asthma comes from the greek word for â€œpantingâ€,which makes sense because it causes chronic inflammation of the airways, making them narrowand more difficult to breathe through. people with asthma can have asthma exacerbationor asthma attacks, which are usually triggered by something in the environment which causesimmune cells to generate inflammation in the lungs which can make them even narrower andpotentially be life-threatening. so, if we take a look at the lungs, youâ€™vegot the trachea, which branches off into right and left bronchi, and then continues to branchinto thousands of bronchioles. in the bronchioles youâ€™ve got the lumen,the mucosa, which includes the inner lining of epithelial cells, as well as the laminapropria, and the submucosa which is where
the smooth muscle lives. in asthma there are typically lots of eosinophilsjust below the epithelium in the lamina propria. eosinophils are white blood cells that carrya cargo of granules full of soluble chemical mediators like histamines, leukotrienes, prostaglandin,and platelet activating factor. when these eosinophils sense an environmentaltrigger like cigarette smoke in the airway, they can release their granules, letting thosechemical mediators spill out and start degrading lipids, proteins, and nucleic acids, literallydestroying all of the major cell components. this creates a strong inflammatory reactionin the bronchiolar walls and causes two changes. first, smooth muscle around the bronchiolesstart to spasm which narrows the airways,
and second, there is increased mucus secretioninto those narrow airways, narrowing them even more, which when these are combined makesit difficult to breathe, and this is why asthma is considered to be a type of obstructivepulmonary disease. initially these inflammatory changes are completelyreversible, but over the years irreversible changes start to take placeâ€”edema, scarring,and fibrosis build up, leading to thickening of the epithelial basement membrane, whichpermanently reduces the airway diameter. alright, but why do some people have lotsof eosinophils and create inflammation in response to a trigger in the first place? well, type 2 t helper cell or th2 cell, whichis an immune cell subtype, is known to be
involved in asthma, as well as atopic dermatitis,and allergic rhinitis, making up whatâ€™s called the atopic triad. these th2 cells release cytokines to communicatewith other cells, one cytokine is interleukin-5, which is a small peptide that attracts andactivates eosinophils. it turns out that blocking il-5 has been shownto help some patients with asthma. on the other hand, there are other patientswith asthma that have low levels of th2 cells, but high levels of another class of immunecellsâ€”neutrophils. neutrophils are highly inflammatory phagocyticcells that gobble up infected or dead cells. how neutrophils promote asthma, though, isnâ€™tknown, but, another interleukin, il-8 released
by the neutrophils, seems to play a key rolein the disease. patients with neutrophilic disease tend tohave a more severe form of asthma than patients with th2/eosinophilic asthma. although the specific causes of asthma areultimately unknown, itâ€™s thought to be caused by a combination of genetic and environmentalfactors, since certain genes have been identified that increase the risk of developing asthmaand having a family history of asthma seems to increase risk as well. for environmental factors, thereâ€™s the hygienehypothesis, which suggests that reduced early immune-system exposure to bacteria and viruseswhich might actually increase the risk of
later developing asthma, possibly by alteringthe overall proportion of immune cell subtypes. in general, causes of childhood asthma diagnosedbefore age 12 are thought to be due to a stronger genetic influence, whereas later onset asthmais more likely to be largely due to environmental factors. now, the triggering substance that leads tothe asthma attack can differ from person to person, but some common ones include air pollution,like cigarette smoke and car exhaust, as well as allergens like dust, pet dander, cockroaches,and mold. medications like aspirin and beta-blockershave also been known to trigger symptoms in some individuals with asthma.
that said, symptoms of asthma include coughing,a feeling of chest tightness, dyspnea, or difficulty breathing, and wheezing, or a high-pitchedwhistling sound that usually happens during exhalation. occasionally in the sputum there might curschmannspirals, which are spiral shaped mucus plugs which are basically elongated mucous castsfrom small bronchi of people with bronchial asthma. mucus plugs can be particularly dangerousbecause they not only block exchange of air, but they also block inhaled medications fromgetting to the site of inflammation. the mucus may also contain charcot-leydencrystals which are shaped like needles and
are formed by the breakdown of eosinophils. now, asthma can be classified according tothe frequency of symptoms, in particular night-time and early morning symptoms, the fev1, or forcedexpiratory volume in one second, the pefr, or peak expiratory flow rates, both of whichmeasure the amount of obstruction in the airways, and finally how often a person is using asthmamedication to help with the symptoms. from least to most severe, the types of asthmaare intermittent asthma, mild persistent asthma, moderate persistent asthma, and finally severepersistent asthma. while there is no cure for asthma, there aretreatments available that can manage the symptoms and prevent the development of an asthma attack.
first, people with asthma should avoid orminimize contact with triggering substances by vacuuming, removing carpets and rugs, andchanging the environmental conditions, like for example drying out a room in the caseof molds that grow well in moist areas. there are also a number of medications thatcan reduce the symptoms of asthma. bronchodilators such as short-acting beta-adrenoceptoragonists and anticholinergic medications are often administered through emergency inhalers. these fast-acting medications cause the smoothmuscles in the lungs to relax and therefore dilate the airways, opening them up so thata person can breath. individuals with more severe forms of asthmamight need additional treatments like daily
corticosteroids, long-acting beta-adrenoceptoragonists, or leukotriene antagonists. in very severe cases, intravenous corticosteroids,magnesium sulfate, and oxygen therapy might be needed. alright, as a quick recap, asthma is characterizedby chronic inflammation in the lungs as well as asthma exacerbations or attacks, wherecertain triggers starting up more inflammation which leads to smooth muscle spasms and mucusproduction, both of which make it hard to breathe. thanks for watching, you can help supportus by donating on patreon, or subscribing to our channel, or telling your friends aboutus on social media.