96. A construction worker with sustained trauma later develops tetanus. What is the causativeorganism?

A. Gram-negative anaerobic rod

B. Gram-positive cocci

C. Gram-positive anaerobic rod

D. Gram-positive aerobic rod

 

The correct answer is C. The causative organism of tetanus is Clostridium tetani , which is a gram-

positive, spore-forming anaerobic rod. Bacteroides is gram-negative anaerobic rod (choice A).

Examples of gram-positive cocci (choice B) are staphylococci and streptococci. The causative

organism of anthrax, Bacillus anthracis , is a gram-positive, spore-forming aerobic rod (choice D).

 

 

97. Last year's influenza A vaccine is unlikely to be effective today because influenza A

A. has a heavy polysaccharide coat

B. immunosuppresses the patient

C. kills lymphocytes

D. resists inactivation by complement

E. undergoes genetic reassortment

 

The correct answer is E. The difficulty with developing a vaccine against influenza A arises because

the influenza virus genome is composed of eight strands of single-stranded RNA. Minor shifts

(antigenic drift) in surface antigens that occur as point mutations in the genes accumulate. Influenza A

can also undergo larger, abrupt changes in antigen expression (antigenic shift), however, as a

consequence of reassortment of some of the RNA fragments between human and nonhuman hosts.

 

Thus, last year's vaccine does not necessarily work against this year's virus. Polysaccharide coats

(choice A) are a virulence factor of some bacteria, not of viruses. Influenza A can compromise the

lungs sufficiently to predispose to secondary infections, producing a functional immunosupression

(choice B), but this attribute does not make it difficult to produce vaccines against the virus. Unlike

AIDS, influenza virus does not selectively target lymphocytes (choice C). Influenza A, bound to

antibody and complement, can be effectively phagocytized (compare with choice D).

 

98. Infections in hyaline cartilage typically destroy the cartilage because

 

A. cartilage contains chondroitin sulfate

B. cartilage contains collagen

C. cartilage is not innervated

D. cartilage is relatively avascular

E. cartilage tends to become calcified

 

The correct answer is D. Hyaline cartilage contains very few, sparsely distributed, small blood

vessels. The tissue consequently is very vulnerable to infection because the immune system (white

cells and serum with clotting factors and antibodies) cannot access the cartilage in an efficient

fashion. Chondroitin sulfate (choice A) is an important constituent of cartilage that can be attacked by

bacteria, but this is not the cause of uncontrollable infections in the cartilage, because if the infection

is controlled, chondrocytes will continue to synthesize chondroitin. Collagen (choice B) is present in

cartilage, but does not predispose the cartilage for uncontrollable infection. Collagen is not innervated

(choice C), but this does not contribute to the development of uncontrollable infection. The tendency

of cartilage to undergo calcification (choice E), even when not acting as the site of ossification, does

not predispose for uncontrollable infection.

 

99. The highest level of chronic disease state is associated with which of the following

diseases?

A. Hepatitis A

B. Hepatitis B

C. Hepatitis C

D. Hepatitis D

E. None of these diseases have chronic carrier stages

 

The correct answer is choice C. Hepatitis C is a disease about which much has been learned

recently, but much more is unknown. It seems to be transferred through both bloodborne and sexual

routes (not fecal/oral). It is harder to contract than HBV, but easier than HIV. It is distinguished by

having the highest percentage of cases going into a chronic destructive stage, of all hepatitis types. It

is a single stranded RNA virus. It was formerly known as NANB (Non-A Non-B) or "transfusion

hepatitis" because tests for hepatitis A or B did not detect it. Hepatitis B also has a destructive carrier

state, but it is less common. Hepatitis A has NO carrier state, and exposure to Hepatitis A gives

lifelong immunity.

 

100. Which of the following organisms would most likely be isolated from the vagina of a

normal 5-year-old girl?

A. Candida

B. Lactobacillus

C. Neisseria

D. Staphylococcus

E. Streptococcus

 

The correct answer is D. The vagina of prepubertal girls and postmenopausal women is colonized

by colonic and skin bacteria, including Staphylococcus epidermidis, which is normally found on the

skin. The vagina of women of childbearing age tends to be colonized by Lactobacillus (choice B)

species, yeasts such as Candida (choice A), and Streptococcus species (choice E). The presence of

Neisseria (choice C), such as N. gonorrhoeae (the cause of gonorrhea), in the vagina of a 5-year-old

girl strongly suggests sexual abuse.

