Ch 24 Urinary System, Ch 25 Fluid + Electrolyte Balance

Glomerulus

"ball of yarn" tangle of capillary loops (the glomerular capillaries) enters via afferent arteriole and exits by efferent arterioles

Protein Reabsoption - what types of proteins and how much - what is a better name / the actual name for this process - what generally occurs to the protein during this process (read pg 965 right side middle paragraph)

( note: most proteins are not filtered because too large and negatively charged) some small peptides such as insulin and angiotensin and a very small amount of larger proteins (.02% of albumin) may appear in filtrate proteins are *transported* (not reabsorbed) in PCT back into blood *proteins undergo a transformational change* - move via pinocytosis or receptor mediated endocytosis through luminal membrane and into tubule cell - in cells = broken down to amino acids by lysosomes - amino acids move through basolateral membrane and back into blood via facilitated diffusion

Nephrons - 2 types + define - which is more common / % total of each type

*Cortical Nephrons*- have short nephron loop that barely penetrates the medulla = *85%* *Juxamedullary Nephrons* - renal corpuscle lies at corticomedullary junction = nephron loop extends well in medulla . important for developing salt concentration gradient = 15%

Extrinsic Controls of GFR: *Decreasing GFR* mechanism and results what might cause the need for this (pg 961)

*Decreasing GFR* = sympathetic stimulation = vasoconstriction = stimulates release of *Renin* from JG apparatus = Mesengial cells contract due to Angio II = decrease SA of filtration membrane * allows your body to conserve fluid in times of stress = exercise, hemorrhaging, etc*

What controls water reabsoption - 2 main hormones + what does each do / result in

*aldosterone* -from adrenal cortex = increase in K/Na pumps in principal cells increase in Na+ and thus water reabsorption (via obligatory reabsorption) *ADH* - from posterior pituitary due to dehydration - causes increase in aquaporons in luminal membrane of principal cells = more channels for water to move via osmosis down concentration gradient into interstitial fluid = *facultative water reabsorption*

Tubuloglomerular Feedback Mechanism it is the ____________ _________ mechanism goal describe process and results (2)

*back up mechanism to myogenic* goal : maintain Glomular BP and GFR if myogenic is unsuccessful at controlling GFR and glomular BP increases = it will cause an increase in solutes (namely *NaCl*) in the tubular fluid. the increase in NaCl is detected by the *Macula Densa* in the juxtaglomerular apparatus Macla Densa cells secrete a signalling molecule (ATP?) = Paracrine Stimulation Results: smooth muscle contraction / vascoconstriction at afferent arteriole + contraction of *Mesangial Cell* = decrease in filtration membrane surface area = returns GBP and GFR to normal

Establishing a concentration gradient in the kidneys Nephron Loop

*countercurrent multiplier*

Formation of Urine - 3 steps - where does each occur - general process

*glomerular filtration* = movement of water and solutes from the blood into the capsular space *passive diffusion* *tubular reabsorption* = movement of substances from tubular fluid back into blood *diffusion, osmosis and active transport* *tubular secretion* = movement of substances from blood into tubular fluid to be excreted *active transport* - *secretion results in excretion*

Establishing a concentration gradient in the kidneys -Ascending Limb

*permeable to salts* = active transport of salts/ions from tubulule fluid into *IF of Medulla* solute concentration in tubule fluid dilutes from 1200 mOsm - 100 mOsm

Establishing a concentration gradient in the kidneys - Descending Limb

*permeable to water* = passive transport of H2O from tubule fluid into IF + impermeable to salts = remains in tubule fluid solute concentration in tubule fluid 300 mOsm to as much as 1200 mOsm

Tubular Reabsorption + Secretion - define each / when does each take place - what is the barrier that substances must cross - 2 ways for substances to cross barrier. + which is more common

*reabsorption* = when substances move from the tubular fluid back into the blood. *secretion* = when substances that were not filtered at the glomerulus but must be eliminated from the blood become a component of urine substances must cross the *simple epithelium* of the tubule wall either via: *paracellular transport* = between cells *transcellular* transport = through epithelial cells = more common

Elimination of Drugs and Bioactive substances what types of substances where are they primarily secreted give an example of how this is practically used in medicine

*secretion of harmful substances (and most other substances, other than K) occurs in PCT* Substances secreted in PCT: drugs- such as penicillin, morphine and marijuana metabolic wastes - billirubin and hormone metabolites hormones - ex *human chorionic gonadotropin (hCG) = released when a women is pregnant and is used in pregnancy tests to determine if a women is pregnant

