Excretory System

Abstract

The kidney is the central organ of body fluid and electrolyte homoeostasis and metabolic waste excretion, the conditions of which were settled early in the evolution of multicellular organisms. Life in different environments such as sea water, fresh water, or arid land implies complex challenges for kidneys to maintain body fluid and electrolyte homoeostasis, which is achieved by distinct hormonal pathways regulating water and salt handling via transporter channels across cell membranes. For this to occur there is a tight link between the anatomy and physiology of the nephrons, the independent functional units of the kidney. Adaptation to life on land went along with a loss of de novo nephron formation, once nephrons get lost during kidney injury. The limited capacity of mammals to regenerate injured kidneys is one of the reasons for chronic kidney disease being common in humans, especially in ageing populations. This chapter provides an overview on human kidney physiology in view of its evolution across species. A better understanding of the stepwise adaptation processes provides unexpected explanations for numerous human renal diseases and associated health conditions such as hypertension and gout resulting from evolutionary trade-offs. In addition, recent changes in human lifestyle created a mismatch between kidney function and novel environmental challenges, thus representing another source of health conditions affecting the kidney. The evolutionary medicine perspective can offer a better understanding of disease pathogenesis and clues for management and prevention.