Renal Physiology and Function of Kidney.
- 1. RENAL SYSTEM
- 2. Renal system The renal system consists of the kidney, ureters, and the urethra. The overall function of the system filters approximately 200 liters of fluid a day from renal blood flow which allows for toxins, metabolic waste products, and excess ion to be excreted while keeping essential substances in the blood. The kidney regulates plasma osmolarity by modulating the amount of water, solutes, and electrolytes in the blood. It ensures long term acid-base balance and also produces erythropoietin which stimulates the production of red blood cell. It also produces renin for blood pressure regulation and carries out the conversion of vitamin D to its active form.
- 5. INTRODUCTION The kidneys are 1 % of cardiac output and receive 25% of the total blood supply Two kidneys in all mammals located retroperitoneally at the level of lower ribs Protected by the 11th and 12th ribs from the injury Left one is a bit on the anterior side as compared to the right
- 6. PHYSIOLOGICAL ANATOMY OF KIDNEY Outer darker region is cortex Inner lighter region is the medulla Calyces (major and minor) Renal pyramids Renal pelvis Blood vessels
- 7. STRUCTURE OF KIDNEY 1. Renal pyramid 2. Interlobar artery 3. Renal artery 4. Renal vein 5. Renal hilum 6. Renal pelvis 7. Ureter 8. Minor calyx 9. Renal capsule 10. Inferior renal capsule 11. Superior renal capsule 12. Interlobar vein 13. Nephron 14. Minor calyx 15. Major calyx 16. Renal papilla 17. Renal column
- 8. FUNCTIONS OF THE KIDNEY Kidney has two major functions: 1. Filtration of blood: Removes metabolic wastes from the body, especially those containing nitrogen 2. Regulation: Blood volume and composition Electrolytes Blood pH Blood pressure
- 9. NEPHRONS Nephron is the structural and functional unit of the kidney 2,400,000 nephrons collectively in both kidneys Basically composed of: Renal corpuscle (in whish fluid is filtered) A long tubule (converts the filterate into urine on its way to the renal pelvis)
- 10. STRUCTURE OF NEPHRON Bowman’s Capsule Proximal convoluted tubule Loop of Henle (descending limb and ascending limb) Distal convoluted tubule Collecting tubule Collecting duct
- 11. NEPHRON Nephron is composed of: Renal corpuscle (where fluid is filtered) 1. Glomerulus (capillary tuft formed by the afferent arteriole which later on join to form the efferent arteriole) 2. Bowman’s capsule that is cup like start of nephron having two layers: 1. parietal layer 2. visceral layer Between these layers is the capsular space where the ultrafiltrate enters
- 12. Renal corpuscle
- 13. NEPHRON Renal tubule Filtered fluid passes through it and Is divided in 3 portions: 1. Proximal convoluted tubule 2. Loop of Henle (it has 3 portions) 1. Descending limb 2. Thin ascending limb 3. Thick ascending limb 3. Distal convoluted tubule Distil convoluted tubules empty into a collecting duct
- 14. NEPHRON
- 15. Glomerulus A network of at least 50 parallel and anastomosing capillaries covered by epithelial cells and encased in Bowman’s Capsule Pressure of the blood in the Glomerulus leads to filtration of the fluid in the Bowman’s capsule that is called as ultrafiltrate After this the filterate enters in the proximal tubule which lies in the cortex of the kidney along with glomerulus
- 16. BLOOD SUPPLY TO THE GLOMERULUS Blood enters the glomerulus by afferent arteriole and leaves it by efferent arteriole The afferent arteriole divides into the capillaries which rejoin to form the efferent arteriole
- 17. PROXIMAL TUBULE AND LOOP OF HENLE From proximal tubule the fluid enters into the Loop of Henle that dips deeply in the mass of the kidney Some loops of Henle are dipped all the way throughout medulla Each loop has a descending and an ascending limb Thin segment of loop of Henle (wall of descending limb and lower area of ascending limb is thin) Thick segment of ascending limb (located in the renal cortex after its turning back to cortex)
- 18. DISTAL TUBULE AND COLLECTING DUCT Loop of Henle distal tubule (lies in the cortex like proximal tubule) As many as 8 distal tubules coalesce to form collecting tubule Collecting tubule turns down to medulla collecting duct larger collecting duct that penetrates all the way through medulla parallel to loop of Henle
- 19. Cont……. Largest collecting duct via tips of renal papillae (conical projections of medulla) empty into the renal calyces (recesses of renal pelvis) renal pelvis About 240 collecting ducts are present in each kidney each of which receives urine from 4000 nephrons. 99 % of water and varying amounts of its solutes are normally reabsorbed from glomerular filterate while its passage through the tubules Remaining water and dissolved substances urine
- 20. Cont……
- 22. CONT…..
