Respiratory membrane

Electron Transport Between Photosystem I and Photosystem II Inhibitors. The interaction between PSI and PSII reaction centers (Fig. 1) depends on the thermodynamically favored transfer of electrons from low redox potential carriers to carriers of higher redox potential. This process serves to communicate reducing equivalents between the two photosystem complexes. Photosynthetic and respiratory membranes of both eukaryotes and prokaryotes contain stmctures that serve to oxidize low potential quinols while reducing high potential metaHoproteins (40). In plant thylakoid membranes, this complex is usually referred to as the cytochrome b /f complex, or plastoquinolplastocyanin oxidoreductase, which oxidizes plastoquinol reduced in PSII and reduces plastocyanin oxidized in PSI (25,41). Some diphenyl ethers, eg, 2,4-dinitrophenyl 2 -iodo-3 -methyl-4 -nitro-6 -isopropylphenyl ether [69311-70-2] (DNP-INT), and the quinone analogues,... 

The major routes of uptake of xenobiotics by animals and plants are discussed in Chapter 4, Section 4.1. With animals, there is an important distinction between terrestrial species, on the one hand, and aquatic invertebrates and fish on the other. The latter readily absorb many xenobiotics directly from ambient water or sediment across permeable respiratory surfaces (e.g., gills). Some amphibia (e.g., frogs) readily absorb such compounds across permeable skin. By contrast, many aquatic vertebrates, such as whales and seabirds, absorb little by this route. In lung-breathing organisms, direct absorption from water across exposed respiratory membranes is not an important route of uptake. 

Headache and irritation of the ocular and upper respiratory membranes may result from prolonged exposure to excessive concentrations of the vapor. ... 

Figure 27.6. Ultrastructure of the alveolar respiratory membrane shown in cross section. (Adapted from Guyton, A. C., and Hall, J. E. Textbook of Medical Physiology, 10th edition, W.B. Saunders, Philadelphia, 2000. This figure was completely redrawn by the author from materials cited.)...

The efficiency of oxygen diffusion across the respiratory membrane can be estimated by performing a test of Tco transfer capacity. 

The ultrastructure of the respiratory membrane is unique by virtue of its function. A diagrammatic representation of the respiratory membrane is shown in Figure 1. The respiratory membrane basically comprises two main layers. The first layer is the alveolar epithelium, which consists of at least three different cell types alveolar types I, II, and III or brush cells and migratory alveolar macrophages. 

Figure 1 Diagrammatic representation of the ultrastructure of the respiratory membrane. Arrows indicate the passage of drugs (horizontal heavy lines) through the respiratory membrane after alveolar or capillary exposure, or of metabolites (horizontal broken lines) generated in the epithelial or endothelial layers. Key (1) monomolecular surfactant layers, (2) thin fluid film, (3) interstitial space, (4) endothelial capillary basement membrane, (5) drug transport from the alveoli, (6) absorption of drug into endothelial cells from the circulation, (7) transport of drug from the circulation to alveolar epithelium, (8) transport of drug from the circulation to the alveoli. (From Ref. 102. Reproduced by permission, CRC Press, Inc.)...

Squamous cells have an irregular, flattened shape. A one-cell layer of simple squamous epithelium forms the alveoli of the respiratory membrane and the endothelium, and provides a minimal barrier to diffusion. Other sites of squamous cells include the filtration tubules of the kidneys and the major cavities of the body. Squamous cells are relatively metabolically inactive, and are associated with the diffusion of water, electrolytes and other substances. 

In terrestrial animals, oxygen enters the circulatory system at the respiratory membranes of the lungs. 

Because lye is an alkaline substance and can causing burning of the skin or of the respiratory membranes if inhaled, the nurse should wear PPE. This action would not warrant intervention for the charge nurse. 

Systemic damage may occur as a result of systemic absorption of a toxicant through the respiratory membranes (eg, leukopenia following mustard inhalation) with consequent damage to other organ systems. Effects on other organ systems may be more obvious than the respiratory effects of exposure (as with mercury). 

Hou, C. (2005). Scaling laws for oxygen transport across the space-filling system of respiratory membranes in the human lung, PhD thesis. University of Missouri, Columbia, MO. 

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