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Unformatted text preview: 1 BENG 100 Frontiers of Biomedical Engineering Professor Mark Saltzman Chapter 9 SUMMARY Excretion of molecules by the liver and kidney, and biotransformation of compounds in the liver, are responsible for elimination of wastes (such as urea), elimination of toxins (such as drugs), and maintenance of homeostasis. Biotransformation occurs primarily within hepatocytes, the primary functional cells of the liver. The kidneys received 25 % of the cardiac output: this high flow rate of plasma feeds 1 million nephronswhich are organized collections of tubules, blood vessels, and interstitial spaces. The nephrons create, by filtration, an ultrafiltrate of plasma, which is processed during flow through the tubules to reabsorb vital compounds and secrete unneeded compounds. Filtration occurs in the glomerulus, which creates an ultrafiltrate of blood by pressure driven flow. Reabsorption and secretion of compounds within the renal tubules is determined by the properties of tubular epithelial cells. Differences in osmotic pressure between the tubular fluid and the interstitial fluid create the driving force for water reabsorption, which is regulated by hormones such as ADH due to its effects on water permeability. KEY CONCEPTS AND DEFINITIONS afferent arterioles the branch of the artery that supplies blood inot the glomerulus of each nephron. bile a greenish grown alkaline fluid that aids digestion of lipid substances and is secreted by the liver and stored in the gall bladder biotransformation the alteration of a substance, such as a drug by chemical reactions within the body usually from a toxic state to a less toxic state....
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- Spring '08