General Oral Pics Refresher

True regarding Exotoxin

Which of the following is true regarding exotoxin?

A. They are very stable and resist most physical and chemical agents
B. Highly antigenic
C. Produced abundantly by gram negative bacilli
D. Lipopolysaccharide-protein complex in nature

Ans. B. Highly antigenic

Endotoxin	Exotoxin
Liberated after cell disintegration	Excreted by living cells
Lipolysaccharide LPS. -protein complex	Proteins with molecular weight 70,000 — 1,00,000.
Heat stable	Heat labile and lose their toxicity on exposure to 60 degree centigrade. Only exception is enterotoxin of Staphylococcus aureus
Can not be converted to toxoid	Can be converted to toxoid
Nonspecific in action	Highly specific in action
Weakly toxic	Highly toxic substances
Poorely antigenic	Highly antigenic
Produced by gram negative bacteria	Produced by gram positive and negative bacteria

Treatment of peptic ulcer may lead to xerostomia

Which of the following drugs used in the treatment of peptic ulcer may lead to xerostomia?

a. Sucralfate 
b. Omeprazole
c. Ranitidine 
d. Atropine

Ans. D: To eliminate H. pylori infection metronidazole, with amoxicillin or tetracycline is used.  Anticholinergic drug atropine is used to decrease acid production.  I causes xerostomia, which may lead to increased incidence of caries.

Tetracyline staining of the teeth

Tetracyline staining of the teeth is commonly seen in patients of:

a. Pneumonitits 
b. Actinomycosis
c. Recurrent aphthous ulcers 
d. Cystic fibrosis

Ans. D: Cystic fibrosis affects all exocrine glands, its affect being most apparent in mucous producing glands.  Its therapy involves tetracycline which may cause staining of teeth.

Destruction and perforation of hard and soft palates Location

Destruction and perforation of hard and soft palates are found in

a. Wegener’s granulomatosis 

b. Midline granuloma
c. Pyogenic granuloma 
d. Giant-cell granuloma

Ans. B: Midline granuloma is a chronic progressive disease affecting the midline structures of the face.  Localized destruction of tissues in the midline of the face may lead to perforation of hard and soft palate.

Blood pressure is defined as the product of :

Blood pressure is defined as the product of:-

A. Systolic pressure X pulse
B. Diastolic pressure X Pulse rate
C. Pulse pressure X pulse rate
D. Cardiac output X peripheral resistance

Ans. D 

The overall blood flow in circulation of adult at rest is about 5 liter / min which equals to cardiac output because it is the amount of blood pumped by heart per unit time. 

Blood pressure =	Cardiac output X peripheral resistance or Blood flow X resistance (R)
Venous return =	MSFP – RAP                MSFP = mean systemic filling pressure        RVR                       RAP   =  Right atrial pressure                                       RVR   =  Resistance to venous return

Shape of the arterial pulse

Shape of the arterial pulse is influenced by:

A. Viscosity of blood 
B. Velocity of blood 
C. Arterial wall expansion 
D. Cross sectional area of artery

Ans. C  The blood forced into the aorta during systole not only moves the blood in the vessels forward but also sets up a pressure wave that travel along the arteries.  The pressure wave expends the arterial wall as it travels, and expansion is palpable as the pulse.

Oxygenation during one-lung ventilation

Oxygenation during one-lung ventilation may be improved by: 

A. Increasing the tidal volume to 15 ml/kg of body/wt 

B. Applying PEEP 5cm of H20.  to the ventilated dependant.  lung
C. Maintaining CPAP 5 cm of H20.  in the non- ventilated non-dependant.  lung
D. All of the above

Ans. D.  All of the above

CPAP applied to unventilated lung is usually effective in restoring adequate oxygenation during one lung ventilation when excessive pulmonary shunt develops 

Ventilation with differential PEEP to manipulate regional blood flow is also necessary. 

Maintaining CPAP 5 cm of Ho.  in the nonventilated lung also improves oxygenation during one lung ventilation. 

another potential MCQ asked from the same topic is:

-               m/c cause of hypoxia during one lung ventilation is: malposition, shunt, collapse of lung

Hypersensitivity vasculitis

Hypersensitivity vasculitis most commonly involves 

A. Arterioles
B. Post capillary venules
C. Capillaries
D. Medium sized arteries

Ans. B.  Post capillary venules 

Vasculitis of Small Vessels 

Hypersensitivity vasculitis primarily affects postcapillary venules and arterioles of the skin. 

This disorder usually presents as palpable purpura, although lesions may occasionally be urticarial or ulcerative. 

