Edward R.M. O'Brien, MD
- Professor of Medicine, Cardiology
- Research Chair, Canadian Institutes of Health Research/Medtronic
- University of Ottawa Heart Institute
- Ottawa, Ontario, Canada
The cells overlap both longitudinally and laterally to surround the hair completely and hold the cortex together asthmatic bronchitis 10 buy generic singulair 5mg line. In the follicle these edges interlock with opposing scales of the cuticle of the inner root sheath asthma medscape singulair 10mg discount, helping at least in part to hold the hair in place in the follicle (Montagna and Van Scott asthma symptoms test discount singulair 4 mg amex, 1958; Straile asthma definition 740 purchase singulair 10mg without prescription, 1965). Thus pulling a growing hair with a quick, sharp tug will sometimes yield a hair root with inner root sheath material still attached (Ludwig, 1967). In the mature hair the cuticle cells are roughly rectangular in shape (Kassenbeck, 1981), about 5060 µm long and about 0. However, they overlap to such an extent that only about one-sixth of each cell is visible on the surface (Ryder, 1963), and the cuticle is effectively multilayered with a thickness of about six cells (about 35 µm) and scale edges about 5 µm apart (Swift, 1981). Cuticle cells form a pattern which can be visualized microscopically on the hair surface and is called the hair scale pattern. The pattern differs between species and can be used for species identification (see Noback, 1951; Wildman, 1954; Brunner and Coman, 1974). In spite of these changes, the scale counts (which are a measure of how far apart the edges are) are relatively constant for scalp hair for an individual providing sufficient counts are made, but they can vary between individuals (Gamble and Kirk, 1940). The scale count also varies on an individual depending on site, the count being significantly smaller. Smaller scale numbers are seen for the scalp hairs of younger people than older, and for facial, axillary and abdominal hairs of females as compared to hairs from the same sites from males (Wyatt and Riggott, 1977). The scale pattern of human hair corresponds to the edges of the cuticle cells (Kassenbeck, 1981). Three different hairs are used for illustration; in all cases the tip end is towards the right, (a) Near the root. Nevertheless, the cuticle itself is damaged by processes such as weathering, combing, brushing, washing, and abrasion against other hairs, and the scale edges chip away (Swift, 1981). This causes the scale edges to become more irregular and produces the pattern typically seen for human hair (Figure 1. Since the hair shaft is dead tissue and cannot repair itself, greater damage will be seen towards the tips of hairs as compared with near the root (Bottoms et al. Jones) and ongoing it will reduce the thickness of the overlapping cell layer eventually to the point where there is no longer a cuticle, and the cortex will be exposed (Swift and Brown, 1972). Without the protection of the cuticle the hair feels rough and the cortex frays and falls apart (Figure 1. These layers are clearly delineated in electron micrographs by the density of their electron staining (Figure 1. The cuticle cell contents are amorphous; filaments are not visibly prominent but lamella structures resulting from fused granules can be seen (Swift, 1981). The proteins of the exocuticle are cysteine and glycine-rich proteins (Fraser et al. The endocuticle also consists mainly of protein, but this contains very little cysteine and large amounts of acidic and basic amino acids (Swift, 1981). Nuclei, or the remnants of them, can be seen in the endocuticle (Swift, 1977; Kassenbeck, 1981). It is resistant to chemical and enzymic attack, presumably because its protein is highly cross-linked by both disulphide bonds and isopeptide bonds (Zahn et al. This phenomenon helps the hairs remove dentritis and irritants from the skin, and it also assists in keeping the hairs aligned (and thus not tangled and matted). The multilayering of the cuticle can cause it to be a large proportion of the overall diameter of the hairs, especially fine ones, and it therefore can make a large contribution to the hair stiffness. This effect is particularly seen in hairs of non-circular cross-section (for example, Negroid hairs) where the preferred bending will be in the direction of the minor axial diameter (Swift, A. Most of this advance in knowledge has been in studies of the genes for wool keratins, but the findings are largely applicable to human hair. The sequences are sheep because complete sequences of human are not yet available. The consequent secondary structure of an a-helical region, shown in bold, is also highly conserved between species including human.
