In histology, the bulk, functional tissue of an organ is known as:

• A. Cortex
• B. Parenchyma
• C. Substratum
• D. Epithelium

Answer: (B)

The functional, bulk tissue of an organ is called parenchyma. Parenchyma consists of the specific cells that perform the organ’s main activities—such as hepatocytes carrying out metabolism in the liver or nephron components doing filtration in the kidney. Surrounding this functional tissue is the stroma, the supportive framework made up of connective tissue, blood vessels, and nerves that hold things together but don’t carry out the organ’s primary work. For comparison, the cortex refers to an outer region of some organs, not the entire functional tissue; epithelium is the covering or lining tissue (and glands) rather than the organ’s main active tissue; substratum isn’t the standard term used for the bulk functional tissue.