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Renal System
Physiology
| Term | Definition |
|---|---|
| Blood hydrostatic pressure | Pressure generated by pumping action of heart |
| Blood colloid osmotic pressure | Force generating absorption of fluid caused by suspension of proteins |
| Filtration | Promoted by blood hydrostatic pressure and interstitial fluid |
| Reabsorption | Promoted by blood colloid osmotic pressure |
| Net Filtration Pressure Equation | NFP = (BHP + IFPO) - (BCOP + IFHP) |
| Net filtration pressure function | Determines whether fluids leave or enter capillaries |
| Net Outward Pressure (filtration) | 10 mm Hg at arterial end of a capillary bed |
| Net Inward filtration (reabsorption) | 9 mmHg at venous end of a capillary bed |
| 7 Functions of the kidney | 1. Regulation of blood ionic composition 2. Regulation of blood pH 3. Regulation of blood volume and BP 4. Maintains blood osmolarity 5. Hormone Production 6. Regulation of blood glucose 7. Excretion of wastes |
| Regulation of blood ionic composition | Electrolyte balance |
| Regulation of blood pH | Acid-base balance |
| Blood osmolarity | 300 mOsm/L |
| Hormone production | Renin, Aldosterone, ADH, Calcitrol (Bone), EPO (RBC) |
| Regulation of blood glucose | Glutamine & GNG |
| Excretion of wastes | Metabolites, drugs, excess water and solutes |
| Left side of the kidney | Kidney structure |
| Right side of the kidney | Path of urine drainage |
| Percentage of cardiac output from renal blood supply | 25% |
| 4 Major sources of the nephron | 1. Filtration 2. Reabsorption 3. Secretion 4. Excretion |
| Filtration Definition | Movement of water and solutes from the blood plasma across the wall of the glomerular capillaries, into the glomerular capsule and into the renal tubule |
| Amount of Blood flow to the kidneys during filtration | 1200-1300 ml/min at rest |
| Glomerular Filtration Rate (GFR) | Volume of plasma filtrate that passes through the gloeruli every minute |
| 3 Factors regulating GFR | 1. Renal Autoregulation 2. Neural 3. Hormonal |
| Renal Autoregulation of GFR | Mechanisms that maintain a constant GFR despite changes in arterial BP |
| Myogenic Mechanism | Smooth muscle contracts and reduces the diameter of the arteriole and returns GFR to its previous level in seconds |
| Tubuloglomerular Feedback | Increases in BP raise the GFR so that fluid flows too rapidly through the renal tubule |
| Neural Regulation of GFR | Blood vessels of the kidney are supplied by sympathetic fibers that cause vasoconstriction of afferent arterioles |
| Hormonal Regulation of GFR | Atrial natriuretic peptide (ANP) and Angiotensin II |
| Atrial Natriuretic Peptide | Increased in blood volume causes atria to stretch and ANP is released in response |
| Angiotensin II | Potent vasoconstrictor that narrows both afferent and efferent arterioles reducing GFR |
| Reabsorption definition | Movement of substances from the renal tubule to the bloodstream |
| Reabsorption is the return of | Most of the filtered water and solutes from the tubular fluid to the blood stream |
| Secretion Definition | The "Dumping" of waste, drug residuals, excess ions from blood into the tubular fluid |
| Proximal Tubial | Site of most reabsorption and secretion |
| Loop of Henley | Alternate between water impermeable and sodium permeable and sodium impermeable and water permeable |
| Distal Tubial and Collecting Duct | - ADH Dependent water reabsorption - Aldosterone dependent sodium reabsorption - ANP inhibits ADH and aldosterone - Responsible for fluid balance |
| RAAS | Aldosterone causes reabsorption of Na and Cl and secretion of K in the collecting duct |
| ADH | Increases permeability to water in cells of the distal tubule and collecting duct causing higher water reabsorption |
| ANP | Decreases Na and water reabsorption, inhibits aldosterone, and ADH release |
| Colloid Osmotic Pressure | Osmolarity of plasma proteins |
| COP Influences | The magnitude of fluid movement into or out of plasma perfusing the kidney |
| Steady State | When intake equals output |
| Output is less than intake | Positive balance |
| Renal Failure | Excessive increase in body fluid and salt |
| Output is greater than intake | Negative balance |