Multiple Choice Questions

Basic Sciences

Test your knowledge , learn more and get ready for your orthopaedic exam

100. A researcher compared the mean weight loss in 2 groups of obese patients who were randomised to either standard treatment or standard treatment + new drug.


The data collected was parametric an continuous

Which one of the following is the most appropriate statistical test?

A) Chi square test
B) Life table analysis (log rank test)
C) Paired t test
D) Pearson correlation
E) Unpaired t test

Correct Answer: E

The two sample unpaired t test is used to test the null hypothesis that the two populations corresponding to the two random samples are equal.

A t test is appropriate for continuous data that is assumed to follow the normal distribution, therefore it is appropriate for comparisoin of weight loss between two groups.

For a paired t test, the data are dependent, that is, there is a one-to-one correspondence between the values in the two samples; for example, the same subject measured before and after a process change, or the same subject measured at different times.

Author: Firas Arnaout

99. Which is true of the shoulder joint?

A) Supraspinatus is active in abduction
B)The nerve to serratus anterior is derived from the lower roots of the brachial plexus
C) The rotator cuff muscles are attached to the capsule which is deficient anteriorly
D) The subacromial bursa communicates with the shoulder joint
E) She subscapular nerve arises from the lateral cord of the brachial plexus

Correct Answer: A

During abduction the supraspinatus muscle fixes the humeral head against the glenoid cavity while deltoid contracts.
The rotator cuff muscles (supraspinatus, infraspinatus, teres minor and subscapularis) serve to hold the head of the humerus in the shallow glenoid cavity during movement. They are attached to the capsule of the joint.
The rotator cuff is deficient inferiorly which results in an area of potential weakness. During abduction the supraspinatus muscle fixes the humeral head against the glenoid cavity while deltoid contracts.
The subacromial bursa does not connect with the shoulder joint.
The nerve to serratus anterior, that is, the long thoracic nerve has nerve roots C5-C7.
Both the upper and lower subscapular nerves are derived from the posterior cord of the brachial plexus.

Author: Firas Arnaout

98. What lies in the lateral first layer of the knee?

A) Arcuate ligament, fabellar ligament, capsule, LCL
B) Iliotibial tract, biceps femoris, fascia
C) Patellar retinacular and PFL ligament
D) Sartorius and fascia hyperparathyroidism
E) Superficial MCL, posterior oblique ligament, semimembranosus

Correct Answer: B

Iliotibial tract, biceps femoris, fascia is the lateral first layer and therefore the correct answer.
Of the other options:
Arcuate ligament, fabellar ligament, capsule, LCL is the third layer
Patellar retinacular and PFL ligament is the second layer
Sartorius and Fascia is the medial first layer
Superficial MCL, posterior oblique ligament, semimembranosus is the medial second layer, and the third layer is the deep MCL and capsule

Author: Firas Arnaout

97. A 58-year-old woman with a longstanding history of chronic renal failure who has been on haemodialysis for five years complains of bone pain affecting her left hand.
An x ray is performed and is reported as demonstrating osteitis fibrosa cystica.
What is the clinical diagnosis?

A) Osteoarthritis
B) Osteoporosis
C) Paget’s disease
D) Primary hyperparathyroidism
E) Secondary hyperparathyroidism

Correct Answer: E

Osteitis fibrosa cystica is a radiological feature of severe hyperparathyroidism (primary or secondary), subperiosteal erosion being a more common feature.
Secondary or renal hyperparathyroidism is a common finding in chronic renal failure.
It is associated with hypocalcaemia and hyperphosphataemia and in most cases it may be managed with phosphate binders and calcium supplementation. If surgery is required then a subtotal parathyroidectomy is the procedure of choice.
Osteitis fibrosa cystica is a radiological feature of severe hyperparathyroidism (primary or secondary), subperiosteal erosion being a more common feature.

Author: Firas Arnaout

 

96. A surgeon is planning the application of a single plane external fixation construct as provisional fixation for an unstable knee dislocation. 

There are two pin sizes available, one with twice the diameter of the other. 

The bending stiffness of the larger pin is greater than that of the smaller by a factor of which of the following?

A) 2
B) 4 
C) 8
D) 16
E) 32

Correct Answer: D

The increase in bending stiffness is proportional to the radius to the 4th power, so a doubling results in an increase by a factor of 16.

Author: Firas Arnaout

 

95. The rigidity or bending stiffness of a plate is proportional to:

A) The thickness of the plate
B) The thickness of the plate to the second power
C) The thickness of the plate to the third power
D) The length of the plate
E) The number of screws

Correct Answer: C

The second moment area (SMA) is a variable that describes the spatial distribution of a material within a structure. The type of material does not affect the SMA, but affected by the organization and shape of the material.

For materials with rectangular cross-sections (Plate), the perpendicular distance away from the neutral axis has a 3rd power effect on the SMA. 

Material with a solid circular cross section, the radius (which is the distance from the neutral axis) has a fourth power effect on SMA. 

For material with a hollow circular cross-section (IM Nail) the total SMA eqauls the SMA of the solid outer portion minus the SMA of the missing inner hollow portion.

Rigidity incorporates both the nature of a material and it's shape, size and structure. 

Author: Firas Arnaout

 

94. Which of the following statements regarding diathermy is true?

A) Bipolar diathermy never has any effect on a pacemaker heart lead system
B) Coagulation setting uses continuous current
C) Cutting setting has a sinus wave form
D) Diathermy applied to an implant is likely to result in significant heating of the implant and surrounding tissues
E) Diathermy is always contraindicated when a patient has a cardiac device in situ

Correct Answer: C

Diathermy uses high frequency current.

Bipolar has less of an effect on pacemakers than monopolar but can still cause electromagnetic disturbance and heating of the heart lead system.

Even if diathermy is applied to a single screw the surface area is so great compared to the contact point that there is no significant heating effect.

Cutting diathermy uses continuous current and has a sinus wave form and coagulation uses pulses with a square wave form.

