(C4-8) Slide 62: Gall bladder, human - H & E

The nomenclature will become slightly more complicated in this slide, because there are modifications of the epithelium that must be included in its name. The lumen of the gall bladder is lined by tall simple columnar epithelium with microvilli (C4). Where the section is oblique to the surface, it appears that the epithelium is thick and stratified (C5). However, when cut perpendicular to the surface, the nuclei form a single, regular row (C6).

We told you that this epithelium has microvilli, but how can you tell? If there were no abundant apical modifications, the apical surface should have a crisp edge (see the previous two slides). Here, the apical surface is a blur made of the microvilli (C6). Microvilli are very short and narrow, so you cannot see individual ones; they just blend together. We will see another, better example of microvilli on the next slide. Beneath the microvilli, the dark horizontal line is the terminal web, interrupted at regular intervals by dark notches, the terminal bars, which are junctional complexes. In some areas, the lateral intercellular spaces are dilated slightly, reflecting the function of the gall bladder in concentrating the bile that it stores.

The epithelium rests on a layer of connective tissue called the lamina propria where numerous blood vessels are seen as clear circles or ovals, usually with a darkly staining nucleus to one side (C6). Blood vessels are lined by simple squamous epithelium called endothelium. The smallest vessels, very close to the base of the epithelium, are the capillaries. Recall that there are no blood vessels in epithelia, so they must get their nutrients from blood vessels in the underlying connective tissue.

Continue scanning across the connective tissue, moving away from the lumen, to reach the opposite surface (C7). The simple squamous epithelium lining this surface is called mesothelium; it is the visceral peritoneum covering the gall bladder (C8).