Renal Tubule composed of describe structure

*simple epithelium on basement membrane* 3 continuous sections proximal convoluted tubule nephron loop (*extends into medulla*) distal convoluted tubule

Elimination of Nitrogenous Wastes - 3 main substances + where does each come from - which are reabsorbed , secreted or both

*urea* - small water soluble molecule produced when liver breaks downs proteins *uric acid* - produced from nucleic acid breakdown in liver *creatinine* - produced from creatine metabolism in muscles urea and uric acid = both creatinine = only secreted

Sodium (Na+) in Urine - what % (of what) - 2 main hormones + results (pg 967 table)

0-2% of total filtered Na+ *aldosterone* - from adrenal cortex - stimulates synthesis of protein channels and K/Na pumps in Principal Cells =*NA+ reabsorption increases* *H20 follows via osmosis + reabsorption increases* = movement is of an isotonic solution *Atrial natriuretic peptide (ANP)* - from atria of heart - inhibits Na+ reabsorption in PCT + CTs + the release of aldosterone = *more Na+ and thus more H20 excreted in urine*

How much urine can the bladder hold

1 Liter

What two properties of peritubular capillaries help to facilitate bulk flow from tubular fluid back into blood

1. low hydrostatic pressure (8 mm Hg) = due to loss of fluid during glomular filtration 2. high colloid osmotic pressure = due to the fact that most proteins remain in the blood

Formation of Filtrate how much formed per day by kidneys 3 categories of substances based on filtration rates + what does each include formed in __________ + moves to ____________ what about substances that are not filtered?

180 L per day *Freely filtered* = small substances - water, glucose, water soluble vitamins, urea, ketones and some hormones *Not Filtered* = large solutes - formed elements + large proteins *Limited filtration* = medium sized proteins - are generally blocked either due to size or (-) charge which is repelled by the membranes negative charge formed in the capsular space and then funneled to the proximal convoluted tubule (PCT) substances that are not filtered continue out of the glomerulus via the efferent arteriole and then on to the second set of capillary beds

how much blood flows through the Kidney

20-25% of resting cariac output = 1L /min

Sodium (Na+) Reabsorption what % reabsorbed where does it take place relative Na concentration between tubule cells / fluids describe process (3 steps) where is there a lot of energy expenditure in this process

98-100% reabsorbed all along the: - PCT (65%) - Nephron loop (25%) - DCT + collecting tubules/ducts = varying / regulated amounts Na+ = high concentration in tubule + IF fluids vs. low in Tubule cells 1. moves passively down concentration gradient via facilitated diffusion from tubular fluid, across luminal membrane and into tubule cells 2. K/Na pumps in the basolateral membrane move Na from inside tubular cell to IF (while K+ is moved back into cell) = *keeps Na+ concentration in cells low* = *high cost = K/Na pumps in basolateral membrane = 80% of all energy invested in active transport in nephrons* 3. Na+ enters blood via peritubular and vasa recta capillaries via intracellular clefts

Vasa Recta - what is it - structure / orientation - function + name process

= straight arterioles of nephron which lie parallel to the loop of henle = turn into peritubular capillaries *blood in vasa recta travels in opposite direction to the tubular fluid in the loop of henle (ie up towards cortex next to descending loop and down towards medulla in ascending loop) *helps to maintain medullary concentration gradient via countercurrent exchange system* (separate card)

Glomerular Capsule aka

Bowmans capsule composed of internal visceral layer capsular space external parietal layer (simple squamous)

Countercurrent Multiplier - what is it (break down the name) - where does it take place (which part or nephron and which type of nephron primarily) -what type of mechanism is it + explain - what is the end result

Countercurrent = bc descends and then ascends + Multiplier= bc causes an increase in the concentration of salts in the interstitial fluid takes place in the *nephron loop* especially in *juxtamedullary nephrons* bc have long nephron loops Positive feedback mechanism- bc addition of salt to IF in medulla drives more H2O reabsorption in descending limb *makes medulla "salty" / high solute concentration*

Physiologic functions of the Kidneys (8)

Elimination of metabolic wastes Regulation of ion levels Regulation of acid-base balance Regulation of Blood Pressure Elimination of Biologically active Molecules Formation of Calcitriol = increases blood Ca+ Production/release of EPO Gluconenogenesis (during prolonged starvation)

Facultative vs. Obligatory Water Reabsorption

Facultative = movement of water down its concentration gradient (via osmosis) due to ADH =increases the number of Aquaporons in the principal cells which allows H20 to be pulled into Interstitial fluid vs. Obligatory = water follows Na+ reabsorption in PCT

What are the 4 layers protecting the Kidney (inner most to outter most)

Fibrous Capsule (aka renal capsule) - dense IR CT directly adheres to kidney - keeps shape and location Perinephric fat (aka adipose capsule) - provides cushioning Renal Fascia -dense IR CT = anchors kidneys to surrounding structures Paranephric fat - outer most layer composed of adipose ct

Fluids of the Urinary system - name all 3 in order of "production" - where is each type found pg 954

Filtrate - in the *capsular space* of the glomerulus Tubular Fluid - PCT -nephron loop -DCT Urine - Papillary duct until bladder/excreted *same as tubular fluid, just renamed*

How does Glomular Hydrostatic Pressure (HPg) compare to the Hydrostaic Pressure in other systemic capillaries throughout the body what causes this? why is this important?

