AIM EXAM ARENA • 3RD YEAR MBBS

Question:
A skin biopsy taken several days after a deep traumatic wound shows macrophages, newly formed capillaries and increasing numbers of fibroblasts. Which event most logically follows as healing progresses?

Correct Answer: Increasing collagen deposition in the wound

Explanation: Fibroblasts in developing granulation tissue synthesize extracellular matrix, particularly collagen, which progressively converts the healing tissue into a fibrous scar.

Question:
A histological section from a healing wound contains many fibroblasts. A locally released mediator stimulates migration and proliferation of these mesenchymal cells. Which mediator best accounts for this response?

Correct Answer: Platelet-derived growth factor

Explanation: PDGF promotes migration and proliferation of fibroblasts and other mesenchymal cells, thereby contributing to connective tissue repair.

Question:
Following a limited epithelial injury, surviving cells receive extracellular signals and begin replacing the lost population. What is the earliest essential cellular event after these signals bind to responsive cells?

Correct Answer: Activation of intracellular signalling pathways

Explanation: Growth-factor receptor activation triggers intracellular signalling that promotes cell-cycle entry and subsequent proliferation of responsive cells.

Question:
A patient undergoes removal of part of the liver. During recovery, a growth factor contributes specifically to proliferation of the remaining hepatocytes. Which mediator has the strongest association with this regenerative response?

Correct Answer: Hepatocyte growth factor

Explanation: HGF is an important mediator of hepatocyte proliferation and contributes to restoration of liver mass after tissue loss.

Question:
A superficial skin injury removes a population of epithelial cells. During recovery, a mediator stimulates proliferation of nearby epithelial cells. Which factor is most directly associated with this effect?

Correct Answer: Epidermal growth factor

Explanation: EGF promotes proliferation of several epithelial cell types and therefore supports epithelial regeneration following tissue loss.

Question:
Two wounds contain equally viable epithelial cells. In the first, the basement membrane and stromal framework remain organized; in the second, the supporting matrix is extensively disrupted. Why is restoration of normal architecture more difficult in the second wound?

Correct Answer: Cells lose structural guidance for organized growth

Explanation: The extracellular matrix provides both structural support and signals for cell growth and organization; its destruction makes accurate reconstruction difficult and favors repair.

Question:
A student examines a healing wound and incorrectly identifies the vascular fibroblastic tissue as a granuloma. Which finding most strongly supports the correct interpretation of the specimen?

Correct Answer: Numerous new capillaries with proliferating fibroblasts

Explanation: Newly formed capillaries, fibroblasts and loose matrix characterize granulation tissue, an active component of wound healing rather than a granuloma.

Question:
During wound healing, endothelial cells and fibroblasts proliferate in response to local signals despite having a low rate of division in uninjured tissue. How should these cells be classified according to proliferative capacity?

Correct Answer: Stable cells

Explanation: Fibroblasts and endothelial cells have low baseline proliferative activity but can enter the cell cycle when stimulated during tissue repair.

Question:
A patient sustains renal tubular epithelial injury. After the damaging stimulus is removed, surviving tubular cells proliferate and contribute to restoration of the affected tubules. Which cellular property permits this response?

Correct Answer: Recruitment from quiescence into proliferation

Explanation: Renal tubular epithelial cells are stable cells that can be recruited from a resting state into active proliferation following appropriate injury and stimulation.

Question:
A researcher compares cell populations during tissue repair. One population continuously replaces cells lost during normal physiological turnover, whereas another proliferates mainly after stimulation. Which pair best represents these two populations respectively?

Correct Answer: Epidermal cells and fibroblasts

Explanation: Epidermal cells are labile and continually proliferate, whereas fibroblasts are stable cells that increase proliferation after appropriate stimulation.

Question:
A proliferating cell from a healing wound is actively duplicating its genetic material. A laboratory marker confirms ongoing DNA synthesis. Which regulatory protein is most closely associated with progression through this part of the cycle?

Correct Answer: Cyclin A

Explanation: Cyclin A-associated CDK activity contributes to progression through S phase, when the cell replicates its DNA.

Question:
Growth-factor signalling in a healing tissue increases the concentration of a regulatory protein that binds a specific kinase. The resulting complex phosphorylates target proteins and advances the cell through its cycle. What is the role of the regulatory protein in this process?

Correct Answer: It activates a cyclin-dependent kinase

Explanation: Cyclins bind and activate specific CDKs; the activated complexes phosphorylate target proteins that drive orderly cell-cycle progression.

Question:
A cell in regenerating tissue reaches a control point before proceeding to the next stage of proliferation. The control system confirms that essential cellular events have been completed appropriately. What is the principal purpose of this mechanism?

Correct Answer: To maintain orderly cell-cycle progression

Explanation: Cell-cycle checkpoints verify that critical events are satisfactory before progression, preventing inappropriate advancement through successive phases.

Question:
During regeneration, a cell receives an adequate mitogenic stimulus but fails to produce functional cyclins. Which cellular response would be most directly impaired?

Correct Answer: Progression through cell-cycle phases

Explanation: Cyclins activate CDKs at specific stages; loss of functional cyclins therefore disrupts the regulated progression required for cellular proliferation.

Question:
A pathologist compares an early healing wound with a mature scar from the same patient. Which change would be expected as the lesion progresses from the early to the late stage?

Correct Answer: More collagen with reduced cellularity

Explanation: Maturation replaces highly cellular, vascular granulation tissue with a less cellular and less vascular collagen-rich scar.

Question:
A tissue defect is initially filled by highly vascular healing tissue. Over time, extracellular matrix is reorganized and the lesion becomes mechanically stronger. Which phase of repair is primarily responsible for this later change?

Correct Answer: Matrix remodeling

Explanation: Remodeling reorganizes deposited extracellular matrix and collagen, producing a progressively stronger and more mature scar.

Question:
A wound contains dead tissue that has not yet been adequately cleared. Despite the presence of viable surrounding cells, subsequent repair is delayed. Why is removal of the damaged material important early in healing?

Correct Answer: It prepares the injured site for effective repair

Explanation: Inflammatory clearance of necrotic material prepares the wound bed for subsequent cellular proliferation, angiogenesis and connective tissue deposition.

Question:
After tissue loss, surviving cells proliferate until an adequate cell population has been restored. Continued unrestricted proliferation is not required once tissue mass has recovered. Which principle best explains this coordinated response?

Correct Answer: Reduction of proliferative signalling after restoration

Explanation: Regeneration is regulated by growth signals; after the required cell population is restored, proliferative stimulation decreases and growth returns toward baseline.

Question:
Microscopy of an early healing wound shows abundant small blood vessels supplying metabolically active repair tissue. Why is this vascular response important at this stage?

Correct Answer: It supplies oxygen and nutrients to healing tissue

Explanation: Angiogenesis establishes a vascular supply that supports the oxygen and nutritional requirements of proliferating cells in the healing wound.

Question:
A pathologist reviews serial sections from a deep wound. The earliest specimen shows inflammatory clearance, a later specimen shows proliferating vessels and fibroblasts, and the final specimen shows dense connective tissue with reduced vascularity. Which sequence best describes the biological progression?

Correct Answer: Inflammatory clearance → proliferative repair → scar maturation

Explanation: Healing progresses from clearance of damaged tissue to vascular and fibroblast proliferation, followed by collagen accumulation and remodeling into a less vascular mature scar.