Chapter 14, short outline
Chapter 14, short outline BISC306010
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This 6 page Study Guide was uploaded by Kelcie on Wednesday September 23, 2015. The Study Guide belongs to BISC306010 at University of Delaware taught by Laverty,Gary H in Fall 2014. Since its upload, it has received 26 views. For similar materials see General Physiology in Biosystem Engineering at University of Delaware.
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Date Created: 09/23/15
Ch 14 Physiology Book Review14 A1 Renal Structures Renal pertaining to the kidneys Kidneys process the plasma portion of blood by removing or adding substances to it Table 141 Functions of the kidneys 0 Regulation of water inorganic ion balance and acidbase balance 0 Removal of metabolic water including urea from the catabolism of protein uric acid from the nucleic acids creantine from muscle creantine end products of hemoglobin etc from the blood and their excretion in the urine 0 Removal of foreign chemicals including drugs pesticides and food additives and their metabolites from the blood and their excretion in the urine 0 Gluconeogenesis synthesis of glucose from amino acids and other precursors 0 Production of hormonesenzymes Erythropoietin which controls erythrocyte production Renin an enzyme that controls the formation of angiotensin and in uences blood pressure and sodium balance 125 dihydroxyvitamin D which in uences calcium balance 14 A2 Structures of the Kidneys and Urinary System The two kidneys are in the back of the abdominal wall but not actually in it Kidneys are retroperitoneal just behind the peritoneum Urine ows from the kidneys through ureters into bladder and then is eliminated via urethra Nephrons consist of an initial ltering component called the renal corpuscle and a tubule that extends from the renal corpuscle Renal tubule is very narrow hollow cylinder made up of a single later of epithelial cells Glomerulus compact tuft of interconnected capillary loops that are in each renal corpuscle and also called glomerular capillaries Afferent arteriole supply blood to each glomerulus Bowman s capsule uid lled capsule and 20 percent of the plasma owing through the glomerulus goes into the Bowman s capsule E erent arteriole where the remaining blood leaves the glomerulus Bowman s space protein free uid lters from the glomerulus into here 0 Blood in the glomerulus is separated from the uid in Bowman s space by a ltration barrier consisting of three layers 0 Endothelium singlecelled capillary o Basal lamina noncellular layer of proteinaceous layer of basement membrane 0 Single celled epithelial lining of Bowman s capsule Podocytes have octopus like structure that are epithelial cells in the Bowman s capsule lining area Mesangial cells modi ed smooth muscle cells that surround the glomerular capillary loops but are not part of the ltration pathway Proximal tube drains Bowman s capsule Loop of Henle sharp hairpin like loop consisting of descending limb an ascending limb the distal convoluted tubule the collectingduct system which is comprised of the cortical collecting duct and then the medullary collecting duct 0 Renal pelvis is continuous with the ureter draining that kidney 0 Renal cortex outer part of kidney contains all the renal corpuscles Renal medulla inner part of kidney Peritubular capillaries surround each tubule Nephrons are two general types juxtamedullary and cortical o Juxtamedullary nephrons make up about 15 percent of all nephrons and are responsible for generating an osmotic gradient in the medulla responsible for the reabsorption of water Vasa recta loop deeply into the medulla and then return to the corticalmedullary junction 0 Cortical nephrons make up the majority of nephrons meaning their renal corpuscles are located in the outer cortex and their Henle s loops do not penetrate deep into the medulla some do not have Henle loops at all they are involved in reabsorption and secretion 0 The ascending loop of each loop of Henle passes between afferent and efferent arterioles of the loop s own nephron Macula densa a patch of cells in the wall of the ascending limb 14 A3 Basic Renal Processes Glomerular ltration urine formation beginning with the ltration of plasma from the glomerular capillaries into the Bowman s space Glomerular ltrate is the ltrate Tubercular reabsorption when the direction of movement is from the tubular lumen to peritubular capillary plasma Tubular secretion movement in the opposite direction peritubular capillary plasma to tubular lumen Amount excreted amount lter amount secreted amount reabsorbed Glomerular ltration rate determined not only by the net ltration pressure but also by the permeability of the corpuscular membranes and the surface area available for