Chapter 29 Outline

Basic Mechanisms of Kidney Function

  • Primary urine is introduced into kidney tubules by ultrafiltration or secretion
  • The predominant regulatory processes in kidney function: After primary urine forms, solutes and water are recovered from it for return to the blood, and some solutes are added from the blood

Urine Formation in Amphibians

  • The proximal convoluted tubule reabsorbs much of the filtrate—returning it to the blood plasma—without changing the osmotic pressure of the tubular fluid
  • The distal convoluted tubule can differentially reabsorb water and solutes, thereby regulating the ratio of water to solutes in the body fluids
  • BOX 29.1 Quantity versus Concentration
  • BOX 29.2 Methods of Study of Kidney Function: Micropuncture and Clearance
  • ADH exerts an elaborate pattern of control over nephron function
  • The bladder functions in urine formation in amphibians
  • The amphibian excretory system has mechanisms to promote excretion of urea

Urine Formation in Mammals

  • The nephrons, singly and collectively, give the mammalian kidney a distinctive structure
  • Comparative anatomy points to a role for the loops of Henle in concentrating the urine
  • Countercurrent multiplication is the key to producing concentrated urine
  • BOX 29.3 Countercurrent Multipliers versus Countercurrent Exchangers
  • The regulatory roles of the kidney tubules in overview: the concentrating and diluting kidney and the control of transitions
  • Modern molecular and genomic methods create new frontiers in the study of kidney function

Urine Formation in Other Vertebrates

  • Freshwater and marine teleost fish differ in nephron structure and function
  • The reptiles other than birds have nephrons like those of amphibians, but birds have some mammalian-type nephrons

Urine Formation in Decapod Crustaceans

Urine Formation in Molluscs

Urine Formation in Insects

  • The Malpighian tubules form and sometimes modify the primary urine
  • The hindgut modulates urine volume and composition in regulatory ways

Nitrogen Disposition and Excretion

  • Ammonotelism is the primitive state
  • Urea is more costly to synthesize but less toxic than ammonia
  • Uric acid and related compounds remove nitrogen from solution
  • BOX 29.4 Why Are Mammals Not Uricotelic?
Copyright 2016 Sinauer Associates
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