Domain: Healthcare — Pathophysiology
Target concept: Mechanism of Increased Capillary Filtration Pressure in Edema

Video generation prompt: Under a microscope, the venous end of capillaries in mouse mesenteric specimens were observed. The perfusion pressure was gradually increased, and the vessel wall was monitored for any fluid leakage.

Evaluation guide:
(i) Target concept: Edema formation via hydrostatic pressure-driven capillary filtration imbalance.
Minimum mechanism: The capillary wall must stay intact (no rupture); the venous end must be more compliant (thinner-walled, more distensible) than the arteriolar end, while plasma oncotic pressure stays essentially the same at both ends; raising perfusion pressure at the venous end pushes local hydrostatic pressure above the oncotic pressure that normally favors reabsorption there, producing a net outward (filtration) force sufficient to drive visible leakage.
(ii)Storyline: [Phase 1] Baseline: Stable mesenteric tissue, quiescent capillaries, no leakage. [Phase 2] Pressure initiation: Reservoir rises or pump activates; capillary lumen widens visibly at venous end. [Phase 3] Leakage onset: Translucent fluid emerges *only* from venous capillary wall junctions; no delay, no spread to arteriolar side. [Phase 4] Leakage progression: Fluid accumulates continuously in pericapillary interstitium with natural diffusion front. [Perspective constraint: Fixed microscopic view; no zoom/pan; venous capillaries must remain centered and in-focus throughout; no occlusion by debris or bubbles.]

Manual:
Experimental Procedure
1. Mount fresh mouse mesenteric tissue on microscope stage.
2. Identify venous end of capillaries (adjacent to post-capillary venules).
3. Gradually increase intravascular perfusion pressure using controlled reservoir elevation.
Observation of Experimental Phenomena
Fluid leakage emerges exclusively from venous capillary walls during pressure increase, forming expanding translucent interstitial accumulations — no leakage at arteriolar ends or baseline pressure.
Summary of Experimental Principles
Capillary filtration follows Starling forces: net outward fluid movement depends on the balance between hydrostatic pressure (pushing fluid out) and plasma oncotic pressure (pulling fluid back in). The thinner-walled, more compliant venous-end capillaries widen more readily under rising pressure; when perfusion pressure there rises enough to exceed the local oncotic pressure that normally favors reabsorption, the balance tips toward net filtration and visible fluid leakage, producing localized edema at the venous end.

Prompt Grounding rubric:
level_1: No mouse mesenteric tissue is shown; no capillary structures are visible; no distinguishable venous-end capillaries appear; no perfusion apparatus (reservoir, pump, or tubing) is shown; no fluid leakage of any kind is depicted.
level_2: Mesenteric tissue appears but does not look like real tissue (missing the thin, lace-like vascular network); capillaries are drawn as simple stylized lines with no distinction between arteriolar and venous segments; a perfusion apparatus appears but is not visibly connected to the tissue or shows no sign of function; leakage, if shown, appears only as static droplets not connected to any vessel.
level_3: Mesenteric tissue is recognizable (thin, translucent, with a branching network of small vessels); the venous end of the capillary bed is distinguishable from the arteriolar end (e.g., by position, width, or an accompanying label); the perfusion apparatus is visibly connected to the tissue and shows some indication of flow or pressure; some fluid leakage adjacent to a capillary is shown at some point in the sequence.
level_4: Everything in the 3-point level is present, and additionally: the tissue's natural translucent, lace-like morphology is clearly rendered; the venous-end capillaries are clearly localized near post-capillary venules rather than near arterioles; the apparatus visibly applies increasing pressure (e.g., a rising reservoir or an actuating pump); at least one visible leakage event is shown emerging from a capillary wall rather than appearing from nowhere.
level_5: Everything in the 4-point level is present, and additionally: the venous-end capillaries stay the visual focus of the shot, in-focus and unobstructed by debris or bubbles; the apparatus, tissue, and leakage site keep a consistent spatial relationship throughout; the leakage is clearly shown emerging directly from a capillary wall junction rather than from a torn or ambiguous part of the tissue.

Scientific and Causal Correctness rubric:
level_1: Fluid leakage is shown at the arteriolar end of capillaries, or leakage appears without any preceding pressure increase; the leaking fluid looks like blood (red) rather than clear/translucent fluid; the capillary walls appear rigid, showing no ability to widen under pressure.
level_2: Leakage occurs but at both venous and arteriolar segments roughly equally; the fluid resembles plasma in color but looks thick or grainy rather than clear; leakage begins at the same time as the baseline, pre-pressure-rise view rather than growing as pressure increases; the venous end is not visually distinguished from the arteriolar end.
level_3: Leakage is confined to venous capillary segments (visibly wider-lumened, less pulsatile, near venules) rather than arteriolar ones; the leaking fluid is translucent, not red or opaque; a pressure increase is shown (e.g., a rising reservoir), but the leakage begins before the pressure has clearly started rising, or continues unchanged well after the pressure has leveled off, so the timing link is weak; little or no visible widening of the capillary wall accompanies the leakage.
level_4: Leakage occurs only at venous capillaries, never at arteriolar ones; the fluid is translucent; the leakage grows only while the pressure is actively rising, not before it starts or after it levels off; the venous capillary wall visibly widens or bulges alongside the leakage, consistent with a Starling-forces-driven filtration imbalance.
level_5: Everything in the 4-point level holds, and additionally: the capillary wall widens continuously and progressively as pressure rises; the leaking fluid clearly emerges from the wall itself, at the junctions between endothelial cells, rather than from any tear or rupture; there is no accompanying bleeding, clotting, or inflammation; the fluid spreads outward into the surrounding tissue in a gradual, diffusion-like pattern consistent with genuine edema formation from raised hydrostatic pressure.

Spatiotemporal Consistency rubric:
level_1: The tissue disappears and reappears between frames; capillary segments jump from one place to another with no motion shown between; leakage fluid appears instantly at full size with no gradual emergence; the perfusion apparatus changes position or angle abruptly; the scene swings between very bright and very dark with no visible cause.
level_2: The tissue stays in view but stretches or warps unnaturally; capillary segments flicker in and out; the leaked fluid appears as a single fixed blob that never grows or spreads; the perfusion apparatus moves in a jerky, unnatural way; shadows on the tissue shift in ways that don't match any visible light source.
level_3: The tissue holds its position and scale without drifting or resizing; the capillaries stay continuously visible; the leaked fluid grows as an accumulation next to the venous capillary, but its growth is uneven: it jumps in size or appears detached from the vessel wall at times; the perfusion apparatus moves smoothly, but its own state change (e.g., the reservoir rising) is not clearly timed with when the leakage begins.
level_4: The tissue, capillaries, and perfusion apparatus keep a consistent spatial relationship to one another; the leaked fluid grows continuously and always stays attached to the venous capillary wall rather than floating free; the reservoir's rise (or pump's action) proceeds smoothly and its timing visibly lines up with when the leakage starts and grows; the capillary wall's widening under pressure looks like a gradual, natural deformation rather than a sudden snap to a new shape.
level_5: Everything in the 4-point level holds, and additionally: every motion (reservoir rise, wall widening, fluid spread) unfolds smoothly with no skipping or juddering between frames; the leaked fluid's edge looks soft and diffuse as it spreads into the tissue rather than having a hard geometric boundary; there are no structural breaks, sudden occlusions, or rendering glitches affecting the tissue, capillaries, or apparatus at any point.