Author: Firas Arnaout

 

93. In a gait lab, temporal-spatial parameters include all of the following except:

A) Step count
B) Stride length
C) Joint angles
D) Step width
E) Swing time and percentage

Correct Answer: C

Temporal-spatial parameters include the following variables:

  • velocity
  • step count
  • cadence
  • step length
  • stride length
  • base or step width
  • swing time and percentage
  • stance time and percentage
  • single support time and percentage
  • double support time and percentage
  • Joint angles are a type of kinematic, but not temporal-spatial parameter

Author: Sharon Zammit

 

92. Which of the following statements regarding the peroneal division of the sciatic nerve is true?

A) It crosses anterior to the lateral head of the gastrocnemius muscle through the posterior intermuscular septum
B) An injury at the level of the thigh will denervate the branches to the short head of the biceps and the tibialis anterior
C) It is most commonly injured during an anterior knee dislocation
D) The deep division initially runs medial to the tibial artery and later crosses over to become lateral
E) It originates from the L3-S1 nerve roots

Correct Answer: B

injury to the peroneal division of the sciatic nerve at the level of the thigh will denervate the branches to the short head of the biceps and the tibialis anterior.
The peroneal division of the sciatic nerve travels through the posterior compartment of the thigh and supplies the short head of the biceps femoris muscle before separating from the tibial nerve in the upper popliteal fossa. The same fibers that run laterally in the sciatic nerve to innervate the short head of the biceps femoris will form the common peroneal nerve at the knee. Thus, to differentiate between an injury to the peroneal nerve branch of the sciatic nerve in the thigh or at the knee, it is necessary to assess the innervation to the short head of the biceps femoris. An injury at the level of the thigh will denervate the branches to the short head of the biceps and to the tibialis anterior, whereas an injury at the level of the knee will spare the biceps femoris. If a nerve is found to be transected, the optimal time to definitive repair is within 1-3 weeks from injury in order to allow time for the zone of injury to declare itself. 
 

Author: Firas Arnaout

 

91. 21-year-old infantryman dislocates his shoulder during basic training. He is able to make it through training but continues to experience recurrent dislocations. 

A CT demonstrates anterior glenoid bone loss and your sports colleagues indicate him for a Latarjet procedure. 

The procedure successfully restores stability to his shoulder, but the patient is referred to your office just over 3 months later because he has persistent difficulty with abduction when the arm is internally rotated. You suspect an iatrogenic nerve injury sustained during anterior shoulder exposure and offer him a nerve transfer procedure involving the branch of the radial nerve that innervates the medial head of triceps. 

The nerve that is injured in this patient innervates what muscles?

A) Deltoid, teres minor, and supraspinatus
B) Deltoid, teres minor, and teres major
C) Teres minor and teres major
D) Deltoid and teres major
E) Deltoid and teres minor

Correct Answer : E

This patient sustained an axillary nerve injury during a large anterior exposure to the shoulder. The patient is offered a Leechavengvongs radial to axillary nerve transfer, as this will potentially restore the lost axillary nerve function to the deltoid and teres minor. The axillary nerve branches off of the posterior cord (along with the radial nerve) of the brachial plexus, travels just inferior to the subscapularis, then winds posterior and travels through the quadrangular space with the posterior circumflex humeral artery. The anterior branch innervates the anterior half of the deltoid, while the posterior branch innervates the posterior portion of the deltoid and the teres minor. This posterior branch also supplies the lateral cutaneous nerve of the arm. Axillary nerve injury is an uncommon but potentially debilitating complication of shoulder surgery. Physical exam would be significant for partial or complete deltoid paralysis, which would be most evident with tested shoulder abduction while in internal rotation. In internal rotation, the supraspinatus is rotated anteriorly and thereby contributes less to abduction. The Leechavengvongs procedure involves the transfer of one branch of the radial nerve (to medial, lateral, or long head of the triceps) to the axillary nerve. The goal is to get as much excursion of the radial nerve as possible and transferring the branch as proximally as possible on the axillary nerve
 

Author : Firas Arnaout

 

90. Based on the stress-strain curve in Figure, which of the following materials has the highest modulus of elasticity?

A) Ceramic
B) PMMA
C) Titanium
D) Cancellous bone
E) Cartilage

Correct Answer : A

Based on the stress-strain curve in Figure A, ceramic has the highest modulus of elasticity.
Young’s modulus is a measure of the stiffness (ability to resist deformation) of a material in the elastic zone that is calculated by measuring the slope of the stress-strain curve in the elastic zone. 
A higher modulus of elasticity indicates a stiffer material. Relative values of Young’s modulus include: (1) ceramic, (2) alloy, (3) stainless steel, (4) titanium, (5) cortical bone, (6) matrix polymers, (7) PMMA,  polyethylene, (9) cancellous bone, (10) tendon/ligaments, and (11) cartilage.

 
Author : Firas Arnaout

 

89. Which of the following statements is true regarding polymethylmethacrylate (PMMA)?

A) Barium sulfate initiates the polymerization of monomethacrylate
B) It is a ductile material
C) The Young’s modulus is between cortical and cancellous bone
D) It resists shear better than compressive forces
E) The polymerization of PMMA is endothermic

Correct Answer : C

Young’s modulus measures the ability of a material to resist deformation. PMMA has a Young’s modulus between cortical and cancellous bone.
PMMA, or bone cement, is frequently used in joint replacement surgery, tumor surgery, and spine surgery. Bone cements are provided as two-component materials, a powder and a liquid. The powder usually contains a polymer, benzoyl peroxide (initiator), and barium sulfate (radio-opacifier). The liquid usually contains a monomer, DMPT (accelerator), and hydroquinone (stabilizer). The two components are mixed and a free radical polymerization occurs when the initiator is mixed with the accelerator.

Author : Firas Arnaout

 

88. Which of the following types of corrosion is defined by the formation of pits, grooves, and oxide debris due to the relative micromotion between two affixed materials placed under a load?

A) Crevice
B) Fretting
C) Galvanic
D) Pitting
E) Stress

Correct Answer : B

Fretting corrosion results from the relative micromotion between two affixed materials placed under a load and is characterized by the formation of pits, grooves, and oxide debris. This may be seen at modular junctions.
The process of fretting corrosion involves the physical disruption of the passivated layer at the junction of two materials due to friction caused by micromotion under pressure. The increased surface roughness and release of metallic oxide debris may then, in turn, lead to other types of corrosion such as crevice corrosion. Fretting corrosion has been described at the head-neck junction in total hip arthroplasty, and the risk is increased with an increasing number of component interfaces

Author : Firas Arnaout

 

87. Which of the following statements defines creep, as it relates to material properties?

A) Progressive deformation response to constant force over an extended period of time
B) A solid material’s ability to deform under tensile stress
C) The ability of a material’s mechanical properties to vary according to the direction of load
D) The rupture of a material under repeated cyclic stresses, at a point below the normal static breaking strength
E) The ability of a material to absorb energy and plastically deform without fracturing

Correct Answer : A

Creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material. Creep is an undesirable property of orthopaedic bio-materials because they release frictional forces necessary to maintain rigid internal fixation. In total hip arthroplasty polyethylene liners, creep is the plastic deformation of the acetabular liner that occurs due to loading without the production of wear debris or particles
anabolic effect .

Author : Firas Arnaout

 

86. In post menopausal Osteoporosis, the women are losing the Oestrogen effect on bone metabolism.

How does Oestrogen affect bone?

A) Stimulates bone production and prevents resorption
B) Inhibits activation of adenyl cyclase
C) Decrease RANKL
D) All of the above
E) B&C

Correct Answer : D

Estrogen works mainly through decreasing the RANKL, which interfere with activation of adenyl cyclase which is important for osteoclasts activation , and net result it prevents or decreasing the resorption , in addition to its anabolic effect .

