3B-AUBF-LEC-MODULE1.pdf

Analysis of Urine and Body Fluids Lecture Notes I BSMLS-3B MODULE 1 o Renal capsule - thin & fibrous membrane that covers each RENAL PHYSIOLOGY kidney Four (4) main components composin...

Analysis of Urine and Body Fluids Lecture Notes I BSMLS-3B MODULE 1 o Renal capsule - thin & fibrous membrane that covers each RENAL PHYSIOLOGY kidney Four (4) main components composing the Urinary System: o Adrenal gland – an endocrine gland situated above each 1. Kidney – where urine is formed from filtration of blood. kidney. 2. Ureters – carry the urine to the bladder. o Contains approximately 1 to 1.5 million nephrons. 3. Bladder – stores the urine. Nephron 4. Urethra – delivers the urine for excretion outside the body. - functional unit of the kidney - controls the kidney’s ability to clear waste products from the blood and maintain the body’s essential water & electrolyte balance by renal function:  Renal Blood flow  Glomerular filtration  Tubular reabsorption  Tubular secretion Renal function is influenced by:  Blood volume  Pressure  Composition  Hormones (from Adrenal & Pituitary glands) Kidneys: - paired organs located on the posterior wall of the abdominal cavity, one on each side of the vertebral column. - bean-shaped organ. - renal hilum – indention on the medial border which the renal - has two (2) types: artery enters and the renal vein & ureter leaves. Cortical Nephrons Juxtamedullary Nephrons - Function: - 85% of the nephrons - “juxta” = near or beside  maintains homeostasis through regulation of body fluids. located in the cortex - concentrates urine.  acid-base balance - removal of waste from - have longer loops of henle that  electrolyte balance the blood and extends to the medulla.  excretion of waste products reabsorption of - where adjustment of  maintains blood pressure & erythropoiesis. nutrients. electrolytes (e.g. sodium- - End product: Urine - waste products that are potassium) in water takes removed or processed: place. o toxins o medication & drugs o antibiotics o urea o ammonia o excess hydrogen & ammonium ions KIDNEY FUNCTION Inferior vena cava 1. Renal Blood Flow Abdominal aorta – supplies the renal vein i. Renal artery – supplies blood to the kidney originated – supplies renal artery from the Abdominal aorta. *Kidneys receives appx. 25% of the blood from the heart. ii. Blood enters the capillaries through afferent arterioles. iii. Flows through glomerulus. iv. Then exits through efferent arterioles. *Different sizes of the arterioles help creates the hydrostatic pressure differential. AGDALIPE, AMUAN, AUJERO, BERJAMIN, DORADO C, ERMITANIO, 1 GUPITEO, LARIOSA, RESURRECCION Analysis of Urine and Body Fluids Lecture Notes I BSMLS-3B - Important for glomerular filtration. *Filtration process: - Maintains consistency of glomerular capillary i. Blood travels through the capillaries of the glomerulus. pressure & renal blood flow in the glomerulus. ii. Filtration causes a lot of plasma contents to spill out in v. Blood then enters the peritubular capillaries and the Bowman’s space due to the glomerular filtration vasa recta that flows slowly through the cortex and the membrane. medulla. iii. The fluid (composed of plasma contents) in the bowman’s space is called a Filtrate & forms the primary *Peritubular capillaries - surrounds the Proximal urine. Convoluted Tubule (PCT), where immediate iv. Glomerular pressure. reabsorption of essential substance takes place, and - hydrostatic pressure from smaller size of efferent Distal Convoluted Tubule (DCT) for the final adjustment arterioles & glomerular capillaries enhances filtration. of urinary composition. - necessary to overcome the opposition of pressures *Vasa recta – located adjacent to the ascending & from the fluid within the Bowman’s & oncotic pressure descending loop of henle in the juxtamedullary of the unfiltered plasma proteins in the capillaries. nephrons. - juxtamedullary apparatus – contains an auto-regulatory - Major exchanges of water & salt between blood & mechanism that maintains the glomerular blood medullary interstitium. pressure at a constant rate regardless of the *Maintains osmotic gradient (salt concentration) fluctuations in systemic blood pressure through which is necessary for renal concentration. increasing or decreasing the size of the afferent vi. Blood is then returned to the renal vein. arteriole. *Average body size of 1.73 m2 of surface = 1200 mL/min (total Blood pressure Decrease Increase renal blood flow), 600 – 700 mL/min (renal plasma flow). Afferent Dilation Constriction arterioles Efferent Constriction Dilation arterioles Effect Prevents an Prevents over- increase in the filtration or blood level of toxic damage to the waste products. glomerulus. v. Renin-angiotensin-aldosterone