Glandular epithelium

Glandular epithelium, also known as glandular tissue, is a kind of epithelial tissue that produces and releases a variety of secretory products, including perspiration, saliva, breast milk, digestive enzymes, and hormones, among others. Glandular epithelium is organised into glands, which can be a single cell or a group of cells that specialise in manufacturing and releasing a particular material. 

Along with connective tissue, muscular tissue, and nerve tissue, epithelial tissue is one of the four primary tissues present in the human body. The basement membrane, a thin film of collagen that provides structure to the epithelium, separates one or more layers of epithelial cells from the underlying connective tissue in epithelial tissues. Most of the body’s exterior and interior surfaces, including the skin, urogenital system, digestive and respiratory systems, are covered by epithelium. Non-secretory surface epithelium (e.g. stratified epithelium), which acts as a protective layer against external and interior invaders, and secretory glandular epithelium, which serves as a protective layer against external and internal invaders, are the two types of epithelial tissue.

Formation of glandular epithelium

The growth of epithelial cells into the connective tissue beneath the epithelium forms the glandular epithelium throughout foetal life. A tube termed a duct connects all glands to the surface epithelium at first. However, depending on the existence or lack of ducts, each gland will subsequently develop into exocrine or endocrine glands.

Exocrine glands have a secretory component and a duct that distributes secretory products into an epithelial surface, such as the skin or the gastrointestinal and respiratory tracts. Endocrine glands, on the other hand, lack ducts and instead release their secretory products, or hormones, into surrounding blood arteries, from which they travel to various areas of the body.

Glandular Epithelium in human body

The secretory section of glands, which creates and secretes the secretory substance, is made up mostly of glandular epithelium. A gland can be a single secretory cell, as the goblet cells in the digestive and respiratory tracts, or a collection of secretory cells that comprise a larger gland.

The salivary glands (e.g., parotid gland, submandibular gland, and sublingual gland), which emit saliva and digestive enzymes; sweat glands on the skin, which secrete sweat; and the lacrimal glands of the eyes, which shed tears, are some of the larger exocrine glands. Furthermore, glandular epithelium is a secretory layer of cells that lines the interior of an entire organ, such as the stomach.

Endocrine glands, which are ductless glands that produce hormones into the blood, contain glandular epithelium. The pituitary gland, which is positioned at the base of the brain, the thyroid gland, which is placed in the neck, and the adrenal glands, which are located on top of the kidneys, are among them. The pancreas is a unique gland because it has both an exocrine component that secretes digestive enzymes and an endocrine portion that secretes many hormones, including insulin and glucagon.

Role of Glandular Epithelium in the body

The glandular epithelium’s primary role is to create and release a variety of secretory products, including perspiration, saliva, breast milk, digestive enzymes, and hormones, among others. These substances are usually kept in tiny membrane-bound vesicles that are later released from the cell. Specialised contractile cells (myoepithelial cells) are found in many glands and assist squeeze secretory products into the extracellular space.

Glands are categorised as merocrine, holocrine, or apocrine according to how they secrete. The most frequent kind of secretion is merocrine secretion, which includes the release of secretory vesicles into the extracellular space without causing harm to the cell. Holocrine secretion, on the other hand, entails the death of a whole cell and the subsequent release of its contents. 

One of the few holocrine glands in the body, sebaceous glands create oils for the skin and hair follicles. Apocrine secretion includes the discharge of secretory vesicles, as well as a tiny amount of the cell, from the cell membrane. Apocrine secretion includes sweat glands in the underarm and vaginal region, as well as lactating mammary glands in the breasts.

Conclusion

The glandular epithelium is an epithelial tissue that produces and releases various secretory secretions (e.g. sweat, saliva, mucus, digestive enzymes, hormones etc.). It is organised into glands, which can consist of a single secretory cell (such as goblet cells) or a group of secretory cells (e.g. salivary glands). In turn, glands can be classed as exocrine or endocrine depending on whether or not they have ducts. The secretory products of exocrine glands are released into a duct that leads to a specific portion of the body (e.g. skin, stomach, respiratory tract). Sweat glands, salivary glands, and lacrimal glands are just a few examples of exocrine glands. Endocrine glands, on the other hand, secrete their secretory products, or hormones, into surrounding blood arteries, from which they might travel to other areas of the body. The pituitary gland, thyroid gland, and adrenal glands are examples of endocrine glands.