in Cell Structure and Function by

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Structure of endoplasmic reticulum:

It consists of membrane lined channels or spaces.  The channels or spaces contain a fluid called endoplasmic matrix.  It is quite different from cytoplasmic matrix present out side the reticulum. The membranes of endoplasmic reticulum or 50-60 A° thick.

Cisternae are flattened, unbranched, saclike elements with a diameter of 40-50 nm.  The lie in stacks parallel to one another and the sacs in the stack are interconnected with one another.

Tubules tube light extensions which may be connected with cisternae or to form a reticular system.

Functions of endoplasmic reticulum:

The ER facilitates transport of materials from one part of the cell to another, thus forming the cells circulatory systems.

Tubular ER extensions called desmotubules extend to the plasma desmata to make ER continue in the two adjacent plant cells.

ER acts as an intra cellular supporting frame work that also maintains the form the cell.

It keeps the cell organelles proper stationed and distributed in relation to one another.

The ER provides space for temporary storage of synthetic products such as glycogen.

Sarcoplasmic reticulum helps in muscle contraction by regulating calcium ions concentration in the sarcoplasm.