7. URINE FORMATION. Urine formation. Tubular. Glomerular filtration. secretion. Tubular. reabsorption. Filtration. Tubular reabsorption

Save this PDF as:
 WORD  PNG  TXT  JPG

Size: px
Start display at page:

Download "7. URINE FORMATION. Urine formation. Tubular. Glomerular filtration. secretion. Tubular. reabsorption. Filtration. Tubular reabsorption"

Transcription

1 glomerulus is excreted in the urine. The most obvious element following this pattern is water (Fig. 7-2c). 7. URINE FORMATION In order to form urine the kidneys have to carry out three processes: glomerular filtration, tubular reabsorption and finally tubular secretion (Fig. 7-1). The last pattern consist in filtering a determined quantity in the glomerulus and then further have a net addition to the filtrate by tubular secretion of the same element, thus more Urine formation Filtration Crossing of filtration membrane Formation of filtrate Glomerular filtration Tubular reabsorption Tubular secretion Solutes and water cross from filtrate into interstitial fluid and peritubular capillaries Tubular secretion Solutes are secreted into filtrate Tubular reabsorption Filtrate = Urine Figure 7-1. General processes involved in the formation of urine The addition of the effects of each portion determines the composition and concentration of the urine. Different substances reach urine through different routes within this general pattern of filtration, reabsorption and secretion. Some materials are filtered in the glomerulus and are not reabsorbed at all in the tubules, thus, all what is filtered is excreted in urine. Understandable, since these products are not required by the organism, most waste, toxic materials follow this pattern of secretion (Fig. 7-2a). The opposite situation takes place with substances which are filtered in the glomerulus are shortly after reabsorbed in their entirety through the tubules, thus, urine under normal conditions does not carry any of these elements. Glucose, amino acids and small proteins follow this pattern of circulation (Fig. 7-2 b). of what was originally filtered appears in the urine (Fig. 72d). A C B D Figure 7-2. Alternative paths taken by different substances in the kidney. A =waste, B=glucose, aa, small prot., C=water, D= ions. Two other patterns of secretion can be identified in the nephrons. Some substances are filtered in the glomerulus but some portion of it is reabsorbed in the tubular component, thus, less of what is initially filtrated in the V BS 122 Physiology II 47 Class of 2013

2 GLOMERULAR FILTRATION The initial filtrate is formed in the renal capsule and consists in the passage of a large proportion of all the component of plasma, from the circulation to the tubular structure of the kidney. Here the filtration barrier selectively permits the passage of water, solutes (electrolytes), amino acids, glucose, waste products and some small proteins, therefore the concentration of most components of the filtrate are almost identical to that of the plasma left in the capillaries. Large proteins, cellular components and cells are retained within the capillaries and do not enter the filtrate. Some material such as fatty acids, steroids and calcium can be partially retained in the capillaries because a fraction may be bound to proteins. The rate at which the filtrate is formed is called the glomerular filtration rate (GFR) (Fig. 7-3). Use of inulin to calculate GFR To be able to determine the GFR we have to be able to determine the clearance of a substance that behaves as water in the glomerulus. The most common is to inject the plasma with inulin. Inulin is a natural polysaccharide synthesized by many plants (Fig 7-4). Natural polysaccharide Produced in plants Fibre (fructan) 5200 D MW Filters completely Not reabsorbed or secreted Figure 7-4. Characteristics of Inulin Figure 7-3. Glomerular filtration rate HOW TO CALCULATE OR ESTIMATE GFR There are several techniques to measure or closely estimate the GFR. Renal clearance rate of a substance (C s ) can be established if we know the volume of urine being produced (V), the concentration of the substance in the urine (U s ) and the concentration of the substance in the plasma (P s ). It is a type of fibre classified as a fructan with a molecular weight of 5200 daltons. Inulin has the special characteristic that the kidney is capable of completely filter it in the glomerulus but it does not get reabsorbed or secreted by the tubules. For the purposes of estimating GFR inulin behaves like water in the glomerulus. Therefore, once injected in the plasma its rate of excretion is directly proportional to the rate of filtration of water and solutes across the filtration barrier. Replacing plasma and urinary concentration of inulin and the urinary flow rate in the above equation we can calculate GFR (Fig. 7-5). Plasma concentration of inulin (P inu ) = 0.1µmol/mL Urinary concentration of inulin (U inu ) = 6µmol/mL Urinary flow rate (V) = 2 ml/ min Then GFR= C inu = V x U inu / P inu = 2 x 6/0.1 = 120 ml/min C s = U s x V / P s V BS 122 Physiology II 48 Class of 2013

3 Plasma inulin (P Inu ) = 0.1 µmol/ml Urinary inulin (U Inu ) = 6 µmol/ml Urinary flow rate (V) = 2 ml/min GFR = C Inu = V x U Inu / P Inu = 2 x 6/ 0.1= 120 ml/min Use of PAH to estimate renal plasma flow Para-aminohippuric acid (PAH), a product of aromatic amino acid metabolism can be used to estimate Renal Plasma Flow (RPF). When a substance is completely cleared from the plasma, then the clearance rate of such substance is equivalent to the total renal plasma flow. Such a substance does not exist but about 90 % of the PAH is excreted. That means in the average normal kidney the extraction rate of PAH is 90 % (Fig. 7-7). Figure 7-5. Estimating GFR using inulin Use of creatinine to estimate GFR Muscle metabolism generates a waste by-product called creatinine (Fig. 7-6). This compound can be used to estimate GFR. Unlike inulin, creatinine does not have to be injected, thus makes the estimation techniques simpler. Creatinine clears in the glomeulus as water but the tubules also secret a small amount of creatinine into the filtrate, generating an overestimation of the amount cleared. Fortunately, there is also a similar overestimation in the technique to measure creatinine, thus, the combination of these two errors tend to balance out. Protein metabolism waste product Fairly constant Does not require injection Clears glomerulus as water Tubules secrete small amount Technique to measure overestimate it They balance out Product of aromatic AA metabolism Used to estimate RPF 90 % is filtered in in kidney Figure 7-7. Characteristics of PAH Remember that ideally, if a compound is totally cleared from the plasma, the clearance rate of that compound would be equal to the total amount of that compound in the RPF. What gets in the kidneys (RPF x P s ) is the same quantity that is eliminated in the urine (U s x V) (Fig. 7-8). RPF = U s x V / P s = C s But, since the extraction rate is only 90 % then Clearance of PAH/ Extraction rate of PAH RPF= And the extraction rate of PAH (E PAH ) is the difference between the amount of PAH in the renal artery (A PAH ) and the amount left in the renal venous return (V PAH ) divided by the concentration of PAH in the renal artery. Figure 7-6. Estimating GFR using inulin E PAH = A PAH - V PAH /A PAH For example an animal with the following values: (Fig. 7-9) V BS 122 Physiology II 49 Class of 2013

4 Furthermore, once we know the plasma flow rate, by knowing the blood hematocrit value we can determine the total blood flow through the kidney. Volume of plasma flowing through the kidneys per minute RPF = U s x V/P s = C s Since PAH extraction rate = 90% RPF = C PAH / E PAH and E PAH = A PAH V PAH / A PAH Figure 7-8. Characteristics of PAH If we measured hematocrit value is 0.45 then the total plasma flow would be 430 / (1 0.45) or 782 ml/min Filtration fraction Of all the plasma that circulates through the glomerulus about 19% is filtered into the tubular compartment. The exact amount at any given time is determined by several physiological factors. The hydrostatic and colloidal osmotic forces across the filtration barrier and the capillary filtration coefficient, which is in turn determined by the permeability and the surface area of the capillaries, determine the GFR. The volume of filtrate formed or filtrate fraction is = GFR x renal plasma flow. P PAH = mg/ml U PAH = 5.8 mg/ml V = 1 ml/min RPF = U s x V/P s =C s C PAH = 5.8 mg/ml x 1 ml/min mg/ml = 387 ml/min = 430 ml/min 0.9 The components of the filtration barrier all contribute to determine the filtering capacity of this structure (Fig. 7-10). The fenestrations in the endothelial cells of the glomerular capillaries are large enough to permit the passage of all materials in blood except very large proteins and cells such as erythrocytes. The endothelial cells are, however, are densely loaded with negatively charged components. Figure 7-9. Estimating renal plasma flow Plasma concentration PAH of mg/ml. Urinary concentration of PAH of 5.8 mg /ml Urinary flow rate of 1 ml/min The clearance of PAH in urine would be 5.8 mg/ml x 1 ml/min divided by the plasma concentration of PAH or mg/ml= 387mL/min. If the extraction rate of PAH is 90% then the real plasma flow rate (PFR) can be determined by dividing 387 ml/min by 0.9 which would yield 430 ml/min. Maximum size allowed through 7µm or 40 kd Most proteins, cell components and cells are retained in capillaries Small protein hormones cross Protein bound FA and steroids are retained Filtrate may contain 0.03% protein Figure Characteristics of the filtration barrier This feature prevents the passage or filtration of many smaller proteins that would comfortably fit through the fenestrations. V BS 122 Physiology II 50 Class of 2013