system (RAAS) - controls the regulation of the flow of blood to & 2. Glomerular Filtration within the glomerulus. - Glomerulus – serves as a nonselective filter of plasma - responds to changes in substance with molecular weight of >70,000. blood pressure & - First step in filtering the blood. plasma sodium content. - Capillary tuft – a coil of appx. eight (8) capillary lobes *Monitored by located within the Bowman’s capsule. juxtaglomerular - Bowman’s capsule – thin, double-walled capsule. apparatus consists of: - Bowman’s space – space inside the capsule and surround  Juxtaglomerular the glomerulus. cells (afferent *Factors affecting the actual filtration process: arterioles) Cellular structure of glomerulus  Macula densa (DCT) - plasma filtrate must pass three (3) cellular layers: - Low plasma sodium content = decreases water 1) Capillary wall membrane (endothelial cells) retention (circulatory system) ---> decreased overall - endothelial cells contain pores (fenestrated). blood volume & subsequent decrease in BP. - pores increase capillary permeability but does *Macula densa senses these changes and a cascade not allow the passage of large molecules & reaction within RAAS occurs: blood cells. o Renin (enzyme produced by Juxtamedullary 2) Basement membrane (basal lamina) cells) – secreted & reacts with angiotensinogen - large molecules are further restricted when it (blood-borne substrate secreted by the liver in passes the basement membrane and thin response to low BP and sodium content)  inert membranes formed by intertwining foot hormone angiotensin I. processes of the podocytes (inner layer of o Angiotensin I passes through the lungs, Bowman’s capsule). Angiotensin Converting Enzyme (ACE) changes it 3) Visceral epithelium of the Bowman’s capsule to angiotensin II (active form). o Angiotensin II corrects renal blood flow through: - vasodilation of afferent & constriction of efferent. - stimulating reabsorption (through PCT) of sodium-retaining hormone by:  Aldosterone (Adrenal cortex) – Sodium reabsorption & excretion of potassium in the DCT and CD.  Antidiuretic hormone (ADH) (hypothalamus) – Water reabsorption in the Collecting duct (CD). AGDALIPE, AMUAN, AUJERO, BERJAMIN, DORADO C, ERMITANIO, 2 GUPITEO, LARIOSA, RESURRECCION Analysis of Urine and Body Fluids Lecture Notes I BSMLS-3B o Symporters – cotransporter proteins. *Sodium is transported via cotransport proteins that also transports glucose, amino acids, & vitamins. o Tubular cells of PCT have sodium-potassium pumps that moves sodium back into the interstitium. *ATP is used to create interstitial sodium gradient which helps to drain out sodium. o Paracellular movement – sodium and other ions that moves through leaky cell junctions between the cells. o Active transport can be influenced by concentration of the substance being transported. *When a plasma concentration of a substance that is normally completely reabsorbed become abnormally high and the filtrate concentration exceeds the maximal reabsorptive capacity (Tm), the substance appears in the urine. *Renal threshold – plasma concentration at which active transport stops.  Renal threshold of glucose: 160 to 180 mg/dL = glucose appears in the urine.  Knowledge in renal threshold & plasma concentration can be used to distinguish excess solute filtration & renal tubular damage. Tubular Concentration i. Begins in the Descending & Ascending loops of Henle. *Filtrate is exposed to high osmotic gradient of the renal medulla. *As systemic BP & plasma sodium content increases = secretion ii. Water is removed by osmosis in the D. loop of Henle. of Renin decreases. iii. Sodium & Chloride are reabsorbed in A. loop of Henle. *Actions of Angiotensin II produce a constant pressure within iv. Water - impermeable walls of ascending loop of Henle the nephron. prevents excessive reabsorption of water. *Result of above glomerular mechanism: every one (1) minute *Countercurrent mechanism – a selective reabsorption = 2-3 million glomeruli filter appx. 120 mL of water-containing- process which maintains the osmotic pressure of the low-molecular-weight substance. medulla; only happens in the loops of Henle. 