The Squamous epithelial cells Are thin, flat cells found in layers or sheets that cover surfaces such as the skin and the lining of blood vessels and the esophagus.
Epithelia are tissues consisting of cells closely juxtaposed without intervening intercellular substances. Epithelia are avascular, but all epithelia"grow"in an underlying layer of vascular connective tissue. The connective tissue and epithelium are separated by a basement membrane and cover all free surfaces of the body.
Epithelium are also lines of the great internal cavities of the body, in which it is called mesothelium. In addition, the inner surfaces of blood vessels and lymphatics are lined by epithelium, here called endothelium.
Epithelia are classified on the basis of the number of cell layers and the shape of the cells in the surface layer. If there is only one layer of cells in the epithelium, it is called simple; If there are two or more layers of cells, it is called stratified; And cells in the surface layer are generally described according to their height as squamous (scalars or plaques), cuboidal or columnar.
Squamous epithelial cells are flatter cells compared to rectangular (columnar) and square (cubic) cells. They are found in many parts of the body, including the cervix, layers of the skin, mouth and lips.
Because of this thin, flat shape, these cells act as good mediators of diffusion and filtration. In this sense, they allow an easy movement of molecules through their membranes.
characteristics
Squamous epithelial cells are typically discrete in cross section, appearing as thin lines with a protrusion in the nucleus.
- A simple squamous epithelium is so thin that it is barely visible by light microscopy.
- A stratified squamous epithelium is quite thick, with squamous cells on the surface coating deeper layers of higher cells.
Simple squamous epithelium
Simple squamous epithelial cells allow easy transmembrane movement of small molecules (ie, through the membrane, and through the cell).
Some molecules, such as oxygen and carbon dioxide, diffuse freely through squamous simple epithelia according to concentration gradients.
Other molecules, such as ions, use channels of transmembrane proteins that diffuse through the cells. Therefore, the types of proteins that are present in a simple squamous epithelial tissue given, determines the function of that tissue.
In summary, it helps determine what is able to move from the lumen and into the capillary bed that is in the basement membrane, and vice versa.
Stratified squamous epithelium
Although this epithelium is called squamous, many cells within the layers can not be flattened. This is due to the agreement to name epithelia according to the type of cell on the surface.
In the deeper layers, these cells may be columnar or cuboidal. There are no intercellular spaces. This type of epithelium is well suited for areas of the body subjected to constant abrasion as it is the thickest and the layers can be sequentially detached and replaced before the basement membrane is exposed.
The stratified squamous epithelium forms the outermost layer of the skin and the inner lining of the mouth, esophagus and vagina.
Difference between transitional epithelial cells and squamous epithelial cells
Transitional epithelial cells are found in the ureters, the bladder, and the urethra. Its shape is variable in the original location (round or ovoid), however, the cells will become flat if they are stretching.
In contrast the squamous epithelial cells are different from the previous type of epithelial cells since they have larger size, their nuclei are smaller, and the border of the cells is irregular.
Diseases
In general, when contamination of a urine sample occurs the presence of squamous epithelial cells is evidenced. However, there could be some worrying if these cells increase in quantity because it can sometimes be related to cancer such as squamous cell carcinoma or urothelial carcinoma.
Thus, these cells are affected by squamous cell carcinoma, the most common type of cancer of the oral cavity. This type of cancer also occurs in the cervix and the skin.
Abnormal results from pap smears have indicated abnormalities in squamous epithelial cells in the cervix. This means that the cells have developed an anomaly, but they are not yet cancerous.
Although many people think that epithelial cells are only on the skin, the truth is that they are also present in the deepest layers of the body. Since squamous epithelial cells are flat and thin, they have a large surface area, in fact they are the thinnest of all types of epithelial cells.
Another rare but rare disease is squamous cell thyroid carcinoma (SCTC) which is a rare malignant neoplasm of the thyroid gland where tumor cells are shown with distinct squamous differentiation. SCTC occurs in less than 1% of thyroid malignancies.
Squamous epithelial cells are not localized in the normal thyroid, so the origin of SCTC is not clear yet, although it could originate from the embryonic remains such as the thyroglossal duct or the clefts of the branches. The primary STCT is usually diagnosed in both lobes of the thyroid gland.
Sufferers often show dyspnea, dysphagia, voice changes, and local neck pain. The treatment for SCT is thyroidectomy and neck dissection, as they have shown good results in the early stages of SCTC.
However, since the phenotype is extremely aggressive, the surgical procedure is not always feasible. SCTC is a tumor that is reluctant to radioiodine. Radiation therapy may be effective in some cases, resulting in a quality of life and a partially better survival rate.
References
- School of Anatomy and Human Biology - The University of Western Australia (2009).
- MI Syed; M Stewart; S Syed; S Dahill; C Adams; DR Mclellan; LJ Clark (2011).
- Booya F, TJ Sebo, Kasperbauer JL, Fatourechi V (2006).
- Introduction to the Human Body. The Essentials of Anatomy and Physiology (9th edition).
- Finazzo, S. (2009). Epithelial tissue.