Anatomy Test 4: Urinary & Electrolytes
extracellular fluid (ECF)
*38%* -interstitial fluid/extracellular: 28% -plasma: 7% -other body fluids, CSF: 3% -fluid outside the cells
intracellular fluid (ICF)
*63%* -includes all the fluid w/n the cytosol of the cells -LOTS OF CELLS, so there is more fluid in the cells
glomerulus anatomy
-podocytes: cells associated with the glomerular capillaries ---project into capsular space from the visceral border of the glomerulus -pedicles: projections from the podocytes that wrap around the capillaries forming filtration slits ---blood is filtered through the filtration sites
what is ADH produced by?
-produced by hypothalamus, and secreted by post. pit gland
what are the functions of the nephron?
-production of filtrate in the glomerulus -reabsorption of organic nutrients, water, and ions -secretion of waste products into tubular fluid -reabsorption and secretion are opposites
reabsportion during urine formation?
-removal of water and solutes from the filtrate back into the blood --the key substances are "reclaimed"
what does the nephron do in the DCT?
-secretes ions, toxins and durgs -reabsorbs Na ions from tubular fluid -water & sodium reabsorb in this area by hormone secretion --hormones regulate water --aldosterne reabsorbs Na
descending loop of henle
-simp squamous, no microvilli or mitochondria -no carrier proteins -VERY permeable to water, so water can easily move form the filtrate to the blood of the peritubular capillaries -solutes remain at bottom of loops in the filtrate concentrate
external sphincter
-skeletal muscle -somatic motor neurons
internal sphincter
-smooth muscle -visceral motor neurons
how does urine production maintain homeostasis?
-the secretion of wastes into the tubular fluid helps to regulate blood volume and normal blood composition
autonomic regulation with sympathetic activation
-this occurs when the BP is so low, and the sym div shuts off BF to kidneys, so the GFR ensures O2 delivery to the brain -systlolic BP = below 70 mm Hg -renal hypoxia stimulates renin release by JG cells -person is given fluids to correct the low BP
secretion of urine production?
-transport of solutes from the peritubular blood into the tubular fluid
absorption at DCT
-tubular cells actively reabsorb Na and Cli --in exchange for potassium or H ions (eliminated) -aldosterone pumps regulate Na reabsorption and K excretion -ADH secretion regulates water reabsorption along the collecting ducts --as water is reabsorbed, the tubular fluid concentrates = facculative reabsorption
filtration of urine formation
-water and solutes move across glomerular capillaries into capsular space -driving force behind filtration is the hydrostatic pressure of blood (beating heart) -left ventricle
what happens if NFP is down?
-we won't be able to produce filtrate, therefore, the blood won't be filtered appropriately
when is ADH secreted?
-when osmolarity receptors are stimulated due to and increase in blood osmolarity
electrolyte balance
-you lose electrolytes in urine and sweat, and you need to gain those electrolytes back from food or drinks to remain the balance of Na (for example)
how to calculate net filtration pressure? (NFP)
NHP - BCOP (60-15) - 28 = 17 mmHg -17 mm Hg is responsible for production of filtrate
cotransport
coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient
what is the transport of sodium at the luminal membrane dependent upon? (PCT)
dependent upon the transport of sodium at the basolateral membrane -because it prevents a sodium buildup, and you need to push Na towards blood to keep an appropriate balance of Na
peritubular captillaries
effertent arteriole attaches to this
what is net hydrostatic pressure?
pressure exerted or transmitted by the fluid (e.g. water) at rest
homeostatis is disturbed, but hormones help out
prob: low filtrate flow, and low BP -decrease GFR -cells of macula densa release less vasoconstrictors @ afferent -releases renin to vasoconstrict at efferent arteriole, and vasocontricts b/c of ang 2 -ang 2 - adh and aldosterone promote Na & water reabsorption --these effects increase HP & GFR by increasing resistance w/n glom --increase BV b/c of water reabsorption -GFR becomes normalized
what does aldosterone regulate?
sodium reabsorption!!
obligatory water reabsorption
when solutes are reabsorbed, water follows
what is the max osmolarity in the interstitium?
-1200 mOsml/L
what is in the medulla of the kidney?
-6-18 renal pryamids
what are impermeable to urea?
-ALH and DCT
how does the function of the vasa recta occur?
