Excretory System

Figure 44.8a Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes Many reptiles (including birds), insects, land snails Ammonia Urea Uric acid

Figure 44.2 Selectively permeable membrane Solutes Water Net water flow Hyperosmotic side: Hypoosmotic side: Lower free H 2 O concentration Higher solute concentration Higher free H 2 O concentration Lower solute concentration

Figure 44.14b Kidney Structure Renal cortex Renal medulla Renal artery Renal vein Ureter Renal pelvis

Figure 44.14d Nephron Organization Afferent arteriole from renal artery Glomerulus Bowman’s capsule Proximal tubule Peritubular capillaries Distal tubule Efferent arteriole from glomerulus Collecting duct Branch of renal vein Vasa recta Descending limb Ascending limb Loop of Henle

200  m Blood vessels from a human kidney. Arterioles and peritubular capillaries appear pink; glomeruli appear yellow. Figure 44.14e

Figure Thirst Hypothalamus ADH Pituitary gland Osmoreceptors in hypothalamus trigger release of ADH. STIMULUS: Increase in blood osmolarity (for instance, after sweating profusely) Homeostasis: Blood osmolarity (300 mOsm/L) Drinking reduces blood osmolarity to set point. H 2 O reab- sorption helps prevent further osmolarity increase. Increased permeability Distal tubule Collecting duct

ADH receptor COLLECTING DUCT CELL LUMEN Second-messenger signaling molecule Storage vesicle Aquaporin water channel Exocytosis H2OH2O H2OH2O ADH cAMP Figure 44.20