Simple Epithelial Tissue

A simple epithelium can be defined as an epithelia tissue that is made up of only one thin layer of epithelial cells. The cells of this kind of epithelium are very thin and arranged in a single layer. All the cells of simple epithelial tissue are rested on the basement membrane. The main function of simple epithelial tissue is absorption and filtration.

Types of Simple Epithelial Tissue

According to the form and structure of cells, the simple epithelial tissue is further divided into many subtypes.

1. Simple Squamous Epithelium

Structure: It is composed of thin flat cells, arranged like the tiles in a floor like that of a pavement, hence is called a membrane. The cells of squamous epithelia have a central nucleus with a little matrix. Polygon shape and have high regenerating power.

Location: This epithelium forms the peritoneal lining of the coelom and the endothelium, which line the inner surface of blood vessels. It also forms the inner lining of the heart, lungs alveoli, the outer and inner layer of Bowman’s capsule, membranous labyrinth, the internal wall of the cheek, etc.

Function: Its main function is to protect the internal musculature of the body. In respiratory surfaces such as the lining of the lungs or the skin of a frog are only one cell thick so that gases can pass through quickly.

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2. Simple Cuboidal Epithelium

Structure: It consists, as the name implies of cube-like cells or the cells that are more or fewer squares in shape. These appear to be polygonal in surface view. The nucleus is rounded and central.

Location: It is found in the lining of salivary glands, sweat glands, respiratory bronchioles, and thyroid follicles. It also lines the ovary and seminiferous tubules of the testis as germinal epithelium because it produces ova and sperms. The free surface of cells of cuboidal epithelium often gives a brush-like appearance called brush bordered cuboidal epithelium or microvilli, found in the small intestine.

Function: In the lining of glands it acts as secretory cells. It’s the lining of the ovary and testis help in the formation of gametes; as microvilli, it increases the absorptive area.

3. Simple Columnar Epithelium

Structure: It consists of tall pillar-like narrow cells, which are placed side by side like columns. Each cell has an oval nucleus, at basal ends. All the cells rest on a thin basement membrane.

Location: The intestinal and gastric glands are lined by columnar cells containing mitochondria, which actively secrete digestive enzymes. It also lines the gall bladder, bile duct, pancreatic lobules, etc. the mucosal lining of the stomach and intestine consist of certain mucus-secreting columnar cells called goblet cells. These cells produce a slimy substance that forms a protective layer on the mucosal epithelium.

Function: It secretes mucus to protect the lining and lubricates the passage. It also helps in partial absorption of nutrients, etc.

4. Simple Ciliated Epithelium

Structure: They are the modification of columnar or cuboidal cells bearing numerous protoplasmic, hairs like cilia on their free surface. The cilia are arising from basal granules. The cilia can move back and forth rhythmically, producing a very peculiar, ciliary motion. In between the ciliated cells are found glands cells, secreting mucus.

Location: This epithelium lines most of the respiratory tract; fallopian tubes and certain parts of the nephron of the kidney. It is also present in the tympanic cavity and eustachian tube.

Function: The ciliated columnar epithelium helps to flow the fluids in fallopian tubes and certain nephrons in a particular direction. In the mucus membrane of the respiratory tract where the movement of the cilia serves to remove foreign particles. In tympanic cavity and eustachian tube prevents the entrance of dust particles or other harmful substances.

5. Pseudo-Straight Epithelium

Structure: A single layer of columnar cells is present but some cells are shorter than other cells. The long cells are shorter than other free surfaces and the short cells do not reach the outer free surface. The long cells have oval nuclei, but short cells have rounded nuclei. This type of arrangement of cells gives the false multilayered appearance hence it is called the pseudo-stratified epithelium.

Location: Pseudo-stratified epithelium found in the urethra of human male and parotid salivary glands. The ciliated pseudo-stratified epithelium line the trachea and primary bronchi.

Function: Its secretion helps in the removal of mucus laden with bacteria and dust particles.

Thus simple epithelium tissue is a one-layered epithelium tissue. The study of this layer is very important for clinical purposes. Changes in these types of tissue can cause adverse effects in our body. Dysplasia, Neoplasms, Metaplasia, etc are some abnormal changes in tissue. If this content is helpful for you then please say something about this content in the comment section. Feel free to comment if you have any confusion.

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