medicinal plants top

Cell Nucleus


Cell Nucleus


Round cell nucleus (detail section) to illustrate the nuclear membrane. In

light microscopy, cell nuclei are surrounded by a darkly stained line, which

represents the nuclear membrane.

This nuclear membrane consists of two cytomembranes, which separate the

karyoplasm from the hyaloplasm. Between the two membranes is the

20–50nm wide perinuclear space, the perinuclear cisterna 1 , which communicates

with the vesicular spaces between the endoplasmic reticulum

membranes. The outer nuclear membrane is confluent with the endoplasmic

reticulum and shows membrane-bound ribosomes. The perinuclear cisterna

is perforated by nuclear pores which form pore complexes.

Their width is about 30–50nm, and they are covered with a diaphragm. At

these covered pores, the outer and inner nuclear membrane lamellae merge.

In the adjacent cytoplasm, close to the nuclear membrane, are cisternae of

the granular endoplasmic reticulum  . The inner lamella of the nuclear

membrane is covered with electron-dense material. This is heterochromatin,

which is localized at the inner nuclear lamina


Cell nucleus and adjacent cytoplasm from an enterocyte (jejunum) in a

freeze-fracture plane (cryofracture, freeze-etching), which renders a profile

viewof the nuclear membranes. The viewis on the inner side of the inner lamella

of the inner nuclear double membrane  . The white fracture line in

this figure corresponds to the perinuclear cisterna The lower plane

2 gives a view of the inner side of the inner lamella of the outer nuclear

double membrane. Note the abundance of nuclear pores  , which allow the

intracellular transport of materials between nucleus and cytoplasm. Note

that the two nuclear membranes merge at the pore region. Above the nucleus

are vesicles of various sizes and an array of Golgi membranes


Detail section showing two secretory cells from the mucous membranes of

the tuba uterina (oviduct). Their long, oval nuclei showmultiple indentations

of different depths. Therefore, the nucleus appears to be composed of

tongues and irregular lobes in this preparation. The cytoplasm extends into

the deep nuclear indentations. The distribution of the finely granular chromatin

(euchromatin) is relatively even. Only at the inner nuclear membrane

is the chromatin condensed in a fine osmiophilic line. The cytoplasm in the

immediate vicinity of the nucleus contains cisternae from granular endoplasmic

reticulum 1 , secretory granules 2 and sporadically, small mitochondria