Skin biopsy usually shows leukocytoclastic angiitis. 

> Small-vessel vasculitis may also be associated with visceral involvement, including alveolar hemorrhage or glomerulonephritis. 

Visceral involvement most commonly occurs in Henoch-Schönlein purpura, cryoglobulinemia and vasculitis associated with autoimmune diseases, such as SLE. 

Vander de hoeve syndrome

Vander de hoeve syndrome is characterized by: 

A. Otosclerosis 
B. Osteogenesis imperfecta 
C Blue sclera 
D. All of the above

Ans. D. Vander de hoeve syndrome is characterized by mixed hearing loss fixation of foot plate of stapes. , osteogenesis imperfecta blue sclera and dental anomalies. Hearing loss is gradually progressive and mixed.

Objective tinnitus

Objective tinnitus is seen in all of the following except: 

A. Palatal myoclonus 
B. Glomus Jugulare Tumour 
C. Otoscierosis 
D. Patulous Eustachian tube

Ans. C. Objective tinnitus refers to the tinnitus which is audible to the physician or another person. It may be pulsatile or nonpulsatile. Palatal myoclonus is rhythmic contraction of soft palate muscles. The diagnosis is established by flexible nasopharyngoscopy. Vascular abnormalities like glomus tumour, arteriovenous malformations, venous hums causes pulsatile tinnitus. Otosclerosis is not a cause of objective tinnitus. 

MDS entrance preparations | Causes of Eosinophilia

All of the following are causes of eosinophilia except:

A. Hodgkin’s disease
B. Filariasis
C. MI
D. HIV infection

Ans. C.

• Conditions producing allergic reactions & resulting eosinophilia are: 

* Drugs: Iodides, Aspirin, Sulfonamides, Nitrofurantoin, Penicillin, Cephalosporins. 

* Disease conditions : Hay fever, Asthma, Eczema, Serum sickness, Allergic vasculitis, Pemphigus. 

* All types of parasitic infection. 

* Collagen vascular disease : RA, Eosinophillic fasciitis, Allergic angiitis, Polyarteritis nodosa. 

* Malignancy : Hodgkins disease, Mycosis fungoides, CML, Ca stomach, ovary, lung, pancreas 

and uterus. 

* Other diseases Job’s syndrome, Sarcoidosis, Skin disease. 

* Viral infection like HIV and human T-cell lymphotropic virus HTLV-1.  

* In MI polymorphonuclear leukocytosis seen.

* Most dramatic hypereosinophilia syndromes are eosinophil count 50,000 to 1,00,000/pA.  

- Loeffler’s syndrome 

- Tropical pulmonary eosinophlllia 

- Loeffler’s endocarditis 

- Eosinophilic leukaemia 

- Idiopathic hypereosinophillic syndrome. 

* In eosinophilia, eosinophil count>500

* Eosinopenia seen in 

- Stress 

- Acute bacterial infection 

- After Rx of glucocorticoids. 

MDS entrance preparations | Streptococci Facts

Regarding streptococci false is 

a. Streptococcus pyogens or group A streptococci is responsible for pharyngitis and post infections syndromes like acute rheumatic fever and poststreptococcal glomerulonephriatis
b. Group A streptococci are among few bacterial pathogen that produce signs of infection and surrounding cellulitis within first 24 hr of surgery 
c. Necrotising fasciitis of bowel is usually polymicrobial involving anaerobic bacteria and ram negative bacilli
d. UTI’s are quite commonly associated with group B streptococcus

Ans . D

Streptococci are gram positive cocci in short chains, long and some in pairs (diplococcic). Classification is based on carbohydrate protein Lancefield  grouping.

Gp. A (pyogens), pharngitis, erysipelaspost streptococcal  sequelae(AGN, Rhemmatic fever) impetigo, wound infection in 24 hrs with lymphangitis

GB (agalactiae) early and late onset meniggitis acquired from a infected / colonized birth canal.

gpD (enterococcal or non enterococcal) enterococcal (faecalis, faecium) causes UTI wound infection and endocarditis, non enterococcal group(bovis)

Causes endocarditis

Viridans streptococci (mutans, sanguis, milleri) causes dental caries, infective endocardits and visceral abcess , brain abcess Bacterial endocarditis is commonly associated with splenoctomy  commonly due to streptococcus, followed by staphylococcus then  gram negative bacilh like salmonella and about 5% due to anaerobic organism. 

