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18. What is the difference between basal lamina and basement membrane? 19. What are the steps of tissue preparation for light microscopy?
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18. The basal lamina and basement membrane are both extracellular matrices that provide structural support to cells, but they have some key differences:- Basal lamina: It is a thin, sheet-like structure that is secreted by the epithelial cells and the underlying connective tissue. It is composed of glycoproteins, such as laminin and collagen, and provides a foundation for the epithelial cells to attach to. The basal lamina is a component of the basement membrane.- Basement membrane: It is a thicker, more complex structure that consists of the basal lamina, the reticular lamina, and the lamina densa. The basement membrane provides additional structural support and helps to separate the epithelial tissue from the underlying connective tissue. It also plays a role in tissue repair and development.19. The steps of tissue preparation for light microscopy are as follows:1. Fixation: The tissue sample is fixed in a fixative, such as formalin, to preserve its structure and prevent degradation.2. Dehydration: The tissue is dehydrated by gradually replacing the water in the tissue with ethanol or acetone.3. Clearing: The dehydrated tissue is then cleared by replacing the ethanol or acetone with a clearing agent, such as xylene or benzene.4. Embedding: The cleared tissue is embedded in a solid medium, such as paraffin wax or resin, to provide support and facilitate thin sectioning.5. Sectioning: The embedded tissue is cut into thin sections, typically 3-10 micrometers thick, using a microtome.6. Staining: The tissue sections are stained with one or more dyes to enhance the contrast and highlight specific cellular structures.7. Mounting: The stained tissue sections are mounted on a glass slide and covered with a coverslip.8. Examination: The prepared tissue slides are examined under a light microscope to study the cellular structures and organization.