1, microvilli

Also known as villi and villous processes, they are widely found on the surface of animal cells. Under the electron microscope, it can be observed that microvilli are tiny finger-like protrusions protruding from the cell membrane and cytoplasm on the free surface of cells, surrounded by the cell membrane, perpendicular to the cell membrane surface, with a diameter of about 0.65438 0 microns, and the length varies greatly with the cell type or cell physiological state.

It is widely found in animal cells, but it is rich in growing oocytes, epithelial cells of small intestine and renal tubules, sensory cells such as inner ear, nose and lateral lines. The surface of microvilli is plasma membrane and sugar quilt, and the inside is the extension of cytoplasm.

2. Brush edge

The proximal tubule of renal tubule can be divided into curved part (proximal curved tube) and straight part (proximal straight tube). The proximal curved tubule has a brush-like edge on the lumen surface of epithelial cells Under the electron microscope, it can be seen that a large number of long microvilli are arranged in order, which obviously expands the surface area of the free surface of cells. The cell membrane of brush margin is rich in alkaline phosphatase and ATPase, which participate in the reabsorption function of cells.

3, cilia

It is a long, swinging protrusion extending from the free surface of the cell, which is thicker and longer than microvilli and can be seen under the optical microscope. A cell can have hundreds of cilia. The cilia are about 5- 10μ m long and 0.2μm thick, and there is a dense particle at the root, which is called matrix. Cilia have the ability to swing rhythmically in a certain direction.

The coordinated oscillation of many cilia is like the fluctuation of wind-blown wheat waves, pushing secretions and granular substances attached to epithelial surfaces in a certain direction. For example, most of the cavity surface of respiratory tract is ciliated epithelium, which can discharge inhaled dust and bacteria due to the directional swing of cilia.

4. Striped edges

The striated edge refers to the shape of the free surface of intestinal epithelial absorption cells under light microscope, which is similar to the wavy edge. Under the electron microscope, they are composed of dense and regularly arranged microvilli, and each absorbing cell has 2000-3000 cells, which looks like a wavy edge under the optical microscope.

5, static cilia

One of the hair cell cilia of vestibular organs. It plays a direct role in depolarization and hyperpolarization of hair cells in vestibular organs.