Epithelium mucus secretion

Figure 1. Solute transfer across an idealised eukaryote epithelium. The solute must move from the bulk solution (e.g. the external environment, or a body fluid) into an unstirred layer comprising water/mucus secretions, prior to binding to membrane-spanning carrier proteins (and the glycocalyx) which enable solute import. Solutes may then move across the cell by diffusion, or via specific cytosolic carriers, prior to export from the cell. Thus the overall process involves 1. Adsorption 2. Import 3. Solute transfer 4. Export. Some electrolytes may move between the cells (paracellular) by diffusion. The driving force for transport is often an energy-requiring pump (primary transport) located on the basolateral or serosal membrane (blood side), such as an ATPase. Outward electrochemical gradients for other solutes (X+) may drive import of the required solute (M+, metal ion) at the mucosal membrane by an antiporter (AP). Alternatively, the movement of X+ down its electrochemical gradient could enable M+ transport in the same direction across the membrane on a symporter (SP). A, diffusive anion such as chloride. Kl-6 refers to the equilibrium constants for each step in the metal transfer process, Kn indicates that there may be more than one intracellular compartment involved in storage. See the text for details...

Transepithelialpotential the voltage measured across an epithelium. Unstirred layer, a relatively nonmobile layer of water and/or mucus secretions adjacent to a biological membrane. 

Falk, H. L.. P. Kotin, and W. Rowlette. Factors affecting mucus and its secretion The response of mucus-secreting epithelium and mucus to irritants. Ann. N.Y Acad. Sci. 106 583-608, 1%3. 

The airway surface is formed by columnar ciliated and nonciliated cells interspersed with mucus-secreting goblet cells. The surface area of the epithelium is increased by the presence of numerous microvilli. The epithelial cells are held together at their apical surface by tight... 

Changes in the bronchorespiratory epithelium from mucus secretion to keratinization lead to increased incidence of respiratory infections in the deficiency state. There also is a decrease in elasticity of the lung and other tissues. 

Q2 Unlike the small intestinal mucosa, the colonic mucosa does not contain any villi. There are columnar epithelial cells and mucus-secreting goblet cells in the mucosa the columnar epithelium reabsorbs fluid and electrolytes. 

Thus, along with the secretion of surface epithelium mucus and its mechanical shedding, there must be a constant digestion of mucus by a mucolytic enzyme present in the mucus itself (G26, G33, G34). However, the mechanism of removal of mucus from gastric mucosa with formation of its degradation product, detectable in the gastric juice as "dissolved mucoproteose (G27) needs clarification. 

Saliva Mucus secretion of surface epithelium and/or pyloric glands ... 

The relative importance of many of the mediators is not precisely defined but they interact to produce mucosal oedema, mucus secretion and damage to the ciliated epithelium. Breaching of the protective epithelial barrier allows hyperreactivity to be maintained by bronchoconstrictor substances or by local axon reflexes through exposed nerve fibres. Wheezing and breathlessness result. The bronchial changes also obstruct access of inhaled drug to the periphery, which is why they can fail to give full relief. 

Oral mucosae are composed of multiple layers of cells, which show various patterns of differentiation dependent on the functions of different regions in the oral cavity. The oral mucosa is covered by a stratified, squamous epithelium, and three different types of mucosa can be distinguished the masticatory, the lining, and the specialized mucosa. Blood supply to the oral cavity tissues is delivered via the external carotid artery, which branches to the maxiliary lingual and facial artery. There are no mucus-secreting goblet cells in the oral mucosa, but mucins are found in human saliva. These mucins are water-soluble and form a gel of 10-200 pm thickness. Saliva, mainly composed of water (99%), is continuously secreted in the oral cavity and exists as a film with a thickness of 0.07-0.1 mm. ... 

The goblet cells of the epithelium form mucus secretions are stored in granule form in the apical cell region and are liquefied on contact with water to form mucus, which is composed of protein and carbohydrate. 

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