HPg is much higher than most capillaries due to the need for greater pressure necessary to drive filtration due to the afferent vessels of the glomerulus having a greater diameter compared to the efferent vessels = bottleneck = increase pressure is important because the high pressure of these vessels make them more susceptible to injury

Extrinsic Controls of GFR: *Increasing GFR* mechanism + results what causes the need for this (Pg. 961)

Hormonal Control via *Atrial Natriuretic Peptide (ANP) increases GFR to eliminate fluid released from atria in response to barorecpetors due to increase in BP or blood volume travels to kidneys = *vasodilates arterioles, inhibits the release of renin and causes the relaxation of mesengial cells* = increase SA of filtration membrane results in an increase in urine volume and a decrease in blood volume back to normal limits

How does Net Filtration Pressure (NFP) affect overall urine formation (secretion + reabsorption)

Increased NFP = glomerular filtration rate (GFR) and the overall amount of filtrate formed this also leads to an increase in the amounts of solutes and water remaining in the tubular fluid as they are pushed through the tubules without being given time to reabsorb thus: increases substances in urine + decreases substances reabsorbed

Intrinsic and Extrinsic controls for Renal Autoregulation

Intrinsic = myogenic and tubuloglomerular feedback =*keep GFR at homeostatic levels* vs. Extrinsic = neural + hormonal = change GFR to meet physiologic needs

Urinary System 4 Parts + General Function

Kidneys to ureters to urinary bladder out the urethra Generally = to take care of our blood

Myogenic Response the __________ response goal reaction to higher vs lower systemic BP

Muscle response goal: maintain Glomular BP and GFR decrease in systemic BP: = lower blood volume entering afferent arteriole so smooth muscles *relax*= vasodilation = wider opening allows more blood at lower rate into glomerulus vs. increase in systemic BP: = increased volume into afferent arteriole so smooth muscle *contract*= vasoconstriction = smaller opening allows less blood at higher rate into glomerulus

Juxtaglomerular (JG) apparatus what is it / location 2 parts + functions of each

Point where *afferent arteriole* and *DCT* make contact *Granular Cells* - modified smooth muscle cells of the afferent arteriole located near the entrance to the renal corpusle 1. contract when stimulated by stretch or sypathetic division 2. synthesize and store *renin* *Macula densa* modified epithelial cells in the wall of the distal convoluted tubules next to the afferent arteriole = detects changes in NaCl = stimulate granular cells to release renin through paracrine stimulation

Where does most reabsoption take place + why

Proximal convoluted tubule due to extensive microvilli which increase the surface area on the luminal surfaces of the cells

Female Urethra

Single function : urine excretion lined with stratified squamous is 4 cm (1.6 inches) in length

Intercalated cells What are they Where are they found

Specialized epithelial cells found in the DCT, collecting tubules and collecting ducts help regulate urine and blood pH Type A = eliminate H+ Type B = eliminate HCO3 (base)

Male Urethra 2 functions length of whole + each section sections (3) - name in order of location from bladder - which is the most vs least expandable - which are located near sphincters name of erectile tissue of penis

Two functions: urine and semen 19 cm ( 7.5 inches) long Sections: *prostatic urethra* - immediately posterior to bladder through prostate gland - most expandable section - 3.5 cm (1.5 inches) in length - lined with transitional epithelium *membranous urethra* - from prostate gland to urogenital diaphragm - least dilatable portion - *surrounded by skeletal muscle fibers that form the external urethral sphincter* - lined with stratified or pseudostratified columnar epithelium *spongy urethra* -aka penile urethra - longest part (15 cm or 6 inches) - encased in *corpus spongiosum* = erectile tissue - extends to *external urethral orifice* - proximal half = pseudostraftifed columnar vs. distal = stratified squamous epithelium

Innervation of Urinary bladder + Urethral Sphincters - what type of innervation at each and what does each control

