Erythrocytes respiratory system

Figure 3.10 The structure of the mammalian respiratory system (A) trachea, (B) bronchiole, (C) alveolar sac with blood supply, (D) arrangement of blood vessels around alveoli, (E) arrangement of cells and airspaces in alveoli showing the large surface area available for absorption, (F) cellular structure of alveolus showing the close association between (G) the endothelial cell of the capillary (H) with erythrocytes and (I) the epithelial cell of the alveolar sac. The luminal side of the epithelial cell is bathed in fluid, which also facilitates absorption and gaseous exchange. Source From Ref. 1.

DAAB is a respiratory tract, skin, and eye irritant. DAAB yields benzene and aniline as metabolites. The proposed metabolic pathway for DAAB is that it is cleaved reductively by liver enzymes or gut flora to form aniline, benzene, and nitrogen. DAAB metabolism also results in the formation of a reactive phenyl radical, which could account for an additional risk of toxicity or carcinogenicity. The erythrocyte and lymphoid systems are major targets of DAAB toxicity. Induction of lymphoid atrophy of the thymus and other lymphoid tissues were observed, as well as methemoglobin formation, accompanying anemia, increased spleen weights, and regenerative hematopoiesis. 

As discussed in Chapter 1, at a blood pH of 7.4, the ratio of [HCO3 ] to [H2CO3] is 20 1 and the system s buffering capacity can neutralize a large amount of acid. The system is independently regulated by the kidneys, which control the plasma HCOj level, and by the respiratory rate, which regulates the Pco2- Protein and phosphate buffer systems also operate in plasma and erythrocytes. Proteins are especially important buffers in the intracellular fluid. The hydroxyapatite of bone also acts as a buffer. 

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