Page 85 - Atlas of Histology with Functional Correlations

nonnucleated.

The nucleus consists of chromatin, one or more nucleoli (singular,

nucleolus), and nuclear matrix. The nucleus contains the cellular genetic
material deoxyribonucleic acid (DNA), which encodes all cell structures and
functions. A double membrane called the nuclear envelope surrounds the
nucleus, whereas the nucleolus is not surrounded by a membrane. Both the inner

and outer layers of the nuclear envelope have a structure similar to the lipid
bilayer of the cell membrane. The outer nuclear membrane is studded with
ribosomes and is continuous with the rough endoplasmic reticulum of the
cytoplasm. The inner nuclear membrane lacks ribosomes and is in contact with

the nuclear chromatin.

At intervals around the periphery of the nucleus, the outer and inner
membranes of the nuclear envelope fuse to form numerous nuclear pores. These
pores function in controlling the movement of metabolites, macromolecules, and
ribosomal subunits between the nucleus and cytoplasm.

Supplemental micrographic images are available at

www.thePoint.com/Eroschenko13e under Cell and Cytoplasm.

FIGURE 2.3 | Internal and External Morphology

of Ciliated and Nonciliated Epithelium

A low-magnification electron micrograph shows the internal morphology and
surfaces of ciliated and nonciliated cells in the epithelium of the efferent ductules

of the testis. The numerous cilia (2) in the ciliated cells are attached to the dense
basal bodies (8) at the cell apices, from which they extend into the lumen (1) of
the duct. In contrast to cilia, the microvilli (7) in the nonciliated cells are much
shorter and have a different internal structure than the cilia (see Fig. 2.7 for

details and comparison).

Note also the dense structures in the apices between the adjacent epithelial
cells. These are the junctional complexes (3, 9) that hold the cells tightly
together. Distinct cell membranes (10) separate the individual cells. Located in

the cytoplasm of these cells are numerous, elongated or rod-shaped
mitochondria (4, 11) and numerous light-staining vesicles (6). Each cell also
contains various shaped nuclei (12) with dispersed, dense-staining nuclear
chromatin (5) that is arranged around the nuclear periphery.

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