class notes for exam 3
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This 19 page Class Notes was uploaded by Allie Newman on Sunday April 5, 2015. The Class Notes belongs to BSC 215 at a university taught by Jason Pienaar in Fall. Since its upload, it has received 270 views.
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Date Created: 04/05/15
Allie Newman BSC 216 Class Notes 31215 LECTURE 19 URINARY SYSTEM Clicker Quiz 0 Metabolic wastes include both nitrogenous wastes and C02 true or false 0 TRUE 0 The 4 kinds of nitrogenous wastes secreted by the kidneys include o Urea Ammonia Uric Acid and Creatinine 0 Which of the following is nota function of kidneys o Converts ammonia to urea 0 Which of the following represent the correct order of ltrate ow in the urinary system 0 Glomerular ltrate PCT loops of Henle DCT and Collecting Duct Urine Formation Glomerular ltration Tubular ltration and reabsorption Water conservation Basic Stages of Urine Formation 0 Conversion of glomerular ltrate to urine involves the removal and addition of chemicals by tubular reabsorption and secretion 0 Occurs through PCT to DCT o Tubular uid is modi ed 0 Steps involved include o 1 Glomerular ltra6on o 2 Tubular reabsorption o 3 Tubular secretion 0 4 Water conservation 0 1 Glomerular Filtration o Creates a plasma like ltrate of the blood 0 2 Tubular reabsorption o Removes useful solutes from the ltrate returns them to the blood 0 3 Tubular secretion 0 Removes additional wastes from the blood adds them to the ltrate o 4 Water conservation 0 Removes water from the urine and returns it to blood concentrates wastes Glomerular Filtration 0 Important to understand that as we trace uid through the nephron it has different names that re ect changing composition Glomerular ltrate l the uid in the capsular space 0 Similar to blood plasma except that it has almost no protein Tubular uid l uid from the proximal convoluted tubule through the distal convoluted tubule o Substances have been removed or added by tubular cells 0 Sodium has been taken back up along the way chloride follows sodium thus attracting water 0 Urine l uid that enters the collecting duct 0 Undergoes little alteration beyond this point except for changes in water content 0 Mostly waste product with mainly water absorption 0 Send off to ureter for excretion of waste products The Filtration Membrane Glomerular ltration l a special case of the capillary uid exchange process in which water and some solutes in the blood plasma pass from the capillaries of the glomerulus into the capsular space of the nephron o Filtration membrane l three barriers through which uid passes o 1 Fenestrated endothelium of glomerular capillaries 70 to 90 nm ltration pores exclude blood cells Highly permeable o 2 Basement membrane Proteoglycan gel negative charge excludes molecules greater than 8 nm Albumin repelled by negative charge Blood plasma is 7 protein the ltrate is only 003 protein 0 3 Filtration slits Podocyte cell extensions pedicels wrap around the capillaries to form a barrier layer with 30 nm ltration slits Negatively charged which is an additional obstacle for large anions 0 All three of these have negatively charged but strongest is basement membrane Filtration membrane l allows passage of water and solutes small into glomerular capsule o 1 Fenestrated endothelium of glomerular capillaries o 2 Basement membrane l gluing endothelium and capsule together 0 3 Filtration slits l Podocytes of visceral membrane of glomerular capsule 0 Almost any molecule smaller than 3 nm can pass freely through the ltration membrane 0 Water electrolytes glucose fatty acids amino acids nitrogenous wastes and vitamins Some substances of low molecular weight are bound to the plasma proteins and cannot get through the membrane 0 Most calcium iron and thyroid hormone Unbound fraction passes freely into the ltrate The anatomy is what allows pressure gradient example largewide diameter The Glomerular Filtration Membrane Turned back 0 Blood cells 0 Plasma proteins 0 Large anions o Proteinbound minerals and hormones 0 Most molecules are greater than 8 nm in diameter 0 Endothelial cell of glomerular capillary o 1 Filtration pore fenestrations o 2 Basement membrane 0 3 Filtration slit 0 Parts foot process of podocyte capsular space and bloodstream Passed through lter 0 Water Electrolytes Glucose Amino acids Fatty acids Vitamins Urea Uric acid OOOOOOO o Creatinine Filtration Pressure 0 Blood hvdrostatic pressure BHP 0 Much higherin glomerular capillaries 60 mm Hg compared to 10 to 15 in most other capillaries due to the fact that afferent is much Wider in diameterthan efferent arteriole 0 Because afferent arteriole is larger than efferent arteriole larger inlet and smaller outlet 0 Primary means of pushing solutes and water out of blood across ltration membrane Hvdrostatic pressure in capsular Space 