(ER) a system of membranes present in the cytoplasm of cells. ER is described as rough when it has *ribosomes attached to its surface and smooth when ribosomes are absent. It is the site of manufacture of proteins and lipids and is concerned with the transport of these products within the cell (see also Golgi apparatus).... endoplasmic reticulum
an arrangement of membranous vesicles and tubules found in the cytoplasm of striated muscle fibres. The sarcoplasmic reticulum plays an important role in the transmission of nervous excitation to the contractile parts of the fibres.... sarcoplasmic reticulum
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