2
UNIT 1
Basic Principles of Cell Structure and Function
Descriptive Terms for Normal Cells
Cell Shape
Squamous
: This is an epithelial cell that has
a
fl attened, “squamous” shape. Usually, the
squamous cells we see in sections are cut edgewise
so that they appear very thin, and about all we see
is the fl attened nucleus. The example here shows
nuclei of three endothelial cells lining a vein full of
erythrocytes.
Spherical or ovoid
: These terms describe ball-shaped or egg-shaped cells, respectively. The
examples here are two spherical cells, a mast cell on the left and a plasma cell on the right.
These residents of connective tissue can assume other shapes depending on pressures from
neighboring structures.
Fusiform
: These cells are elongated and tapering at the
two ends. The examples here are smooth muscle cells
packed together in parallel. The elongated nucleus of each
cell is easy to see, but the boundaries of the long spindle-
shaped cells are difF cult to distinguish.
Polarized
: These cells have a distinct orientation with one end of the cell being different from
the other. Each columnar cell in the above example of intestinal epithelium has an apical end
on the right that is different than the basal end on the left. The apical ends are exposed to
the lumen. Most of the cells are absorptive cells that have a brush border and a dense row of
microvilli extending from their apical surfaces. The cell that appears to have vacuoles F lling
the apical two thirds of its cytoplasm is a goblet cell, a mucus-secreting cell. What appear to be
vacuoles are actually secretory vesicles that lost their contents during processing of the tissue.
Cuboidal
: This is an epithelial cell with equal
height and width. The example here is a layer of
cuboidal epithelial cells lining a small duct in the
pancreas.
Columnar
: This is an epithelial cell with the height
distinctly greater than the width. The example here
is a layer of columnar cells lining a large duct in
the pancreas.
10
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Polyhedral
: Multiple fl attened surfaces give the appearance of a
pentagon, hexagon, and so on. The hepatocyte shown displays
six sides.
D. Cui
D. Cui
D. Cui
20
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20
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