Author : Amin Mohamed Abdel Motaleb EL HELW

 

 

85. A 70 yr old woman presents to the ED with complaints of inability to bear weight on her Rt lower limb and Rt hip pain following a trivial fall in her nursing home. 

X-ray showed Rt femoral neck fracture.

Which of the following is a histological feature of bone death seen in the marrow?

A) Appearance of histiocytes
B) Fibrosis
C) Round cell infiltration
D) Fibrinoid necrosis
E) Granuloma

Correct Answer : A

Bone cells die after 12-48 hours of anoxia, yet the gross appearance of the affected segments remains unaltered.
The most striking histological features are seen in the marrow which includes the loss of fat cell outlines, and the appearance of tissue histiocytes.

Author : Ridhwanullah A. SALAWU

 

84. The following are common sites for Paget’s diseases except:
A) Pelvis
B) Clavicle
C) Femur
D) Tibia
E) Fibula

Correct Answer : E

The pelvis and tibia are the commonest sites of involvement in Paget’s disease. others are femur, skull and clavicle

Author : Ridhwanullah A. SALAWU

 

83. Which of the following is responsible for the short neck appearance in paget’s disease?
A) Kyphosis
B) Platybasia
C) Steal syndrome
D) Pathological fracture
E) Osteosclerosis

Correct Answer : B

If the skull base becomes flattened, it gives the appearance of a short neck.

Author : Ridhwanullah A. SALAWU

 

82. Which of the following cells has receptors for parathyroid hormone (PTH)

(A) Osteoblasts, osteoclasts, and distal kidney nephron
(B) Osteoblasts, osteoclasts, and gastrointestinal cells
(C) Osteoclasts and osteoclast progenitor cells
(D) Osteoblasts and distal kidney nephron
(E) Osteoclast progenitor cells

Correct Answer : D

PTH actions:
– Facilitates absorption of calcium in the gastrointestinal system
– Increases 1,25 dihydroxy vitamin D in the kidney by stimulating 1 alpha hydroxylase
– Facilitates reabsorption of calcium from the distal tubular renal tubular cells ,Calcium is reabsorbed in the proximal and distal tubules, but only distal tubule is PTH dependent
– Inhibits reabsorption of phosphate in the kidney
– Stimulates release of calcium and phosphate from bone (indirectly)
– Causes release of receptor activator of nuclear factor -kB ligand (RANKL) from the surface of the osteoblasts
Parathyroid hormone exerts its effects through receptors on osteoblasts and kidney nephron cells. 

Parathyroid hormone effects on the gut are indirect through an increased synthesis of 1,25 dihydroxy vitamin D. 

Parathyroid hormone acts on osteoblasts to release RANKL, which then acts on the osteoclast progenitor cells to differentiate into osteoclasts.

Author : Rajesh Bahadur Lakhey

 

81. A woman has an X-linked recessive condition. 

Which of the following is true concerning her offspring?

(A) 100% of the daughters will be affected
(B) 50% of the daughters will be affected
(C) 100% of the sons will be affected
(D) 50% of the sons will be affected
(E) 50% of the sons and daughters will be affected

Correct Answer : D

With X-linked dominant, heterozygotes will have the condition. If a woman has this condition, then she will transmit it to 50% of her sons and daughters.
In contrast, affected men transmit the condition to all of his daughters (because the daughter gets his X chromosome), but to none of the sons because the son gets the Y chromosome.
With X-linked recessive, the patterns are different between women and men. X-linked recessive woman: An X-linked woman with the recessive allele is a carrier, but she is not affected because the allele is recessive. Carrier females (X-linked recessive) transmit the condition to 50% of her daughters (who become carriers) and 50% of her sons (the sons are affected because their only X chromosome has the recessive gene).

Author : Rajesh Bahadur Lakhey

 

80. Which of the following conditions is transmitted by an X-linked dominant inheritance pattern:

(A) Haemophilia A
(B) Hypophosphatemic rickets
(C) Duchennes muscular dystrophy
(D) Achondroplasia
(E) Hypophosphatasia

Correct Answer : B

There is only one condition that must be remembered for examinations that is transmitted through an X-linked dominant pattern – hypophosphatemic rickets.
Remember: the conditions which are x-linked recessive
Haemophilia A, B – X-linked recessive
Duchennes muscular dystrophy – X-linked recessive
Achondroplasia – Autosomal dominant
Hypophosphatasia – Autosomal recessive

Author : Rajesh Bahadur Lakhey

 

79. Which of the following describes the inheritance pattern of Marfan’s syndrome:

(A) Autosomal recessive
(B) Autosomal dominant
(C) X-linked recessive
(D) X-linked dominant
(E) Sporadic

Correct Answer : B

Structural defects are usually transmitted by an autosomal-dominant pattern. 

In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal recessive
pattern.
Remember the major autosomal-dominant conditions:
Achondroplasia
Spondyloepiphyseal dysplasia
Multiple epiphyseal dysplasia
Marfan’s syndrome
Ehlers-Danlos syndrome
Osteogenesis imperfecta (I, IV)
Multiple hereditary exostosis
Polydactyly

Author: Rajesh Bahadur Lakhey

 

78. Which of the following has a catabolic effect on articular cartilage

(A) Bone morphogenetic protein (BMP)-2
(B) BMP-7
(C) Smad3
(D) Insulin-like growth factor 1
(E) Cyclooxygenase (COX-2)

Correct Answer : E

Cartilage Metabolism and Regulation
A. Nutrition through diffusion (low oxygen tension, 1% to 2%)
B. Energy through glycolysis
C. Transforming growth factor beta (TGF-B)
1. Chondroprotective effect
2. Smad3 which is transcription factor activated by TGF-B also is chondroprotective
D. Insulin-like growth factor increases collagen and proteoglycan synthesis
E. Bone morphogenetic protein (BMP)-2 and BMP-7 increase proteoglycan synthesis and maintain chondrocyte phenotype
F. Interleukin-1
1. Inhibits proteoglycan synthesis
2. Stimulates metalloproteinase activity (catabolic enzymes)
G. Tumor necrosis factor alpha
1. Inhibits collagen synthesis
2. Stimulates metalloproteinase activity (catabolic enzymes)
H. Other catabolic enzymes
1. Cyclooxygenase (COX-2)
2. Nitric oxide synthetase

Author : Rajesh Bahadur Lakhey

 

77. Which of the following statements is true regarding gout:

(A) Gout is more common in females than males
(B) Urate overproduction is the most common cause
(C) Gout is very common in heart transplant patients on cyclosporine
(D) The serum uric acid level is always elevated in an acute attack
(E) Joint space destruction is an early radiographic finding

Correct Answer : C

Gout is caused by the deposition of monosodium urate crystals in tissues typically around joints. Common locations include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first attack is in the great toe. 
reasons:
The synovial fluid is a poorer solvent than plasma
Lower temperatures (as in peripheral joints) favour crystallization
One should remember the following:
Gout is much more common in males (ratio of 20:1).
An inability to excrete uric acid is the primary cause.
Gout is very common in transplant patients taking cyclosporine.
Serum uric acid level is often normal in an acute attack.
Joint space is usually preserved on plain radiographs (early disease).