ltration Tubular secretion moves substances from peritubular capillaries into the tubular lumen 0 Most important substances secreted by tubules are H and K Usually coupled with the reabsorption of Na 14 A4 The Concept of Renal Clearance 0 Renal clearance volume of plasma from which that substance is completely removed by the kidneys 14 81 Total Body Balance of Sodium and Water 0 Four sites lose water to the external environment skin respiratory airways gastrointestinal tract and urinary tract lnsensible water loss when loss of water through evaporation of the skin occurs and the lining of the respiratory passageways is a continuous process Gastrointestinal water loss can occur through feces diarrhea and vomiting 0 The excretion of Na and Cl via the skin and gastrointestinal tract is usually small but increases during severe sweating vomiting or diarrhea 14 82 Basic Renal Processes for Sodium and Water Na reabsorption is an active process occurring in all tubular segments except the descending limb of the loop of Henle Water reabsorption is by osmosis and is dependent upon Na reabsorption Vasopressin or antidiuretic hormone is the major determinant of controlled permeability and therefore of passive water reabsorption in the collecting ducts is a peptide hormone secretedby posterior pituitary Water diuresis increased urine excretion resulting from low vasopressin but not an increase in solute excretion Diuresis a large urine ow from any cause 0 Diabetes insipidus caused by the failure of posterior pituitary gland to release vasopressin or the inability of the kidneys to respond to vasopressin Osmotic diuresis increased urine ow is the result of primary excretion of a solute Hypoosmotic having total solute concentration less than that of normal extracellular uid lsoosmotic having the same total solute concentration as extracellular uid Hyperosmotic having total solute concentration greater than normal extracellular uid 0 When vasopressin is high the kidneys produce a small volume of urine meaning that it is hyperosmotic to plasma Obligatory water loss loss of minimal volume of urine contributing to dehydration when water intake is zero Ascending limb is relatively impermeable to water so little water follows the salt 14 83 Renal Sodium Regulation Urinary Na excretion increases when there is an excess of sodium in the body and decreases when there is a sodium de cit Na excreted Na ltered Na reabsorbed Amount of Na in the body can determine extracellular uid volume plasma volume component of which helps determine cardiovascular pressure which initiate the responses that control Na secretion The hormone aldosterone is a steroid and is a major factor in determining the rate of tubular Na reabsorption Aldosterone is produced by the adrenal cortex it stimulates Na reabsorption by the distal convoluted tubule and the cortical collecting ducts High diet of sodium gives you a low secretion of aldosterone whereas it is high if you ingest a low sodium diet Renin enzyme secreted by the juxtaglomerular cells of the juxtaglomerular apparatuses in thekidneys Mechanisms that sodium depletion causes an increase in renin production 0 1 the renal sympathetic nerves o 2 intrarenal baroreceptors o 3 macula densa An increase in arterial pressure inhibits Na reabsorption and thereby increases Na excretion Increased blood pressure reduces Na reabsorption by two mechanisms o It reduces the activity of the reninangiotensinaldosterone o Acts locally on tubules Decreased blood pressure decreases Na excretion both by stimulation reninangiotensinaldosterone and by acting on the tubules to enhance Na reabsorption 14 B4 Renal Water Regulation Osmoreceptors sensory receptors that initiate the re exes controlling vasopressin in the hypothalamus responsible for changes in osmolarity 14 C1 Sources of Hydrogen lon gain or loss Nonvolatile acids organic and nonorganic acids from sources other than C02 Kidneys can remove or add H ions to plasma 14 C2 Buffering of Hydrogen lon in the Body Buffer any substance that can reversibly bind H Most H is buffered by extracellular and intracellular buffers 14 C3 The kidneys are responsible for balancing hydrogen ion gains and losses so as to maintain plasma hydrogen ion concentration within a narrow range 0 Respiratory system also plays a homeostatic role in balancing hydrogen ions 0 Hyperventilation can play a role in H imbalance 14 C4 Renal Mechanisms The kidneys eliminate or replenish H from the body by altering plasma bicarbonate concentration HCO3 excretion HCO3 secreted HCO3 reabsorbed 14 C5 Classi cations of Acidosis and Alkalosis Acidosis refers to any situation in which the hydrogen ion concentration of arterial plasma is elevated Alkalosis denotes a reduction
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