Mucus-producing cells

A. Proteoglycans are found in the extracellular matrix or ground substance of connective tissue, synovial fluid of joints, vitreous humor of the eye, secretions of mucus-producing cells, and in cartilage. 

Mucus-Producing Cells Release mucus, which protects the stomach lining from gastric juices... 

Mucus hypersecretion is present early in the course of the disease and is associated with an increased number and size of mucus-producing cells. The presence of chronic inflammation perpetuates the process, although the resulting airflow obstruction and chronic airflow limitation may be reversible or irreversible. The various causes of airflow obstruction are summarized in Table 27-3. 

Mucus-producing cells release mucus that protect the stomach Kning from the gastric juices. 

Conjunctiva is squamous, nonkeratinized epithelium with numerous mucus-producing cells for lubrication of the eyelids and cornea. 

Mucus is produced by the mucus neck cells and by the surface epithelial cells of the stomach wall. A thick layer of mucus adheres to the wall of the stomach, forming the gastric mucosal barrier. The function of this barrier is to protect the gastric mucosa from injury — specifically, from the corrosive actions of HCl and pepsin. Together with bicarbonate ion released into the lumen of the stomach, mucus neutralizes the acid and maintains the mucosal surface at a nearly neutral pH. 

The typical symptoms begin with the sudden onset of nausea and vomiting and profuse diarrhea without abdominal cramps. The stools produced are characteristically ricewater -like and contain mucus, epithelial cells, and ibrio cholerae bacteria. The dehydration resulting from rapid loss of fluid and electrolytes leads to circulatory collapse and kidney shutdown. Mortality rate without treatment can be as high as 50%.3... 

HT29 Human colon Co-culture containing mucus-producing goblet cells... 

Mucus produced by submucosal glands and goblet cells located throughout the GI tract is largely made up of glycoprotein molecules called mucins, is extremely hydrophilic and can form gels that contain up to 95% water (see Section 1.3.2). Two forms of mucus are found in the stomach, a soluble and an insoluble form. Soluble mucin results from the degradation of insoluble mucus by peptic action. The insoluble fraction forms... 

Q9 The stomach secretes a very acid gastric juice with a pH of 1.5-2. The mucosa is normally protected from acid by a number of mechanisms. Mucus is produced by the large number of mucous cells in the body and fundus. It contains glycoproteins called mucins, and the mucus produced forms a kind of gel which coats the mucosal surface. In addition these cells secrete HCO3-, which is trapped in the mucus and increases the local pH to form a less acidic environment at the surface of the epithelial cells. 

An example of a disease that results from a deletion mutation is cystic fibrosis. The presence of mutated genes in which three thymine bases are absent produces cells in the lungs that are defective in the transport of molecules such as sodium. A result is the accumulation of mucus in the lungs. Bacteria readily colonize the mucus and become resistant to treatments intended to kill them. As... 

Several techniques have been used to estimate the rate of mucus secretion, but their accuracy seems to be doubtful. Nevertheless, it has been concluded that a slow baseline secretion of mucus is maintained by exocytosis from goblet cells in the gastrointestinal tract, which appears to be under cholinergic control. Rubinstein and Tirosh used carbachol (cholinergic agonist) at different doses to increase the mucus thickness in different parts of the gastrointestinal tract. Attempts were also made to estimate the rate of turnover of the mucus gel. Lehr et al. measured the amount of mucus produced per time unit, using an in situ perfused intestinal loop model in the rat. They found that this turnover time varies between... 

The mucociliary escalator functions when inhaled particles between 2 to 10 pm are deposited on the sticky mucous lining of the tracheobronchial tree and are propelled upward by the movement of this mucous layer in response to the beat of the cilia on the ciliated epithelial cells. This phenomenon is made possible because the mucous layer is biphasic, consisting of a watery solution in direct contact with the epithelia cells in which the cilia are free to beat. This watery solution is covered by a stickier, more adhesive gel layer that can trap and hold inhaled particles. The cilia beat in the wall layer at a rate between 1000 and 1500 strokes per minute such that at the point of their maximum upward velocity, the tips of the cilia come in contact with the gel layer to propel it upward. All recovery strokes subsequently occur in the water layer. This mechanism moves the mucus upward at a rate between 1 and 3 cm/minute. Ultimately, the mucus reaches the pharynx, where it is swallowed. Disease states that either alter the mucus-producing properties of cells in the tracheobronchial tree or decrease ciliary activity will obviously have a deleterious effect on this important clearance mechanism. 

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