0 18 mm Hg due to high ltration rate and continual accumulation of uid in the capsule 0 Pressure within capsule tends to push water back in to glomerulus Colloid osmotic pressure COP of blood due to proteins in blood 0 About the same here as elsewhere 32 mm Hg 0 Glomerular ltrate is almost proteinfree and has no signi cant COP 0 Proteins in glomerular blood tend to pull water back into glomerulus 0 Water osmosis anything else diffusion all related to concentration gradients Higher outward pressure of 60 mm Hg opposed by two inward pressures of 18 mm Hg and 32 mm Hg 0 Normally want it to be positive 0 Net ltration pressure p 600ut 18in 32in 10 mm Hg out Glomerulus a more ef cient lter than other capillaries because 0 Filtration membrane with large surface area 0 High blood pressure within glomerulus 60mmHg vs 15mmHg 0 Result high net ltration pressure Blood hydrostatic pressure BHP 60 mm Hg out minus Colloid osmotic pressure COP 32 mm Hg in minus Capsular pressure CP 18 mm Hg in equals Net ltration pressure NFP 10 mm Hg out o Efferent arteriole has a lot less water than that of afferent we stopped here in our notes on 31215 Glomerular Filtration Rate 0 Glomerular ltration rate GFR the amount of ltrate formed per minute by the two kidneys combined 0 GFR z 125 mLmin or 180 Lday male 0 GFR z 105 mLmin or 150 Lday female 0 One can of soda 355 mL 0 Total amount of ltrate produced equals 50 to 60 times the amount of blood in the body 0 99 of ltrate is reabsorbed since only 1 to 2 L urine excreted per day Regulation of Glomerular Filtration GFR must be precisely controlled 0 If GFR too high 0 Fluid ows through the renal tubules too rapidly for them to reabsorb the usual amount of water and solutes o Urine output rises o Chance of dehydration and electrolyte depletion o If GFR too low 0 Wastes reabsorbed o Azotemia may occur accumulation of harmful wastes GFR controlled by adjusting glomeruar blood pressure from moment to moment GFR control is achieved by three homeostatic mechanisms 0 1 Renal autoregulation o 2 Svmbathetic control 0 3 Hormonal control Renal Autoregulation 0 Renal autoregulation l the ability of the nephrons to adjust their own blood ow and GFR without external nervous or hormonal control 0 Enables them to maintain a relatively stable GFR in spite of changes in systemic arterial blood pressure 0 Two methods of autoregulation l myogenic mechanism and tubuloglomerular feedback 0 1 Renal Autoregulation Mvodenic mechanism l based on the tendency of smooth muscle to contract when stretched Increased arterial blood pressure stretches the afferent arteriole l arteriole constricts and prevents blood ow into the glomerulus from changing much 0 When blood pressure falls l afferent arteriole relaxes and allows blood ow more easily into glomerulus 0 Result Filtration remains stable Tubulodlomerular feedback mechanism by which glomerulus receives feedback on the status of the downstream tubular uid and adjusts ltration to regulate the composition of the uid stabilize its own performance and compensate for uctuation in systemic blood pressure juxtaglomerular apparatus complex structure found at the very end of the nephron loop where it has just reentered the renal cortex 0 Three special kinds of cells occur in the juxtaglomerular apparatus 0 1 Macula densa Senses variations in ow or uid composition and secretes a paracrine that stimulates jG cells 0 2 juxtaglomerular jG cells When stimulated by the macula they dilate or constrict the arterioles o 3 Mesangial cells Connected to macula densa and jG cells by gap junctions and communicate by means of paracrines Constrict or relax capillaries to regulate ow a Negative feedback control of GFR 0 High GFR l Rapid ow of ltrate in renal tubules l sensed by macula dense l paracrine secretion l constriction of afferent arteriole l reduced GFR The juxtaglomerular Apparatus includes 0 Podocytes mesangial cells efferent arteriole nephron loop sympathetic nerve ber juxtaglomerular cells afferent arteriole smooth muscle cells and macula dense Sympathetic Control Sympathetic nerve bers richly innervate the renal blood vessels Sympathetic nervous system and adrenal epinephrine constrict the afferent arterioles in strenuous exercise or acute conditions like circulatory shock o Reduces GFR and urine output o Redirects blood from the kidneys to the heart brain and skeletal muscles 0 GFR may be as low as a few milliliters per minute Hormonal Control 0 Renin Angiotensin Aldosterone Mechanism Renin secreted by juxtaglomerular cells if BP drops dramatically Renin converts angiotensinogen a blood protein into angiotensin I o In the lungs and kidneys angiotensinconverting enzyme ACE converts angiotensin I to angiotensin II the active hormone 0 Works in several ways to restore uid volume and BP 0 Result these 3 mechanisms raise blood pressure 0 1 Thirst and drinking 0 2 Vasoconstriction