TUBULAR MUCOUS GLAND – 1
Mucous tubules are a particular type of tubular glands that are very commonly found in several organs. They are present in various locations of the digestive tract (oral mucosa, salivary glands, esophagus), respiratory system and other places of the body.
Mucous tubules can be found isolated and scattered (for example, within the tongue, cheeks and lips) or in larger groups, as in the duodenum. Very large clusters of these tubules constitute macroscopic glands such as the sublingual salivary glands.
Their secretion is composed mainly of mucus, which is rich in a group of glycoproteins called mucins, that have a slight viscous consistency.
The secretory portion of the mucous tubules is elongated. Their length can vary, as well as their shapes, which can range from almost straight to convoluted and may be branched. The initial excretory duct is formed by a simple cuboid epithelium. Depending on the size of the gland it may join other small excretory ducts becoming progressively wider.
The figure shows a diagram of a simple, short and straight mucous tubule. The secretory portion as well as its internal cavity are much wider than that of the conducting portion – the excretory duct at the right
The columnar or pyramidal secretory cells are disposed in a simple layer. In sections their cytoplasm is seen in a faint bluish color after hematoxylin and eosin staining. It is usually filled with large secretory vesicles. However, mucus does not stains well with these stains and it is often difficult to notice these vesicles.
The nuclei of the secretory cells are quite characteristic: elongated, elliptic, strongly stained blue by hematoxylin and typically placed in the most basal part of the cell, parallel with respect to the basal lamina.
Mucous tubules can be found isolated and scattered (for example, within the tongue, cheeks and lips) or in larger groups, as in the duodenum. Very large clusters of these tubules constitute macroscopic glands such as the sublingual salivary glands.
Their secretion is composed mainly of mucus, which is rich in a group of glycoproteins called mucins, that have a slight viscous consistency.
The secretory portion of the mucous tubules is elongated. Their length can vary, as well as their shapes, which can range from almost straight to convoluted and may be branched. The initial excretory duct is formed by a simple cuboid epithelium. Depending on the size of the gland it may join other small excretory ducts becoming progressively wider.
The figure shows a diagram of a simple, short and straight mucous tubule. The secretory portion as well as its internal cavity are much wider than that of the conducting portion – the excretory duct at the right
The columnar or pyramidal secretory cells are disposed in a simple layer. In sections their cytoplasm is seen in a faint bluish color after hematoxylin and eosin staining. It is usually filled with large secretory vesicles. However, mucus does not stains well with these stains and it is often difficult to notice these vesicles.
The nuclei of the secretory cells are quite characteristic: elongated, elliptic, strongly stained blue by hematoxylin and typically placed in the most basal part of the cell, parallel with respect to the basal lamina.
