Presentation on theme: "Chapter 24 Structure and Function of the Kidney"— Presentation transcript:
1 Chapter 24 Structure and Function of the Kidney Essentials of PathophysiologyChapter 24 Structure and Function of the Kidney
2 Pre lecture Quiz true/false Large molecules, such as protein, easily cross the glomerular wall.During times of decreased cardiac output, the glomerular filtration rate is also decreased.The activation of vitamin A, which is important for intestinal reabsorption of calcium, occurs in the kidney.The kidneys perform excretory and endocrine functions.In the adult, the kidneys are perfused with 20% to 25% of the cardiac output.
3 Pre lecture Quiz The functional unit of the kidney is the __________. Fluid and particles from the blood are filtered through the capillary membrane into a fluid-filled space in the __________ capsule.The loop of __________ plays an important role in controlling the concentration of the urine, and is divided into three segments.The kidney synthesizes __________, which stimulates bone marrow production of red blood cells.Serum __________ reflects the GFR (glomerular filtration rate) and can be used as an estimate of renal function.Bowman’sCreatinineerythropoietinHenlenephron
4 Functions Kidneys filter the blood Remove water- soluble wastes Help control blood pressure and compositionHelp maintain red blood cell levelsDiaphragmT11Renal arteryT12Adrenal glandRenal veinLeft kidneyRight kidneyAortaInferior vena cavaUreterBladder
5 Nephrons are Microscopic Tubules That Form the Urine Insert fig 23-4
6 Three Components of Urine Formation FiltrationReabsorptionSecretion
7 Filtration Happens in the Glomerulus Proximal tubuleEfferent arterioleBowman’s spaceAfferent arteriole
8 Glomerular Filtration Glomerular capillary cells sit along a basement membraneBowman’s capsule epithelium cells sit along the same basement membraneThey stand up away from the membrane on pseudopodsFluid filters across the basement membrane and between the pseudopods
9 Glomerular Filtration Rate Glomerular filtration rate = 125 mL/minDiscussion:How would it change if you:Constricted the efferent arterioles?Constricted the afferent arterioles?Decreased the blood pressure?Which of the following will increase GFR?Epinephrine – ProstaglandinsNO – Endothelin
10 If 125 mL of Ultrafiltrate Is Formed Each Minute, How Much Is Formed in a Day? 60 min/hr X 24 hr/day = 1440 min/day X 125 ml/min = 180,000 ml/day =180 L/day of ultrafiltrateActual urine excretion is 1.5 L a dayProximal convoluted tubule reabsorbs about 60% of nutrients and ions in the urineAbsorbs at an automatic rateThe amount of a solute it can reabsorb is the transport maximumNutrients not reabsorbed pass out in the urineWater follows the solutes back into the blood
11 QuestionTell whether the following statement is true or false. If GFR increases, urine output (UO) will decrease.
12 AnswerFalse Rationale: If GFR increases, it means that fluid is moving more quickly across the basement membrane/through the pseudopods. This means that more fluid will become filtrate and less fluid will be reabsorbed into the blood. If less fluid is reabsorbed, more fluid is left to be excreted (increasing UO).
13 When FILTRATE Reaches Distal Tubule Juxtaglomerular cells measure blood flow in the afferent arteriole and urine flow and compositionThey can release reninJuxtaglomerularcells(Image modified from Bowne, P.S. . Kidneys tutorial. Used with author’s permission.)
14 Renin Starts the RAA Pathway Which turns on the Na+/K+ ATPase in the distal tubuleNa+ and water are reabsorbedK+ is secretedJuxtaglomerularcells(Image modified from Bowne, P.S. . Kidneys tutorial. Used with author’s permission.)