o 3 Sodium and water retention Allie Newman BSC 216 Class Notes Urinary System 31015 Urinary System Organs Six Organs o 2 kidneys multiple functions 0 2 Ureters transport urine 0 1 bladderstore urine 0 1 Urethra transports excretes urine Kidney Functions 0 Urinary system rids the body of metabolic waste products 0 Kidneys are the primary functional organ 0 Filter blood plasma separate waste from useful chemicals 0 Return useful chemicals to blood 0 Eliminate waste Kidneys also have a multitude of other functions 0 Regulate blood volume amp pressure by eliminating or conserving water Regulate body uid osmoarity by controlling watersoute elimination ratio Secrete renin an enzyme that activates hormonal control of blood pressure Secrete erythropoietin that stimulates red blood cell synthesis Collaborate with lungs to regulate Ph of body uids Add hydroxyl group to calcitriol calcium homeostasis lnitiate gluconeogenesis from amino acids during extreme starvation OOOOOO IOWU39lbULJNH Excretion Separation of wastes from body uids amp elimination Metabolic waste waste substance produced by the body food residue in feces is NOT metabolic waste 0 Four body systems carry out excretion 0 Respiratory system CO2 trace amounts of other gases 0 lntedumentarv svstem inorganic salts lactic acid urea in sweat o Digestive system salts CO2 lipids bile pigments cholesterol other metabolic wastes amp food residue 0 Urinary system nitrogenous metabolic wastes toxins drugs hormones salts Kidney excretes 4 kinds of Nitrogenous wastes o Ammonia NH2 removed from amino acids forms NH3 Liver converts to Urea o Urea Less toxic than ammonia o Uric acid Product of nucleic acid metabolism 0 Creatinine Product of creatinine phosphate metabolism Blood Urea Nitrogen BUN Level of toxic nitrogenous wastes in blood stream 0 Normal 10 20 mg dL 0 Elevated BUN Azotemia 0 Can progress to Uremia Diarrea vomiting dyspnea cardiac arrhythmia convulsions coma and death Anatomy of Kidney Located retroperitoneally Protected by lower rib cage fat and a brous capsule Fat capsule attached kidney to body wall cushions Fibrous capsule hard protects against infection Fascia dense connective tissue anchors kidney in place 0 Gross Kidney Anatomy Fibrous capsule Renal cortex Renal medulla Renal papilla Renal sinus Adipose tissue in Renal sinus Renal pelvis major calyx minor calyx Renal column Renal pyramid Ureter Renal blood vessels Renal Circulation Kidneys make up 04 of body weight but receive 25 of cardiac output The Nephron 0 Each kidney 12 million nephrons Each is an identical functional unit Comprised of 2 parts 0 Renal corpuscle lters blood plasma Goumeruar Capsule Parietal layer simple squamous Capsule space ltrate collecting Visceral layer podocytes 0 Renal tubule coiled tube that converts ltrate into urine l simple cuboidal 4 Regions Proximal convoluted tubule PCT 0 Long tubule 0 Simple cuboidal epithelium with prominent microvilli brush border 0 Lots of absorption Nephron loop Loop of Henle 0 Simple cuboidal thick segments 0 Lots of mitochondria o Involved in active transport of salts 0 Simple squamous thin segments 0 Permeable to water Distal convoluted tubule DCT o Shorter less coiled than PCT o Cuboidal epithelium devoid of microvii 0 End of the Nephron Collectind duct 0 Receives uid from the DCT s of several nephrons 0 Numerous collecting ducts converge near the tip of the medullary pyramids to from papillary ducts o Papillary ducts end in pores where urine passes into the minor calyx Cortical amp Juxtmedullary Nephrons Cortical Nephrons o 85 of all nephrons 0 Short nephron loops 0 E erent arterioles branch into peritubular capillaries surrounding distal and proximal convoluted tubules luxtmedullary Nephrons o 15 of nephrons 0 Long nephron oops maintain salinity gradients o E erent arterioles branch into vase recta around each nephron oop Fluid Flow Summary 0 1 Glomerular ltrate PCT Nephron oop DCT Collecting duct Papillary duct Minor calyx Major calyx o 9 Renal pelvis o 10 Ureter 11 Urinary bladder o 12 Urethra O m eweww Allie Newman BSC 216 Class Notes 32515 Lecture 20 Urinary System Basic Stages of Urine Formation 4 Steps 0 1 Glomerular ltration creates a plasma like ltrate of the blood 0 2 Tubular reabsorption removes useful solutes from the ltrate returns them to the blood 0 3 Tubular secretion removes additional wastes from the blood adds them to the ltrate o 4 Water conservation removes water from the urine and returns it to blood concentrates wastes 0 Conversion of gomeruar ltrate to urine involves the removal and addition of chemicals by tubular reabsorption and secretion 0 Occurs through PCT to DCT o Tubular uid is modi ed 0 Steps involved include Glomerular ltration Tubular reabsorption Tubular secretion Water conservation 0000 The Proximal Convoluted Tubule PCT reabsorbs about 65 of glomerular ltrate removes some substances