5 The composition of the basement membrane determines its filtering capacity. This membrane is primarily made of proteoglycans and collagen chains interlocked, leaving large spaces through which most solutes and water can filter. Proteoglycans are charged with strong negative charges, thus preventing the passage of most proteins that could have crossed the fenestrations. The interdigtation of their extension create a series of filtration slits which further contribute to the filtration process. These elements are also charged negatively, thus further preventing the passage of proteins. If the filtration barrier is normal, this permits the passage of molecules smaller than 7µm in diameter or with a molecular mass of about 40,000 daltons (Fig. 7-10). Because most proteins are larger than these they are unable to be filtered out and they remain within the capillaries. Some proteins are, however, smaller than these thus, they cross the filtration membrane. Many protein hormones fall in this category. It is estimated that the filtrate can have about 0.03% of proteins in the glomerular space. Proteins are nonetheless, actively reabsorbed in the proximal convoluted tubule to the point that very little protein ever reach the urine. How much urine is formed? To understand the process of urine formation is necessary to understand all the intermediary steps between blood moving through the circulatory system and the total amount of urine excreted by an animal. There are several concepts (Fig. 7-11) which will be explained with a mathematical example. The last component of the filtration barrier is the layer of specialized epithelial cell that lay on top of the basement membrane, the podocytes (Fig. 6-11). For example an 80 kg hog under resting conditions will have a cardiac output (CO) of approximately 5.7L/min. As stated earlier the kidney receives approximately 20% of the volume of the CO so, in our case, the kidneys would be irrigated by about 1.14 L of blood/min that is the Renal Blood Flow (Fig 7-12). Volume of blood flowing through the kidneys per minute Cardiac output x % entering kidneys 80kg hog CO = 5.7L/min Renal fraction 20% RBF = 5.7 L/min x 0.2 = 1.14 L/min Figure Calculation of renal blood flow Renal Blood Flow= CO X % Renal fraction RBF = 5.7 L/min X 0.2 = 1.14 L/min Of the volume of blood entering the kidney, only certain percentage is plasma. The rest is made up principally by hematocrites. Although these values can vary tremendously a standard percentage for a normal animal is 60% plasma (Fig 7-13). Renal Plasma Flow = RBF X % of plasma in blood RPF= 1.14 L/min X 0.6 = L/min or 684 ml/min Renal blood flow Renal plasma flow Glomerular filtration rate Urine Daily urine volume Of the plasma which enters the kidneys only about 19% goes through the filtration barrier. The rest leaves the glomerulus through the efferent arteriole with all the hematocrits and large proteins (Fig. 7-13). Glomerular Filtration Rate = RPF X % filtration fraction GFR = 684 ml/min X 0.19 = 130 ml of filtrate/min Figure Renal flow rates between circulation and urine Of the volume that enters the capsular space only a very small fraction is excreted in urine, the rest is all reabsorbed V BS 122 Physiology II 51 Class of 2013

6 at different places in the nephron. The average volume which is not reabsorbed under normal conditions is onlyabout 0.8% of the filtrate (Fig. 7-14). Volume of plasma flowing through the kidneys per minute Renal blood flow x % plasma (blood-hematocrit) RBF = 1.14 L/min % plasma in blood = 60% RPF = 1.14 L/min x 0.6 = L/min = 684 ml/min Volume of no reabsorbed filtrate leaving the kidney per minute GFR x % no reabsorbed filtrate GFR =130 ml/min Non reabsorbed filtrate (NRF) = 0.8% Urine = 130 ml x = 1.04 ml/min Figure Rate of urine formation Figure Calculation of renal plasma flow Urine = 1.04 ml/min Volume of plasma (filtrate) entering Bowman s capsule per minute Renal plasma flow x plasma entering the renal capsule RPF = 684 ml/min Filtration fraction (FF) = 19% GFR = 684 ml/min x 0.19 = 130 ml /min Day = 60 min x 24 h= 1440 min/day L = 1000 ml Daily volume urine = urine x min / 1000 Volume of urine = 1.04 ml/min x 1.44 = 1.49 L/Day Figure Calculation of daily urine production volume Figure Calculation of glomerular filtration rate Urine = GFR X % no reabsorbed filtrate Urine = 130 m L/min X = 1.04 ml/min (Fig. 7-15). This volume per minute can be converted to L/day by multiplying by 1.44 (Number of minutes in one day/1000 ml) (Fig 7-16). Thus, this animal produces 1.04 ml/min X 1.44 = L/day Minimum obligatory volume of urine In order to eliminate all the solutes that are ingested over a given period of time the animal has to produce an obligatory volume of urine. The obligatory volume depends on the ability of the animal to concentrate urine. The more it can be concentrated the smaller is the required volume of urine excreted. Some animals adapted to life in the dessert have the ability to concentrate urine to levels as high as 10, mosm/l while animals living in water can only concentrate urine to about 500 mosm/l. Let s assume that our 80 Kg hog has a daily solute intake of about 690 mosm/day and it is only able to concentrate urine to 200 mosm/l (Fig. 7-17). Then the obligatory volume for this animal will be: 690mOsm/day/1200mOsm/L = 575 ml/day V BS 122 Physiology II 52 Class of 2013

7 The GFR is determined by the filtration pressure and the filtration coefficient (Kf) (Fig. 7-19). GFR = FP X Kf Smaller volume of urine As concentrated as possible Intake = 690 mosm/day Max. concentration = 1200 mosm/l 690 mosm/day = 575 ml/day 1200 mosm/l Figure Calculation of the minimum obligatory daily volume of urine production This equation explains why animals, that in desperation drink sea water, undergo rapid dehydration. The sea water has a solute concentration of about 2400 mosm/l. If they can only eliminate 1200 mosm for each litter of urine, then, to eliminate the 2400 that they ingest with each litter of sea water that they drink they need to eliminate 2400mOsm/ 1200 mosm = 2 L of water. Since they only ingested 1 litter the other litter has to come from internal sources causing rapidly an unbalance resulting in dehydration (Fig 7-18). Sea water = 2400 mosm/l Max concentration = 1200 mosm/l For each litter drank need 2400 mosm = 2L to eliminate 1200 mosm/l Figure Minimum obligatory volume of urine required to eliminate all the ingested solutes The above described example assumes constant ideal conditions. In a living organism that is never the case. There are always physiological changes that influence the rate at which most processes take place. The glomerular filtration rate is no exception. Filtration pressure (P G P B π G + π B ) Glomerular capillary pressure (P G or GCP) Capsular pressure (P B or CP) Blood colloid osmotic pressure (π G or BCOP) Capsular osmotic pressure (π B or COP) Filtration coefficient (K f ) Permeability FB Capillary area GFR= K f x (P G P B π G + π B ) Figure Factors influencing glomerular filtration rate The filtration coefficient is determined by the area of the capillary and the permeability of the filtration barrier. As a result there are many possible mechanisms to alter the GFR. A change in the filtration coefficient will change the GFR. These changes are, however, not responsible for the fine tuning of the GFR. Changes in K f usually are observed under pathological conditions. A reduction in the total capillary surface resulting from loss of nephrons will reduce the K f and in turn diminish the overall GFR. Thickening of the filtration barrier, as a result of hypertension, will also reduce the K f and the GFR. The rate at which the glomerular filtration takes place is drastically influenced by the filtration pressure. The filtration pressure is the balance between the forces trying to push material out of the capillaries into the Bowman s space, against those forces trying to prevent it (Figs. 7-19, 7-20). The main force in favour of filtration is the glomerular capillary pressure (GCP). This pressure is about 50 mm Hg and it is generated by low resistance (vasodilation) of the afferent capillary in conjunction with high resistance (vasoconstriction) of the efferent arteriole. Modifications in the resistance of these two arterioles can increase further or drastically reduce the GCP with the consequent increase or reduction in production of filtrate, respectively. V BS 122 Physiology II 53 Class of 2013