87. Which nerve passes through Menke’s cave?

1. Abducent.

2. Facial.

3. Trigeminal.

4. Trochlear.

Ans: 3

88. Angle of the jaw is supplied by:

1. Great auricular nerve.

2. Lesser occipital nerve.

3. Greater occipital nerve.

4. Posterior auricular nerve.

Ans: 1

89. Which is true about opening of jaw?

1. Lateral pterygoid muscle contracts.

2. Movement in vertical axis.

3. Articular disc moves backwards.

4. Head of the mandible moves forwards.

Ans: 1

90. The branches of the external carotid artery do not include:

1. Facial artery.

2. Lingual artery.

3. Maxillary artery.

4. Inferior thyroid artery.

Ans: 4

91. Which vertebra has the most prominent spine?

1. C2.

2. C7.

3. T10.

4. L2.

Ans: 2

92. All are tributaries of cavernous sinus except:

1. Superior ophthalmic vein.

2. Central vein of retina.

3. Superficical middle cerebral vein.

4. Superior sagital sinus.

Ans: 4

93. Which is palpable at the anterior border of masseter?

1. Stensons duct.

2. Submandibular duct.

3. Facial nerve.

4. Maxillary artery.

Ans: 1

94. Which is true regarding parotid gland?

1. Stenson's and Wharton's duct join and open at the upper second molar teeth.

2. Stenson's duct opens opposite upper second molar teeth.

3. Parotid duct pierces the masseter.

4. Developed from mesoderm.

Ans:2

95. Which of the following is derived from cartilage of the third arch?

1. Styloid process.

2. Malleus.

3. Incus.

4. Greater cornu of hyoid.

Ans: 4

86.During a cranial nerve test, the patient cannot elevate her right eye from the abducted position. Which of the following muscles is paralyzed?

A.Rt IO
B.Rt IR
C.Rt LR
D.Rt SO
E. Rt SR

ANS.E. The superior rectus muscle can elevate and adduct the eye from the
neutral position. From the abducted position, it is the only muscle that can elevate the eye.
The inferior oblique muscle (choice A) can elevate and abduct the eye from the neutral position.
From the adducted position, it is the only muscle that can elevate the eye.
The inferior rectus muscle (choice B) can depress and adduct the eye from the neutral position. From
the abducted position, it is the only muscle that can depress the eye.
The lateral rectus muscle (choice C) can abduct the eye.
The superior oblique muscle (choice D) can depress and abduct the eye from the neutral position.
From the adducted position, it is the only muscle that can depress the eye.

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85.Axial bones in skull are:

1. 8. 2. 14.

3. 22. 4. 28.

ANS. 4

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84.Which of the following amino acids would most likely be found on the surface of a protein molecule?

A. Alanine B. Arginine
C. Isoleucine D. Leucine
E. Phenylalanine

The correct answer is B. This question requires two logical steps. First, you need to appreciate that hydrophilic amino acids are more likely to appear on the surface of a protein molecule, whereas hydrophobic amino acids are most likely be found in the interior. Next, you need to figure out which of the amino acids listed is hydrophilic. If you recall that arginine is a basic amino acid that is positively charged at physiologic pH, you should be able to answer this question right away.

All the other choices have neutral side chains and are uncharged at physiologic pH. They would most likely be found in the hydrophobic core of the protein structure. Alanine (choice A), isoleucine (choice C), and leucine (choice D) all have aliphatic side chains; phenylalanine (choice E) and tryptophan have aromatic side chains.

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83.Which of the following will cause reduction of the size of the pulp chamber in mid-life?

A. Formation of primary dentin
B. Formation of secondary dentin
C. Internal resorption
D. External resorption
E. Pulp fibrosis

The correct answer is B. Primary dentin (choice A) surrounds the pulp chamber when the tooth is
first formed and erupts. It is the initial dentin that makes up the base of both the crown and root. If the
young tooth has a given size pulp chamber, further dentin formation, secondary dentin, later in life, will
begin to fill the chamber with dentin, making it smaller. Internal resorption (choice C) is loss of dentin,
resulting in a larger pulp chamber. External resorption (choice D) involves the exterior of the root and
does not change the pulp chamber size. Pulp fibrosis (choice E) would change the histology of the cells in the chamber, but not the chamber's size


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82.Towne’s projection is a:

a. A-p view b. P-a
c. Lateral d. Panoramic

Ans: a. Antero-posterior view

This view is primarily used to observe the occipital area of skull and sometimes the

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81.In restoring a mandibular first molar, lingual cusps are important for which movement?

A. Centric occlusion B. Protrusive
C. Retrusive D. Working E. Nonworking

ANS. D. To answer this question, place your own teeth in centric occlusion(maximum intercuspation). Notice that the occlusion is held in place by the lingual cusps of maxillary teeth and the buccal cusps of mandibular teeth. Mandibular lingual cusps are not in contact. In protrusion, the anterior teeth act to separate the maxilla and mandible as the mandible moves forward. The anterior teeth act as guides in retrusion as well (try it). So far the mandibular lingual cusps are not involved. If you make a left working movement (slide your mandible left), notice that the mandibular lingual cusps on the left, drag against the lingual side of the maxillary lingual cusps. In the nonworking side (in this case, the right side), the mandibular lingual cusps move AWAY from contact.


