What is stratified squamous epithelium?

Our skin is very strong because it has relatively strong resistance, which makes the human body not easily affected by external factors. From a medical point of view, human skin is divided into different types. Of course, the concept of "type" is rather vague. For example, stratified squamous epithelium is a type of skin. So, what kind of skin is stratified squamous epithelium?

The stratified squamous epithelium has many cell layers, and only the cells on the surface are flat, so it is called stratified squamous epithelium. The basal cells located in the deepest layer are short columnar or cubical. They are a layer of stem cells with the ability to proliferate and differentiate. They can proliferate new cells through mitosis and continuously replenish the cells shed from the surface layer. The cells in the middle layers are polygonal and have spiny cytoplasmic processes, which connect with the processes of adjacent cells through desmosomes to form intercellular bridges. Moving from the middle cell layer to the surface layer, the cell shape gradually changes from polygonal to flat. Stratified squamous epithelium is mainly distributed in the skin, mouth, esophagus and vagina. This epithelium is thicker, more friction-resistant, and has a mechanical protective effect.

The stratified squamous epithelium distributed in the epidermis of the skin has superficial cells whose nuclei disappear, and the cytoplasm is filled with keratin (i.e. keratinization). The cells are dry and hard, and have strong tolerance to friction and damage. The stratified squamous epithelium distributed in the oral cavity, esophagus, and vaginal mucosa has surface cells that are not keratinized, have nuclei, and have less keratin in the cytoplasm. Stratified squamous epithelium has strong regeneration and repair capabilities.

Stratified squamous epithelium test

Stratified squamous epithelium: Section 65

Cross-section of pig esophagus, fixed with Bouin's solution, sectioned in paraffin, and stained with HE.

First use a low-power microscope to find the lumen of the esophagus. There are mucosal epithelia of varying thicknesses on the surface of the lumen. Select a portion of the thinner mucosal epithelium and switch to a high-power microscope for observation.

Move the slice to find the junction of the epithelium and connective tissue. You can see that the most basic epithelial cells are mostly short columnar, arranged relatively neatly, and have oblong nuclei. The cells in the middle are polygonal with round or oval nuclei. The cells near the surface gradually become flattened and spindle-shaped or flat. The cells in the shallow layer still have nuclei and are non-keratinized stratified flat cells.