensitivity reaction).

Question 11

What are the hypomere and epimere?

Answer 11

Embryonic muscular structures. The myotome is that part of a somite that forms the muscles of the animal. Each myotome divides into an epaxial part (epimere), at the back, and a hypaxial part (hypomere) at the front. The myoblasts from the hypaxial division form the muscles of the thoracic and anterior abdominal walls. The epaxial muscle mass loses its segmental character to form the extensor muscles of the neck and trunk of mammals.

Question 12

What is Ewing sarcoma?

Answer 12

A malignant bone tumor that predominantly affects older children and teenagers. Usually occurs in long bones. Clinically, it may resemble acute osteomyelitis.

Question 13

What is the cause of polymyositis?

Answer 13

Anti-histidyl-tRNA synthestase (anti-Jo-1) antibodies. It is characterized by symmetrical proximal muscle weakness, and typically presents around middle age with insidious onset. Biopsy shows endomysial mononuclear inflammatory infiltrate and patchy muscle fiber necrosis.

Question 14

Where in the cell does post-translational hydroxylation of collagen occur (proline and lysine hydroxylated to hyroxyproline and hydroxylysine)?

Answer 14

The rough ER

Question 15

What cancers have a propensity for metastasizing to bone?

Answer 15

Prostate, breast, kidney, thyroid, and lung (PB/KTL: mnemonic “lead kettle”)

Question 16

What are symptoms of spinal metastasis?

Answer 16

Constant pain (not worse or better with activity), worse at night, not responsive to position changes

Question 17

What processes are responsible for photoaging (wrinkling and epidermal thinning due to UVA damage)?

Answer 17

Decreased collagen fibril production, upregulation of matrix matalloproteinases (including collagenases) that leads to the loss of type I and III collagen and elastin.

Question 18

What bursa is inflamed in “housemaid’s knee”?

Answer 18

Prepatellar bursa (due to chronic repetitive pressure, especially seen in professions in which the person is often on their knees). This bursa is located between the patella and the overlying skin.

Question 19

What part of long bones does hematogenous osteomyelitis most often affect?

Answer 19

The metaphysis. More common in children, particularly boys.

Question 20

What is hallmark in bone of osteoporosis?

Answer 20

Trabecular thinning with fewer interconnections. Vertebrae are predominantly made up of trabecular, or spongy, bone, which is why this is the most common site of osteoporotic fractures. The neck of the femur is the second most common site because it is 50% spongy bone.

Question 21

What is a glomus tumor?

Answer 21

Benign, painful, red-blue tumor, commonly under fingernails. Arises from modified smooth muscle cells of the the thermoregulatory glomus body.

Question 22

What portion of the spine does rheumatoid arthritis tend to affect?

Answer 22

The cervical spine

Question 23

What enzyme helps form the desmosine cross-links between neighboring elastin polypeptides?

Answer 23

Lysyl oxidase (requires copper). It deaminates some of the lysine residues in tropoeslastin, fascilitating the formation of desmosine cross-links which account for the rubber-like properties of elastin.

Question 24

Is metastasis to the bone more commonly spread via hematogenous or lymphatic spread?

Answer 24

Hematogenous

Question 25

Dermatomyositis may be a part of a paraneoplastic syndrome. What neoplasms is it associated with?

Answer 25

Ovarian, lung, colorectal, and non-Hodgkin lymphoma.

Question 26

Thickening of what ligament contributes to spinal stenosis?

Answer 26

Ligamentum flavum

Question 27

What can aconthosis nigricans be a signal of?

Answer 27

Insulin resistance, obesity, or GI (.e.g stomach, liver) or lung malignancy.

Question 28

How does afterload affect the velocity of contraction of skeletal muscle fibers?

Answer 28

Decreasing afterload increases the maximal contractile shortening velocity of skeletal muscle. Afterload refers to the force against which the muscle must contract.

Question 29

What does preload mean in reference to skeletal muscle?

Answer 29

The muscle fiber length prior to contraction (as preload increases, contractile velocity increases to a maximal value, after which it decreases).