Page 39 - Headlines Histology2024_Neat

or heart failure cells in lung alveoli; Kupffer cells in liver, and microglia
in the central nervous system.

3. Pericytes

• Pericytes are elongated connective tissue cells with long cytoplasmic
processes located external to the endothelium of blood capillaries and
small venules.

• They share a common basal lamina with the adjacent endothelial cells.
• They have a fusiform nucleus and scanty cytoplasm that contains many

mitochondria, rER, free ribosomes, and small Golgi complex.
Functions

• The pericytes are undifferentiated cells; they serve as progenitor for
fibroblasts, osteocytes, chondrocytes and smooth muscle cells.

4. Fibroblasts and fibrocytes

• Fibroblasts or fiber-forming cells are the most common type of fixed
connective tissue cells.

• Active fibroblasts are demonstrated in healing wounds. They have large
ovoid lightly stained nuclei with prominent nucleoli.

• The cytoplasm is extensive and strongly basophilic with numerous
interconnected cytoplasmic extensions.

• At the EM level, the cytoplasm is rich in rER and the Golgi apparatus is
well developed.

• The inactive fibroblasts (fibrocytes) are smaller and appear spindle in
shape with fewer processes.

• At the EM level, the small quantities of cytoplasm contain sparse
network of rER, poorly developed Golgi and few organelles.

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