Kidney and urinary system parts and their functions
- 3. • Urinary system is also known as the renal system • It consist of kidneys, ureters, urinary bladder and urethra • 2 kidneys : which secrete urine • 2 ureters : which convey the urine from the kidneys to the urinary bladder • 1urinary bladder: where urine collects and is temporarily stored • 1 urethra :urine is discharged from the urinary bladder to the exterior
- 4. KIDNEYS • The kidneys lie on the posterior abdominal wall, one on each side of the vertebral column • Bean shaped ,reddish brown organs • 11 cm long, 6cm wide, 3cm thick and 150 g weigh
- 5. • Renal capsule: covered by a tough capsule fibrous connective tissue. Which encloses and protects kidney against infections and trauma • Renal cortex : reddish brown layer of tissue contains most of the nephrons • Medulla: inner layer of the kidney ,consisting of pale conical shaped striations, the renal pyramids, renal calyces and renal pelvis. Site for salt, water and urea absorption • Renal pyramid: triangular shaped unit in the medulla. Houses the loop of henle and collecting duct of the nephron
- 6. • Renal column : area b/w the pyramids, located in the medulla. Used as a space for blood vessel • Renal papillae: tips of the renal pyramids. release urine in to the calyces • Renal calyces: collecting sacs that surround the renal papillae. Transport urine from renal papillae to renal pelvis • Renal pelvis : cavity which lies in the center of the kidney and which extends into the ureter. Collects urine from all of the calyces in the kidney
- 7. • Renal arteries: transport oxygenated blood from the heart and aorta to kidneys for filtration • Renal veins: transport the filtered, deoxygenated blood from kidneys to the posterior venacava and finally the heart NEPHRON • Functional unit of kidney • Each kidney is formed of about 1 million nephrons
- 8. Types of nephron • Two types of nephron • Cortical nephron : 80-85 % of nephrons are cortical nephrons. Renal corpuscles are in outer cortex and loops of henle lie mainly in cortex • Juxtamedullary nephrons : 15-20% of nephrons are juxtamedullary nephrons. Renal corpuscles close to medulla and long loops of henle extend into deepest medulla
- 10. • Renal corpuscle:head of the nephron. It is composed of bowman's capsule and glomerulus • Bowman's Capsule: large double walled cup. It lies in the renal cortex . Sac that encloses glomerulus. Transfers filtrate from the glomerulus to the proximal convoluted tubule • Glomerulus: site for blood filtration. Surrounded by bowman's capsule . Removes both useful and non useful material • Proximal convoluted tubule: active segment of nephron. It reabsorb most useful substance of the fiterate.Sodium(65%),bicarbonate(90%),chloride(50 %)and glucose (nearly100%). It lies in renal cortex
- 11. • Loop of henle: U-shaped tube consist of descending and ascending limb . • Descending limb full permeable to water and completely impermeable to solutes (salt particles) • Receives filtrate from the pct allow water to be absorbed and passes salty filtrate to the next segment • Ascending limb imperable to water and actively transport salt to the interstitial fluid of the pyramids in the medulla • Passing filterate becomes dilute
- 12. • Distal convoluted tubule: highly coiled part of the nephron. receives dilute fluid from the ascending limb of the loop of henle. • Collecting duct : save water for the body BASIC RENAL PROCESS • There are 3 basic renal process • Glomerular filtration • Tubular reabsorption • Tubular secretion
- 13. • Glomerular filtration: the filtration of plasma from glomerular capillaries into the bowman’s space is termed glomerular filtration • During filtration blood enter the afferent arteriole and flows in to glomerulus where filtrate blood components such as water and nitrogenous waste will move towards glomerulus and non filterable components such as cells, albumin will exit efferent arteriole. These filtrate components accumulate in the glomerulus to form the glomerular filtrate. • Efferent arteriole is narrower than afferent helps in building hydrostatic pressure