Author : Rajesh Bahadur Lakhey

 

76. Which of the following zones of the physis is involved in Salter Harris Type I and II fractures?

(A) Proliferative zone
(B) Perichondrial ring
(C) Reserve zone
(D) Node of Ranvier
(E) Zone of provisional calcification

Correct Answer : E

Salter Harris Type I and II fractures occur through the zone of provisional calcification or through the hypertrophic zone. 

The reserve and proliferative zone remain intact and growth can proceed normal after healing of the fracture.

Author: Rajesh Bahadur Lakhey

 

75. Which of the following is the proper sequence when listing biomaterials in order of increasing ultimate tensile strength

(A) Cancellous bone, cortical bone, stainless steel, titanium, cobalt chrome
(B) Cortical bone, cancellous bone, stainless steel, cobalt chrome, titanium
(C) Cortical bone, cancellous bone, cobalt chrome, stainless steel, titanium
(D) Cancellous bone, stainless steel, titanium, cortical bone, cobalt chrome
(E) Cancellous bone, cortical bone, cobalt chrome, titanium, stainless steel

Correct Answer : A

The proper sequence for common orthopedic biomaterials in terms of increasing ultimate tensile strength is: cancellous bone – polyethylene – methylmethacrylate – cortical bone – stainless steel – titanium – cobalt chrome.

Author: Rajesh Bahadur Lakhey

 

74. Which of the following conditions is characterized by decreased osteoclastic resorption of bone and cartilage with normal bone formation:

(A) Type 1 osteoporosis
(B) Type 2 osteoporosis
(C) Osteopetrosis
(D) Paget’s disease
(E) Secondary hyperparathyroidism

Correct Answer : C

Osteopetrosis is a rare disorder in which there is decreased osteoclastic resorption of bone and cartilage with normal bone formation. There are a number of different forms of the condition.
The most common form of osteopetrosis is an autosomal dominant type with mild features (adult or tarda). Patients may have mild anaemia, have one or more fractures, or be asymptomatic.
The juvenile form of osteopetrosis is a severe autosomal disorder. Children have multiple fractures, severe anaemia, thrombocytopenia, and hepatosplenomegaly. Effected children are also immunocompromised.

Author : Rajesh Bahadur Lakhey

 

73. Which of the following features is associated with type 2 osteoporosis

(A) High turnover osteoporosis
(B) Female to male ratio is 6:1
(C) Loss of cortical and trabecular bone
(D) Related to Oestrogen deficiency
(E) Greatest bone loss in the first 6 to 10 years following menopause

Correct Answer : C

Type 1 osteoporosis is the most common form of osteoporosis and is found in women during postmenopausal years. Type 1 osteoporosis is related to Oestrogen deficiency rather than a problem in calcium intake or absorption.
Features of type 1 osteoporosis include:
Female to male ratio is 6:1
High turnover osteoporosis
Bone loss rate of 2% to 3% per year for 6 to 10 years following menopause
Trabecular bone is most affected
Related to Oestrogen deficiency rather than calcium intake
Type 2 osteoporosis, also called senile or involutional osteoporosis, is a low turnover osteoporosis and principally occurs in patients older than 75 years of age.
Features of type 2 osteoporosis include:
Female to male ratio is 2:1
Patients older than 75 years of age
Low turnover osteoporosis
Trabecular and cortical bone affected
Associated with hip fractures
Related to a lifelong deficiency of calcium

Author: Rajesh Bahadur Lakhey

 

72. Parathyroid hormone stimulates which of the following cells to secrete neutral protease that degrades the osteoid bone surface

(A) Osteoblasts
(B) Mast cells
(C) Osteoclasts
(D) Osteocytes
(E) Osteoclast precursor cells

Correct Answer : A

Osteoblasts have receptors for parathyroid hormone. Once stimulated, the cells release interleukin-6 (IL-6). IL-6 signals osteoclasts to resorb bone. 

The osteoblasts secrete neutral proteases that degrade the osteoid surface. Osteoclasts then attach to the bone surface and secrete acid proteases that degrade the bone matrix. 

Parathyroid hormone related protein increases osteoblast expression of receptor activator of nuclear factor –kB ligand (RANKL). RANKL binds to osteoclast precursor cells for the formation of active osteoclasts.

Author : Rajesh Bahadur Lakhey

 

71. Which of the following cells has receptors for parathyroid hormone

(A) Osteocytes
(B) Osteoclasts
(C) Plasma cells
(D) Osteoblasts
(E) Osteoclast precursor cells

Correct Answer : D

Osteoblasts have receptors for parathyroid hormone. Once stimulated, the cells release interleukin-6 (IL-6). IL-6 signals osteoclasts to resorb bone. 

The osteoblasts secrete neutral proteases that degrade the osteoid surface. Osteoclasts then attach to the bone surface and secrete acid proteases that degrade the bone matrix. 

Parathyroid hormone related protein increases osteoblast expression of receptor activator of nuclear factor –kB ligand (RANKL). RANKL binds to osteoclast precursor cells for the formation of active osteoclasts.

Author : Rajesh Bahadur Lakhey

 

70. Which of the following proteins or vitamins influences growth plate chondrocyte maturation as a potent mitogen in the proliferative zone

A) 1,25 Dihydroxyvitamin D3
(B) 24,24 Dihydroxyvitamin D3
(C) Insulin
(D) 1 Hydroxyvitamin D3
(E) Calcitonin

Correct Answer : B

Traditionally, 24,25 Dihydroxyvitamin D3 was considered an inactive form of vitamin D.
Recent studies suggest that 24,25 Dihydroxyvitamin D3 influences growth plate chondrocyte maturation as a potent mitogen in the proliferative zone and may also contribute to bone formation and fracture repair.