8 The main forces opposing filtration are the capsular pressure (CP) and the blood colloid osmotic pressure (BCOP). The CP is generated by the physical pressure exerted by the filtrate against the Bowman s capsule. This usually reaches values of about 10 mm Hg. The BCOP is more variable and it is generated by the osmotic concentration existing in the capillary due to the high concentration of proteins that do not cross the filtration barrier. Filtration pressure pressure, and as a result will increase the filtration pressure, thus increasing the GFR. The capsular pressure does not usually change much, unless there is a pathological situation such as deposit of calcium in the tubule or the formation of stones that prevent emptying of the content in the Bowman s capsule. If this is the case the capsule pressure can increase to the point of eliminating the filtration pressure thus stopping GF. In order to try to maintain a somehow constant glomerular filtration pressure or to modify it according to the needs of the moment, the kidney resort to two mechanisms, autoregulation and sympathetic stimulation (Fig. 7-21). These mechanism permit that the animal maintains relatively constant GFR when mean arterial blood pressure oscillate within a large range (90 to 180 mm Hg). Dropping below that range triggers a significant reduction in GFR. Figure Forces influencing the filtration pressure. GCP=glomerular capillary pressure, CP= capsular pressure, BCOP= blood colloid osmotic pressure Because of its nature, there is an increasing gradient within the capillaries from the end leaving the afferent arteriole towards the end of the capillary where it becomes the efferent arteriole. The increase in osmotic pressure takes place because as the blood flow within the capillary it becomes more concentrated as water leaves the capillary. The average value for the BCOP is about 30 mm Hg. Because the concentration of proteins in the filtrate is so low the capsular osmotic pressure is negligible, thus for calculations is considered to be zero. Therefore the filtration pressure can be equated as: FP= GCP- CP- BOCP or = 10 mm Hg More subtle changes in GFR can be observed as a result of changes in the parameters that determine the filtration pressure. For example a small decrease in resistance by the afferent arteriole or a small increase in resistance by the efferent arteriole will increase the capillary hydrostatic Autoregulation Modify afferent and / or efferent arteriole resistance Tubuloglomerular feedback Initiated by macula densa detecting flow Activate renin angiotensin system Sympathetic stimulation Norepinephrine causes afferent arteriole vasoconstriction Effective under severe stress or shock Figure Mechanisms used to maintain glomerular filtration rate semi constant Autoregulation. The mechanism of autoregulation consists in modifying the resistance in the afferent and / or efferent arterioles. If the systemic mean arterial blood pressure increases, the afferent arteriole vasocontricts and or the efferent arteriole vasodilates reducing the pressure in the glomerular capillaries thus maintaining constant filtration pressure and GFR. The opposite takes place when the systemic mean arterial blood pressure decreases. V BS 122 Physiology II 54 Class of 2013

9 This auto regulatory mechanism can also be triggered by flow rate of filtrate through the distal convoluted tubule. This is described as tubuloglomerular feedback. If the cells in the macula densa detect a large change in the flow of filtrate they convey this information to the juxtaglomerular apparatus which then triggers a vasoconstriction or vasodilation in the afferent arteriole to reduce or increase filtration pressure, thus maintaining GFR constant. The signalling for this regulatory mechanism is not completely understood but it is suggested that it is implemented in the following manner. A decrease in GFR will result in a slower rate of passage of the filtrate though the loop of Henle. As a result there will be more time to reabsorb solutes from the filtrate. The filtrate leaving the loop of Henle and reaching the cells in the macula densa will have lower concentration of NaCl. This will be detected by the cells of the macula densa which will send information to the afferent arteriole to vasodilate, increasing the filtration pressure and the GFR. This signal also triggers the release of renin by the juxtaglomerular cells. Renin elevation translates in elevation of angiotensin II and, since this is a powerful vasoconstrictor for the efferent arteriole, it elevates filtration pressure and brings back the GFR to the normal rate (Fig. 7-21). Sympathetic stimulation. Sympathetic innervations uses norepinephrine as their neurotransmitter and this catecholamine has an effect in the afferent arterioles causing their vasoconstriction. This mechanism has a negligible effect when the stimulation is mild because the autoregulation mechanism takes over, but it may have a drastic effect when the stimulation is very strong. In situations of severe stress or shock, there is a drastic reduction in the irrigation of the kidney and if maintained for a long period it may cause kidney damage. A short term reduction is not harmful but provide the resources to maintain irrigated other vital organs (heart, brain, liver), and maintain homeostasis. Changes from filtrate to urine The second step in the process of making urine is to reduce the volume of the filtrate by removing most of their content, leaving the undesirable compounds to be voided in a small volume of fluid. This reduction is initiated in the tubular component of the nephron with the reabsorption of a large volume of water. The majority of the filtrate is reabsorbed in the proximal convoluted tubule. About 65% of the water is reabsorbed in this section. Another 15 % is reabsorbed in the loop of Henle and the final 19 % is reabsorbed in the collecting tubes leaving only about 1 % of the volume to be secreted as urine (Fig. 7-22). Reabsorption of filtrate Figure Areas of the nephron where different volumes of filtrate are reabsorbed Reabsorption of the different components of the filtrate is achieved by active and passive mechanisms. The active mechanisms involve the expenditure of energy in the form of ATP to drive the movement of sodium against a concentration gradient from the intracellular space into the interstitial space through the basal membrane or the basolateral membrane of the tubular cells. This generates a Na + gradient in the tubular cell with respect to the lumen of the tubule where the filtrate is located. The passive mechanisms involve diffusion, facilitated diffusion, cotransport or symport, and antiport. Proximal convoluted tubule Tubular cells are equipped with a variety of proteins, normally incorporated to the apical, lateral or basal membrane, which participate in the movement of ions and other molecules from the filtrate to the tubular cell and then to the interstitial fluid, so they can be eventually translocated to the capillaries and to circulations. These proteins make ATPases, symports, antiports, as well as, leek channels (Fig. 7-23). V BS 122 Physiology II 55 Class of 2013

10 Materials that are transported through this mechanism into the cell are, among others, amino acids, small proteins, glucose, fructose, Cl -, Ca +, K +, HCO 3 - and of course Na +. Water, the most abundantly reabsorbed molecule simply diffuses into the cell by osmosis. Once inside the cell most of the molecules are discarded into the interstitial fluid by facilitated diffusion. Amino acids, glucose, fructose, small proteins and K + are all discarded through facilitated diffusion. Cl - is co transported with K + and HCO - 3 is also co transported with Na + into the interstitial fluid. Water follows by osmosis. From here all the solutes are uptaked by the peritubular capillaries and carried towards the interlobular and arcuate vein respectively. Figure Components of a tubular cell of the proximal convoluted tubule In the proximal convoluted tubule, most of the reabsorption is dependent on the creation and maintenance of a low intracellular concentration of Na +. A low intracellular Na + concentration generates a gradient respect to the filtrate in the tubule. The creation of this gradient is achieved by actively transporting Na + out of the cell into the interstitial space using a pump driven by ATP (ATPase) (Fig. 7-24). In this process, for each Na + which is removed from the cell, one K + is incorporated into the cell from the interstitial space. This process is great to create a deficiency of Na + but, at the same time, it accumulates K + in the cell. After a lot of K + is accumulated inside the cell most of it is discarded into the interstitial space by facilitated diffusion or leak channels. Once the Na + gradient is created, a large variety of cotransporters located in the apical membrane of the tubular cell became active. These symports are proteins capable of binding a variety of solutes and molecules as well as Na +. They bind the substance first and then Na +. When Na + binds then the protein rotate, propelled by the energy of the Na + attraction to the inside of the cell. As it rotates the protein brings into the cell the co-transported material. Once inside the cell both Na + and the accompanying solute or molecules are released and the protein counter rotates back to the original position, again exposing the binding sites to the lumen of the tubule. The net result is that large reduction I filtrate volume (about 65%). Because the cells of the convoluted tubule are so permeable to water, still at this point the filtrate maintains the same osmolal concentration than the interstitial fluid of about 300 mosm/kg. Loop of Henle Depending on the type of nephron the loop of Henle may only descend a little bit into the medulla (cortical nephrons), or, in the case of Juxtamedullary nephrons, extend the loop of Henle deep into the medulla (Fig. 6-9). The osmolal concentration of the interstitial fluid gradually increases towards the medulla, reaching values of 1200 mosm/kg in the area close to the tip of the renal pyramid (Fig. 7-24). This feature permits progressively increase removal of water from the filtrate. The thin descending segment of the loop of Henle is very permeable to water and less permeable to other substances as urea, sodium and other ions. As the filtrate moves in the descending limb of the loop of Henle an additional 15 % of the water is removed. Since not many solutes are removed in this section the filtrate becomes more concentrated. Furthermore, towards the end of the thin segment of the loop of Henle, some solutes are incorporated into the filtrate making it more concentrated. Once the lowest point is reached, the characteristics of the thin segment changes in such a way that the thin ascending segment of the loop of Henle is totally impermeable to water but permeable to solutes. In this section, then, no further water is removed but many solutes diffuse out of the filtrate in the lumen into the interstitial fluid and then into the vasa recta making the filtrate less concentrated. The thick segment of the ascending limb of the loop of Henle is not permeable to V BS 122 Physiology II 56 Class of 2013

