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Electron microscopy of the tracheal ciliated mucosa in rat.
The ciliated cells have approximately 8–9 cilia per square micron and there are about 270 cilia on each cell, the calculated surface area being 33 square microns.
They are covered by a 70 Å thick membrane.
A number of 0.05 micron thick and 1 micron long filiform projections emerge from the cell surface. No cuticle is present.
The cell membrane facing adjacent cells is 90 Å and separated from their cell membrane by a 105 Å wide space, this space, being expanded towards a level corresponding to the proximal parts of the cell.
A structure that represents terminal bar has been encountered. The cytoplasm is loose and composed of 160 Å thick granules. Spaces enclosed by 50 Å thick membranes with attached 160 Å thick granules (α-cytomembranes) are rare.
The Golgi zone is analyzed and its regular composition of γ-cytomembranes, granules and vacuoles is confirmed.
The mitochondria with a mean width of 0.23 micron differ to their inner structure from the common type in that the triple layered membranes are highly interconnected.
Large opaque granules are encountered in the cytoplasm. Ring-shaped, 850 Å wide, structures are present in the nuclear membrane.
The goblet cells are not as abundant as the ciliated cells, the ratio being 1∶4. Small filiform projections covered by a 95 Å thick membrane protrude from the cell surface. This membrane is continuous with the cell membrane, the latter with the same dimensions as in the ciliated cells.
Terminal bars are present.
The cytoplasm is very opaque due to a dense packing of the 165 Å opaque granules, many in clusters of 4–6.
The α-cytomembranes have the same dimensions as mentioned above for those present in the ciliated cells.
The mitochondria with a mean width of 0.23 micron have an outer triple layered membrane with a total thickness of 180 Å.
The central less opaque layer is 70 Å and the opaque layer on either side is 55 Å. The inner membranes are arranged parallel to each other and have a triple layered composition where the central less opaque layer is 65 Å and the opaque layers each 60 Å.
The brush cells belong to the non-ciliated cells. They are encountered singly, surrounded by goblet cells.
The surface structures are shaped like brushes or clumsy protrusions which emerge from the distal end of the cell, and are covered by a 95 Å thick membrane. There have been no suggestions of the brushes being cilia in a stage of growth, nor is it probable that they represent stereocilia.
The α-cytomembranes are very rare. The Golgi zone is diminutive though of regular composition. The mitochondria are abundant and small with a mean width of 0.14 micron.
The inner membranes are very few, often only one or two are present. Some of the large opaque granules have inside a very regular arrangement of small 60 Å thick opaque granules arranged in a crystalline pattern.
In the cytoplasm 0.5–1 micron long bundles of 30–40 Å wide fibrils are encountered. The nucleolus shows a characteristic structure of concentrically arranged thin membranes.
The basal cells are believed to represent lymphocytes or white blood cells. They sometimes rest on the basement membrane, sometimes are encountered in the distal part of the intercellular spaces.
They are bordered by a 110 Å thick cell membrane and have a rather opaque cytoplasm characterized by 160 Å thick opaque granules. A very small Golgi zone is present.
The mitochondria, the mean width being 0.14 micron, have triple layered outer and inner membranes, where the less opaque central layer is 65–70 Å and the opaque layers 45–50 Å each.
Below the basement membrane is the lamina propria of the trachea, which is composed of collagen and elastin fibers together with fibroblasts, white blood cells and lymphocytes.
The relationship between different types of tracheal epithelial cells in rat has been analyzed. There has been found no indication of a transformation of any type of cells observed into a different type of cell.
The development of basal cells via supporting cells or intermediate cells to goblet cells or ciliated cells has not been noticed.
On the contrary, all cells that in light microscopy could have been considered to be supporting or intermediate cells, we have been able to recognize as brush cells or as goblet cells to a varying degree filled with mucous granules.
If the cells did not seem to reach the cell surface it has been found to be due to a diagonal direction of the sectioning.
In this connection it should be emphasized that this relationship is valid only in rat where it is known that the epithelium is of a simple columnar type as distinct from the conditions in man, that epithelium being of a pseudostratified columnar type.
To learn more about simple columnar epithelium: https://brainly.com/question/17203173
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