Columnar epithelium

Image of a section of stratified cylindrical epithelium. The nuclei of the cells are seen at different levels (strates). Under the optical microscope. Ink with HyE.

The column epithelium or column epithelium is a type of lining epithelium made up of one or several layers of tall cells, which lines the inner surface of hollow or tubular organs such as the intestine, the exocrine glands, the fallopian tubes, the stomach, the gallbladder and the appendix. It has absorptive and secretory functions. Its cells have modifications in the apical end (microvillus and cilia) and also in the basolateral region. The main functions of this epithelium are absorption and secretion.

Classification

Based on its function, this is a lining epithelium. Lines the inner surface of tubular organs such as the intestine, formerly known as the mucous membrane.
The surfaces covered by this epithelium are: gastric mucosa, intestinal mucosa, gallbladder mucosa, uterine tubes, endometrium, glandular interlobular ducts, seminal vesicles, and bulbourethral glands.

Morphology

The simple columnar epithelium is made up of cells in which the height predominates over the width and thickness. The shape of its nuclei is oval, it is located in the basal third. They have modifications at their apical end, they are the microvilli and the cilia.

Function

Its functions are absorption and secretion, for example, the lining of the digestive tract from the cardia, in the stomach, to the anus, gallbladder and major ducts of the glands. Columnar cells have an ovoid nucleus at the same level. They may have a ridged edge or microvilli.
The simple columnar epithelium lining the uterus, oviducts, vas deferens, small bronchioles, and paranasal sinuses is ciliated.
The columnar epithelium has microvilli to enhance absorption.

Types of columnar (columnar) epithelium

There are different types of columnar or columnar epithelium depending on their histological characteristics:

Simple columnar epithelium

Simple spinal epithelium. Schematic drawing.

A characteristic example of simple epithelium is the mucosal surface of the intestine. Its thickness is a single cell. This cell is tall and for this reason it is also called columnar or prismatic epithelium. Their ovoid nuclei are level with the basal part.
Adjacent columnar cells adhere by tight junctions. These tight junctions separate the cell membrane into two sectors or domains: the apical and the basolateral. Thus, tight junctions ensure cell polarization and selective transepithelial transport. The apical domain with microvilli is also called brush border or striated plate.
This type of epithelium forms the lining of the intestine from the cardia to the anus. It is also found in the gallbladder and the greater ducts of accessory exocrine glands.

Another special example of simple columnar epithelium is that of the tube of the uterus. It is made up of ciliated cells and other non-ciliated cells. These cells show phases in their function, which are determined by the ovarian cycle. The increase in estrogen causes the generation of cilia, while the subsequent rise in progesterone increases the number of secreting cells.

Pseudostratified ciliated columnar epithelium

Cells of the pseudo-estratified spinal epithelium of bronchus.

Seudo-estratified column.

Its appearance is identical to nonciliated columnar epithelium in low-magnification preparations, but the cell-free surface is covered with cilia.
It lines the uterus and fallopian tubes, the efferent ducts of the testes, the small intrapulmonary bronchi, and the ependymal duct of the spinal cord.

Glandular columnar epithelium

File:406_Types_of_Glands.jpg

Exocrine gland.

It is characteristic of exocrine glands.