11 water or to solutes but some solutes (Na +, K + and Cl - ) are symported from the filtrate to the inside of the tubular cells and once in the cell they are discarded towards the interstitial fluid by facilitated diffusion. The fact that only solutes are removed in this section make the filtrate reach concentrations of only 100 mosm/kg as it reaches the distal convoluted tubule while the interstitial fluid at this point in the cortex is about 300 mosm/kg (Fig. 7-24). The Starling forces are a combination of hydrostatic and oncotic forces determining the net filtration of fluids across the capillary membranes (Fig. 7-25). These can be represented by the following simplified equation: J v = K f ([P c P i ] [π c π i ]) where J v represents the net movement of fluids between inside and outside the capillaries. It is agreed that a positive value of J v indicates that blood is leaving the capillary while a negative value indicates that fluid is entering the capillary. K f represents the filtration coefficient which in turn depends of the capillary surface area and the permeability. P c represents the hydrostatic pressure of the capillary. Figure Concentration of the filtrate and the interstitial fluid at different depth of the glomerulus The movement of fluid (mainly water) between the interstitial space and the interior of the capillaries in the pericapillary bed, as well as, in the vasa recta is determined by the balance of Starling forces between these two mediums. Hydrostatic and oncotic forces Determine net filtration of fluids across a capillary membrane J v = K f ([P c -P i ] [π c π i ]) J v = Net movement of fluid K f = Filtration coefficient P c = Hydrostatic pressure of capillaries P i = Hydrostatic pressure interstitial space π c = Osmotic pressure of capillaries πi = Osmotic pressure of interstitial space Fig Forces influencing the passage of fluid through capillaries P i represents the hydrostatic pressure of the interstitial space π c represents the capillary osmotic pressure π i represents the osmotic pressure of the interstitial fluid Distal convoluted tubule In the distal convoluted tubule and first section of the collecting duct there is further removal of solutes. Cl - is symported with Na + through the apical membrane into the tubular cells and discarded into the interstitial fluid through the basal membrane by symport with K +. All of this is possible because the intracellular concentration of Na + is maintained very low by the ATPase pump (Fig. 7-26). Collecting Duct As the collecting tube enters the medulla of the kidney the interstitial fluid becomes again more and more concentrated. This concentration gradient will facilitate initially the diffusion of water from the filtrate towards the interstitial fluid. However, the permeability of the collecting duct cells to water becomes hormonal dependent. In the collecting duct the final removal of water takes place leaving the filtrate converted into urine which can be carried towards the ureter and bladder V BS 122 Physiology II 57 Class of 2013

12 Fate of other solutes In the initial filtrate there are many other solutes not mentioned so far. Urea, a product of gluconeogenesis from amino acids is one of them. Creatinine, sulphates, nitrates and phosphates are other compounds that all filtered in the renal corpuscle but eventually only partially reabsorbed. This leaves a large proportion of these materials dissolved in the urine, destined for excretion. As the filtrate reaches the collecting duct these materials are very concentrated in urine. Between 40 and 60 % of the urea in the filtrate is passively reabsorbed. The rest is concentrated and eliminated. Distal convoluted tubule Fig The role of these cells is to further remove solutes and water. No removal of glucose or amino acids takes place in here V BS 122 Physiology II 58 Class of 2013

Chapter 26: The Urinary System

Chapter 26: The Urinary System Chapter 26: The Urinary System Chapter Objectives OVERVIEW OF KIDNEY FUNCTION 1. List and describe the functions of the kidneys. NEPHRONS 2. Describe the two major portions of a nephron and the capillaries

More information

LECTURE 1 RENAL FUNCTION

LECTURE 1 RENAL FUNCTION LECTURE 1 RENAL FUNCTION Components of the Urinary System 2 Kidneys 2 Ureters Bladder Urethra Refer to Renal System Vocabulary in your notes Figure 2-1,page10 Kidney Composition Cortex Outer region Contains

More information

Chapter 26: Urinary System

Chapter 26: Urinary System I. Functions of the Urinary System A. List and describe the six major functions of the kidneys: 1. 2. 3. 4. 5. 6. II. Kidney Anatomy and Histology A. Location and External Anatomy of the Kidneys 1. Describe

More information

April 18, 2008 Dr. Alan H. Stephenson Pharmacological and Physiological Science

April 18, 2008 Dr. Alan H. Stephenson Pharmacological and Physiological Science Renal Mechanisms for Regulating Urine Concentration April 18, 2008 Dr. Alan H. Stephenson Pharmacological and Physiological Science Amount Filtered Reabsorption is selective Examples of substances that

More information

Chapter 23. Urine Formation I Glomerular Filtration

Chapter 23. Urine Formation I Glomerular Filtration Chapter 23 Urine Formation I Glomerular Filtration Urine Formation I: Glomerular Filtration kidneys convert blood plasma to urine in three stages glomerular filtration tubular reabsorption and secretion

More information

Study Guide for the Urinary System (Online version)

Study Guide for the Urinary System (Online version) Study Guide for the Urinary System (Online version) Glomerular Filtration (Page 1007 - ) Filtration Membrane Glomerulus Net Filtration Pressure - -page 1008 Or PP Total of the pressures which drive the

More information

Glomerular Filtration

Glomerular Filtration Glomerular Filtration Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) Page 1. Introduction Formation of urine by the kidney involves

More information

CHAPTER 20: URINARY SYSTEM

CHAPTER 20: URINARY SYSTEM OBJECTIVES: 1. Name the major function of the urinary system, and name and locate (on a diagram) the organs that compose the system. 2. Explain what the term renal refers to. 3. Define the term retroperitoneal.

More information

Renal Blood Flow GFR. Glomerulus Fluid Flow and Forces. Renal Blood Flow (cont d)

Renal Blood Flow GFR. Glomerulus Fluid Flow and Forces. Renal Blood Flow (cont d) GFR Glomerular filtration rate: about 120 ml /minute (180 L a day) Decreases with age (about 10 ml/min for each decade over 40) GFR = Sum of the filtration of two million glomeruli Each glomerulus probably

More information

Body Fluids. Physiology of Fluid. Body Fluids, Kidneys & Renal Physiology

Body Fluids. Physiology of Fluid. Body Fluids, Kidneys & Renal Physiology Pc Remember arterioles have more smooth muscle So SNS effects are greater on arterioles than on venules Net effects: SNS P c (vasoconstriction > venoconstriction) SNS P c (vasodilation > venodilation)

More information

Select the one that is the best answer:

Select the one that is the best answer: MQ Kidney 1 Select the one that is the best answer: 1) n increase in the concentration of plasma potassium causes increase in: a) release of renin b) secretion of aldosterone c) secretion of H d) release

More information

Kidney Structure and Function.