MDS entrance preparations | Test used to differentiate streptococcus pneumonia from other alpha haemolytic streptococcus

Test used to differentiate streptococcus pneumonia from other alpha haemolytic streptococcus are 

a. CAMP reaction 
b. Biken test 
c. Optochin sensitivity 
d. Bacitracin susceptibility

Correct Ans C

Pneumococcal endocarditis is associated with rapid destruction fo heart valves

Streptococcus pneumonia is a capsulated gram positive diplococcic sensitive to optochin and soluble in bile. Colonies and Blood agar shows alphahaemolysis with draughtsman colonies, Strep pneumonia causes middle ear infections, sinusitis, bronchitis, peritonela infection, eye infections. Pneumococcal pneumonia occurs in extremes of age. Inapparent pneumococcal focus can prove fatal in splenectomised patients. Septic arthritis, purulent pericarditis occurs. Endocarditis causes rapid destruction of valves. 

COMEDK MDS entrance preparations | marker of GIST

Most appropriate marker of GIST- 

A. CD117

B. CD 34 

C. CK

D. Vimentin

Ans. A. CD117 

Gastrointestinal stromal tumor 

1. A gastrointestinal stromal tumor GIST.  is one of the most common mesenchymal tumors of the gastrointestinal tract 1-3% of all gastrointestinal malignancies. . They are typically defined as tumors whose behavior is drrven by mutations in the Kit g or PDGFRA gene, and may or may not stain positively for Kit. 

Signs and symptoms

2. Patients present with dysphagia, GIT hemorrhage or metastases mainly in the liver. . Intestinal obstruction is rare, due to the tumor’s outward pattern of growth. 

3. Generally, the definitive diagnosis is made with a biopsy, which can be obtained endoscopically, 

percutaneously with CT or ultrasound guidance or at the time of surgery. 

4. When GIST is suspected—as opposed to other causes for similar tumors—the pathologist can 

useimmunohistochemistrv specific antibodies that stain the molecule CD 117 also known as c-kit.  

95% of all GISTs are CD 117-positive other possible markers include CD34, desmin, vimentin and 

others. . Other cells that show CD 117 positivity are mast cells. 

If the CD117 stain is negative and suspicion remains that the tumor is a GIST, the newer antibody 

DOG-i Discovered On GIST-i.  can be used. Also sequencing of Kit and PDGFRA can be used to prove 

the diagnosis. 

5. Pathophysiology 

GISTs are tumors of connective tissue, i.e.sarcomas unlike most gastrointestinal tumors, they are 

non-epithelial. 

6. GISTs are thought to arise from interstitial cells of Cajal ICC. , that are normally part of 

the autonomic nervous system of the intestine. They serve a pacemaker function in 

controlling motility. 

7. Most 50-80%.  GISTs arise because of a mutation in a called c-kit. This gene encodes 

a transmembrane receptor for a growth factor termed scf stem cell factor. . The c-kit/CD 117 receptor is 

expressed on ICCs and a large number of other cells, mainly bone marrow cells,mast 

cells, melanocytes and several others. In the gut, however, a mass staining positive for CD117 is likely 

to be a GIST, arising from ICC cells. 

8. The c-kit molecule comprises a long extracellular domain, a transmembrane segment, and an 

intracellular part. Mutations generally occur in the DNA encoding the intracellular part exon 11. , 

which acts as a tyrosine kinase to activate other enzymes. 

9. The tyrosine kinase function of c-kit is vital in the therapy for GISTs. 

10. Therapy Surgery is the mainstay of therapy for non-metastatic GISTs. 

The c-kit tyrosine kinase inhibitor imatinib is used 

CD34 molecule is a cluster of differentiation molecule present on certain cells within the human body. It is a cell surface glycoprotein and functions as a cell-cell adhesion factor.

It may also mediate the attachment of stem cells to bone marrow extracellular matrix or directly to stromal cells.

COMEDK MDS entrance preparations | Facts about Blood Capillaries

Which of the following is not correct regarding capillaries?

