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Renal1 - PHGY210 Renal Physiology Tomoko Takano MD...

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Unformatted text preview: 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: March 18 (Tue) 5:30, McIntre 522 1. Lecture hour 2. Vander’s textbook - in regards to exam - 9th and 10th editions 3. Lecture notes - in regards to exam Anatomy of the kidney Functions of the kidneys-1 1. Regulation of water and inorganic ion balance potassium, sodium, chloride 2. Removal of metabolic waste products from the blood and their excretion in the urine Removal of foreign chemicals from the blood and their excretion in the urine 3. e.g. elimination of unmetabolized or metabolized antibiotics Functions of the kidneys-2 4. Production of hormones/enzymes: endocrine function a. Erythropoietin: hormone that controls erythrocyte production in the bone marrow b. Renin: enzyme that controls the formation of angiotensin and influences blood pressure and sodium balance - critical part of the RAA system (renin-angiogensin-aldosterone) c. 1,25-dihydroxyvitamin D: active vitamin that 1 influences calcium balance kidneys are responsible for activation hydroxylation - final step in Gross anatomy Kidneys are paired organs: ~150 grams each - can normally function with a solitary kidney peritoneal cavity Behind the peritoneum on either side of the vertebral column against the posterior abdominal wall - they are situated very close to the back (3-5cm), it is very easy to reach them with needles Renal = pertaining to the kidneys Figure 14.01 parenchyma responsible for making urine Renal cortex - usually continuous Renal medulla - made up of blocks - 'inverted pyramids' - renal pyramids Renal pelvis Ureter - the cortex and medulla are very different in colour and continuity Urine Renal artery Renal vein Afferent arteriole branch of interlobular arteries supplies blood the functional unit of the kidney, the nephron Interlobar artery lies between the lobes (inverted pyramids) of the medulla Arcuate artery branches out at 90 degrees towards the surface of the kidney Renal artery Interlobular artery Nephron - the functional unit of the kidney - blood supply comes from the afferent arteriole, a branch of an interlobular artery Nephron • Each kidney contains ~1 million subunits called nephrons. • Each nephron consists of: continuation of the afferent arteriole Renal corpuscle Glomerulus (capillary loops) Bowman’s capsule Tubule renal corpuscle - first formation of urine - always in the cortex, never found the medulla - urine formation starts in the cortex and continues throughout the medulla Figure 14.02 Glomerulus (glomerular capillaries) Renal corpuscle Bowman’s space in Bowman’s capsule Proximal convoluted tubule Renal tubule Proximal tubule Proximal straight tubule proximal - close to an anatomical reference point - in renal anatomy, the renal corpuscle Descending thin limb of Henle’s loop tubule becomes extremely thin 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 Collecting duct system Medullary collecting duct Renal pelvis many nephrons connect together Renal corpuscle (Glomerulus) entangled capillary loop Renal corpuscle Bowman’s capsule (parietal layer) Bowman’s space where the first urine is made Bowman’s capsulemonolayer of (visceral layer: podocytes) Glomerulus - in the area of the afferent and efferent arterioles - important in the secretion of renin Glomerular capillary wall - 'feet' = secondary processes - tightly surround the glomerular capillary wall Foot processes endothelial cells needed to filter plasma Glomerular capillary wall (filtration barrier) bowman's space Visceral glomerular epithelial cells (podocytes) GBM glomerular basement membrane 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 Cortex Proximal tubule Proximal convoluted tubule (PCT) Proximal straight tubule (PST) Henle’s loop Descending thin limb Medulla Ascending thin limb Thick ascending limb touches to the originating renal corpuscle (macular densa at the end) Cortex Distal convoluted tubule Distal convoluted tubule (DCT) Collecting duct Cortical collecting duct (CCD) Medullary collecting duct (MCD) Medulla Vascular supply of the nephron Peritubular capillaries - provide blood supply to the nephron - site of reabsorption Basics of urine formation Three processes of urine formation 1. 2. 3. Glomerular filtration Tubular secretion 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. - cells and proteins (albumins, Ig) are too large to be filtered - protein-urea is not normal 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 glomerulus --> bowman's corpuscle peritubular capillary --> tubule Amount Amount excreted = filtered Amount Amount + secreted - reabsorbed not the same as excreted Peritubular capillary - everything remaining in the peritubular capillary is secreted - complete elimination from the kidney with one pass through the nephron - some is reabsorbed and some is excreted - substance is completely reabsorbed by the tubule - nothing is excreted Example Example para-amino-hippurate sodium, water is know to be completely (PAH) eliminated through secretion can be used for tests Example glucose - can diagnose diabetes by glc excretion 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. - water is usually reabsorbed 99% ...
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