Kidney Structure and Function. Kidney Structure and Function. Learning Objectives. At the end of this section, you should be able to : 1. describe the structure of the kidney; 2. understand the vascular organisation of the kidneys;

More information

Sign up to receive ATOTW weekly - email worldanaesthesia@mac.com

Sign up to receive ATOTW weekly - email worldanaesthesia@mac.com RENAL PHYSIOLOGY - PART 1 ANAESTHESIA TUTORIAL OF THE WEEK 273 5 th NOVEMBER 2012 Dr Matthew Gwinnutt Mersey Deanery, UK Dr Jennifer Gwinnutt Mersey Deanery, UK Correspondence to: mgwinnutt@doctors.org.uk

More information

Chapter 23. Composition and Properties of Urine

Chapter 23. Composition and Properties of Urine Chapter 23 Composition and Properties of Urine Composition and Properties of Urine urinalysis the examination of the physical and chemical properties of urine appearance - clear, almost colorless to deep

More information

Urinary System. And Adrenal Function

Urinary System. And Adrenal Function Urinary System And Adrenal Function Overview Kidney anatomy and physiology Urine Ureters, Bladder and Urethra Adrenal Function Functions of the Kidney Filter fluids from the blood Regulate volume and composition

More information

Pathophysiology Renal Anatomy and Function II

Pathophysiology Renal Anatomy and Function II Pathophysiology Renal Anatomy and Function II I. Effects of blood volume on the filtration fraction (FF) {Altered Volume Effects in syllabus A. Under normal conditions, ~20% of renal plasma flow becomes

More information

Urinary System: Notes You Gotta be Kidney Me

Urinary System: Notes You Gotta be Kidney Me Urinary System: Notes You Gotta be Kidney Me You kidneys are the primary organs of excretion. Excretion is the removal of wastes from the body. The wastes we are referring to here are the products of metabolism.

More information

RENAL WATER REGULATION page 1

RENAL WATER REGULATION page 1 page 1 INTRODUCTION TO WATER EXCRETION A. Role of the Kidney: to adjust urine formation rate and urine concentration to maintain 1. body fluid osmolar concentration 2. body fluid volume 3. intravascular

More information

The digestive system eliminated waste from the digestive tract. But we also need a way to eliminate waste from the rest of the body.

The digestive system eliminated waste from the digestive tract. But we also need a way to eliminate waste from the rest of the body. Outline Urinary System Urinary System and Excretion Bio105 Lecture 20 Chapter 16 I. Function II. Organs of the urinary system A. Kidneys 1. Function 2. Structure III. Disorders of the urinary system 1

More information

Pathophysiology Introduction/ Renal Anatomy and Function

Pathophysiology Introduction/ Renal Anatomy and Function Pathophysiology Introduction/ Renal Anatomy and Function I. Functions of the kidney A. Maintaining homeostasis of a large number of solutes and water is the main job of the kidney. Total body contents

More information

Regulating the Internal Environment Water Balance & Nitrogenous Waste Removal

Regulating the Internal Environment Water Balance & Nitrogenous Waste Removal Regulating the Internal Environment Water Balance & Nitrogenous Waste Removal 2006-2007 Animal systems evolved to support multicellular life CH CHO O 2 O 2 NH 3 CH CHO O 2 CO 2 NH NH 3 O 2 3 NH 3 intracellular

More information

Components. Urinary System. Formation of Urine. Functions of Kidney. Pathway of Urine. Kidney. Major functions of the kidneys include:

Components. Urinary System. Formation of Urine. Functions of Kidney. Pathway of Urine. Kidney. Major functions of the kidneys include: Components Urinary System To Accompany: Anatomy and Physiology Text and Laboratory Workbook, Stephen G. Davenport, Copyright 2006, All Rights Reserved, no part of this publication can be used for any commercial

More information

Water Homeostasis. Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.

Water Homeostasis. Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc. Water Homeostasis Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) 1. Water Homeostasis The body maintains a balance of water intake

More information

Essentials of Human Anatomy & Physiology. Chapter 15. The Urinary System. Slides 15.1 15.20. Lecture Slides in PowerPoint by Jerry L.

Essentials of Human Anatomy & Physiology. Chapter 15. The Urinary System. Slides 15.1 15.20. Lecture Slides in PowerPoint by Jerry L. Essentials of Human Anatomy & Physiology Elaine N. Marieb Seventh Edition Chapter 15 The Urinary System Slides 15.1 15.20 Lecture Slides in PowerPoint by Jerry L. Cook Functions of the Urinary System Elimination

More information

Lisa Nguyen. Determining Effects of Urine Flow Rate from Fasting, and intake of Water, Gatorade, or Coke

Lisa Nguyen. Determining Effects of Urine Flow Rate from Fasting, and intake of Water, Gatorade, or Coke Lisa Nguyen Determining Effects of Urine Flow Rate from Fasting, and intake of Water, Gatorade, or Coke Introduction Human being s require a balanced internal environment to properly function, this internal

More information

Kidneys, Nephrons, and Urine Production

Kidneys, Nephrons, and Urine Production Valerie ovelace Kidneys, Nephrons, and rine Production Part of the urinary system, our kidneys are vital organs that serve to remove waste from the bloodstream through ultrafiltration and the formation

More information

Correlation of Ingested Fluids to Urine Flow Rate and Urine Specific Gravity. Sonia Malhotra March 14, 2011

Correlation of Ingested Fluids to Urine Flow Rate and Urine Specific Gravity. Sonia Malhotra March 14, 2011 Correlation of Ingested Fluids to Urine Flow Rate and Urine Specific Gravity Sonia Malhotra March 14, 2011 Introduction: The kidneys are a two bean shaped structure, located in the back of the abdomen.

More information

The Effects of Different Types of Fluids on the Renal System

The Effects of Different Types of Fluids on the Renal System The Effects of Different Types of Fluids on the Renal System Lisa Ta March 16, 2012. Biology 611.02 Principles of Human Physiology Butt, Shamim Introduction Kidneys are a key function to the human body

More information

Urinary System! (Chapter 26)! Lecture Materials! for! Amy Warenda Czura, Ph.D.! Suffolk County Community College! Eastern Campus!

Urinary System! (Chapter 26)! Lecture Materials! for! Amy Warenda Czura, Ph.D.! Suffolk County Community College! Eastern Campus! Urinary System! (Chapter 26)! Lecture Materials! for! Amy Warenda Czura, Ph.D.! Suffolk County Community College! Eastern Campus! Urinary System Components:! -Kidneys! -Ureters! -Urinary Bladder!! -Urethra!

More information

Blood Pressure Regulation

Blood Pressure Regulation Blood Pressure Regulation Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) Page 1. Introduction There are two basic mechanisms for regulating

More information

UNIT IV MAJOR INTRA AND EXTRA CELLULAR ELECTROLYTES

UNIT IV MAJOR INTRA AND EXTRA CELLULAR ELECTROLYTES UNIT IV MAJOR INTRA AND EXTRA CELLULAR ELECTROLYTES J.KAVITHA, M.Pharm., Lecturer, Department of Pharmaceutical Analysis, SRM College of Pharmacy SRM University. An electrolyte is any substance that dissociates

More information

Chapter 5 Glomerular Ultrafiltration

Chapter 5 Glomerular Ultrafiltration Chapter 5 Glomerular Ultrafiltration After completing this chapter the student should be able to discuss the following concepts: 1 Biophysical basis of glomerular filtration and the dynamic changes in

More information

Nutrition, Digestion, Absorption, and Excretion

Nutrition, Digestion, Absorption, and Excretion ECOL 182 - Spring 2010 Nutrition, Digestion, Absorption, and Excretion Dr. Regis Ferriere Department of Ecology & Evolutionary Biology University of Arizona Lecture 2 Our main questions in this lecture

More information

Vascular System The heart can be thought of 2 separate pumps from the right ventricle, blood is pumped at a low pressure to the lungs and then back

Vascular System The heart can be thought of 2 separate pumps from the right ventricle, blood is pumped at a low pressure to the lungs and then back Vascular System The heart can be thought of 2 separate pumps from the right ventricle, blood is pumped at a low pressure to the lungs and then back to the left atria from the left ventricle, blood is pumped

