☤ MD ☞☆☆☆ Cross-section of the mammal colon or large intestine. From the lumen outward are the mucosa, submucosa, muscularis externa, and the thin outer serosa. The highly folded layers are typical of an empty organ. SEM **On Page Credit Required**
False-color SEM of retina featuring central fovea, a crater-like depression in the photosensitive layer of the eye. The foveal retina is the area of greatest visual acuity and contains only cone receptor cells.