Author : Rajesh Bahadur Lakhey

 

69. Paget’s disease is common in all of the listed locations except:

(A) England
(B) United States
(C) Northern Europe
(D) Australia
(E) Sub-Saharan Africa

Correct Answer : E

Paget’s is a Remodeling disease caused by excessive osteoclastic activity
Rarely diagnosed in patients younger than 40 years of age; most patients diagnosed after age 50
Most common sites include pelvis, femur, spine, skull, and tibia
Less common sites include clavicles, scapulae, ribs, and facial bones
Rarely found in the hands and feet
Pagetic bone
o is more susceptible to fracture
o is less compact
o is more vascular
o tends to bow in weight bearing areas
Geographic clustering (up to 4% in patients older than 55 years of age)
o England
o Northern Europe
o North America
o Australia, New Zealand
o Rare in Asia, China, Indonesia, Malaysia, and sub-Saharan Africa
Possibly a slow viral disease
o RNA paramyxovirus (e.g., respiratory syncytial virus and measles)

Author  : Rajesh Bahadur Lakhey

 

68. Paget’s disease is common in all of the following bones except

(A) Humerus
(B) Spine
(C) Femur
(D) Hands and feet
(E) Pelvis

Correct Answer : D

Paget’s is a Remodeling disease caused by excessive osteoclastic activity
Rarely diagnosed in patients younger than 40 years of age; most patients diagnosed after age 50
Most common sites include pelvis, femur, spine, skull, and tibia
Less common sites include clavicles, scapulae, ribs, and facial bones
Rarely found in the hands and feet
Pagetic bone:
o is more susceptible to fracture
o is less compact
o is more vascular
o tends to bow in weight bearing areas
Geographic clustering (up to 4% in patients older than 55 years of age)
o England
o Northern Europe
o North America
o Australia, New Zealand
o Rare in Asia, China, Indonesia, Malaysia, and sub-Saharan Africa
Possibly a slow viral disease      o RNA paramyxovirus (e.g., respiratory syncytial virus and measles)

Author : Rajesh Bahadur Lakhey

 

67. The skin of the proximal one-third of the anterior thigh just distal to the inguinal ligament is innervated by which of the following levels

(A) T12
(B) L1
(C) L2
(D) L3
(E) L4

Correct Answer : B

The skin of the proximal one-third of the anterior thigh just distal to the inguinal ligament is innervated by L1, L2, and L3.
Note:
L1 Thigh, proximal third, anterior
L2 Thigh, middle, anterior
L3 Thigh, distal third, anterior

Author : Rajesh Bahadur Lakhey

 

66. The principle blood supply to the humeral head derives from:

(A) The anterior humeral circumflex artery
(B) Axillary artery
(C) The posterior humeral circumflex artery
(D) Acromial branch of thoracoacromial artery
(E) Subscapular artery

Correct Answer: A

The humeral head has been shown to be perfused primarily by the anterolateral ascending branch of the anterior circumflex artery. This branch runs parallel to the lateral aspect of the tendon of the long head of the biceps and enters the humeral head where the proximal end of the intertubercular groove meets the greater tuberosity. 

The posterior circumflex artery provides only the posterior portion of the greater tuberosity and a small posteroinferior part of the head.

Author :Rajesh Bahadur Lakhey

 

65. Which of the following statements is true concerning molecular events at the site of a healing fracture:

(A) Type II collagen production is lowest during the first 2 weeks
(B) Type I collagen production is highest during the first 2 weeks
(C) Periosteal type III collagen serves as a substrate for migration of osteoprogenitor cells and capillary ingrowth
(D) Type IX collagen initiates mineralization of type II collagen
(E) Types V and XI collagen control the maturation of mineralization crystals

Correct Answer: C

Important points to remember concerning molecular events at the fracture site:
Type II collagen production is highest during the first 2 weeks. Cartilage is the first tissue produced at the fracture site. The chondrocytes hypertrophy and release matrix vesicles that prepare the extracellular matrix for mineralization of the cartilage. Blood vessels grow into the hypertrophied cartilage cells and perivascular cells become osteoblasts and begin mineralization. This is the exact same process that occurs at the growth plate with formation of the primary and secondary spongiosa.
Type I collagen production is low during the first 2 weeks as cartilage is initially formed. Type I collagen production is highest as the cartilage is mineralized later.
Periosteal type III collagen serves as a substrate for the migration of osteoprogenitor cells and capillary ingrowth.
Type IX collagen contributes to the mechanical stability of type II collagen.
Types V and XI collagen regulate the growth and orientation of types I and II collagen fibrils.

Author : Rajesh Bahadur Lakhey

 

64. Human calcium absorption occurs in the

(A) Stomach
(B) Small intestine
(C) Large intestine
(D) Liver
(E) Parathyroid glands

Correct Answer: B

Dietary calcium is absorbed in the small intestine. This absorption is stimulated by 1,25 Dihydroxyvitamin D3.

Author : Rajesh Bahadur Lakhey

 

63. With regard to the organic phase of bone, which of the following accounts for 90% of the organic matrix

(A) Type I collagen
(B) Type II collagen
(C) Osteonectin
(D) Osteocalcin (bone Gla protein)
(E) Matrix Gla protein

Correct Answer: A

Bone has the following composition:
Mineral or inorganic phase 70%
Water 5% to 8%
Organic matrix 22% to 25%
Collagen type I 90%
Noncollagenous proteins 5% to 8%

Author: Rajesh Bahadur Lakhey

 

62. Osteoclasts are activated following disruption of the osteoid layer that covers the bone surface. 

Which of the following cells is responsible for this disruption?

(A) Osteoclasts
(B) Resting bone-lining cells
(C) Active osteoblasts
(D) Macrophages
(E) Mast cells

Correct Answer : B

The resting bone-lining cells (flat, elongated osteoblasts) begin the bone resorption process by secreting collagenases that degrade the osteoid layer covering bone. These cells may also contract to expose the bone surface and allow access for the osteoclasts.
Parathyroid hormone (PTH) mediates bone resorption by stimulation of PTH receptors on the osteoblasts. Osteoclasts do not have receptors for PTH.

Author of the question: Rajesh Bahadur Lakhey

 

61. Osteoclasts bind to the bone surface through which of the following proteins

(A) Osteocalcin (bone Gla protein)
(B) Integrins
(C) Osteopontin (bone sialoprotein 1)
(D) Fibromodulin
(E) Bone sialoprotein 2

Correct Answer: B

Active osteoclasts resorb the mineral and organic matrix of bone. Active osteoclasts also attach the cell to exposed bone matrix. 

When osteoclasts are studied with an electron microscope, there are two prominent findings — a ruffled border and a clear zone. 

In the clear zone, the osteoclast seals off the area of bone to be resorbed and attaches to the bone surface through a receptor-mediated process with the assistance of proteins called integrins. 

The ruffled border is an area found in the infoldings of the cell membrane. At the area of the ruffled border, the osteoclasts lower the pH with hydrogen ions through the carbonic anhydrase system. This lowered pH increases the solubility of the apatite crystals and the mineral can be removed. The organic components of the bone are then hydrolyzed through acidic proteolytic digestion.

Author: Rajesh Bahadur Lakhey

 

60. Osteoblasts predominantly form which of the following types of collagen?

(A) Type VI
(B) Type IX
(C) Type X
(D) Type I
(E) Type II

Correct Answer: D

Osteoblasts produce type I collagen. This is the major type of collagen found in bone. 

Type I collagen is the only collagen capable of mineralization.