More information

2. Understand the structure of the kidney, and how this structure facilitates its function

2. Understand the structure of the kidney, and how this structure facilitates its function Objectives 1. Understand the roles of the kidney 2. Understand the structure of the kidney, and how this structure facilitates its function 3. Begin to appreciate the inter-dependence of regulatory mechanisms

More information

23. The Urinary System Text The McGraw Hill Companies, 2003 CHAPTER

23. The Urinary System Text The McGraw Hill Companies, 2003 CHAPTER CHAPTER 23 The kidneys (green), ureters, and urinary bladder (red) of a healthy person (colorized X ray) The Urinary System CHAPTER OUTLINE Functions of the Urinary System 880 Functions of the Kidneys

More information

AORN A.CARDARELLI NAPOLI dr.e.di Florio III SAR

AORN A.CARDARELLI NAPOLI dr.e.di Florio III SAR AORN A.CARDARELLI NAPOLI dr.e.di Florio III SAR Renal Anatomy Renal Artery & Veins 6 cm 3cm Cortex 11cm Pelvis of the ureter Capsule Ureter To the bladder Medulla Medulary Pyramid Renal Anatomy and Physiology

More information

Biology 224 Human Anatomy and Physiology II Week 8; Lecture 1; Monday Dr. Stuart S. Sumida. Excretory Physiology

Biology 224 Human Anatomy and Physiology II Week 8; Lecture 1; Monday Dr. Stuart S. Sumida. Excretory Physiology Biology 224 Human Anatomy and Physiology II Week 8; Lecture 1; Monday Dr. Stuart S. Sumida Excretory Physiology The following ELEVEN slides are review. They will not be covered in lecture, but will be

More information

Urinary System Lab Guide

Urinary System Lab Guide Urinary System Lab Guide I. Prelab Questions Name 1. Describe the location of the kidneys. 2. Describe the following structures: a. renal cortex b. renal pyramid c. renal column d. minor calyx e. renal

More information

Acid/Base Homeostasis (Part 3)

Acid/Base Homeostasis (Part 3) Acid/Base Homeostasis (Part 3) Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) 27. Effect of Hypoventilation Now let's look at how the

More information

Chapter 26: The Urinary System Kidney

Chapter 26: The Urinary System Kidney Chapter 26: The Urinary System Kidney --Overview of Kidney Function a. Regulation of blood ionic composition b. Regulation of blood ph and osmolarity c. Regulate blood glucose level (gluconeogenesis) d.

More information

Acid-Base Balance and Renal Acid Excretion

Acid-Base Balance and Renal Acid Excretion AcidBase Balance and Renal Acid Excretion Objectives By the end of this chapter, you should be able to: 1. Cite the basic principles of acidbase physiology. 2. Understand the bicarbonatecarbon dioxide

More information

Renal Topics 1) renal function 2) renal system 3) urine formation 4) urine & urination 5) renal diseases

Renal Topics 1) renal function 2) renal system 3) urine formation 4) urine & urination 5) renal diseases Renal Topics 1) renal function 2) renal system 3) urine formation 4) urine & urination 5) renal diseases 1/9/2015 Renal Biology - Sandra Hsu 1 Renal Functions 1) excrete metabolic wastes (blood cleaning)

More information

The kidneys play a dominant role in regulating the composition

The kidneys play a dominant role in regulating the composition PART VI RENAL PHYSIOLOGY AND BODY FLUIDS C H A P T E R 22 Kidney Function George A. Tanner, Ph.D. LEARNING OBJECTIVES Upon mastering the material in this chapter you should be able to: Summarize the functions

More information

UNIT 11 - URINARY SYSTEM LECTURE NOTES

UNIT 11 - URINARY SYSTEM LECTURE NOTES UNIT 11 - URINARY SYSTEM LECTURE NOTES 11.01 FUNCTIONS OF THE URINARY SYSTEM A. Regulate the composition and volume of the blood by removing and restoring selected amounts of water and solutes. B. Excretes

More information

Structure of the Kidney Laboratory Exercise 56

Structure of the Kidney Laboratory Exercise 56 Structure of the Kidney Laboratory Exercise 56 Background The two kidneys are the primary organs of the urinary system. They are located in the upper quadrants of the abdominal cavity, against the posterior

More information

LECTURE 2 FLUID IMBALANCES

LECTURE 2 FLUID IMBALANCES LECTURE 2 Copyright 2000 by Bowman O. Davis, Jr. The approach and organization of this material was developed by Bowman O. Davis, Jr. for specific use in online instruction. All rights reserved. No part

More information

Chapter 48. Nutrients in Food. Carbohydrates, Proteins, and Lipids. Carbohydrates, Proteins, and Lipids, continued

Chapter 48. Nutrients in Food. Carbohydrates, Proteins, and Lipids. Carbohydrates, Proteins, and Lipids, continued Carbohydrates, Proteins, and Lipids The three nutrients needed by the body in the greatest amounts are carbohydrates, proteins, and lipids. Nutrients in Food All of these nutrients are called organic compounds,

More information

PHYSIOLOGY AND MAINTENANCE Vol. III - Renal General Functions - László Rosivall, Shahrokh MirzaHosseini

PHYSIOLOGY AND MAINTENANCE Vol. III - Renal General Functions - László Rosivall, Shahrokh MirzaHosseini RENAL GENERAL FUNCTIONS László Rosivall Department of Pathophysiology, Faculty of Medicine, Semmelweis University, Hungary, and Hungarian Academy of Sciences and Semmelweis University Nephrology Research

More information

CHAPTER 11: URINARY SYSTEM. At the end of this chapter, student will be able to:

CHAPTER 11: URINARY SYSTEM. At the end of this chapter, student will be able to: CHAPTER 11: URINARY SYSTEM At the end of this chapter, student will be able to: a) Describe the location and general function of each organ of the urinary system. b) Name the parts of a nephron and the

More information

The Urinary System Urine (pp. 984 985)

The Urinary System Urine (pp. 984 985) Kidney Anatomy (pp. 961 969) Location and External Anatomy (pp. 961 962) Internal Anatomy (pp. 962 963) Blood and Nerve Supply (pp. 963 964) Nephrons (pp. 964 969) Kidney Physiology: Mechanisms of Urine

More information

Sign up to receive ATOTW weekly - HOW MUCH FLUID IS THERE IN THE BODY, AND HOW IS IT DISTRIBUTED?

Sign up to receive ATOTW weekly -  HOW MUCH FLUID IS THERE IN THE BODY, AND HOW IS IT DISTRIBUTED? BODY FLUIDS - PART 1 ANAESTHESIA TUTORIAL OF THE WEEK 184 21 st JUNE 2010 Dr Matthew Gwinnutt Heart of England NHS Foundation Trust Dr Jennifer Thorburn Sandwell and West Birmingham Hospitals NHS Trust

More information

Introduction to Body Fluids

Introduction to Body Fluids Introduction to Body Fluids Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) Page 1: Introduction to Body Fluids The fluids in your body

More information

Drug Excretion. Renal Drug Clearance. Drug Clearance and Half-Life. Glomerular Filtration II. Glomerular Filtration I. Drug Excretion and Clearance

Drug Excretion. Renal Drug Clearance. Drug Clearance and Half-Life. Glomerular Filtration II. Glomerular Filtration I. Drug Excretion and Clearance t/.drugexcretion AINTRAVENOUSDOSE 36848765430TIME(hours) t/ Drug Excretion Dr. Robert G. Lamb Professor Pharmacology & Toxicology Drug Excretion and Clearance Drug Excretion: is the movement of drug from

More information

Part I Clinical Chemistry of the Kidney and Renal-Associated Physiology

Part I Clinical Chemistry of the Kidney and Renal-Associated Physiology Part I Clinical Chemistry of the Kidney and Renal-Associated Physiology 1 Kidney Anatomy and Function (Lecture 1) 2 Functions of Kidney A) Regulation of water B) Regulation of electrolytes C) Acid-base

More information

Anatomi & Fysiologi The Cardiovascular System (Chapter 21) Types of blood vessels. Sympathetic innervation (ANS) of vascular smooth muscle

Anatomi & Fysiologi The Cardiovascular System (Chapter 21) Types of blood vessels. Sympathetic innervation (ANS) of vascular smooth muscle Types of blood vessels The Cardiovascular System (Chapter 21) Principles of Anatomy & Physiology 2008 arteries arterioles capillaries venules veins served by their own blood vessels in the walls The vessel

