List of abbreviations
Every attempt was made to provide correct information and labelling, however any liability for eventual errors or incompleteness is rejected!
|Detail of SER||ultra high magnification
of SER (rat)
|SER in 2 neighbouring
Clara cells (rat)
|SER in a rat
|Detail thereof||SER and RER
in a liver cell (rat)
|SER & RER, Clara cell
|SER Leydig cell
testis (rat) 1
|SER Leydig cell
Testis (rat) 2
|SER in a cell of the
adrenal cortex (rat)
|membranes outer segment rod,
+ pigment epithelium SER (monkey)
|idem Detail, Stäb-
|SER as L- Tubuli, Heart-
muscle cell (Rat)
|SER of a cell of an
eye muscle (monkey)
|SER of a liver cell
|SER as L- Tubuli of skeletal
muscle 1 (Ratte)
|SER as L- Tubuli 2
|SER as L- Tubuli 3
|SER in supporting cells,
olfactroy epithelium (rat)
The agranular or smooth endoplasmic reticulum
(SER; Terminologia histologica: Reticulum endoplasmicum nongranulosum)
is a complex three-dimensional network of membranous tubules showing
wider cisterns (Terminologia histologica: Cisternae) as well as tubules
(Terminologia histologica: Tubuli) partly with sac-like protrusions, i.e.
saccules (Terminologia histologica: Sacculi). Its paired membranes
(Terminologia histologica: Membranae) have a distance of 20-50
nm, and in contrast to
surface = cytosolic surface (Terminologia histologica: Facies externa)
borders the cytoplasm while the inner
surface = luminal surface (Terminologia histologica: Facies interna) of
the membranes encloses the lumen (Terminologia
histologica: Lumen). The membranes follow the structural principle
of biological membranes with two electron-dense outer layers enclosing
an inner less-dense lipophilic layer and have a thickness of 6
- 7 nm when cut at right angle. Most cells show much more rough (RER)
than smooth endoplasmic reticulum. However, a continuity of smooth into
rough ER is not rare and may be seen best in hepatocytes.
This means parts of the membrane system lack ribosomes while other sections
show many of them.
Steroid producing cells possess larger amounts of SER, e.g. adrenal gland, testosterone secreting Leydig's cells of the testis or hormone producing cells of the ovary [granulosa- and thekalutein cells]), cholesterin releasing hepatocytes. Furthermore plenty of SER is typical for pigment epithelium of the retina, for Clara-cells of bronchioles or for supporting cells of olfactory epithelium. Also the membrane stacks typical for outer segments of retinal rods and cones can be regarded as a special form of SER. In skeletal and heart muscle cells SER forms a network of thin tubules encompassing each myofibril. Here the SER is called sarcoplasmic reticulum (Terminologia histologica: Reticulum sarcoplasmicum). Due to the longitudinal orientation parallel to the myofibrils (photo) also the term L-tubule has been established for the sarcoplasmic reticulum.
The SER is similar to the nuclear sheath consisting of an inner and an outer nuclear membrane which surrounds the entire nucleus in form of a capsule-like cistern of the RER showing ribosomes only on the outer surface directed towards the cytoplasm. The rare anulate lamellas also derive from the SER.
An English page with detailed information and more images is available in the professional version of this atlas.
--> rough endoplasmic reticulum, cytoplasm,
heart muscle, liver
--> Electron microscopic atlas Overview
--> Homepage of the workshop
Two pictures were kindly provided by Prof. H. Wartenberg, other images, page & copyright H. Jastrow.