The gallbladder is a hollow, pear-shaped organ that concentrates and stores the bile. The full thickness of its wall is shown here. It is composed of a mucosa (Muc), muscularis (Mus), and adventitia (Adv) and, on its free surface (not shown), a serosa. The mucosa is considered at higher magni fication in figure below. The muscularis consists of interlacing bundles of smooth muscle (SM). The adventitia (Adv) consists of irregular dense con660 nective tissue through which the larger blood vessels (BV) travel and, more peripherally, of varying amounts of adipose tissue (AT).
Mucosa, gallbladder, human, H&E ×325.
The mucosa consists of a tall simple columnar absorptive epithelium (Ep) resting on a lamina propria of loose irregular connective tissue (CT). The epithelium has characteristics that distinguish it from the absorptive epithelium of other organs, such as the intestines. Only one cell type, tall columnar cells, is present in the epithelial layer (see upper right figure). The nuclei are in the basal portion of the cell. The cells possess a thin apical striated bor-
Mucosa, gallbladder, human, H&E ×550.
The smaller of the two gland-like structures is composed of mucous cells (MC) and represents a section through a mucous gland. This specimen was taken from a site near the neck of the gallbladder where mucous glands are often present. Note the characteristic flattened nuclei at the base of the cell and the lightly stained appearance of the cytoplasm, features  characteristic
The mucosa is thrown into numerous folds that are particularly pronounced when the muscularis is highly contracted. This is the usual histologic appearance of the gallbladder unless, of course, steps are taken to fix and preserve it in a distended state. Occasionally, the section cuts through a recess in a fold, and the recess may then resemble a gland (arrows). The mucosa, however, does not possess glands, except in the neck region, where some mucous glands are present (see lower right figure).
der. However, this is not always evident in routine H&E–stained sections. The cytoplasm stains rather uniformly with eosin. This is related to its absorptive function and is in contrast to the staining of cells that are engaged in the production of protein. Lastly, with respect to its absorptive function, the epithelial cells frequently exhibit distended intercellular spaces at their basal aspect (see upper right figure arrows). This is a feature associated with the transport of fluid across the epithelium and, as noted above, commonly seen in intestinal absorptive cells.
Mucosa, gallbladder, human, H&E ×550.
The lamina propria underlying the epithelium is usually very cellular. In this specimen, in addition to lymphocytes (L), a relatively common finding, a large number of plasma cells (PC) is also present within the lamina propria. (The high concentration of plasma cells suggests chronic inflammation.)
Another feature of note in the lamina propria is the presence of several out-pouching of the mucosa, called Rokitansky-Aschoff sinuses (RAS), other than those seen in the mucosa and noted above. These are readily apparent in figure on right and two of these structures, marked by RAS are shown at higher magnification in figure below.
of mucin-secreting cells. In contrast, the epithelium of the large gland-like profile that is only partially included in the micrograph has rounded or ovoid nuclei. This epithelial-lined structure is not a true gland but represents an invagination of the mucous membrane that extends into and often through the thickness of the muscularis. These invaginations are known as Rokitansky-Aschoff sinuses.