- 14. • Flow of blood in the glomerulus creates hydrostatic pressure which forces molecules through glomerular filtration membrane • Tubular reabsorption: process by which solutes and water are removed from the tubular fluid and transported into the blood . • Removes useful solutes from the filtrate ,returns them in to blood • Tubular secretion: Substances move in to distal and collecting tubule s from the blood in the cappillaries around these tubules • removes additional wastes from the blood and adds them to the fitrate
- 17. Micturition • Process by which urine is voided from the urinary bladder • It is reflex process • Two sphincters, or valves the internal and external urethral sphincter control the flow of urine from the bladder
- 18. • Bladder continues to collect urine untill about 200ml have accumulated • Stretching of the bladder wall activates stretch receptors • Impulses transmitted to the sacral region oof the spinal cord and back to the bladder via splanchnic nerves cause the bladder to go in to reflex contractions • As the contraction s become stronger, stored in urine is forced past the internal urethral sphincter in to the upper part of the urethra
- 19. • It is then that a person feels the urge to void because the lower external sphincter is skeletal muscle is voluntarily controlled, choose to keep it closed and postpone bladder emptying temporarily • If it is convenient the external sphincter can be relaxed so that urine is flushed from the body • when one chooses not to void, the reflex contractions of the bladder will stop with in a minute and urine will continue to accumulate in the bladder • After 200 to 300 ml more have been collected , the micturition reflex occurs again
- 20. Plasma clearance • Amount of plasma cleared off a substance in given unit of time. It is also known as renal clearence • C=UV/P • C is plasma clearance • U is urine conc. • V is volume of urine • Plasma conc.
- 21. • Determination of clearance value for certain substances helps in assessing the following renal functions a. Glomerular filtration rate b. Renal plasma flow c. Renal blood flow • Glomerular filtration rate describes the flow rate of filtered fluid through the kidney • A substance that is completely filtered but neither reabsorbed nor secreted should be used to measure GFR • Inulin is the ideal substance used to measure GFR
- 22. • Inulin clearance- a known amount of inulin is injected into the body. After sometime, the conc of inulin in plasma and urine and the volume of urine excreted are estimated • To measure renal plasma flow ,a substance which is filtered and secreted but not reabsorbed should be used. such a substance is para-aminohippuric acid (PAH). PAH clearance indicates the amount of plasma passed through kidneys • Renal blood flow is volume of blood delivered to the kidneys per unit time • Renal blood flow can also be calculated RBF=RPF÷1-Hematocrit
- 23. BODY FLUIDS • Body is formed by solids and fluids • Fluid part is more than two third of the whole body Significance of body fluids • Homeostasis-body cells survive in fluid medium called internal environment. internal environment contains substances such as glucose, amino acids, lipids, vitamins etc.. Essential for growth & function of cell. water not only form the major constituent of internal environment and play an important role in homeostasis
- 24. • Transport mechanism- body water transport medium by nutrients and other essential substances enter the cells and unwanted substances come out. • Metabolic reaction-water inside the cells forms the medium for various metabolic reaction which are necessary for growth & functional activity of the cells • Temperature regulation- water maintaining normal body temperature
- 25. COMPARTMENT OF BODY FLUIDS • Total water in the body is 40L • It divided in to 2 major compartments • Intracellular fluid(ICF) – Its volume is 2.2L and it forms 55% of the total body water • Extracellular fluid (ECF)-Its volume is 18L and it forms 45% of the total body water • ECF is divided in to 5 subunits • Interstitial fluid and lymph • Plasma • Fluid in bones • Fluid in dense connective tissues like cartilage • Transcellular fluids
