Sometimes a disorder results from faulty instructions for routing of a molecule, such is apparently the case in cystic fibrosis, a deadly inherited disease. Cystic fibrosis is an inherited disease of secretory epithelia that affects the respiratory passageways, pancreas, salivary glands and sweat gland. It is the most common lethal genetic disease of white people: 5% of the population are thought to be genetic carriers.
In some cases, the product of the mutated cystic fibrosis gene fails to reach the plasma membrane, where it should be inserted to help pump chloride ions out of certain cells.
Evidently, the pump protein becomes stuck in the endoplasmic reticulum or golgi complex and never reaches its correct destination.
The result in an imbalance in the transport of fluid and ions across the plasma membrane and excessive build up of mucus outside certain types of cells. the mucus clogs the lining of the airways to the lungs, causing breathing difficulty.
Among the most common signs and symptoms are pancreatic insufficiency, breathing difficulty, and cirrhosis of the liver. It is characterized by the production of thick secretions that do not drain easily from the respiratory passageways.
The buildup of the secretions leads to inflammation and replacement of injured cells with connective tissue that blocks these passageways. One of the prominent features is blockage of the pancreatic ducts so that the digestive enzymes cannot reach the intestine Since pancreatic juice contains the main fat-digesting enzyme, the person fails to absorb fats or fat-soluble vitamins and thus suffers from vitamin A,D and K deficiency diseases.
A child suffering from cystic fibrosis is given pancreatic extract and large doses of vitamins A, D and K. The therapeutic diet is low, but not lacking, in fats and high in carbohydrates and proteins that can be used for energy and can also be converted by the liver into the lipids essential for life processes.
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