Ions participating in clotting mechanism are:

 # Ions participating in clotting mechanism are:

 A. Iron

B. Copper

C. Calcium

D. Aluminium

The correct answer is C. Calcium.

In the presence of calcium ions and other clotting factors, factor X activates an enzyme called prothrombin activator. This enzyme then converts the plasma protein prothrombin into thrombin. Thrombin is an enzyme that, in turn, converts fibrinogen to fibrin which causes the blood to clot.

Side effects of Phenytoin do not include:

 # Side effects of Phenytoin do not include:

 A. Osteomalacia

B. Gum hypertrophy

C. Folate deficiency

D. Blindness

The correct answer is D. Blindness. 

Adverse effects:  After prolonged use numerous side effects are produced at therapeutic plasma concentration; others occur as a manifestation of toxicity due to overdose.

At therapeutic levels

• Gum hypertrophy is common (20% incidence), especially in younger patients. It is due to the overgrowth of gingival collagen fibers. This can be minimized by maintaining oral hygiene.

• Hirsutism, coarsening of facial features (troublesome in young girls), acne.

• Hypersensitivity reactions are—rashes, DLE, and lymphadenopathy; neutropenia is rare but requires discontinuation of therapy.

• Megaloblastic anemia: Phenytoin decreases folate absorption and increases its excretion.

• Osteomalacia: Phenytoin interferes with metabolic activation of vit D and with calcium

absorption/metabolism.

• It can inhibit insulin release and cause hyperglycemia.

• Used during pregnancy, phenytoin can produce ‘fetal hydantoin syndrome’ (hypoplastic phalanges, cleft palate, hare lip, microcephaly), which is probably caused by its areneoxide metabolite.

Reference: Essentials of medical pharmacology, KD Tripathi.

At what temperature is blood stored in blood banks?

 # At what temperature is blood stored?

 A. -4 degrees

B. 4 degrees

C. 6 degrees

D. 8 degrees

The correct answer is B. 4 degrees celsius.

With the modern surgical and medical procedures, the demand for blood has greatly increased. It is for this reason that blood banks were started where blood from voluntary donors could be stored, so that it was always available on demand. Most blood banks have lists of would-be donors so that they may be contacted when required.

Storage of blood: After a donor has been screened for donation, one unit of blood (450 ml) is collected, under aseptic conditions, from the antecubital vein directly into a special plastic bag containing 63 ml of CPD-A (citrate-phosphate-dextrose-adenine) mixture. The blood bag is suitably sealed, labeled, and stored at 4 degree C, where it can be kept for about 20 days. (Faulty storage, i.e. overheating or freezing can lead to gross infection and hemolysis). The citrate prevents clotting of blood, sodium diphosphate acts as a buffer to control decrease in pH, dextrose supports ATP generation via glycolytic pathway and also provides energy for Na+- K+ pump that maintains the size and shape of red cells and increases their survival time, and adenine provides substrate for the synthesis of ATP, thus improving post-donation viability of red cells.

Blood is stored at low temperatures for 2 reasons: one, it decreases bacterial growth, and two, it decreases the rate of glycolysis and thus prevents a quick fall in pH.

Reference: A TEXTBOOK OF PRACTICAL PHYSIOLOGY Eighth Edition CL Ghai

Which mandibular plane is considered while calculating FMA (Frankfort mandibular plane angle) in cephalometry?

The mandibular plane used for FMA measurement is : A plane tangent to the lower border of mandible which connects with the menton anteriorly and posteriorly it bisects the distance between the right and left lower borders of the mandible in the region of the gonial angle. See Figure. 

The FMA angle is defined as the angle formed by the following two reference planes:

i. FH plane (Frankfort horizontal plane—A line between the most superior point of the external auditory meatus and inferior border of the orbit).

ii. Mandibular plane (A plane tangent to the lower border of mandible which connects with the menton anteriorly and posteriorly it bisects the distance between the right and left lower borders of the mandible in the region of the gonial angle). 

In most cephalometric analyses, the occlusal and mandibular planes are measured relative to the sella-nasion (SN) line, the basion-nasion (BaN) line, or the Frankfort horizontal plane. Ideally, according to Tweed, the incisor mandibular plane angle (IMPA) should be 90 degrees, the Frankfort mandibular angle (FMA) 25 degrees, and thus the Frankfort mandibular incisor angle (FMIA) 65 degrees. (The sum of three angles of a triangle equals 180 degrees.) Moreover, the IMPA angle also relates to creating additional space in the mandibular arch in that for each 3 degrees advancement of the lower incisor, 2.5 mm of space is gained in the mandibular dental arch. Conversely, reduction of the IMPA from 90 degrees, for example, to 87 degrees would decrease the available space for tooth alignment in the mandibular dental arch by 2.5 mm. 

