PAVING CELLS: CHARACTERISTICS, FUNCTIONS, ANALYTICS - BIOLOGY - 2025

The squamous cells are epithelial cells with large nuclei and coating large amount of cytoplasm. These cells are present in almost all tissues of eukaryotic organisms. In animals, squamous cells form the lining epithelial tissue that lines the outer body surface, internal organs, and ducts.

Pavement cells are easy to identify under the microscope using silver nitrate, as they appear with a typical ordered mosaic appearance composed of hexagonal cells with irregular contours.

Anatomy of the skin. Paving cells are part of the epidermis (Source: Wong, DJ and Chang, HY Skin tissue engineering (March 31, 2009), StemBook, ed. The Stem Cell Research Community, StemBook, doi / 10.3824 / stembook.1.44.1, http://www.stembook.org. via Wikimedia Commons)

Typical pavement cells have a very thin and elongated cytoplasm, distributed longitudinally with a central bulge where the nucleus is located. These cells have the appearance of a spaceship or flying saucer.

The skin is made up almost entirely of paving cells, where they perform protection functions, increase the number of cells, secretion and perception and detection of external stimuli.

characteristics

Paving cells are classified into three types according to the anatomical area they occupy, their topological and morphological characteristics. The three known types of pavement cells are:

- Flat paving cells: they are elongated with large nuclei. They are found in the blood and lymphatic vessels, kidney, heart, and lungs.

- Cubic squamous cells: they have a large amount of cytoplasm and are involved in the secretory functions of tissues. These line the ovaries, the oral cavity, the esophagus, the anus and some areas of the brain.

- Prismatic paving cells: found in the basal laminae of the tissue, they may have cilia to facilitate transport. These cells make up almost all the glands in the body.

In animals, squamous cells are part of monostratified, pseudostratified, and multilayered epithelial tissue.

In monostratified epithelial tissue, squamous cells form a thin layer organized in rows of cells, this being the most superficial portion of the tissue.

The pseudostratified tissue is composed exclusively of a single layer of squamous epithelial cells, which are found in a disorderly manner.

Paving cells in polylayer epithelial tissue are stacked in layers of axially elongated cells, almost completely flat. In this epithelium, cells are closely adhered to each other and arranged in several layers on the basement membrane.

Features

Paving cells act as a protective barrier that prevents the entry of pathogenic microorganisms into our body. These cells are part of our primary immune system, protecting us from external aggressions and mechanical trauma.

Paving cells regulate the degree of hydration and the loss of water by evaporation. In serous cavities, the lining with these cells facilitates the movement of the viscera and food.

In the endotheliums of the blood vessels, the squamous cells allow the diffusion of water and ions by active transport (pinocytosis), and at the same time prevent the entry of macromolecules into the tissue.

In women, squamous cells are part of the cervix, vagina, vulva, and vaginal secretions. The gynecological study of these cells is of great informative value to know the health of the reproductive organ.

Some of these cells are endowed with nerve endings and serve an important sensory function in the reproductive organs.

In organisms such as teleost fish (trout), it has been proposed that squamous cells are directly involved in the ion transport of sodium, which is actively diffused by flat squamous cells.

Meaning in analytics

Pavement cell screening is a common technique for finding vesicular skin pathologies in stratified epithelium. Squamous cells with secretory functions are highly susceptible to viral and bacterial infections.

In women, the squamous cells shed in a cyclical way, depending on the variable hormonal levels and according to the stage of the organism's life cycle.

It is customary to study vaginal squamous cells using the Papanicolaou staining method, introduced by Dr. GN Papanicolaou in 1942. This method relates cell type morphology with endocrinology and histology.

Cytological studies of the squamous epithelial cells of the uterine area allow to determine if there is the presence of the Human Papilloma Virus (HPV).

The identification of morphological changes in pavenous cells provides useful information for the cytodiagnosis of cancer, allowing to differentiate preneoplastic and neoplastic alterations.

Anomalies

Paving cells can present mild alterations, benign abnormalities, inflammatory and reactive changes. These alterations can be the product of the normal behavior of the organism or they can be related to pathological disorders and relevant diseases.

Minor alterations

Paving cells have normal phenotypic growths and masses mediated by hormones, which modify their texture, degree of secretion and metabolism. These changes can be typical of tissue aging.

Benign abnormalities

Benign abnormalities may include mild inflammation, an increase or decrease in the number of epithelial squamous cells, and rarely scarification or keratinization of the epithelial cells.

Inflammatory abnormalities

Inflammatory abnormalities in squamous cells are identified in the nucleus, which implies a decrease or loss of cellular activity. This decrease in cell activity typically leads to cell death by necrosis.

Typical inflammatory abnormalities include:

1. Increase in the number and size of the chromocentres, which decreases the amount of euchromatin and gives the nucleus a blurry appearance. Commonly this process occurs due to the denaturation of histones, which leads to chromosomal instability.
2. Thickening of the nuclear membrane due to an excessive concentration of heterochromatin.
3. Increase in cell volume due to the alteration in the mechanism that controls the exchange of sodium and potassium.
4. Cytoplasmic modifications product of vacuolization, which occurs due to the rupture of the vesicular membranes that have a high enzyme content.
5. Changes in cell staining due to denaturation of structural proteins.
6. Undefined or imprecise cell borders as a result of the lysis of the plasma membrane.
7. Perinuclear halos, which occur due to protein denaturation and loss of the cytoskeleton.

There are inflammatory abnormalities that are directly related to certain pathologies. Among these are the presence of deep cells and atrophic colpitis or vaginitis.

Deep cells in women of childbearing age are normal, as they are the product of menstrual cycles that exfoliate the squamous cells of the cervix and vagina. However, its existence in infants and elderly women is related to diseases.

These diseases include some severe inflammatory reactions in the cervix and vagina, damage to the reproductive system, hormonal imbalances, or the presence of pathogenic agents.

Atrophic Colpitis is caused by the disappearance of layers of pavement cells during differentiation, reducing the epithelia to a few rows of parabasal cells.

The reduction in the differentiation of the epithelia is the product of hypoestrogenism, since this stops the mechanisms of cell division and differentiation.

Reactive changes

Reactive changes are generally benign and are associated with abnormalities that clinicians cannot accurately define on cytologic examinations. However, these changes can appear when there are infections or other irritations.

References

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