Page 69 - Atlas of Histology with Functional Correlations

FIGURE 1.11 | Planes of Section through a Hollow

Structure or a Tube

Tubular structures are often seen in histologic sections. Tubes are most easily
recognized when they are cut in transverse (cross) sections. However, if the

tubes are sectioned in planes other than transverse, their appearance is different.
To be recognized as a hollow tube, they must first be visualized as three-
dimensional structures. To illustrate how a blood vessel, duct, or a hollow

glandular structure may vary in appearance in a histologic section, a curved tube
with a simple (single) epithelial cell layer is sectioned in longitudinal, transverse,
and oblique planes.

A longitudinal (a) plane of section that cuts the tube in the midline produces
a U-shaped structure. The sides of the tube are lined by a single row of cuboidal

(round) cells around an empty lumen except at the bottom, where the tube begins
to curve; in this region, the cells appear multilayered.

Transverse (d and e) planes of section of the same tube produce round
structures lined by a single layer of cells. The variations that are seen in the

cytoplasm of different cells are related to the planes of section through the
individual cells, as explained above. A transverse section of a straight tube can
produce a single image (e). The double image (d) of the same structure can
represent either two tubes running parallel to each other or a single tube that has
curved in the space of the tissue or organ that is sectioned.

A tangential (b) plane of section through the tube with a single layer of cells
produces a solid, multicellular, oval structure that does not resemble a tube. The
reason for this is that the plane of section has grazed the outermost periphery of
tube as it made a turn in space; the lumen was not present in the plane of section.

An oblique (c) plane of section through the same tube and its single layer of
cells produces an oval structure that includes an oval lumen in the center and
multiple cell layers at the periphery.

A transverse (f) section in the region of a sharp curve in the tube grazes the
innermost cell layer and produces two round structures connected by a multiple,

solid layer of cells. These sections of the tube also contain round lumen,
indicating that the plane of section passed perpendicular to the structure.

Figure 1.12 shows a section from the testis. This organ is filled with
numerous and convoluted (twisted) tubular structures, the seminiferous tubules.

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