Understanding Membrane Terminology

Learning Objectives:

  1. Understand the key terms related to membranes and their roles in body function and organization.
  2. Recognize the differences and similarities between various types of membranes.
  3. Appreciate the role of mucous membranes in the protection and functioning of body cavities open to the outside.
  4. Comprehend how membranes contribute to the protection, separation, and support of body structures.
  5. Familiarize with the functions of specific membranes like the dura mater, basement membrane, cell membrane, and myelin sheath.

Membranes are vital to the physiological organization of the body, serving as intricate networks that compartmentalize interstitial fluid and create fluid pressure pockets. These pockets play key roles in the body’s function, but when imbalanced, can lead to conditions of pain and mobility restrictions. With a comprehensive understanding of membrane anatomy and physiology in the context of pressurized fluid pathology, therapists can better discern and target areas of concern, facilitating the release of pressurized fluid pockets through focused therapeutic methods. This knowledge, which involves identifying and defining key membrane-related terms, is crucial for a more in-depth appreciation of their role in health and disease.

  1. Layer: In membranes, a layer denotes a single level of material or substance. Membranes often comprise several layers, each comprising different types of cells and substances contributing to overall function.
  2. Lamina: A thin layer, plate, or scale of sedimentary rock, organic tissue, or other material. In membranes, it refers to the thin layers forming the membrane structure.
  3. Lining: A layer of different material that covers the interior surface of a structure, such as an organ or vessel. For example, the stomach’s lining is a protective mucous membrane.
  4. Septa (singular: septum): These are walls or divisions between cavities or masses of tissue. They can be membrane-like structures separating different areas within an organ or body cavity.
  5. Sac: A hollow, bag-like structure in the body, containing fluid, air, or other substances. The amniotic sac, for instance, holds the amniotic fluid and the developing fetus in utero.
  6. Sheet: Refers to a flat, thin piece of membrane covering a surface or dividing a space.
  7. Dura Mater: The outermost layer of the meninges, the three membranes surrounding the brain and spinal cord. This thick, durable membrane lies closest to the skull and vertebrae.
  8. Lobules: Smaller divisions within a lobe of an organ, typically separated by a thin layer of tissue (often a membrane-like structure). The liver, composed of thousands of lobules, serves as an example.
  9. Mucous Membranes (Mucosae): These epithelial tissues line body cavities opening to the outside, such as the digestive, respiratory, urinary, and reproductive tracts. Mucous membranes secrete mucus, a viscous fluid that lubricates, protects, and often aids in the transport of substances. For example, the mucous membrane in the respiratory tract traps dust particles, while that in the digestive tract aids the passage of food.
  10. Serous Membranes (Serosae): These line the closed, internal body cavities and cover the organs within these cavities, providing lubrication that reduces friction from muscle movement.
  11. Cutaneous Membrane (Skin): The body’s outer covering and the largest membrane.
  12. Synovial Membranes: These line the cavities of joints, tendon sheaths, and bursae (small fluid-filled sacs), reducing friction between body parts during movement.
  13. Basement Membrane: A thin, fibrous membrane that separates the epithelium from the underlying connective tissue.
  14. Cell Membrane (or Plasma Membrane): A semipermeable membrane surrounding the cytoplasm of a cell.
  15. Nuclear Membrane (or Nuclear Envelope): A double membrane structure that surrounds the nucleus in eukaryotic cells.
  16. Myelin Sheath: In the nervous system, this protective layer or membrane surrounds the axons of many neurons, aiding in the speedy transmission of neural signals.


  1. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2014). Molecular Biology of the Cell (6th ed.). Garland Science.
  2. Saladin, K. (2018). Anatomy & Physiology: The Unity of Form and Function (8th ed.). McGraw-Hill Education.
  3. Tortora, G., Derrickson, B. (2017). Principles of Anatomy and Physiology (15th ed.). Wiley.