3. Tubular Reabsorption v. Sodium & Chloride that leaves the filtrate in A. loop prevents - the body can’t lose 120 mL of water-containing essential the dilution of the medullary interstitium by the water substances per minute reabsorbed from D. loop. - movement of substance from PCT to peritubular *Maintenance of osmotic gradient is essential for the final capillaries. concentration. - nephrons in PCT reabsorbs water and essential vi. The concentration of the filtrate leaving the A. loop is low due substances through cellular transport mechanism as the to the reabsorption of salt and not water (due to the part of plasma ultra-filtrate enters it. tubule). *Tubular Reabsorption Mechanism: vii. Reabsorption of sodium continues in DCT but it is now controlled by aldosterone (regulates reabsorption in Substance Location response to the body’s need for sodium). Active transport Glucose, PCT - substance to reabsorb amino acids, must combine with a salts carrier protein Chloride Ascending loop contained in the of Henle membranes of the Sodium PCT & DCT renal tubular cells. - electrochemical released in this interaction transfers substance across the membranes and back into the blood stream. Passive transport Water PCT, A. loop of - movement of Henle, & molecule across a Collecting duct Collecting Duct Concentration membrane as a result Urea PCT & A. loop - Final concentration of the filtrate through reabsorption of of differences in of Henle water begins in DCT & continues to Collecting Duct (CD). concentration or Sodium A. loop of Henle *This depends in the osmotic gradient of the medulla and the electrical potential on hormone vasopressin (antidiuretic hormone/ADH). opposite sides of the - As the diluted filtrate in CD comes in contact with higher membrane. osmotic concentration of the medullary interstitium, passive - gradients – physical reabsorption of water occurs but the process is controlled by differences. AGDALIPE, AMUAN, AUJERO, BERJAMIN, DORADO C, ERMITANIO, 3 GUPITEO, LARIOSA, RESURRECCION Analysis of Urine and Body Fluids Lecture Notes I BSMLS-3B the presence or absence of ADH (renders the wall of DCT & 2. Tubular Reabsorption Test CD permeable or impermeable to water). - First function to be affected in a renal disease. *Act as a guard. - Concentration tests: *High level of ADH = increase permeability  increased  Specific gravity reabsorption of water & low concentration of urine. - most useful screening procedure & quantitative *Absence of ADH = impermeable to water  large volume measurement of renal concentrating ability. of urine. - it is influenced by the number & density  Production of ADH is determined by the state of the (molecular weight) of the particles. body hydration.  Osmometry *NOTE: - performed for more accurate evaluation of renal ↑ BODY HYDRATION = ↓ ADH = ↑ URINE VOLUME concentrating ability. ↓BODY HYDRATION =  ADH =  URINE VOLUME - measure only the number of particles in a solution. *Chemical balance in the body is the final determinant of urine  Obsolete tests volume & concentration. - Fishberg test – patients are deprived of fluids for 24 4. Tubular Secretion hourse before measuring specific gravity. - passage of substances from the blood (peritubular - Mosenthal test – compares the volume & specific capillaries) to the tubular filtrate. gravity of day & night urine samples to evaluate - two (2) major functions: concentrating ability. 1. Elimination of waste products nit filtered by 3. Tubular Secretion & Renal Blood Flow Test glomerulus. - Total renal blood flow through the nephron is used. 2. Regulation of acid-base balance through secretion - It must be measured by a substance that is secreted of hydrogen ions. rather than filtered. - foreign substance (e.g. medications) can’t be filtered by - Excretion of the dye Phenolsulfonphthalein (PSP) was glomerulus since it is bound to plasma proteins. used to evaluate these functions. *When these substances enter peritubular capillaries, it - P-aminohippuric acid (PAH) test – most commonly develops strong affinity for tubular cells and dissociate from associated test with this function. carrier proteins resulting to their transport into the filtrate. - Titratable acidity & urinary ammonia – normal person: *its major site is PCT. appx. 70 mEq/day of acid in the form of titratable acid (H+), hydrogen phosphate ions, or ammonium ions. RENAL FUNCTION TESTS 1. Glomerular Filtration test - Earliest GFT measures urea. - Inulin was the original reference method. - In present, primary substance used are:  Creatinine  Beta2-microglobulin  Cystatin C  Radioisotopes (possible) - Greatest source of error: use of improperly timed urine specimens. - Clearance Test – the rate to remove the substances in the blood *Criteria: 1. The substances should not be absorbed not secreted 2. The substances are stable in urine for 24 hours 3. The substances are stable in the blood for 24 hours 4. The substances are naturally produced by the body 5. The reagents should be readily available. - Creatinine clearance: a. UV/P b. UV/P X 1.73/A o U= urine, P = plasma creatinine mg/dL, V = urine volume in mL/min o Normal creatinine clearance value: 120 mL/min o Men: 107 to 139 mL/min o Women: 97 to 107 mL/min AGDALIPE, AMUAN, AUJERO, BERJAMIN, DORADO C, ERMITANIO, 4 GUPITEO, LARIOSA, RESURRECCION