-BF in the vasa recta is in the opposite direction to filtrate flow, so when blood flows toward the high osmolarity of the medulla, Na & Cl move into the blood and water flows out of the blood. -However when the capillary blood flows toward the cortex, water moves into the blood and some of the sodium and chloride move back to the interstitium
example of autoregulation (bp ^)
-BP ^^ -GFR ^^ bc there is an increase in BP @ afferent arteriole (stimulates receptors) -afferent arteriole vasoconstricts (less blood flow into glomerulus, decreasing BP, HP, and normalizing GFR)
example of autoregulation
-BP declines, GFR declines (bc of decline in HP), inhibition of stretch receptors at the afferent arteriole wall, afferent arteriole vasodilates and allows more blood to flow into glomerulus --increases HP & increases the GFR to normal
what does the blood plasma regulate?
-BV (glomerulosa), ion concentrations, pH, and conserving nutrients (reabsbortion)
overhydration
-ECH becomes hypotonic to cells and fluid can flow into cells through osmosis -cells fill with fluid AND CAN BURST treated: decreasing salt & fluid intake, diuretics & electrolyte replacement
what is NFP based on?
-GHP (glomerular hydrostatic pressure): that is created by the hydrostatic pressure -CsHP (capsular hydrostatic pressure): created by the filtrate will oppose GHP -BCOP (blood colloid osmotic pressure) opposes GHP
basolateral membrane of ascending loop of henle
-Na is transported via active transport and K and Cl are transported by co transport --glycoprotein coats the limb, restricting water reabsorption, so the filtrate dilutes as it ascends
what does the nephron do in the PCT?
-REABSORB 70% of filtrate and ALL glucose and amino acids -the simple cuboidal w/ microvilli help with reabsporbtion -carrier proteins and mitochondria
positive feedback of the loop
-The solute pumping at the ALH sets up the conditions for the DLH. As solutes move into the ISF from the ALH, water leaves the DLH via osmosis. -as osmosis occurs & water leaves the DLH, the solutes concentrate, setting up the conditions for the ascending loop to function (pump solutes to the interstitium).
how does fluid leave the ECF compartment?
-WATER LEAVES THE CELLS BY OSMOSIS
what is at filtrate?
-a liquid measured as a volume
glomerular filtration rate (GFR)
-amt of filtrate produced by both kidneys in 1 min ---125 mL/min (but most gets reabsorbed) -GFR is a volume -NOT NFP, but it is a function of NFP (because pressure if responsible for volume of GFR)
fluid balance in the body
-amt. of water gained each day (usually = to the amt. of water lost each day) -any alteration to water balance can affect the electrolyte balance
what is the GFR controlled by?
-autoregulation -hormones -autonomic regulation through the sympathetic division of ANS
afferent arteriole
-blood ENTERS the glomerulus through this
efferent arteriole
-blood travels OUT OF the glomerulus through this
what is the renal corpuscle composed of?
-bowman's capsule & the glomerulus
what is the vasa recta?
-capillary loops that deliver oxygen and nutrients to the medullary regions
how do nephron accomplish transport, diffusion, and osmosis?
-carrier mediated proteins -facilitated difusion, active transport, contransport, counter transport
where do many nephrons empty their tubular fluid?
-collecting tubes -> minor/major calyx, renal pelvis
what is the driving force behind the transport of solutes? (PCT)
-concentration gradient of sodium
what is in the cortex of the kidneys?
-contains most corticol nephorns
what do the juxtameduallary nephrons do?
-contribute more to the concentration gradient needed to produce low volumes of concentrated urine
the PCT
-cuboidal cells w/ microvilli (^SA, ^ABS) that reabsorb *70 %* of the filtrate produced by the glomerulus -100% reabsorb most organic nutrients -active & passive reabsorption of NA and other ions -many carrier proteins & mitochondria to facilitate diffusion in and out
ascending loop of henle
-cuboidal w/ some microvilli -carrier proteins --@ luminal membrane, co transport Na, K, and (2) Cl from the filtrate to the cuboidal cells of the ALH -greatest transport is at beginning of ascending limb, and the transport is driven by sodium -transport of solutes = create osmotic gradient (2/3) needed to produce small volumes of concentrates urine
what is uric acid?
-derived from the breakdown of nucleic acids from foods or cellular destruction -it tends to crystallize due to its insolubility -common component of kidney stone -secreted in DCT
what does the nephron do in the loop of henle?
-descending (thin): water leaves (bc simp squa), solutes concentrate -ascending (thick): water stays, solutes are diluted -regulate final volume & solute concentration of the tubular fluid
when does dehydration develop?
-develops when water loss outpaces water gain -fluid is lost, and electrolytes are lost too (electrolyte imbalances) ex. lots of sweating, not enough water, hyposecretion of ADH, eating disorders
what does net filtration pressure do?