from the blood and secretes them into the tubular uid for disposal in urine Prominent microvilli and great length Abundant mitochondria provide ATP for active transport PCTs alone account for about 6 of one s resting ATP and calorie consumption Tubular reabsorption l process of reclaiming water and solutes from the tubular uid and returning them to the blood a Two routes of reabsorption o Transcellular route Substances pass through the cytoplasm of the PCT epithelial cells and out their base 0 Paracellular route Substances pass between PCT cells Junctions between epithelial cells are quite leaky and allow signi cant amounts of water to pass through Solvent drag water carries with it a variety of dissolved solutes Ta ken up by peritubular capillaries Two routes of reabsorption o Transcellular route l through cytoplasm of PCT epithelial cells 0 Paracellular route l between PCT epithelium cells Tubular uid l tubule epithelial cells l tissue uid l peritubular capillary Tubular Reabsorption Sodium reabsorption is the key to everything else Creates an osmotic and electrical gradient that drives the reabsorption of water and other solutes Most abundant cation in ltrate Creates steep concentration gradient that favors its diffusion into the epithelial cells a Two types of transport proteins in the apical cell surface are responsible for sodium uptake Symports that simultaneously bind Na and another solute such as glucose amino acids or lactate Na H antiport that pulls Na into the cell while pumping out H into tubular uid Two types of transport proteins in the apical cell surface are responsible for sodium uptake 1 Symports l that simultaneously bind Na and another solute such as glucose amino acids or lactate Sodium glucose transport protein SGLT symport 2 Na H antiport I that pulls Na into the cell while pumping out H into tubular uid Na H antiport Sodium is prevented from accumulating in the epithelial cells by Na K pumps in the basal surface of the epithelium Pumps Na out into the extracellular uid Picked up by peritubular capillaries ATP consuming active transport pumps Negative chloride ions follow the positive sodium ions by electrical attraction Various antports in the apical cell membrane that absorb CI in exchange for other anions they eject into the tubular uid K Cl symport drives chloride and potassium OUT of epithelial cells Potassium magnesium and phosphate ions diffuse through the paraceuar route with water Some calcium is reabsorbed through the paraceuar route in the PCT but most Ca2 reabsorption occurs later in the nephron 4060 of urea is reabsorbed through paraceuar route with water Nearly all uric acid is reabsorbed but secreted back later All of these paraceuar movements are driven by solvent drag Reabsorption of all the salt and organic solutes makes the tubule cells and tissue uid hypertonic Water follows solutes by osmosis through both paraceuar and transcellular routes through water channels called aquaporins ln PCT water is reabsorbed at a constant rate called obligatory water reabsorption The Transport Maximum There is a limit to the amount of solute that the renal tubules can reabsorb Limited by the number of transport proteins in the plasma membrane If all transporters are occupied as solute molecules pass Excess solutes appear in urine Transport maximum is reached when transporters are saturated Each solute has its own transport maximum Any blood glucose level above 220 mgdL results in glycosuria Normoglycemia normal urine volume glucosefree Hyperglycemia increased urine volume with glycosuria Tubular Secretion Tubular secretion l process in which renal tubule extracts chemicals from capillary blood and secretes them into tubular uid Two purposes in proximal convoluted tubule and nephron loop Waste removal Urea uric acid bile acids ammonia catecholamines prostaglandins and a little creatinine are secreted into the tubule Secretion of uric acid compensates for its reabsorption earlier in PCT Clears blood of pollutants morphine penicillin aspirin and other drugs Explains need to take prescriptions three to four timesday to keep pace with the rate of clearance Acidbase balance Secretion of hydrogen and bicarbonate ions help regulate pH of body uids The Nephron Loop Primary function of nephron loop is to generate salinity gradientthat enables collecting duct to concentrate the urine and conserve water Electrolyte reabsorption from ltrate Thick segment reabsorbs 25 of Na K and Cl lons leave cells by active transport and diffusion NaC remains in the tissue uid of renal medulla Water cannot follow since thick segment is impermeable Tubular uid very dilute as it enters distal convoluted tubule The Distal Convoluted Tubule and Collecting Duct Fluid arriving in the DCT still contains about 20 of the water and 7 of the salts from glomerular ltrate If this were all passed as urine it