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FINAL:Urinary System
chapter 25
| Question | Answer |
|---|---|
| Kidney Functions | - Removal of toxins, metabolic waste, and excess ions from the blood - Regulation of blood volume, chemical composition, and pH - Gluconeogenesis during prolonged fasting - Activation of vitamin D - Endocrine functions (renin and erythropoietin) |
| Renin | regulation of blood pressure and kidney function |
| Erythropoietin | regulation of RBC production |
| Vascular Resistance in Microcirculation | High resistance in afferent and efferent arterioles Causes blood pressure to decline from ~95 mm Hg to ~8 mm Hg in kidneys |
| Mechanisms of Urine Formation | Glomerular filtration Tubular reabsorption Tubular Secretion |
| Tubular Reabsorption | Returns all glucose and amino acids, 99% of water, salt, and other components to the blood |
| Tubular Secretion | Reverse of reabsoprtion: selective addition to urine |
| Glomerular Filtration | Passive process driven by hydrostatic pressure Molecules >5 nm are not filtered (e.g., plasma proteins) and function to maintain colloid osmotic pressure of the blood |
| Why is the glomerulus an efficient filter | -Its filtration membrane is very permeable and it has a large surface area - Glomerular blood pressure is higher (55 mm Hg) than other capillaries |
| Net Filtration Pressure (NFP) | The pressure responsible for filtrate formation (10 mm Hg) |
| Net Filtration Equation | NFP = HPg – (OPg + HPc) net filtration pressure = glomular hydrostatic pressure - (Colloid osmotic pressure of glomerular blood - capsular pressure) |
| NFP determined by... | Glomerular hydrostatic pressure (HPg) the chief force Two opposing forces: Colloid osmotic pressure of glomerular blood (OPg) Capsular pressure (HPc) |
| Glomerular Filtration Rate (GFR) | Volume of filtrate formed per minute by the kidneys (120–125 ml/min) |
| GFR determined by... | - Total surface area available for filtration - Filtration membrane permeability - NFP |
| GFR mechanisms | Intrinsic controls (renal autoregulation) Extrinsic controls |
| Intrinsic control of GFR | Act locally within the kidney Maintains a nearly constant GFR Two types of renal autoregulation - myogenic mechanism - Tubuloglomerylar feedback mechanism, which senses changes in the juxtaglomerular apparatus |
| Extrinsic control of GFR | Nervous and endocrine mechanisms that maintain blood pressure, but affect kidney function |
| Myogenic Mechanism | increased BP: contraction of afferent arterioles - Helps maintain normal GFR - Protects glomeruli from damaging high BP decreased BP: dilation of afferent arterioles - Helps maintain normal GFR |
| tubular reabsoprtion routes | transcellular paracellular |
| transcellular route (tubular reabsorption) | Apical membrane of tubule cells -> Cytosol of tubule cells -> Basolateral membranes of tubule cells -> Endothelium of peritubular capillaries |
| paracellular route (tubular reabsorption) | Between cells - Movement through the interstitial fluid and into the capillary - Limited by tight junctions, but leaky in proximal nephron - Water, Ca2+, Mg2+, K+, and some Na+ in the PCT |
| What gets reabsorbed in tubular reabsoption | - all nutrients -> glucose & amino acids - Ions: Na+, Ca2+, Mg2+, K+ - water |
| urinary bladder function | - temporary urine reservoir |
| paired ureters | - transport urine from the kidneys to the bladder |
| urethra | - transports urine from the bladder out of the body |
| kidney anatomy | - Retroperitoneal and in superior lumbar region - Right kidney is lower than the left - Convex lateral surface, concave medial surface - Renal hilum ->renal sinus - Ureters, renal blood vessels, lymphatics, and nerves enter and exit at the hilum |
| kidney layers | - renal fascia - perirenal fat capsule - fibrous capsule |
| Renal fascia | - The anchoring outer layer of dense fibrous connective tissue |
| Perirenal fat capsule | - A fatty cushion |
| Fibrous capsule | - Prevents spread of infection to kidney |
| Renal cortex | - A granular superficial region |
| Renal capsule | - The cone-shaped medullary (renal) pyramids separated by renal columns |
| Lobe | - A medullary pyramid and its surrounding cortical tissue |
| Papillary | - Tip of pyramid; releases urine into minor calyx |
| Renal Pelvis | - The funnel-shaped tube within the renal sinus |
| regions of internal kidney | - renal cortex - renal medulla - renal pelvis |
| Renal cortex | - granular-appearing superficial region |
| Renal medulla | - medullary renal pyramids: cone shaped - pyramids separated by renal columns (made of cortical tissue) - Lobe: medullary pyramid and its surrounding cortical tissue; about eight lobes per kidney |
| Renal pelvis | - Funnel-shaped tube continuous with ureter -minor calyces - Cup-shaped areas that collect urine draining from pyramidal papillae -major calyces - Areas that collect urine from minor calyces + Empty urine into renal pelvis |
| Flow of urine | - Renal pyramid -> minor calyx -> major calyx -> renal pelvis -> ureter |
| Blood and Nerve supply | - 1/4 (1200 ml) of cardiac output to the kidneys each minute - Arterial flow into and venous flow out of the kidneys follow similar paths - Nerve supply is via sympathetic fibers from the renal plexus |
| Nephrons | - Structural and functional units that form urine - 1 mill. per kidney - 2 main parts - renal corpuscle - glomerulus - bowman's capsule (surrounds glomerulus) - renal tubule: tube |
| Glomerular capsule | - Parietal layer: simple squamous epithelium - Visceral layer: branching epithelial podocytes |
| Renal Tubule | - single layer of epithelial cells - Proximal convoluted tubule (PCT) - Proximal, closest to renal corpuscle - Nephron loop - ascending and descending loops - Distal convoluted tubule (DCT) - Distal, farthest from renal corpuscl |
| PCT histology | - Cuboidal cells - Functions in reabsorption and secretion - Confined to the cortex |
| Loop of Henle histology | - Thin segment usually in descending limb - Simple squamous epithelium - Freely permeable to water Thick segment of ascending limb - Cuboidal to columnar cells |
| DCT histology | - Cuboidal cells with very few microvilli - Function more in secretion than reabsorption - Confined to the cortex |
| Collecting ducts | - receive filtrate from many nephrons - Fuse together to deliver urine through papillae into minor calyces - 2 types of cells - intercalated cells - principal cells |
| intercalated cells | - Cuboidal cells with microvilli - Function in maintaining the acid base balance of the body |
| principal cells | - Cuboidal cells without microvilli - Help maintain the body’s water and salt balance |
| types of nephrons | - cortical nephrons - juxtamedullary nephrons |
| Cortical nephrons | - 85% of nephrons; almost entirely in the cortex |
| Juxtamedullary nephrons | - Long loops of Henle deeply invade the medulla - Extensive thin segments - Important in the production of concentrated urine |
Created by:
davisobr
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