endoplasmic reticulum

American  

[en-doh-plaz-mik ri-tik-yuh-luhm] / ˈɛn doʊˌplæz mɪk rɪˈtɪk yə ləm /

noun

Cell Biology.

1. a network of tubular membranes within the cytoplasm of the cell, occurring either with a smooth surface smooth endoplasmic reticulum or studded with ribosomes rough endoplasmic reticulum, involved in the transport of materials.

---

endoplasmic reticulum British  

noun

1. an extensive intracellular membrane system whose functions include synthesis and transport of lipids and, in regions where ribosomes are attached, of proteins

---

endoplasmic reticulum Scientific  

/ ĕn′də-plăz′mĭk /

1. An organelle consisting of a network of membranes within the cytoplasm of eukaryotic cells that is important in protein synthesis and folding and is involved in the transport of cellular materials. The endoplasmic reticulum can be continuous in places with the membrane of the cell nucleus. The function of the endoplasmic reticulum can vary greatly with cell type, and even within the same cell it can have different functions depending on whether it is rough or smooth.

2. ◆ The rough endoplasmic reticulum is a series of connected flattened sacs that have many ribosomes on their outer surface. Rough endoplasmic reticulum synthesizes and secretes serum proteins (such as albumin) in the liver, and hormones (such as insulin) and other substances (such as milk) in the glands.

3. ◆ The smooth endoplasmic reticulum is tubular in form and is involved in the synthesis of phospholipids, the main lipids in cell membranes. Smooth endoplasmic reticulum is the site of the breakdown of toxins and carcinogens in the liver, the conversion of cholesterol into steroids in the gonads and adrenal glands, and the release of calcium ions in the muscles, causing muscle contraction. The smooth endoplasmic reticulum also transports the products of the rough endoplasmic reticulum to other cell parts, notably the Golgi apparatus.

4. See more at cell

---

Etymology

Origin of endoplasmic reticulum

First recorded in 1945–50

Example Sentences

One, called LCA, damaged T cell function by causing endoplasmic reticulum stress, while another, UDCA, boosted T cell performance and drew more immune cells to the liver.

From Science Daily • Oct. 17, 2025

By studying late-onset cases, Igdoura and his team uncovered that these diseases begin in the spinal cord, where chronic stress on a cellular component called the endoplasmic reticulum triggers programmed cell death.

From Science Daily • Nov. 14, 2024

"However, our research highlights a novel function of the HLA molecule within skin cells. We revealed that a specific HLA genotype in keratinocytes can recognize certain drugs as foreign, triggering an endoplasmic reticulum stress response."

From Science Daily • May 15, 2024

Moreover, abnormal mitochondrial metabolism and endoplasmic reticulum stress are hallmarks of various disorders, such as cardiac diseases, Alzheimer's, Parkinson's, and cancer.

From Science Daily • Jan. 16, 2024

A fluorescent microscopy image of a cell, with TIS granules shown in red and the endoplasmic reticulum is shown in green.

From Science Daily • Dec. 21, 2023