Location, Structure, and Function of the Simple Cuboidal Epithelium

Simple Cuboidal Epithelium: Location, Structure, and Function
The main function of a simple cuboidal epithelium is the production or absorption of substances. But that's not all. Bodytomy tells you more about this tissue, such as its definition, location, structure, and other characteristics.
Did You Know?
All the surfaces of our body, except the teeth and joints, are covered with some type of epithelium.
Our bodies are made up of different types of tissues or materials. These include the bones and blood (connective tissue), different types of muscles (muscle tissue), and the brain, nerves, and spinal cord (nervous tissue). However, the surface of our body needs to be protected from elements like sunlight and wind, and so do our delicate organs which are located in empty spaces. At the same time, the body needs to control which substances are present inside it, and which are being removed. All these roles are played by a kind of thin tissue called the 'epithelium.' However, this epithelium may be made of a single layer of cells called simple epithelium, or several layers called stratified epithelium. In the following sections, we will learn about a type of simple epithelium, called the simple cuboidal epithelium.
A simple cuboidal epithelium is a tissue made up of cube-shaped cells, which is involved in secreting (producing and releasing) and absorbing substances in various glands and ducts throughout the body.
► The simple cuboidal epithelium is mostly found in the lining of glands (organs that produce substances), and is not common on exposed surfaces.

► It is also found in the ducts that transport the secretions produced by a gland to the organ it is intended for, such as in ducts connecting salivary glands to the mouth, sweat glands to the skin, and so on.
► The simple cuboidal epithelium is found in the following locations.
  • Kidney tubules
  • Ducts of salivary glands
  • Ducts of sweat glands
  • Bile duct
  • Follicles of thyroid gland
  • Pancreas
  • Liver
  • Mammary glands
  • Covering of the lens
  • Germinal epithelium of ovaries and testes
  • Choroid plexus (network of blood vessels in the brain)
  • Lining of bronchioles (air tubes in lungs)
Simple cuboidal epithelium
  • Being a 'simple' epithelium, it has a single layer of cells.
  • Cells are cube-shaped, though from the top they appear like polygons or hexagons, and appear square-shaped from the side.
  • Cells are as wide as they are tall, which means that the distance between adjacent nuclei is equal to the height of the cells.
  • The nuclei are spherical, and located at the center of the cells, or slightly towards the base.
  • All the cells are directly attached to a thin layer called the basement membrane, which is placed on a connective tissue.
  • The cell membranes may not be visible in cases where they merge with each other (called 'interdigitation').
  • In some cases, cuboidal cells may have small projections called 'microvilli' at the top.
It is located in ducts (tubes) of glands that perform secretion, absorption, or both. Examples of secretion include the thyroid gland, which secretes the thyroid hormone directly into the blood stream (called endocrine gland). Secretion is also performed by the ducts of the sweat and salivary glands, which release their fluids into ducts (called exocrine gland). The tubules found in the kidneys use the simple cuboidal epithelium to perform both, absorption and secretion of substances.
It may be designed to act like a semipermeable membrane, i.e., allow some substances to pass through and block others, or perform active transport (transport materials from where they are less common to regions where they are more common). Being taller than the simple squamous epithelium means that they have more control over substances that diffuse through them.

It offers some protection against abrasion, foreign particles, harmful bacteria, chemical stress, and excessive water loss (because of its semipermeable nature).
Simple cuboidal epithelium also covers the lens of the eye, where it controls the movement of nutrients and water, into and out of the lens from the surrounding eye fluid. This ensures that the amount of substances in the lens, and its size, are maintained.
The cells of this epithelium are larger than other epithelia, because they have a higher number of cell organelles (specialized structures), like mitochondria, ribosomes, and Golgi bodies, thus resulting in a larger cell. These organelles are required to produce and package large molecules, like proteins and glycoproteins, or process substances absorbed by the cell. The cuboidal shape of the cells allows their close packing, which enables fluids to pass through tubes lined by them.
Most secretory cells, which are the actual parts of glands that produce substances, are part of a simple cuboidal epithelium. It is present in the convoluted tubules and collecting duct, which are parts of minute units of the kidney, called 'nephrons'. Here, they help in the formation of urine, by secreting and absorbing substances which are filtered by the kidneys. Its semipermeable nature also comes in handy.
The germinal epithelium that covers the ovary is also a type of simple cuboidal epithelium, and so is the germinal epithelium in the testes (in the seminiferous tubule). In the ovary, this epithelium plays an important role in the development and release of the egg from the ovary, and hence its name (germ cell = egg). In the testes, this layer plays an important role in the development of sperms.
The importance of the simple cuboidal epithelium is clear by its widespread presence in our body. It plays a role in everything, right from simple tasks like producing sweat, to more complex ones like filtering substances in the kidneys and producing germ cells in the body.