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MH 001 Nuclear Morphology
The staining pattern of nuclei can be either heterochromatic or euchromatic.
Heterochromatin is a tightly packed form of DNA. Heterochromatic nuclei stain uniformly and intensely with hematoxylin. This is indicative of a cell with low transcriptional activity.
Euchromatin is a lightly packed form of DNA. Euchromatic nuclei show random clumps of hematoxylin staining mostly at the periphery of the nucleus. This is indicative of cells with high transcriptional activity.
Lymph nodes contain many lymphocytes. These small cells have very dark nuclei and a thin rim of pale cytoplasm. At high magnification, examine individual lymphocytes surrounding this capillary.
Lymphocytes are small cells of 7 to 10 µm diameter.
They have heterochromatic nuclei and only a thin rim of cytoplasm.
Their nuclear to cytoplasmic ratio is approximately 1:1.3 (∼75% of cell volume is the nucleus).
Adipose tissue is composed of adipocytes. They are also known as adipose cells or fat cells. Examine the adipocytes in the connective tissue surrounding the lymph node.
These fat cells are ∼50 µm in diameter.
They contain large lipid droplets that are unstained by either hematoxylin or eosin.
Red blood cells have a diameter of ∼7.5 to 8 µm and can be used to estimate the size of other cells and nuclei.
Since these fat cells are quite large, the tissue section often does pass through the part of the cell which contains the nucleus.
The largest cells in the human body are motor neurons in the spinal cord and mature ovum in the ovary. At higher magnification, find motor neurons cut in cross section through its nucleus with or without processes (axons or dendrites).
Nuclei occur in all cells except mature red blood cells (RBC) and blood platelets. RBC are ~7.5 µm in diameter and can be used to estimate sizes of other structures.
Since these cells are quite large, the tissue section frequently does not contain the nucleus. In this case, the nucleus is in the plane of the section.
These cells are of 80 to 100 µm in diameter.
The nucleus is 20 to 30 µm in diameter and is euchromatic.
They have a prominent nucleolus which is intensely stained with hematoxylin.
The nucleolus is 10 to 15 µm in diameter.
The liver is composed primarily of hepatocytes. These cells are closer in size to 'typical' cells than the large motor neurons.
At high magnification, examine hepatocytes sectioned through their nuclei that are near a blood vessel containing RBC.
(Note the RBC are poorly preserved.)
Hepatocytes have an average cell diameter of ∼25 to 30 µm.
Use the nearby red blood cells to estimate the size of the cells and nuclei.
These cells have heterochromatic nuclei and may contain two nuclei (binucleate).
The nuclear cytoplasmic ratio for these cells is ∼1:20 to 1:30.