Submucosal vessels

Airway surfaces, like skin, are continually exposed to the ambient environment. In contrast to skin submucosal vessels, however, w hich shed excess heat by vasodilating when heated and conserve heat by vasoconstricting when chilled, it is unclear how the airway vasculature responds to temperature extremes. Inspiring cold air poses two challenges to conducting airway tissues the risk of tissue injury should inadequate heat reach the airway surface and excessive body heat loss due to increasing the radial temperature gradient. Vasodilation would protect airway tissue but increase heat loss, while vasoconstriction would produce the opposite effect. 

Nasal vasculature may offer some insight into this question, though research to date has been equivocal. Nasal turbinate vessels can be classified as either capacitance vessels or resistive vessels. Capacitance vessels appear to vasodilate in response to infection while resistance vessels appear to respond to cold stimuli by vasoconstriction. Buccal vascular structures also respond to thermal stimuli but appear to respond principally to cutaneous stimuli. How pharyngeal and tracheobronchial submucosal vessels react to thermal stimuli is not known, though cold-induced asthma is believed to result from broncho-spasms caused by susceptible bronchial smooth muscle responding to exposure to cold dry air.- This asthmatic response suggests an inadequate vascular response to surface cooling. 

Normal submucosal vessels are faintly seen in the oesophageal body but are more prominent in the elderly with mucosal atrophy. Distinct, parallel threadlike vessels are regularly seen above the Z-line, most obvious in young patients (Fig. 3.3). Their relation to early oesophagitis is disputed. 

The bronchial histopathology of patients who have died of asthma shows an intense infiltration of the bronchial mucosa with inflammatory ceUs, particularly eosinophils, macrophages, lymphocytes and to a lesser extent neutrophils. Deposition of eosinophil products in the bronchial epithelium and subepithelium is a particularly prominent feature (Filley etal., 1982). Epithelial denudation, dilatation of blood vessels, mucosal oedema and hypertrophy of both submucosal glands and bronchial smooth muscle are other features. Many of these features of asthma deaths are also observed in milder and well-controlled asthmatics. Elevated numbers of eosinophils, moncytes/macrophages and activated lymphocytes are persistent features observed in bronchial biopsies... 

Viral implantation into oropharynx/respiratory tract spreads to regional lymph nodes viremia with virus multiplication in spleen, bone marrow, lymph nodes locates in leukocytes, small dermal blood vessels, and submucosal oral and pharyngeal cells... 

Decongestant A drug that reduces nasal or oropharyngeal mucosal swelling, usually by constricting blood vessels in the submucosal tissue... 

The most important morphological examination prior to insertion of an airway stent is a spiral computed tomography (CT) of the major airways. A CT enables a delineation of the airway obstruction. It further demonstrates the length of stenosis, grade of obstruction, and allows calibrated measurements of the smallest diameter of the obstruction. CT can also differentiate a mucosal obstruction from a submucosal cause of obstruction, and further extra-tracheal or exo-bronchial disease responsible for airway comprise. Another advantage of CT is the possibility to assess the relation of the underlying cause of obstruction to other crucial mediastinal and/or pulmonary structures (e.g., major vessels, esophagus, heart, lymph nodes). 

Fig. 8.7. Enlarged submucosal gastric vessels (arrows). Identification of intramural and adjacent vessels clearly important if trans-gastric biopsy or drainage is being considered...

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