Urinary Bladder: *Sympathetic* ( via spinal cord) = contraction of internal urethral spchinter + inhibits contraction of detrusor muscle = *inhibits mictrition* *Parasympathetic* = (from the Pons to spinal cord to pelvic splenic nerves) = contraction of detrusor muscle and relaxtion of internal urethral sphincter = *stimulates mictrition* External Urethral Sphincter: - innervated by somatic nervous system via *pudendal nerver* = voluntary contraction = *prevents mictrition*

Renal Sinus what is it 4 parts in order from pyramid function

Urine Drainage Area each pyramid = 1 minor calyx 2+ minor calyces = 1 major calyx 3 to 4 major per kidney merge into the renal pelvis renal pelvis merges = ureter

Blood Flow Through the Kidney (Pg. 953) abdominal aorta to glomerulus

abdominal aorta - renal artery - segmental - interlobar - arcuate - interlobular- afferent arteriole - glomerulus

Renal Autoregulation of GFR what is it 2 mechanisms

ability of kidney to maintain constant blood pressure and GFR despite systemic changes Myogenic Response tubuloglomerular feedback mechanism (Pg 959)

Blood Flow Through the Kidney ( pg. 953) glomerulus to interlobular veins what happens at each point

afferent - glomerulus (some filtration) - efferent - - peritubular capillaries = PCT and DCT = in cortex = gas,nutrient,waste, exchange wi kidney tissues *or* -vasa recta = nephron loop = in medulla = gas,nutrient,waste, exchange wi kidney tissues both drain into veins *note: all blood that enters the kidneys flows through two capillary beds. 1. the glomular capillaries = filtration 2. the peritublar or vasa recta *

renal pyramids what are they how many per adult kidney what are its two borders

aka medullary pyramids segments of the renal medulla that appear striped or striated adult = 8 to 15 wide base = corticomedullary papilla tip = renal papilla

Mictrition -aka

aka urination mictrition = to make water 2 reflexes : storage reflex + mictrition reflex

What is the relationship between HPg and substances (such as NaCl) in terms of filtrate concentration

as HPg increase substances in filtrate increase as HPg decreases substances in filtrate decrease

What gives renal pyramids their striated appearance

ascending + descending tubules of nephron loops and the descending collecting tubules/ducts

Calcium and Phosphate Balance why are these 2 considered to be one substance? how much of each is filtered what controls their secretion + what is its goal what is the results of this + explain

bc 99% of stored calcium in the body is stored in bones and most is stored as calcium phosphate 60% of Ca+ in blood ends up in filtrate/tubular fluid while rest is bound to proteins in blood and thus not filtered vs 90-95% of PO4 = filtered Rates of Ca+/PO4 excretion are regulated by *Parathyroid Hormone (PTH)* - released in response to low blood Ca+ to increase blood Ca+ = stimulates Ca+ reabsorption in DCT + inhibits PO4 reabsorption in PCT b/c: - as more PO4 is eliminated less is available to form Calcium Phosphate and thus less Ca+ is stored in bone and there in an increasein blood Ca+ levels

Regulation of Glomular Filtration Rate why is it important what is the primary means of control two types of control + describe

bc GFR influences which substances are reabsorbed vs. excreted and how much filtrate is formed = the body can use it to control urine production based on physiological needs and hydration levels *primarily controlled by lumen diameter of afferent arteriole + surface area of the filtration membrane* Includes: 1. Intrinsic Control (within the Kidney) = renal autoregulation 2. Extrinsic Control (outside the Kidney) = nervous system or hormonal regulation

Why is the Countercurrent Multiplier in the Nephron Loop (aka loop of Henle) a Positive Feedback system

because water moves out of tubule into the IF in descending limb which increases the solute concentration in tubule fluid which then drives more salt to be driven out into the IF in the ascending limb this causes the IF of the medulla to increase its solute concentration = pulls more H2O out in the descending limb = the process drives itself to continue rather than driving itself to stop

Regulation of Blood / Urine pH which regulates which what is it dependent upon describe 2 possible outcomes + cell types in each *pg 971 diagram*

blood pH is regulated by urine pH depends on the amount of H+ in blood 1. excess H+ in blood = diet high in animal proteins + wheat = HCO3 is synthesized and released into blood and H+ is secreted (for excretion) into tubular fluid by *Type A intercalated Cells* =* increase in blood pH (more alkaline) and a decrease in urine pH = more acidic* vs. 2. decreased blood H+ = fruits + vegetables + little animal protein = *type b intercalated cells* = reabsorb H+ into blood and secrete HCO3 = *lower blood pH and increase urine pH* *intercalated a and b cells = key to blood pH*

