All are true about cytoplasmic inclusions except:
These are the non-living component of cells and first observed by O F Muller in 1786. They are temporary structures that are metabolically inactive and are not bound by a membrane, unlike other cellular organelles. These inclusions can be secretory granules, pigment granules, neutral fat, lipid droplets, and glycogen. As an exception, secretory granules and pigment granules are surrounded by a membrane whereas lipid droplets and glycogen are not membrane-bound. If present, these structures usually compress the other cell organelles as seen in goblet cells, adipose cells. The density of the inclusions depends on the signaling agents.
Examples of Inclusions:
Glycogen is the most commonly seen in liver and striated cells. Under an electron microscope, they appear as granules of 25-30nm diameter in the form of clusters or a rosette near the smooth endoplasmic reticulum.
2. Lipid inclusion:
Also known as "fat droplets" where the lipids are stored in the form of triglycerides in adipocytes, hepatocytes.
3. Crystalline inclusions:
These are found in Sertoli and Leydig cells of the testis and lesser extent in macrophages. These are crystalline forms of proteins and are found in all parts of the cell inclusion nucleus and cytoplasmic organelle.
The most common pigments are hemoglobin followed by melanin and lipofuscin. Melanin is seen in the melanocytes of skin, hair, retina, substantia nigra of the brain. Cardiac and central nervous tissue show brown pigment called lipofuscin.