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THE DIGESTIVE SYSTEM OF
VERTEBRATES
TOPIC: Secretion & absorption of electrolytes & water
Table 10.1. (From CD Chapter 10)
Values for human are estimates for an individual starved 24 hours prior to measurements (Soergal & Hofmann 1972). Other values are means for sheep (Denton 1957, Harrison 1962, Hill 1965, Kay 1960, Kay & Pfeffer 1970, Magee 1961, Taylor 1962), and means for ponies (Alexander & Hickson 1970, Argenzio et al. 1974a) (from Stevens and Hume 1995)
Table 10.2. (From CD Chapter 10)
(Stevens & Hume 1995)
Figure 10.1. Electrolyte composition of extracellular and intracellular fluid compartments of humans. (Modified from Guyton 1986) (From CD Chapter 10)
Extra Figure (not in CD). Electrolyte composition of sea water and human fluid compartments (from Gamble 1954)
Figure 10.2. Osmotic regulation in a typical elasmobranch, the dogfish shark (Squalus acanthias). Values for NaCl, Na+, Cl- and urea are given in mM or mEq per liter. Osmotic pressures (OP) of sea water (SW), body fluids and urine are given in mOsmoles per liter. (Modified from Kormanik 1992). (From CD Chapter 10)
Figure 10.3. Mean digesta osmolality and concentrations of the major electrolytes along the gastrointestinal tract of the pony obtained from four measurements over a 12-h period after a meal. Segments represent the stomach (S), three equal segments of the small intestine (SI), the cecum (C), and the ventral (VC), dorsal (DC) and small (SC) colon. Hydrogen was omitted, because it is only a small component (1 mEq/L) of the cations, even in gastric contents. Concentrations of PO4-- were calculated on the basis of a pKa of 6.8 for NaH2PO4 and the mean pH of digesta in each segment. The principal organic acids (OA) are SCFA and lactic acid. At the pH of intestinal contents, ammonia, SCFA and lactic acid exist principally in their ionized form. Concentrations of HCO3- were calculated as the difference in concentration of measured cations and anions. (Modified from Argenzio 1975). (From CD Chapter 10)
Figure 10.4a. Mean (+/- SE) values for digesta pH in the gastrointestinal tract of dogs 2 hours (closed triangle), 4 hours (open circle), 8 hours (x), and 12 hours (closed circle) after a meal. The segments of the tract are the cranial (S1) and caudal (S2) halves of the stomach, equal succeeding segments of small intestine (SI1, SI2, SI3), the cecum (Ce), and equal lengths of succeeding segments of colon (C1, C2). (From Banta et al. 1979) (From CD Chapter 10)
Figure 10.4b. Mean (+/- SE) values for digesta pH in the gastrointestinal tract of pigs 2 hours (closed triangle), 4 hours (open circle), 8 hours (x), and 12 hours (closed circle) after a meal. The segments of the tract are the cranial (S1) and caudal (S2) halves of the stomach, equal succeeding segments of small intestine (SI1, SI2), the cecum (Ce), and equal lengths of succeeding segments of colon (PC, CCp, CCa, TC), plus the rectum (R). (Argenzio and Southworth 1974) (From CD Chapter 10)
Figure 10.4c. Mean (+/- SE) values for digesta pH in the gastrointestinal tract of ponies 2 hours (closed triangle), 4 hours (open circle), 8 hours (x), and 12 hours (closed circle) after a meal. The segments of the tract are the cranial (S1) and caudal (S2) halves of the stomach, equal succeeding segments of small intestine (SI1, SI2, SI3), the cecum (Ce), and equal lengths of succeeding segments of colon (RVC, LVC, LDC, RDC, SC1, SC2). (Argenzio et al. 1974a) (From CD Chapter 10)
Figure 10.5. Mechanisms of electrolyte transport across the lumen- or blood-facing membranes of epithelial cells lining the gastrointestinal tract and the glandular and duct cells of salivary gland, exocrine pancreas, liver, and gallbladder. A through D demonstrate diffusion of electrolytes down their electrochemical gradient via conductance channels in the cell membrane. E through H show mechanisms for the exchange of electrolytes between cell contents and their bathing solution. The last three models show mechanisms for cotransport of electrolytes with one another or with organic solutes. (Modified from Stevens and Hume 1995) (From CD Chapter 10)
Figure 10.6. Organization of the submaxillary gland of the rat. (from Leeson 1967) (From CD Chapter 10)
Figure 10.7. Concentration of major electrolytes in the saliva of humans (From Thaysen et al. 1954) and sheep (From Argenzio 1984) as a function of the rate of salivary flow. (From CD Chapter 10)
Figure 10.8. Electrolyte transport across the acinar cells of the parotid salivary glands of humans, dogs, cats, and rats. (Modified from Cook et al. 1994) (From CD Chapter 10)
Figure 10.9. A model proposed for secretion of HCl by gastric parietal cells. Intracellular production of H2CO3 by hydration of CO2 produces H+, which is secreted into the lumen in exchange for K+, and HCO3-, which is released into the blood in exchange for Cl-. The lumen-facing membrane contains conductive pathways for passive diffusion of Cl- into the lumen. (Modified from Reenstra et al. 1987) (From CD Chapter 10)
Figure 10.10. Effects of an increase in the flow rate of the electrolyte composition of pancreatic fluid of cats. (From Argent and Case 1994) (From CD Chapter 10)
Figure 10.11. Electrolyte transport across centroacinar cells of the exocrine pancreatic gland. (From Argent and Case 1994) (From CD Chapter 10)
Figure 10.12a. Pathways for the transport of sodium ions across human intestinal epithelium. The thickness of arrow heads represents relative degree of transport. (From Chang and Rao 1994) (From CD Chapter 10)
Figure 10.12b. Pathways for the transport of chlorine ions across human intestinal epithelium. The thickness of arrow heads represents relative degree of transport. (From Chang and Rao 1994) (From CD Chapter 10)
Figure 10.12c. Pathways for the transport of ions across human intestinal epithelium. The thickness of arrow heads represents relative degree of transport. (From Chang and Rao 1994) (From CD Chapter 10)
Figure 10.13. A model that would account for Na+, K+, and Cl- transport by flounder intestine. (From Frizzell et al. 1984) (From CD Chapter 10)
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