Histology of Cytoplasmic Organelles Flashcards
What type of Tissue is this?
Spinal Cord
What type of Tissue is This?
Pancreas
What is a significant feature of this Tissue?
Inflammation
is an area of inflammation that has been infiltrated by numerous white blood cells.
PLASMALEMMA OR PLASMA MEMBRANE
The plasma membrane forms the outer boundary of cells and consists of a trilaminar, unit membrane.
Identify the Plasma Membrane
6 and #7
Identify the Plasma Membrane
5
Identify the Plasma Membrane
1
plasmalemma
Note that cells have many membranes; the outermost membrane is the cell membrane or plasma membrane (or plasmalemma)
locate the plasmalemma and note its trilaminar (three-layered) appearance
Dark Line
White Space
Dark Line
Remember that when sufficiently magnified, all plasma membranes and all membranes in the cell appear trilaminar since they have two dark laminae separated by a central light lamina.
Ribosomes
Single ribosomes or multiple ribosomes linked together by mRNA to form polysomes (polyribosomes) may be found either free in the cytoplasm or associated with a membrane system, the rough endoplasmic reticulum (see below).
Identify Significant Features of the Image
Shows cytoplasm that contains ribosomes and polyribosomes. Compare the size of ribosomes to other cell constituents.
Observe that polysomes are formed of evenly spaced ribosomes. These ribosomes are linked together by a strand of messenger RNA, which is not visible in the micrograph. What is the function of polysomes?
ENDOPLASMIC RETICULUM.
Endoplasmic reticulum is a membranous organelle that is formed of flattened cisternae or irregular tubules. A variety of enzymes may be associated with the ER. There are two distinct types of ER, which are often interconnected: rough ER (RER), which has associated ribosomes, and smooth ER (SER), which lacks ribosomes and in which the organization of membranes is different.
Identify the Rough ER
3
Identify the Cisternae
1
Identify the Ribosomes
2
Identify Rough ER
5
Identify Rough ER
1
Identify Rough ER
5
Identify Rough ER
3
Nissel Substances
Rough surfaced endoplasmic reticulum cannot be seen, as such, with light microscopy. But in cells in which it is abundant its presence can be detected and its intracellular distribution determined by staining for the structural RNA (rRNA) associated with the ribosomes that line the surface of the RER. In these cases it is known as cytoplasmic basophilia. In neurons, extensive RER appears as irregularly shaped masses, which are referred to as Nissl substance (red arrows) (J. Fig. 9-3; R. Plate 31), because they stain robustly with a stain called Nissl stain.
Identify Important Features of this Image
Nissel Substance
Identify Important Features of the Image
Nissel Substance
What stain is used in this image?
What tissue?
Important Feature?
Cytoplasmic Basophilia (More Purple/Blue)
H and E of the Pancreas
What stain is used in this image?
What tissue?
Important Feature?
H and E
Pancreas
Cytoplasmic Basophilia
What stain is used in this image?
What tissue?
Important Feature?
H and E
Pancreas
Cytoplasmic Basophilia
(Oil)
How are pancreatic Cells Organized?
Green Outline?
Yellow Outline?
The Lumen? Significance of Lumen?
Are most lumens visible? Why or why not?
Apical side of the cell?
The cells of the exocrine pancreas are organized into acini (see diagram below), which are circular clusters of 10-15 cells (green outline is an acinus, yellow outline is a single cell). The cells in the acinus surround a space, the lumen (Xs in the labeled image), into which the cells release their digestive enzymes.
Note that due to tissue shrinkage, most lumens are not visible on the slide. The side of each cell facing the lumen is the apical side of the cell (pointed region of the yellow outline), and the side of the cell furthest from the lumen is the basal side
What area is the apical aspect of the cell on this EM?
Significance of Exocrine portion of the pancreas and their location
Cells in the exocrine portion of the pancreas secrete an enormous amount of digestive enzymes, which are synthesized on the rough endoplasmic reticulum localized to the basal aspects of these cells
(see EM 3, the apical aspect of this cell is the upper right).
What’s the significance of cytoplasmic basophilia in this image?
The extensive rough endoplasmic reticulum results in intense cytoplasmic basophilia in the basal aspect of the cell (oil).