Author : Rajesh Bahadur Lakhey

 

59. Which of the following cells produce osteocalcin and bone sialoprotein?

(A) Osteocytes
(B) Osteoblasts
(C) Mast cells
(D) Osteoclasts
(E) Fibroblasts

Correct Answer: B

Osteoblasts are metabolically active cells that line the bone surface. Osteoblasts produce type I collagen and many non-collagenous proteins such as osteocalcin, bone sialoprotein, and extracellular matrix proteins. 

Osteoblasts have large amounts of rough endoplasmic reticulum because they prepare large amounts of protein for export out of the cell. The Golgi apparatus exports the protein.

Author : Rajesh Bahadur Lakhey

 

58. Which of the following types of bone behaves in an isotropic manner when loaded in different directions

(A) Lamellar bone
(B) Woven bone
(C) Cortical bone
(D) Cancellous bone
(E) Plexiform bone

Correct Answer: B

Woven bone is immature bone that is found in newborns, fractured bone, and the metaphyses of growing bone. 

In woven bone, the collagen fibers are oriented in a completely random fashion.

When woven bone is loaded, it performs in an isotropic manner. 

The other types of bone (lamellar, cortical, cancellous, and plexiform) contain collagen that is oriented along the long axis of the bone and cause the bone to perform anisotropically.

Author : Rajesh Bahadur Lakhey

 

57. Which of the following statements is true concerning the changes seen in human articular cartilage as a person ages?

(A) Progressive increase in chondroitin 4-sulfate
(B) Progressive decrease in chondroitin 6-sulfate
(C) Progressive decrease in collagen concentration
(D) Progressive increase in collagen concentration
(E) Progressive increase in keratan sulfate concentration

Correct Answer: E

There are several important points concerning aging and articular cartilage. The collagen content increases quickly after birth, attaining adult levels, and then it does not materially change. 

The water level is high in immature individuals but remains constant in the adult. 

In contrast to the stable levels of collagen and water, the proteoglycan composition changes.
Chondroitin 4-sulfate levels progressively decrease.
Chondroitin 6-sulfate levels progressively increase.
Keratan Sulfate levels progressively increase in the human. At age 30, the level increases to 25% to 50% of proteoglycan content.
Aggregation decreases with advancing age.

Author : Rajesh Bahadur Lakhey

 

56. Which of the following is the most prevalent glycosaminoglycan in articular cartilage?

(A) Keratan sulfate
(B) Chondroitin sulfate
(C) Hyaluronate
(D) Dermatan sulfate
(E) Fibromodulin

Correct Answer: B

The three major types of glycosaminoglycans in articular cartilage are Chondroitin Sulfate, Keratan Sulfate, and Dermatan Sulfate. 

Chondroitin sulfate is the most common glycosaminoglycan in articular cartilage. Chondroitin 4-sulfate and chondroitin 6-sulfate isomers account for 55% to 90% of the total amount.
The Glycosaminoglycan chains contain repeating carboxyl and sulfate groups that become ionized in
solution. These free-floating ions account for the Donnan osmotic pressure and the large charge-to-charge
repulsive forces of the glycosaminoglycan chains.
Most of the Glycosaminoglycans are in the form of large aggregates called Aggrecan. Link protein
binds to both the G1 domain of Aggrecan and the Hyaluron to form the Aggrecan-Hyaluronate-link
protein complexes, which are called Proteoglycan Aggregates.

Author of the question: Rajesh Bahadur Lakhey

 

55. Which of the following statements inaccurately describes human bone as a biomaterial?

(A) Bone is isotropic
(B) Bone is viscoelastic
(C) Bone’s strength and elastic modulus are approximately proportional to the square of its density
(D) Bone is a composite
(E) Bone remodels its structure to maintain overall resistance to loading while the material itself weakens

Correct Answer : A

Bone is anisotropic as the properties of the material vary with the direction of loading. 

This is true of most biologic materials .

Author : Rajesh Bahadur Lakhey

54. Which of the following occurs when a joint is immobilized

(A) Slow decrease in collagen concentration
(B) Rapid decrease in collagen concentration
(C) Slow decrease in proteoglycan concentration
(D) Rapid decrease in proteoglycan concentration
(E) No change in either collagen or proteoglycan concentration

Correct Answer: D

Motion is essential for normal articular cartilage function. Many changes occur in the articular cartilage, ligaments, capsules, and bone within a joint when it is immobilized.
There is a rapid loss of proteoglycan when a joint becomes immobilized. This loss of proteoglycan results in an increase of deformation and fluid flux when compressive loads are applied to the joint.
The collagen content of the cartilage does not change and the tensile properties are maintained.
The changes are reversible and the recovery depends upon how long the joint is immobilized.

Author of the question:  Rajesh Bahadur Lakhey

53. The major biochemical component of a ligament is

(A) Water
(B) Collagen
(C) Proteoglycan
(D) Elastin
(E) Link protein

Correct Answer: A

Approximately 60% to 80% of a ligament is composed of water. Collagen is 70% to 80% of the dry weight of a ligament (90% Type I and smaller amounts of Type III). Other components, in lesser amount, include proteoglycans and elastin.

Author of the question: Rajesh Bahadur Lakhey

52. At higher rates of loading, the failure pattern of a ligament will tend to occur at

A) Proximal insertion site
(B) Distal insertion site
(C) Equally at the proximal and distal insertion sites
(D) Mid-substance
(E) Failure patterns have no relationship to site of failure

Correct Answer: D

The rate of loading has a significant effect on the injury pattern of a ligament. With high strain rates,
the strength and tensile modulus of ligament will be increased. The ligament will tend to fail in the
mid-substance rather than the insertion sites.
At slow rates of loading, the ligament will tend to fail at the insertion site.

Author of the question: Rajesh Bahadur Lakhey

51. A 25-year-old man has a destructive lesion in the medial femoral condyle that extends to the articular
surface. Open biopsy shows a giant cell tumor. There is no evidence of pathologic fracture or major soft
tissue extension. What surgical stage would be assigned according to the system of the Musculoskeletal
Tumor Society

(A) Stage 1
(B) Stage 2
(C) Stage 3
(D) Stage I
(E) Stage II

Correct Answer : B

The lesion is a giant cell tumor. These lesions behave very aggressively and grow to a large size. They can cause pathologic fracture and are prone to local recurrence. This would be a Stage 2 lesion because there is no soft tissue
extension, fracture of the joint, etc.
The Surgical Staging System of the Musculoskeletal Tumor Society is a useful system to both predict prognosis and plan treatment. The system for benign lesions is divided into three groups: Inactive (latent), active, and aggressive:

Stage 1
Inactive (latent) Refers to lesions which are not causing pain and show no evidence of active growth. Stage 1 lesions are generally treated with observation only.

Stage 2
Active Refers to lesions which are causing pain or some form of disability. If a lesion has weakened the structure of
the bone such that fracture may occur, the lesion would also be considered a Stage 2 lesion.