15 Renin-Angiotensin-Aldosterone System Turns on the Na+/K+ ATPase in the distal tubuleNa+ and water are reabsorbedRaises blood volumeDoes not change blood osmolarityK+ is secretedLowers blood K+
16 Blood volume Blood K+ Urine volume Urine Na+ Discussion What changes in these variables would turn on the RAA system?Blood volumeBlood K+Urine volumeUrine Na+
17 Reabsorbing Water Alone to Reduce Blood Osmolality This happens in the inner layer of the kidney, the medullaThe loop of Henle contains ion pumps
18 Osmolality cont. The NaCl pumped into the medulla makes it salty It is hypertonic to the urine in the collecting ductWater moves from the collecting duct into the salty medulla and enters the blood
20 AnswerCollecting ductRationale: Reabsorption of water occurs in the medulla (the inner layer of the kidney). Na+Cl- leaves the loop of Henle, which makes it hypertonic to the urine in the collecting duct. Water moves from the collecting duct into the blood (reabsorption).
21 Amount of Water Absorbed Depends on how much can move out of the collecting ductAntidiuretic hormone makes the duct permeable to water
22 Antidiuretic Hormone (ADH) Makes collecting duct more permeable to waterMore water can be reabsorbed from the urine into the bloodBlood osmolarity decreases
23 QuestionTell whether the following statement is true or false. Increased ADH decreases urine output (UO).
24 AnswerTrue Rationale: ADH makes the collecting duct more permeable to water, so that more water can leave the duct and be reabsorbed into the blood. More reabsorption means that there is less fluid to be excreted (↓ UO).
25 ScenarioA man was given a drug that stopped the ion pumps in the loop of Henle.Question:What happened to:Medulla osmolarity?Na+ levels in the distal convoluted tubule?Amount of water reabsorbed from the collecting duct?Renin levels?Blood K+?
26 Removing NaCl and Water From Your Blood Atrial natriuretic peptide and B-type natriuretic peptideANP is made by overstretched atriaBNP is made by overworked ventriclesBoth cause the kidneys to stop reabsorbing NaClThe NaCl and water are lost in the urine, reducing blood volume and decreasing the stretch and workload of the heart
27 brain natriuretic peptide made by the ventricles DiscussionWhat will happen to urine if:Aldosterone is given?ADH levels are high?BNP levels are elevated?brain natriuretic peptide made by the ventricles
28 Discussion A man has severe renal disease. Question: Why does he develop:Anemia?Weak bones?
29 QuestionWhat hormone secreted by the kidneys stimulates RBC formation in the bone marrow?ReninErythropoietinAldosteroneAngiotensin
30 AnswerErythropoietinRationale: Erythropoietin literally means “producing erythrocytes/RBCs.” Decreased levels of this hormone lead to anemia; increased levels lead to polycythemia.
31 Kidney Functions The kidneys clear wastes out of the blood Renal clearance is a measurement of how much blood the kidneys clean in a minuteIf the blood contains 1 mg waste/100 mL blood If the person produces 1 mL urine per minute And if the urine contains 1 mg waste/mL QuestionHow much blood did the kidney clean in one minute?RC = 100𝑚𝐿 𝐵𝑙𝑜𝑜𝑑 1𝑚𝑔 𝑊𝑎𝑠𝑡𝑒 + 1𝑚𝑔 𝑊𝑎𝑠𝑡𝑒 1𝑚𝐿 𝑈𝑟𝑖𝑛𝑒 + 1𝑚𝐿 𝑈𝑟𝑖𝑛𝑒 1𝑚𝑖𝑛RC= 𝟏𝟎𝟎𝒎𝑳 𝑩𝒍𝒐𝒐𝒅 𝒎𝒊𝒏
32 Kidney Functions (cont.) If the kidneys fail, waste builds up in the bloodWhat is the percent of kidney function when serum creatinine is:2 mg/dL?3 mg/dL?10 mg/dL?
33 Kidney Functions (cont.) If the kidneys fail, waste builds up in the bloodKidney function = Normal serum creatinineCurrent serum creatinine
34 Discussion What would each of these test results indicate? Severe proteinuriaCasts with red blood cells in themLow specific gravitySerum creatinine = 6 mg/dLBUN = 35 mg/dL, serum creatinine = 1.2 mg/dL