Page 29 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

The cell (cellula) 11

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1.12 Rough endoplasmic reticulum (rER) in a liver cell 1.13 Rough endoplasmic reticulum (rER) in a cell of
(x14,000). the exocrine pancreas (x8000).

erating cells. The density of the ribosome population produced by rER-associated ribosomes enter the lumen
influences the staining properties of the cell. Cytoplasm of the endoplasmic reticulum where they undergo post-
rich in ribosomal RNA is strongly basophilic as basic translational modification. When proteins are produced
stains (e.g. methylene blue, toluidine blue) bind with the in quantities exceeding the capacity of the rER to export
phosphate groups of free RNA. Ribosomes may also be them, the cisternae become expanded.
attached to the cytoplasmic surface of the membranes of The rough endoplasmic reticulum may merge with
the endoplasmic reticulum (Figures 1.6, 1.12 to 1.14, 1.16). the outer membrane of the nucleus, such that the lumen
of the ER is continuous with that of the perinuclear cis-
ENDOPLASMIC RETICULUM (RETICULUM tern of the nuclear envelope. Transport vesicles arising
ENDOPLASMATICUM) from the free ends of the rER membrane carry specific
The endoplasmic reticulum (ER) is a system of membranes molecules to other organelles or to the cell surface.
manifesting as stacks of flattened, interconnected cisternae
and tubules (Figures 1.6, 1.12 to 1.16). These structures
form an enclosed cavity that extends, typically in a parallel
arrangement, throughout the cell.
The portion of the endoplasmic reticulum in which the
outer surface of the membrane is studded with ribosomes
is termed the rough (granular) endoplasmic reticulum
(rER). Endoplasmic reticulum lacking ribosomes is
referred to as smooth endoplasmic reticulum (sER).
Both of the key structural components of all cellular
membranes – lipids (phospholipids and cholesterol) and
proteins – are synthesised in large part at the membranes
of the ER.

ROUGH ENDOPLASMIC RETICULUM (RETICULUM
ENDOPLASMATICUM GRANULOSUM)
Rough endoplasmic reticulum is found in almost all nucle-
ated cells and is particularly abundant in cells actively
engaged in protein synthesis (Figures 1.6, 1.12 to 1.14,
1.16). These include secretory cells of the salivary glands
and exocrine pancreas, nerve cells (as Nissl bodies) and
lipid-producing cells of the mammary glands. Proteins 1.14 Rough endoplasmic reticulum (rER) (x5000).

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