would amount to 36 Lday DCT and collecting duct reabsorb variable amounts of water salt and are regulated by several hormones Aldosterone atrial natriuretic peptide ADH and parathyroid hormone Aldosterone l the quotsaltretaining hormonequot Steroid secreted by the adrenal cortex Functions of aldosterone Acts on thick segment of nephron loop DCT and cortical portion of collecting duct Stimulates the reabsorption of more Na and secretion of K Water and Cl follow the Na Net effect is that the body retains NaCl and water Helps maintain blood volume and pressure Urine volume is reduced Urine has an elevated K concentration Atrial natriuretic peptide ANP l secreted by atrial myocardium of the heart in response to high blood pressure Four actions result in the excretion of more salt and water in the urine thus reducinq blood volume and pressure Dilates afferent arteriole constricts efferent arteriole Inhibits renin and aldosterone secretion Inhibits secretion of ADH Inhibits NaCl reabsorption by collecting duct Antidiuretic hormone ADH secreted by posterior lobe of pituitary in response to dehydration and rising blood osmolarity Action make collecting duct more permeable to water Water in the tubular uid reenters the tissue uid and bloodstream rather than being lost in urine Parathyroid hormone PTH secreted from parathyroid glands in response to calcium de ciency h ypocacemia Increases phosphate content and lowers calcium content in urine Because phosphate is not retained the calcium ions stay in circulation rather than precipitating into the bone tissue as calcium phosphate PCT reabsorbs 65 of glomerular ltrate and returns it to peritubular capillaries Much reabsorption by osmosis and cotransport mechanisms linked to active transport of sodium Nephron loop reabsorbs another 25 of ltrate DCT reabsorbs Na Cl and water under hormonal control especially aldosterone and ANP The tubules also extract drugs wastes and some solutes from the blood and secrete them into the tubular uid DCT completes the process of determining the chemical composition of urine Collecting duct conserves water GFR Urine Formation Ill Water Conservation The kidney eliminates metabolic wastes from the body but prevents excessive water loss as well As the kidney returns water to the tissue uid and bloodstream the uid remaining in the renal tubules passes as urine and becomes more concentrated Water Reabsorption by the Collecting Duct Collecting duct CD begins in the cortex where it receives tubular uid from several nephrons As CD passes through the medulla it reabsorbs water and concentrates urine up to four times Medullary portion of CD is more permeable to water than to NaCl As urine passes through the increasingly salty medulla water leaves by osmosis concentrating urine The Countercurrent Multiplier The ability of the CD to concentrate urine depends on salinity gradient in renal medulla Four times as salty in the renal medulla than the cortex Nephron loop acts as countercurrent multiplier Multiplier continually recaptures salt and returns it to extracellular uid of medulla which multiplies the salinity in adrenal medulla Countercurrent because of uid owing in opposite directions in adjacent tubules of nephron loop Fluid owing downward in descending limb Passes through environment of increasing osmolarity Most of descending limb very permeable to water but not to NaCl Water passes from tubule into the ECF leaving salt behind Concentrates tubular uid to 1200 mOsmL at lower end of loop Fluid owing upward in ascending limb lmpermeable to water Reabsorbs Na K and Cl by active transport pumps into ECF Maintains high osmolarity of renal medulla Tubular uid becomes hypotonic 100 mOsmL at top of loop Recycling of urea lower end of CD permeable to urea Urea contributes to the osmolarity of deep medullary tissue Continually cycled from collecting duct to the nephron loop and back Urea remains concentrated in the collecting duct and some of it always diffuses out into the medulla adding to osmolarity Countercurrent Multiplier of Nephron Loop 0 1 More salt is continually added by the PCT 2 The higher the osmolarity of the ECF the more water leaves the descending limb by osmosis 3 The more water that leaves the descending limb the saltier the uid is that remains in the tubule o 4 The saltier the uid in the ascending limb the more salt the tubule pumps into the ECF 5 The more salt that is pumped out of the ascending limb the saltier the ECF is in the renal medulla The Countercurrent Exchange System Large volume of water reabsorbed by CD must be returned to blood stream completed by vasa recta Vasa recta l capillary branching off efferent arteriole in medulla Provides blood supply to medulla and does not remove NaCl and urea from medullary ECF Countercurrent system formed by blood owing in opposite directions in adjacent parallel capillaries Descending