- 23. PERITUBULAR CAPALLARIES Extensive network of capillaries surrounding the entire tubular system of the kidney Receives blood from efferent arteriole Most of it lies in the cortex along the sides of proximal tubule, distal tubule and collecting tubule
- 24. VASA RECTA Long straight capillary loops extending from the lower portion of peritubular capillary network Extend into medulla along side by side with loops of Henle Loop back into cortex and empty into the cortical veins
- 25. FUNCTIONs OF NEPHRON Basic function is to clean or clear the blood plasma from unwanted substances as it passes through the kidney Urea, creatinine, uric acid and urates are the substances that must be cleared The excess level of ions in the blood such as sodium, potassium, chloride and hydrogen ions is also cleared
- 26. SUMMARY OF KIDNEY STRUCTURE
- 27. MECHANISMS OF NEPHRON FUNCTION Principal mechanism is: Nephron filters a large proportion of the plasma in the flowing glomerular blood (1/5th of it) through the glomerular membrane into the tubules of nephrone The wanted substances (especially water and electrolytes) are reabsorbed by the peritubular capillaries while the unwanted substances fail to be reabsorbed and pass into urine.
- 28. CONT ….. Excretion (secondary mechanism) Substances are secreted from the plasma directly through the epithelial cells lining the tubules into the tubular fluid So urine filtered substances + secreted substances
- 29. BLOOD SUPPLY TO THE KIDNEY Renal artery Interlobar artery Interlobular artery Arcuate artery
- 30. CONT ….. Afferent arteriole Glomerular capillaries Efferent arteriole Peritubular capillaries and vasa recta
- 31. CONT ….. Arcuate vein Interlobular vein Interlobar vein Renal vein
- 32. BLOOD FLOW THROUGH THE KIDNEY Renal fraction: The portion of total cardiac output that passes through the kidney
- 33. SPECIALTY OF RENAL VASCULATURE Arcuate artery afferent arteriole glomerulus efferent arteriole peritubular capillaries arcuate vein Two capillary beds are associated with the nephron: Glomerular capillary bed Peritubular capillaries The glomerular capillary is a high pressure bed and the peritubular capillary bed is a low pressure bed
- 34. CONT ….. Glomerular capillary bed: Due to high pressure its function is fluid filtration out of glomerulus into the Bowman’s capsule Peritubular capillary bed: Due to low pressure the fluid is continuously absorbed into the blood
- 35. FUNCTIONS OF THE PERITUBULAR CAPILLARIES About 180 liters fluid is filtered from all the glomeruli each day all is reabsorbed from the tubules into the peritubular capillaries except 1 to 1.5 liters (urine) Four times as much fluid as reabsorbed by the venous ends of all the other capillaries of the body Peritubular capillaries are extremely porous so osmosis of the fluid is very rapid resulting into rapid reabsorption
- 36. FUNCTION OF URETER The ureters are a component of the urinary system. Urine, produced by the kidneys, travels along the ureters to the bladder. It does this through regular contractions called peristalsis
- 38. FUNCTION OF URETHRA The urethra is the tube that lets urine leave your bladder and your body. If you were assigned male at birth, your urethra passes through your prostate and into your penis. If you were assigned female at birth, your urethra is much shorter. It runs from your bladder to open in front of your vagina.
- 41. FUNCTION OF BLADDER The bladder is an organ of the urinary system. It plays two main roles: Temporary storage of urine – the bladder is a hollow organ with distensible walls. It has a folded internal lining (known as rugae), which allows it to accommodate up to 400-600ml of urine in healthy adults. Assists in the expulsion of urine – the musculature of the bladder contracts during micturition, with concomitant relaxation of the sphincters.
- 42. Urine formation Urine formation is the primary excretory function of the kidneys. Urine formation consists of three processes: 1. plasma filtration at the glomeruli followed by 2. reabsorption 3. secretion of selective components by the renal tubules. 4. Through these processes, the kidneys play an important role in removal of metabolic waste products, regulation of water and electrolytes (e.g., sodium, chloride), and maintenance of the body’s acid-base equilibrium.
- 44. GLOMERULAR FILTERATION Glomerular ultrafilterate: Fluid that filters through the glomerulus in the Bowman’s capsule Glomerular membrane: The membrane of the glomerular capillaries In general similar to the membrane of other capillaries
- 45. GLOMERULAR FILTERATION Glomerular filtration occurs in the glomerulus where blood is filtered. This process occurs across the three layers- the epithelium of Bowman’s capsule, the endothelium of glomerular blood vessels, and a membrane between these two layers. Blood is filtered in such a way that all the constituents of the plasma reach the Bowman’s capsule, except proteins. Therefore, this process is known as ultrafiltration.
- 46. Reabsorption Around 99 per cent of the filtrate obtained is reabsorbed by the renal tubules. This is known as reabsorption. This is achieved by active and passive transport.
- 47. Secretion The next step in urine formation is tubular secretion. Here, tubular cells secrete substances like hydrogen ions, potassium ions, etc into the filtrate. Through this process, the ionic, acid-base and the balance of other body fluids are maintained. The secreted ions combine with the filtrate and form urine. The urine passes out of the nephron tubule into a collecting duct.