Stage 3
Aggressive Refers to lesions which are large, have broken into the soft tissues, or have caused a pathologic fracture.
These lesions are usually prone to local recurrence and have the potential of causing a major problem for the patient.

Author :Rajesh Bahadur Lakhey

 

50. With a right-sided anterior cervical spine approach, the structure at increased risk is the:

A) Recurrent laryngeal nerve
B) Superior laryngeal nerve
C) Hypoglossal nerve
D) Thoracic duct
E) Esophagus

Correct Answer: A

The left recurrent laryngeal nerve enters the thorax within the carotid sheath before looping around the aortic arch and ascending into the neck between the trachea and the esophagus. 

On the right side, the nerve exits the carotid sheath at a higher level, making the nerve susceptible to injury during the surgical dissection


Author: Rajesh Bahadur Lakhey.

 

49. The triceps tendon insertion has two well-defined components. 

The triceps proper inserts:

A) Directly onto the posterior 40% of the olecranon
B) On to the anconeous muscle
C) On to the entirety of the olecranon tip
D) On to the anterior aspect of the olecranon
E) None of the above

Correct Answer: A

A thorough understanding of the insertional anatomy of the extensor mechanism of the elbow is essential in understanding the treatment principle for chronic triceps tendonitis in throwers. Approximately 20 cm proximal to the olecranon tip, the triceps tendon originates from within the body of the triceps muscle. 

Two components of the triceps extensor mechanism form as the tendon approaches its insertion on the olecranon tip. The triceps proper inserts directly onto the posterior 40% of the tip of the olecranon. The relatively thin triceps expansion inserts distally and laterally primarily through the anconeus. The triceps decussation, which is well defined in 50% of specimens, is a well-defined interval located between the triceps proper and the triceps expansion.

Author: Rajesh Bahadur Lakhey.

 

48. Dynamic muscular stabilizers of the shoulder play an important role in stability. 

Which of the following is the most important dynamic stabilizer?

A) The rotator cuff
B) The labrum
C) The coracobrachialis
D) The latissimus dorsi
E) The biceps brachii

Correct Answer: A

The rotator cuff is an important dynamic anterior stabilizer of the shoulder. The stability of the shoulder is maintained
primarily by the shoulder musculature. 

The biceps brachii has been shown to act as a dynamic stabilizer of the shoulder, but the most important dynamic stabilizer is the rotator cuff.

Author: Rajesh Bahadur Lakhey.

 

47. Using the three layer description of the medial structures of the knee, the medial patellofemoral ligament is described as being within the:

A) First layer
B) Second layer
C) Third layer
D) All three layers
E) The medial patellofemoral ligament does not exist.

Correct Answer: B

The medial patellofemoral ligament (MPFL), which is in the second layer, is the major medial soft-tissue restraint that
prevents lateral displacement of the patella .The MPFL extends from the adductor tubercle to the superomedial border of the patella. 

The medial patellomeniscal ligament and medial patellotibial ligament also contribute varying degrees of
medial patellar restraint.

Author: Rajesh Bahadur Lakhey

 

46. A magnetic resonance image of a patient’s right shoulder is shown. 

The structure marked by the arrows is innervated by which of the following nerves?

A) Musculocutaneous nerve
B) Branch of the posterior cord of the brachial plexus
C) Branch of the lateral cord of the brachial plexus
D) Branch of the medial cord of the brachial plexus
E) Branch of the superior trunk of the brachial plexus

Correct Answer: B

The arrows mark the subscapularis tendon. The subscapularis muscle is innervated by the upper and lower subscapular nerves. The upper and lower subscapular nerves are branches from the posterior cord of the brachial plexus.

Author: Rajesh Bahadur Lakhey

 

45. With regard to the meniscofemoral ligaments, the ligament of Humphrey runs ___ to the posterior cruciate ligament (PCL) and the ligament of Wrisberg runs _____ to the PCL.

A) Posterior, anterior
B) Anterior, posterior
C) Anterior, anterior
D) Posterior, posterior
E) Medial, lateral

Correct Answer: B

The anterior meniscofemoral ligament of Humphrey runs from the femur to the posterior horn of the lateral meniscus
anterior to the PCL. 

The ligament of Wrisberg runs posterior to the PCL. It is occasionally the only posterior horn attachment site for a discoid lateral meniscus and can result in excessive motion and posterior horn instability.

Author: Rajesh Bahadur Lakhey

 

44. Which of the following describes the correct relationship between the suprascapular nerve and the suprascapular vessels as they pass through the suprascapular notch:

A) The suprascapular nerve, artery, and vein all pass below the transverse scapular ligament.
B) The suprascapular nerve, artery, and vein all pass superficially to the transverse scapular ligament.
C) The suprascapular nerve passes superficially to the transverse scapular ligament while the artery and vein pass deep
D) The suprascapular nerve and artery pass deep to the transverse scapular ligament while the suprascapular vein passes superficially to it.
E) The suprascapular nerve passes deep to the transverse scapular ligament while the suprascapular artery and vein pass above it.

Correct Answer: E

The suprascapular nerve is a branch of the upper trunk of the brachial plexus at Erb’s point. The suprascapular nerve receives branches primarily from the fifth cervical nerve root. 

The nerve follows the omohyoid muscle laterally and passes beneath the anterior border of the trapezius muscle to the upper border of the scapula where it joins the suprascapular artery. It passes through the suprascapular notch deep to the transverse scapular ligament. 

The artery and vein pass superficial to the ligament and join the nerve distally in the suprascapular fossa. 

After innervating the supraspinatus muscle, the nerve passes around the lateral free margin of the scapular spine (spinoglenoid notch) to innervate the infraspinatus muscle.

Author: Rajesh Bahadur Lakhey

 

43. The primary restraint to anterior translation of the abducted and externally rotated glenohumeral joint is the:

A) Coracohumeral ligament
B) Superior glenohumeral ligament
C) Middle glenohumeral ligament
D) Inferior glenohumeral ligament
E) Subscapularis muscle

Correct Answer: D

The inferior glenohumeral ligament is the primary restraint to anterior translation of the abducted and externally rotated glenohumeral joint. The Bankart lesion is an avulsion of the inferior glenohumeral ligament and represents the primary pathoanatomy of traumatic anterior shoulder dislocation

Author: Rajesh Bahadur Lakhey

 

42. Which of the following anatomic landmarks of the knee represents the contact area between the lateral femoral condyle and the anterior horn of the lateral meniscus when the knee is in full extension:

A) Outerbridge’s ridge
B) Blumensatt’s line
C) Notch of Grant
D) David’s point
E) Sulcus terminalis

Correct Answer: E

The indentation on the lateral femoral condyle often seen on the lateral radiograph of the knee represents the contact area between the femoral condyle and the anterior portion of the lateral meniscus and is often referred to as the sulcus terminalis. 

After an acute anterior cruciate ligament (ACL) injury or recurrent giving way episode in a chronically ACL deficient knee, the sulcus terminalis is the region in which a bone contusion is typically seen on an magnetic resonance image.