capillaries Exchanges water for salt Water diffuses out of capillaries and salt diffuses in 0 As blood ows back up to the cortex the opposite occurs Ascending capillaries Exchanges salt for water Water diffuses into and NaCl diffuses out of blood Vasa recta gives the salt back and does not subtract from the osmolarity of the medulla Absorb more water on way out than the way in and thus they carry away water reabsorbed from the urine by collecting duct and nephron loop Neural Control of Micturition o Involuntary micturition re ex o 1 Stretch receptors detect lling of bladder transmit afferent signals to spinal cord 0 2 Signals return to bladder from spinal cord segments 2 and S3 via parasympathetic bers in pelvic nerve o 3 Efferent signals excite detrusor muscle 0 4 Efferent signals relax internal urethral sphincter Urine is involuntarily voided if not inhibited by brain 0 Voluntary control 0 5 For voluntary control micturition center in pons receives signals from stretch receptors 0 6 If it is timely to urinate pons returns signals to spinal interneurons that excite detrusor and relax internal urethral sphincter Urine is voided o 7 If it is untimely to urinate signals from pons excite spinal interneurons that keep external urethral sphincter contracted Urine is retained in bladder o 8 If it is timely to urinate signals from pons cease and external urethral sphincter relaxes Urine is voided Allie Newman BSC 216 Class Notes 32715 Chapter 24 Lecture 21 PH Balance Acids Bases and Buffers One of the most important aspects of homeostasis Metabolism depends on enzymes and enzymes are sensitive to pH Slight deviation from the normal pH can shut down entire metabolic pathways Slight deviation from normal pH can alter the structure and function of macromolecules 735 to 745 is the normal pH range of blood and tissue uid Challenges to acid base balance Metabolism constanty produces acid Lactic acids from anaerobic fermentation Ph05phoric acid from nucleic acid catabolism Fatty acids and ketones from fat catabolism Carbonic acid from carbon dioxide pH of a solution is determined solely by its hydrogen ions H Acids any chemical that releases H in solution Strong acids such as hydrochloric acid HCI ionize freely Gives up most of its H Markedly lowers pH of a solution Weak acids such as carbonic acid H2CO3 ionize only slightly Keeps most Hchemically bound Small effects on pH Bases any chemical that accepts H Strong bases such as the hydroxide ion OH have a strong tendency to bind H markedly raising pH Weak bases such as the bicarbonate ion HCO3 bind less available H and have less effect on pH Buffer any mechanism that resists changes in pH Convert strong acids or bases to weak ones Physiological buffer system that controls output of acids bases or C02 Urinary system buffers greatest quantity of acid or base Takes several hours to days to exert its effect Respiratory system buffers within minutes Cannot alter pH as much as the urinary system Chemical buffer a substance that binds Hand removes it from solution as its concentration begins to rise or releases H into solution as its concentration falls Restore normal pH in fractions of a second Function as mixtures called buffer systems composed of weak acids and weak bases Three major chemical buffers bicarbonate phosphate and protein systems Amount of acid or base neutralized depends on the concentration of the buffers and the pH of the working environment The Bicarbonate Buffer System Bicarbonate buffer system a solution of carbonic acid and bicarbonate ions Carbonic acid and bicarbonate ions CO2 H2O H H2CO3 H HCO3 H o Reversible reaction important in ECF CO2 H2O H2CO3 HCO3 H Lowers pH by releasing H CO2 H2O I H2CO3 I HCO3 H Raises pH by binding H Functions best in the lungs and kidneys to constantly remove C02 0 To lower pH kidneys excrete HCO E 0 To LEG pH kidneys excrete H and lungs excrete CO2 Respiratory Control of pH Basis for the strong buffering capacity of the respiratory system The addition of C02 to the body uids raises the H concentration and lowers pH The removal of C02 has the opposite effects 0 Respiratory system neutralizes two or three times as much acid as chemical buffers 0 C02 is constantly produced by aerobic metabolism 0 Normally eliminated by the lungs at an equivalent rate 0 CO2 H2O gt H2CO3 gt HCO3 H Lowers pH by releasing Hi 0 CO2 expired H2O I H2CO3 I HCO3 H Raises pH by binding Hi 0 Increased C02 and decreased pH stimulate pulmonary ventilation while an increased pH inhibits pulmonary ventilation Renal Control of pH The kidneys can neutralize more acid or base than either the respiratory system or chemical bu ers Renal tubules secrete H into the tubular uid Most binds to bicarbonate ammonia and phosphate bu ers Bound and free H are excreted in the urine actually expelling H from the body Other bu er systems only reduce its concentration