A. Greatest cross sectional area      
B. Contain 25% of blood
C. Contains less blood than veins                    
D. Have single layer of cells bounding the lumen

Ans. B

Vessel	Percentage of blood	Cross-sectional area (cm)2
Aorta	2%	4.5
Artery	8%	20
Arteriole	1%	400
Capillary	5%	4500 (maximum)
Venule Vein Vena cava	54% (maximum)	18

Best MDS Coaching | Nerve fibers involved in Proprioception

Nerve fibers involved in proprioception 

A. Type A fiber 
B. Type B fiber
C. Type C fiber 
D. Type IV fiber

Ans. A 

Propioception is carried by A α or type I fibers

Nerve Fiber Types

 

Number	Origin	Fiber type
Ia	Muscle spindle, annulo-spiral	A α
Ib	Golgi tendon organ	A α
II	Muscle spindle, flower-spray ending; touch, pressure	A β
III	Pain and cold receptors; some touch receptors	A δ
IV	Pain, temperature, and other receptor	Dorsal root C

Fiber type	Function
A α β γ δ	Proprioception; somatic motor Touch, pressure, motor Motor to muscle spindles Pain, cold, touch
B	Preganglionic autonomic
C Dorsal root Sympathetic	Pain, temperature, some mechano-reception, reflex responses Postganglionic sympathics

COMEDK MDS entrance preparations | Blood Culture showing gram positive bacteria

A patient is in the ICS and his blood culture shows gram positive bacteria which is catlase positive and coagulase negative. The most likely agent is 

a. Staphylococcus 
b. Staphylococcus epidermidis
c. Stereptococcus pyogenes 
d. Enterpcpccus faecatis

         Correct Ans  B

Staphylococci are gram positive cocci. Based on the coagulase test they can be classified as coagulase positive –staphylococcus auresus and coagulase negative-staphylococcus saprophyticus and epidermidis. Culture of staphylococcus aureus on Blood agar shows βnaemolytic colories are seen on Nutrient agar. Staphylococcus aureus ferments mannitol gives a positive urese test. Infection caused by staphylococcus aureus are carbuncles, furuncles, folliculate, meningitis, UTI, pneumonia, osteo myelitis, food poisoning , Toxicshock syndrome.

Methicillin resistant staphylococcus  aureus strains can be acquired from the hospital , same may also be acquired as community infections. 

COMEDK MDS entrance preparations | Presence of opaque white patches in the enamel

Presence of opaque white patches in the enamel, often arranged in a band-like formation also teeth affected are susceptible to a brown discoloration are seen in

a) amelogenesis imperfecta
b) fluorosis
c) bullemia nervosa
d) ectodermal dysplasia

Ans b: The effect of fluorosis may be recognized by the presence of opaque white patches in the enamel, often arranged in a band-like formation. Unlike the teeth in other forms of hypoplasia, the teeth affected by fluorosis are susceptible to a brown discoloration that may resemble amelogenesis imperfecta. Similar idiopathic mottling may occur in teeth of patients from non-fluoride areas, but this is rare. 

COMEDK MDS entrance preparations | Oral lesions of tuberculosis

What is the most typical presentation of the oral lesions of tuberculosis?

a. Mucosal lesions with a cobblestone appearance 

b. Nonhealing ulcer
c. Mucositis 
d. Erythematous bullseye

The correct answer is B: The oral lesions of tuberculosis are thought to result from the presence of organisms brought into contact with the oral mucosa by sputum. A nonhealing ulcer, which is impossible to differentiate clinically from carcinoma, is the most common presentation in the mouth. Ulcers are most consistently present on the lateral borders of the tongue and may have a purulent center. Lymphadenopathy also may be present. Diagnosis is made by histologic examination and demonstration of organisms in the tissue.

COMEDK MDS entrance preparations | Increase force of muscle contraction

The force of muscle contraction can be increased by all of the following except:

A. Increasing the frequency of activation of motor units 

B. Increasing the number of motor units activated
C. Increasing the amplitude of action potentials in the motor neurons 
D. Recruiting larger motor units

 Ans. C 

Action potential follows an all or none law. If sufficient amplitude is reached to produces a response, increasing the amplitude further will not have any effect on the function to follow.

Factors responsible for grading of muscular activity

Number of motor units (Recruitment)	With minimal voluntary activity only a few motor units. With increasing voluntary effect more and more units are brought into play – ‘Recruitment phenomenon’. With increasing motor units, force of muscle contraction increases.
Frequency of contraction (Summation)	Frequency of discharge in the individual fibre play a role. Tension developed during a titanic contraction (with rapidly repeated stimulation) is greater than during individual twitches.
Large motor units	Force of contraction depend on length of muscle – Starling’s law

COMEDK MDS entrance preparations | Myasthenia gravis

Myasthenia gravis is a disorder of:

A. Motor neuron 
B. Neuromuscular junction 
C. Peripheral nerve 
D. Spinal cord

Ans. B  

   Myasthenia gravis is a neuromuscular disorder characterized by weakness and fatiguability of skeletal muscle. The underlying defect is a decrease in the number of available cicotinic Ach receptor at the Neuromuscular junction due to an antibody mediatd autoimmune attack.