PHGY210 Renal Physiology Tomoko Takano, MD, PhD *Associate Professor of Medicine and Physiology McGill University *Nephrologist, McGill University Health Centre
Lecture plan Lecture 1: Anatomy, basics of urine formation Lecture 2: Glomerular filtration, tubular reabsorption/secretion, concept of clearance Lecture 3: Regulation of sodium balance Lecture 4: Regulation of water balance Lecture 5: Potassium regulation, hydrogen ion regulation-1 Lecture 6: Hydrogen ion regulation-2, diuretics, kidney disease -Tutorial: April 13 (Tue) 5:30, McIntre 522
1. Lecture hour 2. Vander s textbook (11 th edition) - in regards to exam - older editions (9 th, 10 th ) 3. Lecture notes - in regards to exam
Anatomy of the kidney
Functions of the kidneys-1 1. Regulation of water, inorganic ion balance, and acid-base balance 2. Removal of metabolic waste products from the blood and their excretion in the urine 3. Removal of foreign chemicals from the blood and their excretion in the urine
Functions of the kidneys-2 4. Production of hormones/enzymes: a. Erythropoietin: hormone that controls erythrocyte production b. Renin: enzyme that controls the formation of angiotensin and influences blood pressure and sodium balance c. 1,25-dihydroxyvitamin D: active vitamin that influences calcium balance
Gross anatomy Kidneys are paired organs: ~150 grams each Behind the peritoneum on either side of the vertebral column against the posterior abdominal wall Renal = pertaining to the kidneys
Figure 14.01
Renal cortex Renal medulla Renal pelvis Ureter Urine
Renal artery Renal vein
Afferent arteriole Interlobar artery Arcuate artery Renal artery Interlobular artery
Nephron
Nephron Each kidney contains ~1 million subunits called nephrons. Each nephron consists of: Renal corpuscle Glomerulus (capillary loops) Bowman s capsule Tubule
Figure 14.02Glomerulus (glomerular capillaries) Bowman s space in Bowman s capsule Proximal convoluted tubule Renal corpuscle Renal tubule Proximal tubule Proximal straight tubule Descending thin limb of Henle s loop Ascending thin limb of Henle s loop Loop of Henle Thick ascending limb of Henle s loop (containing macula densa at end) Distal convoluted tubule Distal convoluted tubule Cortical collecting duct Medullary collecting duct Collecting duct system Renal pelvis
(Glomerulus) Renal corpuscle
Renal corpuscle Bowman s capsule (parietal layer) Bowman s space Bowman s capsule (visceral layer: podocytes)
Glomerulus
Glomerular capillary wall Foot processes
Glomerular capillary wall (filtration barrier) Visceral glomerular epithelial cells (podocytes) GBM Endothelial cells
Glomerulus (pl. Glomeruli) Entangled capillary loops surrounded by Bowman s capsule Capillary wall consists of: endothelial cells glomerular basement membrane visceral epithelial cells (podocytes) Glomerulus filters blood to make urine.
Consecutive segments of the nephron Renal corpuscle Glomerulus Bowman s capsule Proximal tubule Proximal convoluted tubule (PCT) Proximal straight tubule (PST) Cortex Henle s loop Descending thin limb Ascending thin limb Thick ascending limb (macular densa at the end) Distal convoluted tubule Distal convoluted tubule (DCT) Medulla Cortex Collecting duct Cortical collecting duct (CCD) Medullary collecting duct (MCD) Medulla
Vascular supply of the nephron Peritubular capillaries
Basics of urine formation
Three processes of urine formation 1. Glomerular filtration 2. Tubular secretion 3. Tubular reabsorption
Glomerular filtration Urine formation begins with the filtration of plasma from the glomerular capillaries into Bowman s space (glomerular filtration). Glomerular filtrate (fluid in Bowman s space) is cell-free and except for proteins, contains all the substances in plasma in virtually the same concentrations as in plasma.
Tubular secretion/absorption As the glomerular filtrate passes through the tubules, its composition is altered by movements of substances. Tubules --> Peritubular capillaries Reabsorption Peritubular capillaries --> Tubules Secretion
Formation of urine Amount Amount Amount Amount excreted = filtered + secreted - reabsorbed
Peritubular capillary Example para-amino-hippurate (PAH) Example sodium, water Example glucose
The rate of filtration, reabsorption, or secretion is subject to physiological control. When the body content of a substance goes above or below normal, homeostatic mechanisms can regulate the substance s bodily balance by changing these rates. e.g. If a normal person drinks a lot of water, reabsorption of water is decreased and excess water will be excreted in the urine.