Rabu, 04 April 2012

Cells


Spinal Ganglion Cells

Human and animal cells are dedicated to specialized functions within the organism, and their sizes, shapes and structures vary accordingly. Spinal ganglion cells are mostly pseudounipolar neurons and can be spherical, ellipsoid, or pear-shaped, with diameters between 20 and 120μm. The round cell nuclei, up to 25μmin size, contain little chromatin 1 . The nuclei always have a clearly visible nucleolus (2–4μm). Glial cells form a layer around the spinal ganglion cells. Therefore, they are also called satellite cells 2 . The small or spindle-shaped nuclei of these satellite cells stand out because they are heavily stained. There are delicate connective tissue fibers (endoneurium) and nerve fiber bundles (fascicles) 3 between the ganglion cells. In the upper right of the figure, a wide strand of connective tissue (stained blue) traverses the section

1 Nucleus with clearly visible nucleolus
2 Satellite cells
3 Nerve fibers
4 Capillaries
Stain: azan; magnification: × 400



Multipolar Neurons

Anterior horn motor cells—i.e., motor neurons of the columna anterior from the spinal cord—were obtained by careful maceration of the spinal cord and stained as a “squeeze preparation” (tissue spread out by gentle pressure). This technique makes it possible to preserve long stretches of the numerous long neurites and make them visible after staining. In a tissue section, most of the cell processes would be sheared off (see Fig. 20). In this preparation, it is hardly possible to distinguish between axons (neurites, axis cylinder) and the heavily branched dendrites. Axons extend fromthe nerve cell to the musculature and form synapses.

Stain: carmine red; magnification: × 80




Smooth Muscle Cells

The structural units of the smooth musculature are the band-shaped or spindle-shaped muscle cells, which usually occur in bundles of different sizes. Muscle cells build strong layers, e.g., in the walls of hollow organs They can be isolated from these holloworgans by maceration with nitric acid. However, the long, extended cell processes often break off during this procedure. Dependent on their location and function in the tissue, smooth muscle cells are between 15 and 200μm long. During pregnancy, uterine smooth muscle cells may reach a length of 1000μm. On average, they are 5–10μm thick. The rod-shaped nucleus is located in the cell center. When muscle cells contract, the nucleus sometimes coils or loops into the shape of a corkscrew.


Stain: carmine red; magnification: × 80




Sumber Kuehnel, Color Atlas of Cytology, Histology, and Microscopic Anatomy © 2003 Thieme


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