Author: Rajesh Bahadur Lakhey

 

41. In a congruent patellofemoral joint, the patella centers within the trochlear groove by what degree of flexion:

A) 5° to 10°
B) 10° to 15°
C) 15° to 20°
D) 20° to 25°
E) 25° to 30°

Correct Answer: C

Laurin and colleagues recognized that the normally tracking patella centered within the trochlea by 20° of knee flexion. Fulkerson and Hungerford demonstrated patellar engagement between 15° to 20° using computerized tomography scans.

Author: Rajesh Bahadur Lakhey

 

40. Weight training that employs a constant velocity and variable resistance is referred to as:

A) Isometric
B) Isotonic
C) Isokinetic
D) Plyometric
E) Functional

Correct Answer: C

Isokinetic training employs constant velocity and variable resistance. 

Special equipment, such as a Cybex device , is required for isokinetic training.

Author: Rajesh Bahadur Lakhey

 

39. Which of the following statements is true regarding the effect of anabolic-androgenic steroid on immobilized skeletal muscle:

A) Steroid administration has no effect on immobilized muscle.
B) Steroid administration leads to muscle hypertrophy only in conjunction with strength training.
C) When compared to controls, steroid administration leads to increased muscle mass but not increased contractile force.
D) When compared to controls, steroid administration leads to increased contractile force but not muscle mass.
E) When compared to controls, steroid administration leads to both increased contractile force and muscle mass.

Correct Answer: E

In a randomized, blinded study investigating whether short-term administration of an anabolic-androgenic steroid can limit immobilization-induced muscle atrophy in a rabbit model, Taylor and associates found that dry weights and contractile forces of the involved muscle groups were greater in the steroid-treated rabbits than in controls. This study suggests the possibility of controlled medical treatment with anabolic steroids to prevent muscle atrophy in immobilized patients, or to strengthen muscles in sedentary populations.

Author: Rajesh Bahadur Lakhey


38. A foot is maximally dorsiflexed during this point of the gait cycle:

A) Midswing
B) Midstance
C) Toe off
D) Heelstrike
E) First one-third of stance

Correct Answer: B

During gait, a foot is dorsiflexed during midswing and foot flat. During midswing, the anterior tibial muscle maintains the foot in a dorsiflexed position to facilitate a smooth heelstrike. This is an active dorsiflexion of the foot and ankle. The maximum dorsiflexion of the foot, however, is passive and occurs as the leg moves forward over the foot during foot flat at midstance.

Author: Rajesh Bahadur Lakhey

 

37 .The protein neurofibromin normally acts in which of the following ways:

A) Inhibits fibroblast growth factor 
B) Promotes proteoglycan assembly
C) Down regulates Ras protein 
D) Causes nerve cells to divide
E) Promotes tumor formation

Correct Answer: C

If defective, neurofibromin is the protein that causes neurofibromatosis. Neurofibroma is coded on chromosome 17, and it acts as a tumor suppressor by downregulating Ras protein, which enhances cell growth and proliferation

Author: Fouad Chaudery

 

36. Which of the following mechanisms of bisphosphonate action occurs when used to treat osteoporosis:

A) Increasing calcium absorption in the intestines 
B) Decreasing urinary excretion of calcium 
C) Stimulating osteoblast precursors 
D) Binding to hydroxyapatite crystals 
E) Increasing phosphate reabsorption in the kidney 

Correct Answer: D

Biphosphonates are effective in the treatment of osteoporosis because they bind to the hydroxyapatite crystals and inhibit crystal resorption.

Other effects of biphosphonates include:

Reducing production of lysosomal enzymes by osteoclasts
Inducing osteoclast cell death
Reducing the formation of new osteoclasts After 1 year of treatment

Author: Fouad Chaudhry

 

35. Osteoclasts have receptors for which of the following:

A) 1,25 dihydroxyvitamin D3 
B) Parathyroid hormone 
C) Osteoprotegerin 
D) Receptor activator of nuclear factor –kB 
E) Calcitonin 

Correct Answer: E

Osteoclasts have receptors for calcitonin. Calcitonin causes osteoclasts to shrink in size and reduces their ability to resorb bone

Author: Fouad Chaudhry

 

34. Parathyroid hormone inhibits the production of:

A) Osteoprotegerin 
B) 1,25 dihydroxyvitamin D3 production 
C) Interleukin-6 
D) Kidney 1 alpha-hydroxylase 
E) Receptor activator of nuclear factor –kB ligand (RANKL) 

Correct Answer: A

Parathyroid hormone inhibits the production of osteoprotegerin. Osteoprotegerin is a decoy inhibitor of the receptor activator of nuclear factor –kB. Osteoprotegerin inhibits osteoclast activation.

Author: Fouad Chaudhry

 
 

 

33. Which of the following proteins or hormones assist in the transport of calcium in the kidney against chemical and electrical gradients:

A) Calcitonin 
B) Calbindin 
C) Osteoprotegerin 
D) Parathyroid hormone 
E) Vitamin D3 

Correct Answer: B

Calbindin, a vitamin D dependent and calcium binding protein, assists in the transport of calcium against chemical and electrical gradients. Most calcium resorption in the kidney occurs in the distal convoluted segment. 

Author: Fouad Chaudhry

 
 

 

32. Osteoprotegerin (OPG) has which of the following functions or effects:

A) Inhibits osteoclast apoptosis 
B) Inhibits osteoclast formation 
C) Activates osteoclast precursors 
D) Induces hypercalcemia 
E) Binds to receptor activator of nuclear factor –kB ligand (RANKL) 

Correct Answer: E

The activation of osteoclasts is a complex process. Surface receptors on the osteoclast precursor cells are called RANK. 

Receptor activator of nuclear factor –kB ligand (RANKL) is expressed on the surface of osteoblasts/stromal cells. 

The RANKL proteins leave the osteoblast and attach to the RANK receptor on the osteoclast precursor. 

Macrophage colony stimulating factor then facilitates the production of active osteoclasts from the osteoclast precursor. 

Osteoprotegerin (OPG) is an inhibitor that is produced on the cell surface of haematopoietic precursor cells and mature osteoclasts. OPG binds to RANK receptor to inhibit the activation of osteoclasts.

OPG:

  • Blocks osteoclast formation
  • Reduces hypercalcemia
  • Overexpression induces osteopetrosis
  • Loss of expression induces osteoporosis
  • Prevents calcification of large arteries

Author: Fouad Chaudhry

 
 

 

31. Which of the following proteins binds to osteoclast precursor cells and positively effects their final differentiation into osteoclasts:

A) Receptor activator of nuclear factor-kappa B (RANK) 
B) Osteoprotegerin 
C) Bone morphogenetic protein 7 
D) Core binding factor alpha 1 (Cbfa1) 
D) Parathyroid hormone related protein (PTHrP)