- 26. Acid –base balance • For normal function of body and normal enzyme activity a normal hydrogen ion conc. (normal pH) is essential. • pH is the –ve log of hydrogen ion conc. • A hydrogen ion is a single free proton release from hydrogen atom • pH of arterial blood =7.4 • pH of venous blood =7.85 • pH of urine=8.0 • Acidosis- pH of body fluid less than normal • Alkalosis-pH of body fluid more than normal
- 27. Acids • Acids are molecules that release H+ ion in solutions • Strong acids dissociate rapidly and release large amount of H+ion • HCL H+ + CL- • Weak acids have less tendency to dissociate and release less amount of H+ ion • H2CO3 H++ HCO3 -
- 28. Bases • Bases are molecules that can accept H+ ion • Strong bases react strongly with H+ ion • H + + OH- H2O • Weak bases bind weakly with H+ion • H++ HCO3 H2CO3
- 29. Buffer • A buffer is any substance that can reversibly bind H+ • The general form of buffering reaction • Buffer+H+ Hbuffer • Resists sudden changes in pH
- 30. Renal Control of Acid-Base Balance • The kidneys control acid-base balance by excreting either acidic or basic urine • Excreting acidic urine reduces the amount of acid in extracellular fluid • Excreting basic urine removes base from the extracellular fluid
- 31. • The kidneys regulate extracellular fluid H+ concentration through three fundamental mechanisms: (1)secretion of H+ (2) reabsorption of filtered HCO3 (3) production of new HCO3
- 32. Secretion of hydrogen ions and reabsorption of bicarbonate ions by the renal tubules • About 80 to 90 percent of the bicarbonate reabsorption and H+ secretion occurs in the proximal tubule
- 33. Mechanism of Hydrogen ion secretion and Bicarbonate Reabsorption
- 34. • The secretory begins when co2 either diffuses into the tubulr cells or is formed by metabolism in the tubular epithelial cells • co2 under the influenze of the enzyme carbonic anhydrase combine with h2o to form H2CO3, which dissociates into HCO3 and H+ • H+ secreted from the cell into tubular lumen by sodium hydrogen counter transport • When an Na+ moves from the lumen of the tubule to the interior of the cell,it first combines with a carrier protein in the luminal border of cell membrne • Na+ moves into the cell down a conc. gradient that has been established by the Na-k atpase pump in the basolateral membrane
- 35. • The gradient for Na+ moves in to the cell provides energy for moving H+ in the opposite direction from the interior of the cell to the tubular lumen • The HCO3 generated in the cell then moves downhill across the basolateral membrane to interstitial fluid and peritubular capillary blood • The net result is every H+ secreted into tubular lumen ,an HCO3 enters the blood
- 36. Primary Active Secretion of H+ in the Intercalated Cells of Late Distal and Collecting Tubules
- 37. • It occurs at the luminal membrane of the tubular cell where H+ is transported directly by a specific protein a hydrogen transporting ATPase • The energy required for pumping the H+ is derived from the breakdown of ATP to adenosine diphosphate • Primary active secretion of H+ occurs in a special type of cell called intercalated cells of the distal tubule and collecting duct.
- 38. • Hydrogen ion secretion in these cells is accomplished in to 2 steps • 1) the dissolved CO2 in this cell combines with H2O to form H2CO3 • 2) the H2CO3 then dissociates, which is reabsorbed in to blood plus H+ which is secreted into the tubule by means of the hydrogen ATPase mechanism
- 39. Excretion of Excess H+ and Generation of New Bicarbonate by the Ammonia Buffer System
- 40. • Ammonium ion is synthesised from glutamine which comes mainly from the metabolism of liver. • The glutamine delivered to the kidneys is transported into the epitheliel cells of proximal tubule • Once inside the cell each molecule of glutamine is metabolised ina series of reaction to ultimately form twoNH4+ and twoHCO3- • The NH4+ is secreted in to the tubular lumen by a counter transport mechanism in exchange of sodium, which is rebsorbed • The HCO3 is transported across the basolateral membrane along with the reabsorbed Na+ to the interstial fluid and taken by the peritubular cappilaries
- 41. • For each molecule of glutamine metabolised in the proximal tubules two NH4+ are secreted into the urine and two HCO3 are reabsorbed in to the blood • The HCO3 generated by this process constitutes new bicarbonate