Human Alveolus Air-Blood Barrier Anatomy Infographic

Biological diagram infographic titled "Human Alveolus and Air-Blood Barrier" centered on a clean labeled anatomical cross-section of a terminal bronchiole leading into an alveolar duct and clustered alveoli, with one representative alveolus shown in enlarged editorial-grade cross-section for university undergraduate teaching. Render an educational human respiratory microanatomy diagram with biologically accurate proportions and tasteful medical illustration. Place 7 labels arranged around the central diagram with thin leader lines; each label must include a short heading in English and a one-line function description in English. Required labeled components: 1) "Terminal bronchiole" — "Conducts air to the respiratory zone." 2) "Alveolar duct" — "Distributes inhaled air into alveolar sacs." 3) "Alveolus" — "Primary site of oxygen and carbon dioxide exchange." 4) "Type I pneumocyte" — "Thin squamous cell forming most of the gas-exchange surface." 5) "Type II pneumocyte" — "Secretes surfactant to reduce surface tension and support alveolar stability." 6) "Alveolar macrophage" — "Phagocytoses inhaled particles and microbes within the alveolar space." 7) "Pulmonary capillary" — "Carries blood past the alveolus for rapid gas diffusion." Show the air-blood barrier clearly, including alveolar lumen, delicate septum, and adjacent capillary with red blood cells visible in a simplified scientific manner. Emphasize gas exchange with subtle directional arrows for O2 moving from alveolus to capillary and CO2 moving from capillary to alveolus, but keep the composition primarily a labeled anatomical cross-section rather than a flowchart. Visual style: medical illustration (Netter-style), monochrome scientific palette, refined grayscale with subtle tonal shading, precise ink-like contouring, high legibility, sharp typography, calm academic mood. Include medical-textbook clarity, editorial scientific illustration, vector-clean lines, no photographic textures. All text MUST be written in English (array). Every heading, label, caption, legend and metric name in the image must be in English — not English. Spell each English word correctly using English characters and diacritics. Numbers stay as digits, no graphic gore, no real patient photos, no watermarks No graphic medical gore, no real patient photographs, no surgical blood. For human anatomy, keep illustrations educationally tasteful. For animal anatomy, no cruelty imagery. Scientifically accurate labeling and proportions.