by binding it to other chemicals Riddle 100 gold coins weighing one gram each 0 King go away but needs to gure out how to travel with coins Gives to someone 10 knights each given one gold coin total of 10 gold coins 1 knight is sneaky 0 Electrical scale only take one measurement at a time o 10 of a gram 01 of a gram 0 King needs to take a measurement by guring out which knight is sneaky how will he do this 1 The proximal convoluted tubule reabsorbs around what percentage of glomerular ltrate a 65 2 The proteins that transport sodium across the apical membrane of the PCT are a Symports that simultaneously bind glucose etc and antiports that simultaneously pump H ions into the tubular uid 3 A lower sodium concentration within the PCT epithelial cells than in the tubular uid is maintained because a Sodium potassium pumps continuously pump sodium across the basal surface of the PCT epithelium 4 Chloride ions cross the PCT epithelium into the tissue uid via a Antiports in the apical membrane and symports in the basal membrane 5 Solvent drag moves the following substances from the PCT into the tissue uid through the paracellular route a All of the above i Potassium Magnesium Phosphate Sodium H Urea iii Uric Acid 6 Tubular secretion in the proximal convoluted tubules and loop of Henle serve the following purposes a Waste removal and maintaining acidbase balance 7 The primary function of the nephron loop is to maintain a salinity gradient that allows the collecting duct to concentrate the urine and conserve water a TRUE 8 When the tubular uid rst enter the distal convoluted tubule it is highly diluted because water cannot follow the NACL transported across the thick segments of the nephron loop a TRUE 9 Aldosterone has a big in uence on how much water and salt are retained by the body during urine formation It primarily act as follows a Stimulated more reabsorption of Na in the nephron loop DCT and cortical portions of collection duct 10 The following hormones act to decrease blood pressure through their actions on water retention in the kidneys a Atrial Natriuretic Hormone 11 The medullary portion of the collecting duct is less permeable to water than it is to NaCl a FALSE 12 The countercurrent multiplier which maintains a salinity gradient in the renal medulla refers to the action of a The Nephron Loop 13 Water diuresis refers to the production of a large quantity of hypotonic urine after drinking a large volume of water a TRUE 14 One of the actions that ADH hormone induces is for the collecting duct to transfer aquaporins to the cell surface so that the tubular epithelial cells can absorb more water from the tubular uid a TRUE 15 The chemicals that contribute to the osmolarity gradient produced by the loop of Henle the counter current multiplier include a All of the above i Sodium and chlorine ii Potassium i Urea 16 The act of urination is partly controlled by a micturition re ex which forms part of the sympathetic response a FALSE Chapter 25 The Digestive System 0 Most nutrients we eat cannot be used in existing form 0 Must be broken down into smaller components before the body can make use of them Digestive system essentially a disassemby line 0 To break down nutrients into a form that can be used by the body 0 To absorb them so they can be distributed to the tissues 0 Gastroenterology l the study of the digestive tract and the diagnosis and treatment of its disorders Digestive Function 0 Five stages of digestion o Ingestion selective intake of food 0 Digestion mechanical and chemical breakdown of food into a form usable by the body 0 Absorption uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph o Compaction absorbing water and consolidating the indigestible residue into feces o Defecation elimination of feces 0 Mechanical Digestion l the physical breakdown of food into smaller particles 0 Cutting and grinding action of the teeth 0 Churning action of stomach and small intestines o Exposes more food surface to the action of digestive enzymes 0 Chemical Digestion l a series of hydrolysis reactions that breaks dietary macromolecules into their monomers residues 0 Carried out by digestive enzymes produced by salivary glands stomach pancreas and small intestine 0 Results Polysaccharides into monosaccharides Proteins into amino acids Fats into monogycerides and fatty acids Nucleic acids into nucleotides 0 Some nutrients are present in a usable form in ingested food 0 Absorbed without being digested o Vitamins free amino acids minerals cholesterol and water General Anatomy Digestive system has two anatomical subdivisions 0 Digestive Tract alimentary canal 30 feet long muscular tube extending from mouth to anus Mouth pharynx esophagus stomach small intestine and large intestine Gastrointestinal GI tract is the stomach and intestines o Accessory Organs Teeth tongue salivary glands liver gallbladder