Renal Corpusle

bulbous portion of the nephron found in renal cortex includes glomerulus and glomerular capsule

Mictrition Reflex 4 steps full bladder volume name nerves + muscles involved

controlled by autonomic and somatic 1. bladder = 200-300 mL= full - baroreceptors in bladder wall activated 2. baroreceptors stimulate *mictrition center in pons* 3. mictrition center alters parasympathetic signals down pelvic splanchnic nerves 4. smooth muscle cells of -*detrusor muscles* = contract -*internal urethral sphincter* = relax *This is the point where you have the sensation of having to urinate = this is when infants urinate due to lack of conscious control / toilet training *

Storage Reflex controlled by what part(s) of the nervous system 3 points of action - name each and how does it affect the process / reflex

controlled by both the autonomic and somatic nervous systems as urine flows through the ureters = sympathetic axons cause smooth muscle of: 1. detruser muscle (smooth muscle cells in urinary bladder wall) to relax = allow for expansion 2. internal urethral sphincter (smooth muscle) = to contract to hold urine in bladder and Skeletal muscle of external urethral sphincter = remains contracted to prevent mictrition

Urine Production - what determines how concentrated urine is? - what happens when you are dehydrated? vs. overhydrated? + describe urine

determined by amount of ADH bound to the principle cells more ADH = more fluid reabsorbed and less in urine = more concentrated = dark yellow dehydrated = alot of ADH = less urine (.5L/day) vs less ADH = less fluid reabsorbed and more in urine = less concentrated = clear or pale yellow

Urethra what is it where is it 2 sphincters + describe

epithelial-lined fibromuscular tube from: bladder to urethral opening sphincters: *Internal Urethral Sphincter* = superior - found at neck of bladder - smooth muscle - involuntary - autonomic nervous system *External Urethral Sphincter* = inferior - pelvic diaphragm - skeletal muscle = voluntary - controlled by somatic nervous system

Establishing a concentration gradient in the kidneys (look this up online / pg 972) Describe the General Idea

established by solutes such as Na + Cl which increase in concentration from the cortex to the medulla which exerts osmotic pull to move more water from the tubular fluid into the Interstitial Fluid when ADH is present due to an increase in the number of *aquaporons* - creates a higher concentration of solutes in nephron loop as water diffuses out of tubule in descending loop due to ADH and an increase in aquaporons. - as the fluid moves through the tubule and up the ascending loop (now with a higher concentration of solutes) it becomes impermeable to water but permeable to solutes (salts etc) which diffuse down their concentration gradients and into the blood... returning the tubule fluid to its original solute concentration overall concentration change in tubule/loop: 300 mOsm - 1200 mOsm - 100mOsm overall change in blood is

Urinary Bladder function where is it found shape (empty vs filling/full) area that does not move / changing during filling/emptying 4 Tunics + describe What is the special cell type found here What controls urine release to bladder - where is it found - what is it made of - what controls it what is the name of the smooth muscles of the bladder, where are they found and what is their function

expandable, muscular organ = urine storage immediately posterior to pubic symphysis is retroperitoneal (like kidneys + ureters) empty = pyramid shape vs. fills = expands =oval shape *Trigone* - posterior , inferior region of the bladder between the two ureters and the urethra =*does not move* even while bladder is expanding/contracting = funnels urine to urethra Tunics: *mucosa* = innermost (ie touches bladder lumen) - made up of *transitional epithelium* + highly vascularized *lamina propria* + - has mucosal folds = increased distension ...at Trigone = smooth / no folds *submucosa* - immediately external to mucosa - made of dense IR CT = supports bladder *muscularis* - 3 layers of smooth muscles = *detrusor muscle* *adventitia* - outer most layer or areolar CT *peritoneal membrane covers only the superior surface or urinary bladder* * internal urethral sphincter* = formed by smooth muscle at the neck of the bladder = is involuntary

Distal Convoluted Tubule (DCT)

extends from thick segment of ascending segment of nephron loop lined with simple cuboidal but with minimal microvilli (does not appear fuzzy like the proximal convoluted tubule)

Renal Columns Where do they come from What divisions to they create

extensions of the renal cortex subdivide renal medulla into renal pyramids

Proximal Convoluted Tubule (PCT) composed of

first region renal tubule composed of simple cuboidal epithelium with microvilli = increased surface area

Kidney - size - weight - location

fist to second knuckle 100g located posterior abdominal wall, lateral to the vertebral column are in *retroperitoneal space*

Filtrate Where is it formed + how What is its composition

formed in the renal corpuscle as water and solutes cross the filtration membrane into the *capsular space* forms through passive movement due to a pressure gradient which moves fluid through filtration membrane Water and Solutes from blood plasma

