Page 8 - Headlines Histology2024_Neat

production. Due to their role in energy production, the mitochondria are
likened to powerhouses of the cells.
• Participate in regulation of calcium level within the cytosol.

Endoplasmic reticulum (ER)

• The Endoplasmic reticulum (Endo=inside; plasm=cytoplasm; reticulum =
network) is an irregular network of branching and anastomosing tubules,
cisternae and vesicles.

• Two types of ER are recognized: rough and smooth endoplasmic reticulum.

Rough endoplasmic reticulum (rER)

• The rough endoplasmic reticulum is a membranous organelle concerned
principally with synthesis and secretion of proteins.

• It is called rough due to the presence of large number of ribosomes attached
to its limiting membrane.

• With LM, it appears as basophilic cytoplasmic areas that are referred to as
the ergastoplasm or chromidial substances.

• The cytoplasmic basophilia may be diffuse (plasma cells), localized
(pancreatic acinar cells) or arranged into clumps (Nissl granules in nerve
cells). Aggregates of rER appear basophilic mainly due to the presence of
ribosomes on their outer surface.

• With EM, it consists of an anastomosing network of tubules, vesicles and
flattened cisternae that ramifies throughout the cytoplasm. Much of the
surface of the rER is studded with ribosomes giving the reticulum a rough
or granular appearance.

Functions

• Synthesis of proteins for extracellular use (secretory proteins, lysosomal
proteins and membrane proteins).

• Glycosylation of proteins to form glycoproteins.

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