protein to ‘float’ in the plane of the membrane . Some proteins are
typical cell . This example is a ciliated columnar epithelial cell from human
restricted in their freedom of movement where their cytoplasmic domains
nasal mucosa . The central cell, which occupies most of the field of
are tethered to the cytoskeleton .
view, is closely apposed to its neighbours along their lateral plasma
membranes . Within the apical junctional complex, these membranes form
a tightly sealed zone (tight junction) that isolates underlying tissues from,
charides and polysaccharides are bound either to proteins (glycopro-
in this instance, the nasal cavity . Abbreviations: AJC, apical junctional
teins) or to lipids (glycolipids), and project mainly into the extracellular
complex; APM, apical plasma membrane; C, cilia; Cy, cytoplasm; EN,
domain (Fig. 1.3).
euchromatic nucleus; LPM, lateral plasma membrane; M, mitochondria;
In the electron microscope, membranes fixed and contrasted by
MV, microvilli; N, nucleolus . (Courtesy of Dr Bart Wagner, Histopathology