Mechanism of plasma membrane damage in ischemia

# The major mechanism of damage to plasma membrane in ischemia is:
A. Reduced intracellular pH
B. Increased intracellular accumulation of sodium
C. Increased Ca++ ions in the cytosol
D. Reduced aerobic respiration

The correct answer is C. Increased Ca++ ions in the cytosol.

The ion calcium is critical for cell damage. Influx of calcium acts as second messenger and activates wide spectrum of enzymes that destroy cellular organelles.

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Most reactive free radical

# Out of the various free radical species, the following radical is most reactive:
A. Super oxide (O2
B. Hydrogen peroxide (H2O2
C. Hydroxyl (OH-
D. Nitric oxide (NO)

The correct answer is C. Hydroxyl ion.

Important mechanism of cell injury is by damage to DNA, proteins, lipid membranes, and circulating lipids (LDL) by peroxidation caused by oxygen derived free radicals--super oxide anion (O2-), hydroxy radical (OH-), and hydrogen peroxide (H2O2). Hydroxyl ion is most reactive.

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Folic acid deficiency

# Folic acid deficiency is associated with administration of:
A. Phenytoin
B. Chloramphenicol
C. Isoniazide
D. Streptomycin

The correct answer is A. Phenytoin.

Folic acid deficiency can be caused by drugs that interfere with folate absorption or metabolism. Phenytoin, some other anticonvulsants, oral contraceptives, and isoniazide can cause Folic acid deficiency by interfering with Folic acid absorption. Other drugs such as methotrexate and, to a lesser extent, trimethoprim and pyrimethamine, inhibit dihydrofolate reductase and may result in a deficiency of folate cofactors and ultimately in megaloblastic anemia.

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Fracture of the tooth bearing segment

# The fracture of the tooth bearing segment of the mandible is:
a) Simple
b) Complex
c) Compound
d) Comminuted

The correct answer is C. Compound.

• Simple fracture includes linear fracture of condyle, coronoid ramus and edentulous body or mandible.

• Compound fracture include fractures of tooth bearing portions of mandible.

• Green stick fracture is a rare type of simple fracture and is found exclusively in children.

• Comminuted fracture are due to direct violence to mandible from penetrating sharp objects and missiles.

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Largest organ in the human body

# Largest organ in the body is:
A. Heart
B. Kidney
C. Skin
D. Liver

The correct answer is C. Skin.

Liver is the largest visceral organ in the body and is primarily in right hypochondrium and epigastric region,extending into left
hypochondrium ( or in right upper quadrant , extending into left upper quadrant)


Skin is the largest organ in human body.
Liver is the second largest organ of human body.
Liver is the largest gland in the human body.
The liver Is the largest of the abdominal viscera, occupying a substantial portion of the upper abdominal cavity.

It occupies most of the right hypochondrium and epigastrium, and frequently extends into the left hypochondrium as far as the left lateral line. As the body grows from infancy to adulthood the liver rapidly increases in size. This period of growth reaches a plateau around 18 years and is followed by a gradual decrease in the iver weight from middle age. The ratio of liver to body weight decreases with growth from infancy to adulthood.

The liver weighs approximately 5% of the body weight in infancy and it decreases to approximately 2% in adulthood. The size of the liver also varies according to sex, age and body size. The narrow end of the wedge lies towards the left hypochondrium, and the anterior edge points anteriorly and inferiorly.

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Bisecting angle technique

# Bisecting angle technique is based on:
A. ALARA principle
B. SLOB Technique
C. Rule of Isometry
D. Convergence

The correct answer is C. Rule of Isometry.

The Bisecting angle technique is based on a simple geometric theorem, Cieszynski's rule of Isometry, which states that two triangles are equal when they share one complete side and have two equal angle.

Position of the film as close as possible to the lingual surface of the teeth, resting in the palate or on the floor of the mouth.

The plane of the film and the long axis of the teeth form an angle with its apex at the point where the film is in contact with the teeth.

Construct an imaginary line that bisects this angle and direct the central ray of the beam at right angles to this bisector.

This forms two triangles with two equal angles and  a common side. (the imaginary bisector)

Several methods can be used to support films intra orally for Bisecting angle projections.

The preferred method is to use a film holding instrument (e.g. The Snap-A-Ray) or Bisecting angle instrument. Both provide an external device for localizing the X ray beam.

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Pathognomic sign of mandibular fracture

# The most common pathognomic sign of mandibular fracture is:
a) Malocclusion
b) Sublingual hematoma
c) Deviation of the jaw on opening
d) Paraesthesia of the mental nerve

The correct answer is B. Sublingual hematoma.

Sublingual ecchymosis is considered as pathognomonic sign of mandibular fracture.

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