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80. Which of the following hormones is secreted by anterior pituitary cells that stain with acidic dyes?

A. ACTH B. FSH
C. LH D. Prolactin

E. TSH

ANS. D. The cells of the anterior pituitary can be classified as chromophils (stain
with dyes) or chromophobes (do not stain with dyes). The chromophils can be further divided inacidophils (stain with acidic dyes) and basophils (stain with basic dyes). The acidophils include thesomatotrophs, which secrete growth hormone, and the mammotrophs, which secrete prolactin.The basophils include the corticotrophs, which secrete ACTH (choice A), the gonadotrophs, which secrete FSH and LH (choices B and C), and the thyrotrophs, which secrete TSH (choice E).

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79.The epithelium of the mucous membrane of the mouth is:

A. simple squam. B. strtified squam.

C. simple colum. D. strtified colum.

ANS. B. Squamous cells are flattened, pancake-like cells, and when in layers are known as stratified. The stratified squamous cells lining the mucosa of the oral cavity are similar to those lining the outer skin, although less keratinized. They do, however, flake off continuously into the mouth. Simple squamous tissue would be too thin and not allow for the constant flaking and replacement ^Mcq. Columnar epithelium is found in both the respiratory system and other organs of the digestive system. ^Mcq

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78.The major structural component of the sperm flagellum is the:

A. microtubule
B. microfilament
C. actin filament
D. mysosin filament
E. ciliary body

ANS A. This is a basic histological question of a type found commonly on NBDE, which asks about basic cellular organelles and structures. The sperm cell flagellum is notable for a “9+2” arrangement of fibers formed from microtubules. The 9 single fibers form a circular ring in cross section around the 2 doubled fibers in the center. One of the significant facts about the fibers is
that they are composed of microtubules, made up of tubulin. The other significant fact is that all eucaryotic flagella and cilia have this same structure (for example, cilia form the tracheal lining). Note that procaryotic (bacterial) flagellea do NOT share this structure.


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77.Which muscle is the chief mover of the mandible TOWARD the left?

A. Left medial pterygoid
B. Left lateral pterygoid
C. Right medial pterygoid
D. Right lateral pterygoid

ANS.D. There are two methods for answering this question. The formula method

states that the right lateral pterygoid moves the mandible left, whereas the left lateral pterygoid moves

the mandible right. The understanding method begins with the idea that the medial pterygoid is a

closer (elevator). The lateral pterygoid connects to the condyle and is a protruder. If the right lateral

pterygoid pulls the right condyle out while the left lateral pterygoid and condyle remain stable, the left

side will act as a stationary pivot point while the right side protrudes outward and also toward the left

(medially).

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76.Damage to which of the following structures might produce hair cell loss?

A.Basilar membrane B.Organ of Corti
C.Reissner's membraneD.Scala tympani
E.Scala vestibuli

ANS B.

Hearing is the detection of sound, which consists of pressure waves

conducted through air or water. The receptors of the cochlear duct provide us with a sense of hearing

that allows us to detect the quietest whisper and yet remain functional in a crowded, noisy

environment. The organ of Corti contains hair cells from the cochlear branch of the vestibulocochlear

nerve (CN VIII). These cells rest on the basilar membrane (choice A), which separates the scala

tympani (choice D) from the scala media. The hair cells are embedded in the tectorial membrane,

and movement of the basilar membrane below the cells causes the hairs to bend, which generates

action potentials. The tectorial membrane that lies on the hair cells does not form a boundary between

the different scala; the membrane separating the scala media from the scala vestibuli (choice E) is

Reissner's (vestibular) membrane (choice C).

1H

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75.Which cusp of the maxillary molar is NOT part of the trigon (primitive cusp triangle)?

A. Mesiolingual    B. Mesiobuccal

C. Distolingual     D. Distobuccal

ANS> C. In evolution, three cusps of the maxillary molar are considered to be the 

primary cusp triangle, and the original three cusps of the evolving molar. They form the trigon, and are 

the MB, ML, and DB cusps. The fourth cusp, the DL, is the smallest, is considered to be a minor cusp, 

and is known evolutionarily as the talon, or talon cusp. This cusp is less conspicuous as you go from 

first to second to third maxillary molar. 

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74. At which of the following ages does fetal movement first occur?

A. 1 month B. 2 months

C. 4 months D. 6 months E. 7 months


The correct answer is B. Neuromuscular development is sufficient to allow fetal movement in the

eighth week of life. Other features of Week 8 include the first appearance of a thin skin, a head as

large as the rest of the body, forward-looking eyes, appearance of digits on the hands and feet,

appearance of testes and ovaries (but not distinguishable external genitalia), and a crown-rump length

of approximately 30 mm. By the end of the eighth week, nearly all adult structures have at least begun to 

develop, and the fetus "looks like a baby." 

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