More information

Introduction to the kidneys + urinary system Dr Vikram Khullar (v.khullar@imperial.ac.uk)

Introduction to the kidneys + urinary system Dr Vikram Khullar (v.khullar@imperial.ac.uk) Introduction to the kidneys + urinary system Dr Vikram Khullar (v.khullar@imperial.ac.uk) 1. Draw a simple diagram of the urinary system including the following: kidney, renal pelvis, ureter, bladder,

More information

Cells Need to Exchange Materials with the Extracellular Fluid. Membrane Transport. Plasma Membrane. Cells Must Control Movements of Materials

Cells Need to Exchange Materials with the Extracellular Fluid. Membrane Transport. Plasma Membrane. Cells Must Control Movements of Materials Membrane Transport Chapter 6 Cells Need to Exchange Materials with the Extracellular Fluid Take in nutrients O 2 energy substrates building materials cofactors Dispose of wastes CO 2 Urea Cells Must Control

More information

PASSIVE TRANSPORT PROCESSES

PASSIVE TRANSPORT PROCESSES BIOZONE Assignment #2 Cell Membrane Transport PASSIVE TRANSPORT PROCESSES 1. Describe two properties of an exchange surface that would facilitate rapid diffusion rates*: (a) thin membrane (b) porous membrane

More information

Human Anatomy & Physiology I with Dr. Hubley. Practice Exam 1

Human Anatomy & Physiology I with Dr. Hubley. Practice Exam 1 Human Anatomy & Physiology I with Dr. Hubley Practice Exam 1 1. Which definition is the best definition of the term gross anatomy? a. The study of cells. b. The study of tissues. c. The study of structures

More information

Dr. Johnson PA Renal Winter 2010

Dr. Johnson PA Renal Winter 2010 1 Renal Control of Acid/Base Balance Dr. Johnson PA Renal Winter 2010 Acid/Base refers to anything having to do with the concentrations of H + ions in aqueous solutions. In medical physiology, we are concerned

More information

Friday 11 January 2013 Afternoon

Friday 11 January 2013 Afternoon Friday 11 January 2013 Afternoon A2 GCE BIOLOGY F214/01 Communication, Homeostasis and Energy *F210040113* Candidates answer on the Question Paper. OCR supplied materials: None Other materials required:

More information

CHAPTER 5.1 5.2: Plasma Membrane Structure

CHAPTER 5.1 5.2: Plasma Membrane Structure CHAPTER 5.1 5.2: Plasma Membrane Structure 1. Describe the structure of a phospholipid molecule. Be sure to describe their behavior in relationship to water. 2. What happens when a collection of phospholipids

More information

FIGURE 2.18. A. The phosphate end of the molecule is polar (charged) and hydrophilic (attracted to water).

FIGURE 2.18. A. The phosphate end of the molecule is polar (charged) and hydrophilic (attracted to water). PLASMA MEMBRANE 1. The plasma membrane is the outermost part of a cell. 2. The main component of the plasma membrane is phospholipids. FIGURE 2.18 A. The phosphate end of the molecule is polar (charged)

More information

Modes of Membrane Transport

Modes of Membrane Transport Modes of Membrane Transport Transmembrane Transport movement of small substances through a cellular membrane (plasma, ER, mitochondrial..) ions, fatty acids, H 2 O, monosaccharides, steroids, amino acids

More information

Functions of Blood System. Blood Cells

Functions of Blood System. Blood Cells Functions of Blood System Transport: to and from tissue cells Nutrients to cells: amino acids, glucose, vitamins, minerals, lipids (as lipoproteins). Oxygen: by red blood corpuscles (oxyhaemoglobin - 4

More information

Renal Physiology. Functions. Structure

Renal Physiology. Functions. Structure Functions 1. Regulation of Water & Electrolyte Balance 2. Excretion of Metabolic Waste Products 3. Excretion of Foreign Chemicals & Drugs 4. Regulation of Arterial Blood Pressure 5. Regulation of Erythropoiesis

More information

Cardiovascular Regulation

Cardiovascular Regulation Cardiovascular Regulation Regulation of hemodynamics occurs via local autoregulation, neural control and hormones. Spring 2004 1 Autoregulation of Blood Flow Local regulation of blood flow occurs by vasoconstriction

More information

Total body water ~(60% of body mass): Intracellular fluid ~2/3 or ~65% Extracellular fluid ~1/3 or ~35% fluid. Interstitial.

Total body water ~(60% of body mass): Intracellular fluid ~2/3 or ~65% Extracellular fluid ~1/3 or ~35% fluid. Interstitial. http://www.bristol.ac.uk/phys-pharm/teaching/staffteaching/sergeykasparov.htmlpharm/teaching/staffteaching/sergeykasparov.html Physiology of the Cell Membrane Membrane proteins and their roles (channels,

More information

Digestion and Absorption in the Gastrointestinal Tract. By Sylvan Clark and Angela Posh

Digestion and Absorption in the Gastrointestinal Tract. By Sylvan Clark and Angela Posh Digestion and Absorption in the Gastrointestinal Tract By Sylvan Clark and Angela Posh Content Overview of GI tract Discuss the process by which the carbohydrates, fats and proteins are digested by hydrolysis

More information

Problem 24. Pathophysiology of the diabetes insipidus

Problem 24. Pathophysiology of the diabetes insipidus Problem 24. Pathophysiology of the diabetes insipidus In order to workout this problem, study pages 240 6, 249 51, 318 9, 532 3 and 886 7 of the Pathophysiology, 5 th Edition. (This problem was based on

More information

Absorption of Drugs. Transport of a drug from the GI tract

Absorption of Drugs. Transport of a drug from the GI tract Absorption of Drugs Absorption is the transfer of a drug from its site of administration to the bloodstream. The rate and efficiency of absorption depend on the route of administration. For IV delivery,

More information

Membrane Structure and Function

Membrane Structure and Function Membrane Structure and Function Part A Multiple Choice 1. The fluid mosaic model describes membranes as having A. a set of protein channels separated by phospholipids. B. a bilayer of phospholipids in

More information

Compound extracted from plant Aristolochia. Nephrotoxin and carcinogen. Page 2

Compound extracted from plant Aristolochia. Nephrotoxin and carcinogen. Page 2 Mariana Babayeva MD, PhD Touro College of Pharmacy, New York, NY, USA Page 1 Compound extracted from plant Aristolochia Nephrotoxin and carcinogen Page 2 AA-I is an organic anion eliminated by the kidney

More information

REGULATION OF FLUID & ELECTROLYTE BALANCE

REGULATION OF FLUID & ELECTROLYTE BALANCE REGULATION OF FLUID & ELECTROLYTE BALANCE 1 REGULATION OF FLUID & ELECTROLYTE BALANCE The kidney is the primary organ that maintains the total volume, ph, and osmolarity of the extracellular fluid within

More information

Human Anatomy & Physiology II with Dr. Hubley

Human Anatomy & Physiology II with Dr. Hubley Human Anatomy & Physiology II with Dr. Hubley Summer 2009 Exam 4 Name: Instructions This exam consists of 50 questions. You may write on the exam itself, but be sure to answer all your questions on a Scantron

More information

Fluid, Electrolyte & ph Balance

Fluid, Electrolyte & ph Balance , Electrolyte & ph Balance / Electrolyte / AcidBase Balance Body s: Cell function depends not only on continuous nutrient supply / waste removal, but also on the physical / chemical homeostasis of surrounding

More information

Cell Membrane Structure (and How to Get Through One)

Cell Membrane Structure (and How to Get Through One) Cell Membrane Structure (and How to Get Through One) A cell s membrane is a wall of sorts that defines the boundaries of a cell. The membrane provides protection and structure for the cell and acts as

More information

1.1.2. thebiotutor. AS Biology OCR. Unit F211: Cells, Exchange & Transport. Module 1.2 Cell Membranes. Notes & Questions.

