SIMPLE CUBOIDAL EPITHELIUM: CHARACTERISTICS, FUNCTIONS AND PATHOLOGIES - ANATOMY AND PHYSIOLOGY - 2025

The simple cuboidal epithelium is that epithelium composed of cells whose dimensions are more or less the same; that is, their width, height and length are very similar. In the histological section, these cells look like squares (because the section is two-dimensional), although a 3D view would allow them to be seen as small cubes or dice.

In these cells the nuclei tend to be in the center and with a slight tendency to be located towards the basement membrane. As its name indicates, the simple cuboidal epithelium is made up of a single layer of cells, so they are all in contact with the basement membrane.

Location

In general, it can be said that the simple cuboidal epithelium is found in different glandular structures scattered throughout the body, the only exception to this rule being the eye. In this organ the simple cuboidal epithelium is found in:

- The posterior epithelium of the cornea.

- Immediately behind the anterior capsule of the lens (which it supports).

- The pigment epithelium of the retina (where it fulfills very important metabolic functions for the eye).

For its part, in glandular locations, the simple cuboidal epithelium can be found as part of the lining of the excretory ducts (such as in the kidney) or as part of the excretory or secretory units of the glands, as is the case of the gland. thyroid and mammary gland.

These glandular locations can also be part of protective membranes, as in the case of the ovaries and testis.

characteristics

The characteristics of the cells that make up the simple cuboidal epithelium can vary depending on their location and function; therefore, the histological features can be divided into features common to all simple cuboidal epithelia and specialized features.

Characteristics common to all simple cuboidal epithelia

Simple cuboidal epithelia share certain common morphological features that allow them to be classified as such, regardless of the area in which they are found and the function they fulfill.

Spatial arrangement

All the cells of the simple cuboidal epithelium are located side by side and their basal end comes into contact with the basement membrane; it is therefore a monolayer epithelium.

Morphology

The cells that make up the simple cuboidal epithelium resemble a cube; that is, its three axes (height, length and width) have more or less the same measure. The nucleus is located more or less in the center of the cell, a little below its equator, towards the basement membrane.

Cell junctions

A very important characteristic of simple cuboidal epithelia is that the cell junctions are very tight, of the type known as tight junctions. This is essential so that they can fulfill the secretion / absorption functions for which they are mostly responsible.

Specialized Features

Although most of the simple cuboidal epithelia are part of the glands or their excretory ducts -being in this location where they can perform the function for which they are designed-, those cubic epithelial cells located in special locations present modifications that allow them to carry carry out their duties.

In this way, the cells of the retinal pigment epithelium contain a large amount of pigment in their cytoplasm; Furthermore, they are metabolically very active and have highly specialized ion transport mechanisms, vital in the physiology of the retina.

For their part, the cells that make up the simple cuboidal epithelium that lines the inner surface of the bronchioles have cilia on their apical edge. This allows the mobilization of the secretions that are produced at that level.

Features

The functions of the simple cuboidal epithelium vary depending on the anatomical location and cell specialization; however, they can be divided into four main functions: secretion / excretion, absorption, protection, and specialized functions.

Secretion / excretion

As they are part of the glands, the simple cuboidal epithelia can have a secretory function (in the case of endocrine glands) or a secretory function (exocrine glands).

The classic and best-known example of the secretory simple cuboidal epithelium is the thyroid gland, whose follicles are composed of simple cuboidal epithelium. These cells are specialized in the synthesis of thyroid hormones, being the functional base of the gland.

The same occurs in the mammary gland, where the simple cuboidal epithelium is part of the mammary lobule, this being the portion where milk is produced and excreted.

However, unlike the thyroid - where the glandular epithelium is always simple cubic - in the mammary gland it can be simple cubic, simple columnar or a combination of both.

Absorption

The classic example of a simple cuboidal epithelium with absorptive capacity is that found in the renal tubules.

As part of the functional complex known as the nephron, the function of the renal tubules is to absorb all the components that were filtered in the glomerulus, but that it is not convenient for them to be lost in their entirety.

Thus, part of the water, ions and electrolytes are reabsorbed at the level of the renal tubules, where there is also a process of active excretion of certain compounds.

At this point, the function of the simple cuboidal epithelium is vital, since it is specialized in absorbing the elements that should not be lost since they have the cellular mechanisms of active transport necessary for active excretion.

Protection

The outer surface of the ovaries, as well as part of the seminiferous tubules, are covered by simple cuboidal epithelium.

In these cases its function is clearly protective, forming a thin cellular layer that protects the underlying structures.

In this sense, the simple cuboidal epithelium is very effective since the tight junctions make this epithelium very resistant, although it has only one layer of cells. In addition, it can regenerate very easily, allowing a very fast recovery from injuries.

Specialized functions

The most specialized simple cuboidal epithelium in the body is found in the eye, forming part of the retinal pigment epithelium.

In this location, the simple cuboidal epithelium fulfills highly specialized metabolic and nutritional functions that allow the viability of the retina; these include:

- Transport of nutrients and water from the capillaries to the cells of the retina.

- Light absorption and, therefore, protection against photo-oxidation.

- Retinol recycling.

Pathologies

Like its function, the pathology of the simple cuboidal epithelium depends on its location in the body. However, it could be said that there is a common pathology to all these epithelia, which present it to a greater or lesser extent: cancer.

Because they are tissues with a relatively high cell replication rate and are exposed to chemical and physical factors, the cells of all epithelia are prone to present mutations that lead to the development of cancer, and simple cuboidal epithelia are no exception.

In this sense, considering the different anatomical locations as well as the frequency of appearance, it can be said that the most common pathology of the simple cuboidal epithelium is thyroid cancer, which has its seat in the follicular cells of the gland (simple cuboidal epithelium)..

Second is lobular carcinoma of the breast (the second most common after ductal), which originates in the breast lobule (composed of simple cuboidal, simple columnar epithelium, or a combination of both).

Finally, there are malignant neoplasms, which can have a seat in the ovary or the kidney, although in these organs the origin of cancer is usually more frequently in other cell groups, although it is not impossible for tumors to develop from simple cuboidal epithelia located in such structures.

References

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