and pancreas o Digestive tract is open to the environment at both ends 0 Most material in it has not entered the body tissues 0 Considered to be external to the body until it is absorbed by the epithelial cells of the alimentary canal In a strict sense defecated food residue was never in the body 0 Most of the digestive tract follows the basic structural plan with digestive tract wall consisting of the following tissue layers in order from inner to outer surface 0 Mucosa Epithelium Lamina propria Muscularis mucosae o Submucosa o Muscularis externa Inner circular layer Outer longitudinal layer 0 Serosa Areolar tissue Mesothelium Enteric nervous system a nervous network in the esophagus stomach and intestines that regulate digestive tract motility secretion and blood ow 0 Thought to have over 100 million neurons 0 More than the spinal cord 0 Functions completely independently of the central nervous system CNS exerts a signi cant in uence on its action 0 Enteric nervous system contains sensory neurons that monitor tension in gut wall and conditions in lumen Composed of two networks of neurons o Submucosal Meissner plexus in submucosa Controls glandular secretion of mucosa Controls movements of muscularis mucosae o Myenteric Auerbach plexus parasympathetic ganglia and nerve bers between the two layers of the muscularis interna Controls peristalsis and other contractions of muscularis externa Relationship to the Peritoneum Mesenteries connective tissue sheets that loosely suspend the stomach and intestines from the abdominal wall Allow stomach and intestines to undergo strenuous contractions Allow freedom of movement in the abdominal cavity Hold abdominal viscera in proper relationship to each other Prevent the intestines from becoming twisted and tangled by changes in body position and by its own contractions Provide passage of blood vessels and nerves that supply digestive tract Contain many lymph nodes and lymphatic vessels Serous Membranes Mesentery of small intestines holds many blood vessels Mesocolon anchors colon to posterior body wall Regulation of the Digestive Tract Motility and secretion of the digestive tract are controlled by neural hormonal and paracrine mechanisms Neural control Short myenteric re exes stretch or chemical stimulation acts through myenteric plexus Stimulates parastaltic contractions of swallowing Long vagovagal re exes parasympathetic stimulation of digestive motility and secretion Hormones 0 Chemical messengers secreted into bloodstream and stimulate distant parts of the digestive tract o Gastrin and secretin Paracrine secretions 0 Chemical messengers that diffuse through the tissue uids to stimulate nearby target cells Mastication Mastication chewing breaks food into smaller pieces to be swallowed and exposes more surface to the action of digestive enzymes First step in mechanical digestion Food stimulates oral receptors that trigger an involuntary chewing re ex Saliva and the Salivary Glands Functions of Saliva Moisten mouth Begin starch and fat digestion Cleanse teeth lnhibit bacterial growth Dissolve molecules so they can stimulate the taste buds Moisten food and bind it together into bolus to aid in swallowing Hypotonic solution of 970 to 995 water and the following solutes Salivary amylase enzyme that begins starch digestion in the mouth Lingual lipase enzyme that is activated by stomach acid and digests fat after the food is swallowed Mucus binds and lubricates the mass of food and aids in swallowing Lysozyme enzyme that kills bacteria lmmunoglobulin A lgA an antibody that inhibits bacterial growth Electrolytes Na K Cl phosphate and bicarbonate pH 68 to 70 Intrinsic salivarv glands small glands dispersed amid other oral tissues Lingual glands in the tongue produce lingual lipase Labial glands inside of the lips Buccal glands inside of the cheek All secrete small amounts of saliva at a fairly constant rate Extrinsic salivary glands three pairs connected to oral cavity by ducts Parotid located beneath the skin anterior to the earlobe Mumps is an in ammation and swelling of the parotid gland caused by a Virus Submandibular gland located halfway along the body of the mandible lts duct empties at the side of the lingual frenulum near the lower central incisors Sublingual glands located in the oor of the mouth Has multiple ducts that empty posterior to the papilla of the submandibular duct see gure 259 Salivation Extrinsic salivary glands secrete about of 1 to 15 L of saliva per day Cells of acini lter water and electrolytes from blood and add amylase mucin and lysozyme Salivary nuclei in the medulla oblongata and pons respond to signals generated by presence of food Tactile pressure and taste receptors Salivary nuclei receive input from higher brain centers as well Odor sight thought of food stimulates salivation
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