1.1.2. thebiotutor. AS Biology OCR. Unit F211: Cells, Exchange & Transport. Module 1.2 Cell Membranes. Notes & Questions. thebiotutor AS Biology OCR Unit F211: Cells, Exchange & Transport Module 1.2 Cell Membranes Notes & Questions Andy Todd 1 Outline the roles of membranes within cells and at the surface of cells. The main

More information

7. A selectively permeable membrane only allows certain molecules to pass through.

7. A selectively permeable membrane only allows certain molecules to pass through. CHAPTER 2 GETTING IN & OUT OF CELLS PASSIVE TRANSPORT Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells. Some substances can cross the cell membrane

More information

4. Biology of the Cell

4. Biology of the Cell 4. Biology of the Cell Our primary focus in this chapter will be the plasma membrane and movement of materials across the plasma membrane. You should already be familiar with the basic structures and roles

More information

THE URINARY SYSTEM THE URINARY SYSTEM 2012

THE URINARY SYSTEM THE URINARY SYSTEM 2012 THE URINARY SYSTEM KIDNEYS A. Location: a. under the back muscles b. behind the parietal peritoneum c. just above the waistline d. right kidney a little lower than the left B. internal structure a. cortex:

More information

Transmembrane proteins span the bilayer. α-helix transmembrane domain. Multiple transmembrane helices in one polypeptide

Transmembrane proteins span the bilayer. α-helix transmembrane domain. Multiple transmembrane helices in one polypeptide Transmembrane proteins span the bilayer α-helix transmembrane domain Hydrophobic R groups of a.a. interact with fatty acid chains Multiple transmembrane helices in one polypeptide Polar a.a. Hydrophilic

More information

1. The lipid layer that forms the foundation of cell membranes is primarily composed of molecules called.

1. The lipid layer that forms the foundation of cell membranes is primarily composed of molecules called. Cell Membranes 1. The lipid layer that forms the foundation of cell membranes is primarily composed of molecules called. 2. Due to the repellent nature of the polar water molecules, the tails of the phospholipids

More information

Barrier between plasma and. ECF and ICF. Homeostasis: process of maintaining consistent composition of body s extracellular fluid

Barrier between plasma and. ECF and ICF. Homeostasis: process of maintaining consistent composition of body s extracellular fluid : process of maintaining consistent composition of body s extracellular fluid Extracellular fluid (ECF) Fluid in which the cells live (fluid outside the cells) Major components: Plasma interstitial fluid

More information

Milwaukee School of Engineering Gerrits@msoe.edu. Case Study: Factors that Affect Blood Pressure Instructor Version

Milwaukee School of Engineering Gerrits@msoe.edu. Case Study: Factors that Affect Blood Pressure Instructor Version Case Study: Factors that Affect Blood Pressure Instructor Version Goal This activity (case study and its associated questions) is designed to be a student-centered learning activity relating to the factors

More information

References below to Guyton and Hall, Textbook of Medical Physiology, 9th Edition, 1996 are denoted as G&H.

References below to Guyton and Hall, Textbook of Medical Physiology, 9th Edition, 1996 are denoted as G&H. Osmolarity References below to Guyton and Hall, Textbook of Medical Physiology, 9th Edition, 1996 are denoted as G&H. The osmolarity of body fluids is an important part of many physiological responses.

More information

BIOLOGICAL MEMBRANES: FUNCTIONS, STRUCTURES & TRANSPORT

BIOLOGICAL MEMBRANES: FUNCTIONS, STRUCTURES & TRANSPORT BIOLOGICAL MEMBRANES: FUNCTIONS, STRUCTURES & TRANSPORT UNIVERSITY OF PNG SCHOOL OF MEDICINE AND HEALTH SCIENCES DISCIPLINE OF BIOCHEMISTRY AND MOLECULAR BIOLOGY BMLS II / B Pharm II / BDS II VJ Temple

More information

Renal Acid/Base. Acid Base Homeostasis... 2 H+ Balance... 2

Renal Acid/Base. Acid Base Homeostasis... 2 H+ Balance... 2 Renal Acid/Base By Adam Hollingworth Table of Contents Acid Base Homeostasis... 2 H+ Balance... 2 Acid Base Homeostasis... 2 Role of Kidneys in Acid- Base Homeostasis... 3 Renal H+ Secretion... 3 Proximal

More information

Chapter 25: Metabolism and Nutrition

Chapter 25: Metabolism and Nutrition Chapter 25: Metabolism and Nutrition Chapter Objectives INTRODUCTION 1. Generalize the way in which nutrients are processed through the three major metabolic fates in order to perform various energetic

More information

Acute Renal Failure. usually a consequence.

Acute Renal Failure. usually a consequence. Acute Renal Failure usually a consequence www.philippelefevre.com Definitions Pathogenisis Classification ICU Incidence/ Significance Treatments Prerenal Azotaemia Blood Pressure Cardiopulmonary Baroreceptors

More information

CONTROL OF BLOOD FLOW AND BLOOD PRESSURE (Lectures 3b and 4)

CONTROL OF BLOOD FLOW AND BLOOD PRESSURE (Lectures 3b and 4) CONTROL OF BLOOD FLOW AND BLOOD PRESSURE (Lectures 3b and 4) 63 CONTROL OF BLOOD FLOW 1) REASON: Body needs different levels of nutrient delivery and metabolic removal for differing levels of activities

More information

BIOLOGY 12 - Cell Membrane and Cell Wall Function: Chapter Notes

BIOLOGY 12 - Cell Membrane and Cell Wall Function: Chapter Notes BIOLOGY 12 - Cell Membrane and Cell Wall Function: Chapter Notes The cell membrane is the gateway into the cell, and must allow needed things such as nutrients into the cell without letting them escape.

More information

BIOL 1108 Vertebrate Anatomy Lab

BIOL 1108 Vertebrate Anatomy Lab BIOL 1108 Vertebrate Anatomy Lab This lab explores major organs associated with the circulatory, excretory, and nervous systems of mammals. Circulatory System Vertebrates are among the organisms that have

More information

3. Tunica adventitia is the outermost layer; it is composed of loosely woven connective tissue infiltrated by nerves, blood vessels and lymphatics

3. Tunica adventitia is the outermost layer; it is composed of loosely woven connective tissue infiltrated by nerves, blood vessels and lymphatics Blood vessels and blood pressure I. Introduction - distribution of CO at rest II. General structure of blood vessel walls - walls are composed of three distinct layers: 1. Tunica intima is the innermost

More information

The human respiratory system includes the nose, the larynx, and the lungs. This body system helps maintain homeostasis by

The human respiratory system includes the nose, the larynx, and the lungs. This body system helps maintain homeostasis by Study Island 1. During heatstroke, the body can't dispose of excess heat. As a result, the homeostatic balance is disturbed, and internal body temperatures can reach as much as 110. Heatstroke is dangerous

More information

Epithelial Tissue. Characteristics Functions Recognizing Epithelia Cell-to-cell junctions

Epithelial Tissue. Characteristics Functions Recognizing Epithelia Cell-to-cell junctions Epithelial Tissue Characteristics Functions Recognizing Epithelia Cell-to-cell junctions 4 Types of Tissue Epithelial Connective Muscle Neural Think of 2-3 basic functions for each. Characteristics of

More information

7 Answers to end-of-chapter questions

7 Answers to end-of-chapter questions 7 Answers to end-of-chapter questions Multiple choice questions 1 B 2 B 3 A 4 B 5 A 6 D 7 C 8 C 9 B 10 B Structured questions 11 a i Maintenance of a constant internal environment within set limits i Concentration

More information

BR #5. What part of the cell controls whether or not a virus or nutrient enters? a) Mitochondria b) Nucleus c) Plasma membrane d) Chloroplast

BR #5. What part of the cell controls whether or not a virus or nutrient enters? a) Mitochondria b) Nucleus c) Plasma membrane d) Chloroplast BR #5 What part of the cell controls whether or not a virus or nutrient enters? a) Mitochondria b) Nucleus c) Plasma membrane d) Chloroplast Schedule: Notes: Membrane physiology Microscope Lab Essentials

More information

Quiz Urinary System. 1. The kidneys help regulate blood volume. help control blood pressure. help control ph. All of the above are correct.

Quiz Urinary System. 1. The kidneys help regulate blood volume. help control blood pressure. help control ph. All of the above are correct. Quiz Urinary System 1. The kidneys help regulate blood volume. help control blood pressure. help control ph. All of the above are correct. 2. The location of the kidneys in relationship to the peritoneal

More information