Observe series of membranes of SER
3
Observe series of membranes of SER
6
Observe series of membranes of SER
7
Observe series of membranes of SER
5
continuity of SER membranes with those of RER
Identify Golgi Apparatus:
transport vesicles
flattened cisternae of the cis (forming) face
dilated cisternae of the trans (maturing) face
secretory vesicles
note 11-1, transport vesicles;
11-2 flattened cisternae of the cis (forming) face;
11-3 dilated cisternae of the trans (maturing) face;
and 11-4 secretory vesicles.
Identify Plasma Cells and the Golgi Ghosts
Many of the cells in this region have intense cytoplasmic basophilia; these are antibody-secreting plasma cells (plasma cells unlabeled, plasma cells indicated by arrows). If you look very carefully, the center of the cell is slightly paler than the surrounding cytoplasm; this is the Golgi ghost (best seen in plasma cell in the center of the image).
Note the detailed structure of a mitochondrion
Matrix?
Cristae?
Outer Mitochondrial Membrane?
Granules?
Note the detailed structure of a mitochondrion EM 6-10 (matrix),
6-11 (cristae),
6-12 (outer mitochondrial membrane) and
6-13 (granules);
mitochondrial cristae?
outer mitochondrial membrane?
inner mitochondrial membrane?
2-3 (mitochondrial cristae),
2-4 (outer mitochondrial membrane),
2-5 (inner mitochondrial membrane).
Identify Mitochondria
4
Identify Mitochondria
4
Identify Mitochondria
2
Identify Mitochondria
6
Identify Significant Microscopic Features
Notice that the image includes about four “whole” liver cells and parts of adjacent cells. Even if there were no scale bar on the micrograph, it is evident that this is a low magnification image. Cell boundaries are visible because there is a slight separation (extracellular space) between the cells, but, because the magnification is low, a definitive plasma membrane is difficult to see in this image, and intracellular details such as ribosomes and ER are hard to discern. The micrometer marker indicates the magnification in the print is about 5,500 X.
Identify Significant Microscopic Features
This micrograph is an image of pancreatic acinar cells; one “whole” cell and portions of two adjacent cells are included in the field. If no scale bar were on the micrograph, it would be reasonable to conclude that this image is a higher magnification than #17 because fewer cells are in the field, and intracellular structures are more easily seen in #3. Notice that the item marked 6 and identified, as plasmalemma in the micrograph appears to be a single line, but this single line is actually two closely apposed adjacent plasma membranes that cannot be resolved at this magnification. The cell’s basal surface is readily detected because of the presence of a basal lamina (7). The scale bar indicates magnification of the print is about 10,000 X.
Identify Significant Microscopic Features
The identification of this portion of a cell as an intestinal absorptive cell is based on the knowledge of the source of the image, since characteristics typical of an absorptive cell (apical surface with microvilli) are not included in the field. Many other cell types have the same organelles as shown here. Without the scale bar, it is apparent that this image was photographed at a higher magnification because only a small portion of a cell occupies most of the field, with only small portions of adjacent cells (upper left corner, lower right corner). The mitochondria are larger, their double membrane apparent, and ribosomes are easily identified. The parallel plasma membranes of adjacent cells, item 5, are clearly separated from each other by a small intercellular space. The cell membranes in the lower right corner “disappear” in the image in areas where they are not cut exactly transversely by the plane of section; the membranes in the upper left corner are more transversely cut, thus more distinct over a greater distance. The scale bar indicates that this image is magnified about 66,000 X.
Identify Significant Microscopic Features
EM 4 Is below
Even without the scale bar this image would be determined to be very high magnification because only a small portion of the apical surface of two adjacent cells is shown. No mitochondria are present and most other cell organelles are excluded from this limited apical region. The apical surface with microvilli is evident as well as the junctional complex that includes a zonula occludens (1), a zonula adherens (2), and macula adherens (desmosomes) (3). In ideal transverse planes of section through the plasma membranes, the trilaminar unit membrane is visible. The closely parallel plasma membranes can be viewed as two trilaminar membranes (dark-light-dark) on both sides of a narrow (wide at this magnification!) intercellular space. The micrometer marker on this image indicates the magnification is about 120,000 X. Compare this image in EM 16 with the appearance of two parallel plasma membranes in EM 4 (also dark-light-dark) but not at high enough magnification to reveal the trilaminar unit membranes.
Explain Trilaminar Unit Membranes
