Rough ERFlattened sacs studded with ribosomes. Proteins for the cell membrane and for export are made here.
Smooth ERA network of tubules with no ribosomes. Lipids are made here.
Nuclear envelopeThe double membrane round the nucleus. Its outer membrane runs on into the membrane of the ER.
Transport vesicleA small membrane bubble that leaves the ER. It carries new proteins on to the Golgi apparatus.
Golgi apparatusThe next stop for proteins made in the ER. Transport vesicles carry them here.
Cut open 5
RibosomesRibosomes are where proteins are built. On the rough ER they sit on the outer face of the membrane.
CisternaOne flattened sac of the ER. Rough ER is built of many of them, often stacked.
ER lumenThe space inside the ER. New proteins pass into it and are folded there.
ER membraneThe membrane that walls off the ER. Sacs and tubules all share this one membrane.
TubuleA tube of smooth ER. Tubules branch and join up into a network.
How this list was compiled: Every name was checked on 2026-10-01 in at least two places, for facts only and with nothing copied. (1) University of Vigo, Atlas of Plant and Animal Histology: The cell, Endoplasmic reticulum, https://mmegias.webs.uvigo.es/02-english/5-celulas/5-reticulo.php, and From endoplasmic reticulum to Golgi apparatus, https://mmegias.webs.uvigo.es/02-english/5-celulas/5-reticulo-golgi.php. (2) Wikipedia, text only: Endoplasmic reticulum, https://en.wikipedia.org/wiki/Endoplasmic_reticulum. (3) National Human Genome Research Institute, Talking Glossary: Endoplasmic Reticulum (Rough), https://www.genome.gov/genetics-glossary/Endoplasmic-Reticulum-Rough, and Endoplasmic Reticulum (Smooth), https://www.genome.gov/genetics-glossary/Endoplasmic-Reticulum-Smooth. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
This endoplasmic reticulum cell diagram shows the whole organelle beside the nucleus: rough ER, smooth ER and a vesicle leaving for the Golgi. A second view cuts one sac open. Tap a name, or press Quiz me.
Read the full guide
Rough or smooth: look for the dots
Rough ER is built of flattened sacs dotted with ribosomes. Smooth ER is a net of plain tubules with no ribosomes. The two are joined, and the ER membrane runs on into the outer membrane of the nuclear envelope.
Inside one sac
Each flattened sac is a cisterna. Its wall is the ER membrane, and the space inside is the lumen. Proteins built by the ribosomes pass into the lumen, and transport vesicles carry them on to the Golgi apparatus.
Lumen, cisternal space and inner space all name the same space, and all three are accepted.
Questions and answers
What does the endoplasmic reticulum do?
It makes proteins and lipids for the cell. Ribosomes on the rough ER build proteins, and the smooth ER makes lipids.
What is the difference between rough ER and smooth ER?
Rough ER has ribosomes on its outer face and is built of flattened sacs. Smooth ER has no ribosomes and is built of tubules.
Why is rough ER called rough?
Its outer face is studded with ribosomes, and they give the membrane a rough appearance.
Is the endoplasmic reticulum connected to the nucleus?
Yes. The ER's membrane runs on into the outer membrane of the nuclear envelope, so the two form one system of membranes.