Complications of influenza include both viral pneumonia (due to a spreading of the illness into the lower respiratory tract) and bacterial pneumonia asthma definition ubiquitous buy singulair 10mg with amex. The latter is thought to be due largely to the fact that influenza damages the epithelium of the upper respiratory tract asthma inhaler definition singulair 4mg without prescription, compromising its ability to keep the lower respiratory tract sterile asthma treatment questions buy singulair 10mg fast delivery. Streptococcus pneumoniae asthma like symptoms order singulair 4mg line, Staphylococcus aureus, and Haemophilus influenzae are the organisms most commonly seen in bacterial pneumonia secondary to influenza. This chest x-ray shows a consolidation in the right lower lobe along with a para-pneumonic effusion, highly suspicious for bacterial pneumonia. However, the symptoms of mononucleosis typically last longer than three days, and bacterial pneumonia is not a common complication. Infection with a coronavirus would not be expected to lead to bacterial pneumonia in a healthy individual. Terbinafine is an antifungal agent that blocks ergosterol synthesis by inhibiting squalene epoxidase. From the history, it appears that this man initially experienced nonspecific viral symptoms, but there is not enough information to determine which virus he has. What is clear, however, is that his initial symptoms are distinct from what he experiences on relapse. The radiograph shows that he has lobar pneumonia (lower right lobe), which can be caused by any number of bacterial species. The question that must be asked, Chapter 17: Respiratory · Answers 467 tions are typically mild and uncomplicated in healthy individuals, and a secondary bacterial pneumonia would be atypical. Chronic hypoxemia to the fetus can result in congenital abnormalities such as a patent ductus arteriosus and intraventricular brain hemorrhage. Deficiency of hepatic glucuronyl transferase occurs in all newborns, because the enzyme is not found at adult levels in neonates. Intratracheal administration of artificial surfactant to the newborn can also be performed. In patients who present with insidious onset of dry cough, low-grade fever, headache, myalgias, nausea, or emesis, an atypical pneumonia should be considered. Mycoplasma cannot be cultured and is detected by the cold agglutinin test, which measures the agglutination of immunoglobulins when they are cooled. X-ray of the chest is often more impressive than physical examination findings, and is characterized by a patchy interstitial pattern. Treatment consists of antibiotic therapy with a macrolide, usually azithromycin, for five days. The acid-fast stain is used to diagnose mycobacterial illness, specifically Mycobacterium tuberculosis. India ink stain can be used to visualize mucoid encapsulated yeasts such as Cryptococcus. Epiglottitis is a medical emergency, and 90% of patients require surgery to reestablish an airway. At presentation patients with epiglottitis can have little or no respiratory compromise, but this can progress to life-threatening respiratory distress within a matter of hours. Epiglottitis on x-ray film of the neck reveals a "thumbs up" sign (ie, "thumbprint" on radiograph), which correlates with an inflamed epiglottis. Inflammation of the larynx and sublgottic trachea is not associated with epiglottitis. Patients with epiglottitis do not have the symptoms or physical findings of conjunctivitis or rhinorrhea. In general, the onset of symptoms is abrupt with epiglottitis and gradual with croup. A typical barking cough is seen with croup, which may eventually lead to inspiratory stridor. Increased levels of antineutrophil cytoplasmic autoantibodies are associated with certain small-vessel vasculitic syndromes, including Wegener granulomatosis. Wegener granulomatosis is characterized by granulomatous inflammation of various organs resulting in acute renal failure, pulmonary disease, and other manifestations.
High-volume asthma symptoms baby coughing buy 10mg singulair fast delivery, low-pressure cuffs are designed to conform to the tracheal lumen across a broad area and provide an adequate seal at cuff pressures below that of mucosal perfusion asthma images buy singulair 4 mg with amex, which is 2030 mm Hg asthma symptoms constant purchase singulair 4 mg mastercard. Superficial erosion develops initially asthmatic bronchitis pneumonia buy singulair 4mg cheap, followed by full-thickness mucosal ulceration. Exposure of the underlying tracheal cartilage, which receives its blood supply from the mucosa, results in ischemia. Circumferential damage-Circumferential damage from the cuff is common and results in a greater degree of stenosis than less extensive wounds. Symptoms are rarely present soon after extubation, but develop over several weeks to months as the scar matures. The administration of steroids can occasionally minimize the degree of eventual stenosis; however, it may predispose the area to tracheomalacia instead. Tracheal pseudomembrane and granulation tissue formation-Other lesions that occur at the level of the inflatable cuff include tracheal pseudomembrane and the formation of granulation tissue. The latter responds well to endoscopic laser ablation, although repetitive treatments may be necessary. Obstructive fibrinous tracheal pseudomembrane is a rare but potentially fatal cause of cuff-level postintubation stenosis. Acute airway obstruction is caused by a tubular, fibrinous pseudomembrane, which remains in the trachea following extubation. The tissue, which molds to the tube at the level of the cuff, develops within days of intubation and likely represents an early response to tracheal injury. It contains inflamed and necrotic tracheal epithelium and is associated with hemorrhagic ulceration of the submucosa. Obstructive symptoms that progress to acute respiratory distress develop within hours to days of extubation. Stridor and wheezing may not be present if the patient is too weak to generate sufficient airflow, and obstruction may be positional if the membrane is partially dislodged. Because obstructive fibrinous tracheal pseudomembrane has only recently been characterized and because its presentation may not be typical of tracheal stenosis, symptoms are usually attributed to other causes of postextubation respiratory distress. An accurate diagnosis requires bronchoscopy, which may also aid in reintubation, if necessary. Treatment consists of aggressive respiratory support and the mechanical debridement of the pseudomembrane via rigid bronchoscopy. Several factors affect the eventual degree of stenosis at the stoma site, including the operative technique, pressure necrosis, and infection. At tracheostomy, the smallest size tube that still provides an adequate airway should be used, and the tracheal incision should be just large enough to allow its passage. Secretions, which usually are infected, should not be allowed to accumulate around the stoma or the cuff as localized infection exacerbates tracheal injury and subsequent stenosis. In the latter case, a tracheotomy at the first or second tracheal ring causes a stoma-level injury, as described above, which encroaches on the cricoid cartilage and subglottic larynx. Direct pressure and erosion by the tube at the proximal margin may result in loss of the anterior cricoid arch. Translaryngeal tubes typically cause trauma to the posterior larynx, particularly the interarytenoid area, which may result in glottic stenosis upon healing. As previously described, symptoms usually develop and progress over weeks to months, allowing adequate time for an accurate diagnosis and subsequent evaluation. Lesions that have not fully matured should be managed conservatively to allow acute inflammation to subside. Other types of postintubation stenosis occasionally present emergently as well, because of an acute exacerbation of symptoms. A prolonged misdiagnosis or expectant treatment may allow for the development of a tight stenosis that is tolerated by the patient until factors such as poor underlying lung function, infection due to retained secretions, irritation from cig- B. Upon decannulation, closure of the tracheal defect is effected by collapse and reapproximation of the stomal margins. The emergent management of tracheal stenosis should secure the airway and stabilize the patient, allowing definitive treatment to proceed electively. Initial measures should include the use of humidified oxygen, bronchodilators, inhaled or systemic steroids, inhaled racemic epinephrine, and heliox.
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