Renal Lobes

includes a renal pyramid + parts of the surrounding renal columns and the renal cortex directed superior the given pyramid 8-15 per adult kidney

Blow flow through the Kidney (Pg. 953) Vasa Recta or Peritubular Capillaries to Renal Vein

interlobular - arcuate- interlobar- renal vein read pg 954

Innervation of the Kidney

is innervated by both divisions of *autonomic* NS sympathetic = T10-T12 = decrease urine production parasympathetic = vagus nerve = unknown function

Net Filtration Pressure what is it 3 variables + describe + normal range equation + average NFP

is the driving force behind filtrate production Glomular HSP (HPg) - blood in glomerulus = pushes fluid out of glomerulus into capsular space (60 mm Hg) Blood COP (OPg)- osmotic pressure due to solutes in blood = pull water back into blood (32mm Hg) Capsular HSP (HPc) = pressure in the glomerular capsule due to the filtrate that has already passed through = oppose new fluid coming in (18mm Hg) HPg - OPg -HPc = net filtration pressure (NFP) average = about 10 mm Hg (60- 32- 18)

Transcellular Transport what is it/ where is it found what 2 layers must each substance pass through how are they able to accomplish this

is the primary means of transport for substances through the epithelium of the tubule walls = substances move through epithelium two membranes: *luminal membrane* = contacts tubular fluid *basolateral membrane* = rests on basement membrane accomplished via transport proteins (in membrane) = simple/facilitated diffusion, osmosis, primary and secondary active transport and vesicular transport

Ureters what are they + size where are they found name the 3 tunic + describe each what happens to the ureters as the bladder fills

long, epithelial lined fibromuscular tubes that extend from the renal pelvis to the posterolateral wall of a bladder - each = 25 cm ( 10 inches) in length - is retroperitoneal (like kidneys) = transport urine from kidneys to bladder * 3 Tunics* *Mucosa* = innermost - made up of *transitional epithelium* + laminia propria (dense IR CT) *Muscularis* = middle - smooth muscle - is stimulated by urine in the renal pelvis to contract rhythmically = peristalsis = propels urine to bladder *Adventitia* = outtermost - collegan + elastic fibers + areolar CT - anchor ureter to posterior abdominal wall *as bladder distends = compresses ureters to prevent backflow or urine* mainly innervated by autonomic nervous system

Nephron Loop aka composed of

loop of Henle made up of descending loop to ascending loop *each loop has thick portions = simple cuboidal and thin portions = simple squamous*

Nephron what is it 2 structures location in kidney

microscopic functional unit of the kidney renal corpusle + renal tubule = all are in cortex except for the nephron loop that extends into the medulla

Substances with Regulated Reabsorption what substances why is this important

not all reabsorbed = some excreted in urine allows the nephron to control circulating blood levels of certain substances includes : Na,K, Ca HCO3

Substances that are completely reabsorbed - 2 types of substances - where does this generally occur - what does this mean for their concentration in urine

nutrients ( glucose, amino acids, lactate, etc) filtered plasma proteins (the small amount that make it through filtration) typically occurs in the PCT = not found in urine

Nutrient reabsorption where does it occur describe reabsoption of glucose *DRAW IT* *diagram pg 965*

occurs in PCT 1. glucose = low concentration gradient in tubular fluid ... is moved up it concentration gradient via (Na/Glucose symporter) through *luminal membrane* into tubule cell = (Na moves down its gradient providing energy to move glucose up its gradient) then. 2. diffuses down its concentration gradient through *basolateral membrane* (via uniporters) into IF and then into blood where it is 100% reabsorbed

Podocytes what are they where are they found structure+ function

octopus like cells that form the visceral layer of the glomerular capsule contain *pedicels* that wrap around capillary walls to support it, leaving spaces called *filtration slits* which are covered by a membrane

Mesangial cells

phagocytic/ contractile cells found within the capillary loops of the glomerulus phagocytize macromolecules (such as immunoglobulins) that get caught in the basement membrane = keep the filtration surfaces clean

Bicarbonate Ions and Hydrogen ions - how much of each is filtered? - how much of each is reclaimed (not reabsorbed) +where

plays an important role in both blood and urine pH HCO3 = freely filtered vs. H+ = very little filtered by attached to proteins, etc Filtered HCO3: 80-90% = reclaimed in PCT 10-20% = in ascending loop of nephron loop = *100% reclaimed before entering dct* - important for regulating blood pH