Gangrene due to known infectious agent is:

 # Gangrene due to known infectious agent is:

 A. Wet gangrene

B. Dry gangrene

C. Pyoderma granulosum

D. Fournier gangrene

The correct answer is D. Fournier gangrene. 

Fournier gangrene, a relatively rare form of necrotizing fasciitis, is a rapidly progressive disease that affects the deep and superficial tissues of the perineal, anal, scrotal, and genital regions. Named after Dr. Alfred Fournier, the French dermatology and venereal specialist, it was initially described in 1883 as necrotizing fasciitis of the external genitalia, perineal, and perianal region in five of Dr. Fournier’s patients. Also known as necrotizing fasciitis, the disease involves the rapid spread of severe inflammatory and infectious processes along fascial planes affecting adjacent soft tissue; therefore, the disease may initially go unnoticed or unrecognized as there may be minimal or no skin manifestations in its early stages.

This disease process results from polymicrobial aerobic and anaerobic synergistic infection of the fascia and subcutaneous soft tissue. Gram-positive bacteria such as Group A Streptococci and Staphylococcus aureus and gram-negative bacteria such as E. Coli and Pseudomonas aeruginosa are organisms most commonly grown in wound cultures of Fournier gangrene patients as it is usually polymicrobial. These bacteria can be introduced through several sources, including urinary, bowel, or dermal. Urinary tract infections and other infectious processes of the perineum, such as perianal abscesses or even a simple pimple, may also provide a starting point for the infection. 

Surgical manipulation of the genital and perineal area similarly can provide the initial insult required to develop Fournier gangrene. Any traumatic insult or localized area of skin breakdown to the perineum or scrotum can lead to bacterial access to the subcutaneous tissues and begin the process, ultimately resulting in Fournier gangrene. About 25% of cases had no known or identifiable etiology.

Reference: Leslie SW, Rad J, Foreman J. Fournier Gangrene. [Updated 2023 Jun 5]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549821/

Biosafety level 4 (BSL-4) pathogen is:

 # Biosafety level 4 (BSL-4) pathogen is:

 A. XDR strain of Mycobacterium tuberculosis

B. SARS CoV-2

C. Ebola

D. Measles

The correct answer is C. Ebola.

Biological Safety Levels (BSL) are a series of protections relegated to the activities that take place in particular biological labs. They are individual safeguards designed to protect laboratory personnel, as well as the surrounding environment and community.

These levels, which are ranked from one to four, are selected based on the agents or organisms that are being researched or worked on in any given laboratory setting. For example, a basic lab setting specializing in the research of nonlethal agents that pose a minimal potential threat to lab workers and the environment are generally considered BSL-1—the lowest biosafety lab level. A specialized research laboratory that deals with potentially deadly infectious agents like Ebola would be designated as BSL-4—the highest and most stringent level.

The Centers for Disease Control and Prevention (CDC) sets BSL lab levels as a way of exhibiting specific controls for the containment of microbes and biological agents. Each BSL lab level builds upon on the previous level—thereby creating layer upon layer of constraints and barriers. These lab levels are determined by the following:

• Risks related to containment
• Severity of infection
• Transmissibility
• Nature of the work conducted
• Origin of the microbe
• Agent in question
• Route of exposure

 Summary of Biological Agents and BSL levels

Reference: The University of Texas Rio Grande Valley

Once bone is formed, it grows by:

 # Once bone is formed, it grows by:

 A. Interstitial growth only

B. Appositional growth only

C. Both appositional and interstitial growth

D. Degenerative changes into bony structures

The correct answer is B. Appositional growth only.

Which is growth by the addition of new layers on those previously formed. Bone formation begins in the embryo where mesenchymal cells differentiate into either fibrous membrane or cartilage. 

This leads to two paths of bone development:

1. Intramembranous ossification is so called because it takes place in membranes of connective tissue. Osteoprogenitor cells in the membrane differentiate into osteoblasts: a collagen matrix is formed which undergoes ossification. Note: The maxilla and mandible as well as the cranial vault are forrmed this way.

2. Endochondral ossification is how the remainder of the skeleton forms and takes place within a hyaline cartilage model. Cartilage cells are replaced by bone cells (osteocytes replace chondrocytes), organic matrix is laid down and calcium and phosphate are deposited. This type of ossification is principally responsible for the formation of short and long bones. Note: The ethmoid, sphenoid, and occipital bones (bones of the cranial base) form this way.