Page 132 - Atlas of Histology with Functional Correlations

Cuboidal Epithelium and Simple

Columnar Epithelium

Simple cuboidal epithelium lines ducts of glands in organs for sturdiness
and protection. In kidneys, this epithelium functions in transport, absorption

of filtered substances, and active secretion of substances into the
filtrate.Simple columnar epithelium covers the surface of the stomach
where the cells secrete mucus. The mucus lines the stomach surface and
protects its lining from the corrosive gastric secretions found in the stomach

during food processing and digestion.

FIGURE 4.6 | Simple Columnar Epithelium on

Villi in Small Intestine: Cells with Microvilli

(Brush Borders) and Goblet Cells

The intestinal villi (1), illustrated in transverse section and longitudinal section,

are covered by simple columnar epithelium. In the small intestine, the epithelium
consists of two cell types: columnar cells with microvilli or brush borders (5, 7)
and oval-shaped goblet cells (6, 13). The brush border (5, 7) is seen as a
reddish outer cell layer with faint vertical striations; these striations represent

microvilli on the apices of columnar cells.

Pale-staining goblet cells (6, 13) are interspersed among the columnar cells.
During routine histologic preparation, the mucus is lost; hence, the goblet cell
cytoplasm appears clear or only lightly stained (6, 13). Normally, the mucigen
droplets occupy cell apices (4) and the nucleus cell bases (4).

When the epithelium at the tip of a villus is sectioned in an oblique plane, the
cell apices (4) of the columnar cells appear as a mosaic of enucleated cells,
whereas the cell bases (4) appear as stratified epithelium.

A thin connective tissue basement membrane (8) is visible directly under

the epithelium. The connective tissue lamina propria (12) contains an empty
lymphatic vessel with a very thin endothelium called the central lacteal (2, 9).
Also present in the lamina propria (12) are numerous blood vessels (10) and a
capillary (14) lined with endothelium. Smooth muscle fibers (3, 11) extend into
the villi. In this illustration, smooth muscle fibers (3, 11) are cut in transverse

section (3) and longitudinal section (11).

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