Urine: composition - what should it / should it not include daily volume - average - minimum + why pH - more acidic vs more basic? Specific gravity - average, hydrated vs dehydrated color - what is it + why - hydrated vs dehydrated Smell - name for fresh urine smell - what does it smell like after a long time - what else causes changes in smell

product of filtered and processed blood plasma *composition* -95% water + 5% solutes - including (Na , Cl, K, Mg, Ca, NH4, some hormones, drugs and nitrogenous wastes (urea , uric acid, etc) - *should not include: glucose, proteins, rbc, wbcs, ketones, etc* = shows problems (pg 977 table) *daily volume* average = 1-2 L minimum = .5 L necessary to removes wastes ...less than .4 L = wastes accumulate in blood - volume is dependent on: BP, diet, fluid intake, sweating/other excretion, illness, vomiting, etc *pH* 4.5-8 average = 6 dependent on diet - more acidic = meat + wheat vs - more basic = fruits and vegetables *specific gravity* - density of a substance compared to the density of water -pure water = 1.00 - urine = 1.003-1.035 = normal solute components - 1.010 = relatively hydrated vs. -1.020 = relatively dehydrated *color* - clear to dark yellow - depends on pigment from *urobilin* - more volume = generally lighter - color change due to certain foods (ex. beets) or due to illness or injury (ie rbcs) Smell: *Urinoid* = fresh urine smell -breaks down to ammonia smell if left bc bacteria convert the nitrogen in Urea into ammonia - certain foods (ex. asparagus) change smell - sweet smell = diabetes due to ketoacids

Processing of Urea normal levels of urea in blood + is dependent upon _________ describe the route of urea in the kidney including what % is secreted and/or reabsorbed in each location

range 3-9 mEq/L depending on protein intake is freely filtered: Route: - 50% reabsorbed in PCT via paracellular transport but then secreted back into tubule at nephron loop = *100% of filtered urea is present at DCT* - in DCT = 50% reabsorbed + 50% secreted / excreted in Urine * important because reabsorption establish a concentration gradient in the interstitial fluid of the Kidney*

Limitations to Maintaining GFR Effective System BP range for mygogenic response what happens outside of this range

range= systemic BP of 80-180 mm Hg 80 = maximum vasodilation at afferent - below this = GFR will decrease - if very low = urine formation will stop = build up of toxins in blood 180 = maximum vasoconstriction at afferent - above this = GBP and GFR increase and urine production increases

Glomerular Filtration Rate (GFR) How does NFP affect GFR

rate at which a volume of filtrate is formed = volume / unit time (generally 1 min) increase NFP = increase GFR = more filtrate formed

Urinary Tract 3 parts what does the tract do (generally)

responsible for transporting urine from kidneys to bladder via ureters and then holding it until it is excreted via urethra

Describe Nephron Drainage

several nephrons drain into each *collecting tubules* (1000s per kidney). collecting tubules drain into *collecting ducts* collecting ducts drain into *papillary ducts* all while moving down to the renal papilla

Filtration Membrane what is it / where is it layers (3) *+ describe each structure + what it filters*

small negatively charged porous structure formed between the glomerulus and the visceral layer of the glomerular capsule made up of three layers *endothelium of glomerulus* - fenestrated = allow for passage of plasma to dissolved solutes =block formed elements *basement membrane of glomerulus* - made of glycoproteins + proteoglycan = block large proteins *visercal layer of glomerular capsule* -composed of podocytes which overlap leaving filtration slits = blocks most small proteins * substances that are able to pass through all three layers become filtrate*

Principal Cells What are they Where are they found

specialized epitheilal cells found in the walls of the DCT , collecting tubules and collecting ducts (diagram pg 949) =have cellular receptors that bind to *Aldosterone* and *ADH*

Evaluating Kidney Function : Glomular Filtration Rate - what is it - how is the test performed - Equation - what does GFR show

the amount of filtrate formed per unit time process: - inject subject = *inulin* (up to 1mg/mL in blood) = is freely filtered but neither reabsorbed or secreted ... thus amount in urine = amount filtered - measure amount in urine and amount in blood to assess how much is filtered and how long it takes GFR = UV/P U= urine concentration of inulin V = volume of urine produced per minute P = concentration of inulin in Plasma *normal GFR = 125mL/min if lower than normal = decrease in kidney function = more nitrogenous wastes + unwanted substances in blood

Renal Threshold

the maximum *plasma concentration* of a substance that can be transported in the blood without some eventually ending up in the urine ( ex. glucose = 300 milligrams per deciliter (mg/dL)) above this amount and will lead to saturation in the transport proteins of the epithelial cell walls of the tubules ( when you reach the Tm) = some will remain in tubule fluid + be excreted in urine

