Excretory (Urinary) System Chapter 44

Urinary Components Functions of Urinary System 1. Kidney Functions 2. Urine transport 3. Urine storage. 4. Excretion

Kidney - Internal Anatomy

Kidney Functions 1. Regulate blood ionic composition. 2. Regulate blood pH. 3. Regulate blood volume. 4. Regulate blood pressure. 5. Maintain blood osmolarity. 6. Production of hormones. 7. Regulation of blood glucose levels. 8. Excretion of wastes and foreign substances.

Animation: Nephron Introduction Juxtamedullary nephron Cortical nephron Renal cortex Collecting duct Figure 44.14c The mammalian excretory system Renal medulla To renal pelvis Animation: Nephron Introduction (c) Nephron types

Nephron 1. Glomerular Filtration 2. Tubular Reabsorption 3. Tubular Secretion

1. Glomerular Filtration 2. Tubular Reabsorption Fig. 44-14d Afferent arteriole from renal artery Glomerulus 10 µm Bowman’s capsule SEM Proximal tubule Peritubular capillaries Efferent arteriole from glomerulus Distal tubule 1. Glomerular Filtration 2. Tubular Reabsorption 3. Tubular Secretion Branch of renal vein Collecting duct Descending limb Figure 44.14d The mammalian excretory system Loop of Henle Ascending limb Vasa recta (d) Filtrate and blood flow

From Blood Filtrate to Urine: A Closer Look Proximal Tubule Reabsorption of ions, water, and nutrients takes place in the proximal tubule Molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries Some toxic materials are secreted into the filtrate The filtrate volume decreases Animation: Bowman’s Capsule and Proximal Tubule

Descending Limb of the Loop of Henle Reabsorption of water continues through channels formed by aquaporin proteins Movement is driven by the high osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate The filtrate becomes increasingly concentrated

Ascending Limb of the Loop of Henle In the ascending limb of the loop of Henle, salt but not water is able to diffuse from the tubule into the interstitial fluid The filtrate becomes increasingly dilute

Animation: Loop of Henle and Distal Tubule The distal tubule regulates the K+ and NaCl concentrations of body fluids The controlled movement of ions contributes to pH regulation Animation: Loop of Henle and Distal Tubule

Animation: Collecting Duct The collecting duct carries filtrate through the medulla to the renal pelvis Water is lost as well as some salt and urea, and the filtrate becomes more concentrated Urine is hyperosmotic to body fluids Animation: Collecting Duct

Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle OUTER Fig. 44-15 Proximal tubule Distal tubule NaCl Nutrients H2O HCO3– H2O K+ NaCl HCO3– H+ NH3 K+ H+ Filtrate CORTEX Loop of Henle NaCl H2O OUTER MEDULLA NaCl NaCl Collecting duct Figure 44.15 The nephron and collecting duct: regional functions of the transport epithelium Key Urea Active transport NaCl H2O Passive transport INNER MEDULLA

Composition of Filtrate