Transport Maximum (Tm) what happens if this maximum is exceeded

the maximum amount of a substance that can be reabsorbed or secreted across a tubule membrane in a given period of time. ( it is a rate of movement) *determined by the number of specific transport proteins for that substance found in the epithelial cell membrane* (ex Tm for glucose = 375 milligrams per minute) If the tubular fluid contains more than the Tm amount of a substance the excess is not reabsorbed and is secreted in the urine (see renal threshold)

Countercurrent Exchange what it is breakdown the name describe the process *draw it*

the process by which the vasa recta helps to maintain the solute concentration gradient between the medulla and the tubule fluid in the loop of henle "countercurrent" refers to the fact that the blood in the vasa recta (arterioles to peritubular capillaries) flows in the opposite direction of the tubule fluid "exchange" = passive exchange of water and salts between IF and capillaries around the loop of henle Process: *at ascending limb* = the blood in the vasa recta is moving down deep into the medulla (in opposite direction to limb). As it descends water passively diffuses out of it via osmosis due to the higher solute concentration in the IF fluid . At the same time solutes flow down their concentration gradients into blood =*NET higher solute concentration in blood* *at descending limb* = the blood in the vasa recta is moving up towards the renal cortex (again in opposite direction of the limb). As it ascends it is move into an area where the solute concentration of the IF is lower than in the tubule fluid (due to water diffusing out of tubules). This causes solutes to diffuse down their gradients out of the blood and into the IF while water diffuses in to the blood via osmosis =*NET more H20 into blood = lower solute concentration* * brings salt from the ascending loop side where it is lost from the tubules back to the descending side where it can be used to pull water out of the tubule fluid* Be able to drawn everything that is going on at nephron loop and note that nephron loop and vasa recta are described in opposite directions

Evaluating Kidney Function: Renal Plasma Clearance what is it what is normal what do abnormalities show + ex how is this used in medicine

the volume of plasma that can be completed cleared of a substance in a given period of time (usually 1 min) = is a substance absorbed or secreted: - if it is neither reabsorbed or secreted (inulin) = 125mL/min - if reabsorbed = lower bc less is excreted - if both filtered and excreted = higher than 125 bc more substance added in tubules (ex creatinine) ex. normal for urea = 70 mL/ min thus 55 mL/ min is reabsorbed vs. glucose = 0 ml/min bc all should be reabsorbed used to determine how much and how often meds must be administered bc the higher their clearances are the higher their concentrations in the blood will be

Is there generally more tubular secretion or reabsorption?

tubular reabsorption

Potassium - is unique because - where is it reabsorbed (3 places) + % in each -process of transport in each place -dependent on what in each location - where is it secreted?

unique because it is both secreted and reabsorbed. PCT = 60-80% of K+ in tubular fluid is reabsorbed via paracellular transport -amount is dependent upon the movement of Na+ *Read process on Pg 969* = Na + is reabsorbed from tubular + water follows leaving the tubular fluid with a high solute concentration...K+ (and other solutes) are then able to move down the gradient and be reabsorbed into IF and then into blood Thick Segment of Nephron loop Ascending limb: - 10-20% - via transcellular or paracellular transport Collecting Tubule: * neither net reabsorption or net secretion* - Type A intercolated cells = reabsorb K+ - Principal cell *secrete K+* based on *aldosterone* levels aldosterone stimulates the principal cells to secrete K+ (to be excreted in urine) while Na+ and water are reabsorbed and high elevated levels of K+ are the strongest signal to release aldosterone are elevated K+ levels in blood = negative feedback system to K+ levels normal

Urea Recycling why is it important where does the urea come from + how where is it reabsorbed

urea makes up 50% of solutes in tubule fluid /IF concentration gradient urea is removed from the tubule fluid in the collecting duct via *urea uniporters* reabsorbed in the thin segmenent of the ascending limb which is impermeable to urea so it moves from ascending to DCT back to the nephron loop and then back into the collecting duct and the cycle repeats some urea moves into IF during this process to maintain the concentration gradient

Poles of the Renal Corpusle

vascular pole = afferent + efferent vessels tubular pole = renal tubule

Water Reabsorption occurs via ___________ transport proteins specific to water filtered water reabsorbed vs secreted (avg #s) Where does reabsoption take place + %s Where does reabsorption not occur

via osmosis through *aquaporons* = transport proteins only about 1.5 L of water excreted daily (out of 180 L filtered) % reabsorbed: - PCT = 65% = constant aquaporons = *obligatory water reabsorption* bc follows Na+ - *descending limb* of nephron loop = 10% vs. -ascending limb of Nephron Loop and the DCT = impermiable to water = no reabsorption*