-drives solutes and water over the visceral layer of the glomerulus into the capsular space
what is the regulation of water largely due to?
-due to the effects of ADH @ the DCT and collecting duct --faculative water reabsorption
what are two functions of the urinary system?
-execretion -homeostatic regulation of blood plasma
what is the current mechanism?
-filtrate flow is opposite in the DLH vs. the ALH -exchange process is driven b/c each side of the nephron sets up the conditions for the other side to function -allows for solute & water reabsorption to occur prior to the tubular fluid arriving at the DCT -2/3 is due to solute pumping at ALH and 1/3 due to urea concentration
how does fluid leave the ECF and return?
-fluid leaves the ECF (blood) because of HP, and returns to the blood because of OP
How does fluid leave the interstitial space and enter the lymphatic system?
-fluid leaves the interstitial spaces and enters the lymphatic system due to its higher OP
net filtration pressure
-glomerular hydrostatic pressure (GHP): created by the blood pressure in the glomerular capillaries *60 mm HG* -capsular hydrostatic pressure (CsHP): opposes GHP: *15 mm Hg* -blood colloid osmotic pressure (BCOP): *28 mm Hg)*
what restricts water in the loop of henle?
-glycoprotein
composition of ICF
-high levels of K, phosphate, and magnesium ions -NOT a lot of Na+, Cl-, and bicarbonate
what makes up the composition of the ECF?
-high levels of Na+, Cl-, and bicarbonate ions -NOT a lot of K, Mg, Sulfur, and phosphate ions -plasma & lymph are part of ECF, but blood has more proteins than lymph
what is fluid movement between compartments regulated by?
-hydrostatic pressure and osmotic pressure
how can proteins leave the blood?
-if there is a scar in blood tissue --under normal conditions, proteins STAY in the blood
what is positive feedback in the nephron?
-in the ascending loop of henle, descending side, sets up for the acsending side
edema
-increase in ISF -causes: -caused by obstruction of a lymphatic vessel, or development of scar tissue -or inflammation with an increased capillary permeability (more fluid enters the ISF) -or decrease in plasma proteins due to liver disease, renal failure (loss of plasma protein) -or as plasma proteins decrease, the OP of the blood decreases and fluid increases within the ISF
what is a hilus?
-indentation -entry for renal artery & veins, and renal nerves -exit for the ureter
what are electrolytes?
-ions released when inorganic compounds dissociate -they can conduct an electrical current in a solution
what is urea?
-it is comprised of 60-90% of all nitrogenous material -mostly from the deamination of proteins -in the liver, ammonia combines with Co2 to form urea -made by heptocytes of liver
what is creatinine?
-it is derive from Creatine Phosphate in muscle tissue, 18 grams/day -100% is eliminated
electrolyte balance in the body
-keep osmolarity stable by adjusting the fluid in the extracellular compartment
DCT
-lack microvilli -filtrate arriving here is diff than what arrives at PCT -DCT performs final adjustment of urine via active secretion and reabsorption
how is sodium transported into the cuboidal cells of the PCT?
-leak channels -cotransport with organics -countertransport with hydrogen
how does water usually move in and out of the cells?
-osmosis -therefore, osmosis tends to eliminate differences in osmolarity, exceptions: ALH, DCT, and collecting system
what is ADH inhibited by?
-overhydration -alcohol
what are permeable to urea?
-papillary ducts, and urea enters the interstitium here, and contributes the other 1/3 of the osmotic gradient -gradient is NEEDED to concentrate urine
the micturition reflex
1. cerebral cortex recieves sensation 2. interneuron relays sensation to thalamus 3. parasympathetic preganglionic motor fiber in pelvic nerve 4. sensory fiber in pelvic nerve 5. postganglionic neuron in intramural ganglion stimulates detrusor muscle contraction
what is water reabsorption regulated by along the DCT and collecting ducts?
ADH!!!!!
how to calculate net hydrostatic pressure? (NHP)
GHP - CsHP
when the blood circulates the afferent arterioles what happens
INTERLOBAR ARTERIES afferent arteriole glomerulus efferent arteriole peritubular capillaries venules INTERLOBAR VEINS
GFH regulation by hormones
OCCURES IN JUSTAGLOMERULAR APPARATUS JG cells: release renin in response to low filtrate flow (low BP) Mascula dense: respond to changed in filtrate flow and stimulate the JG cells --renin forms angiotensin 2, increase BV and BP --renin causes the release of ADH
autoregulation
Occurs when a cell, tissue, organ or organ system adjusts its activities automatically in response to some environmental change
what do the renal tubules consist of?
Proximal convoluted tubule (PCT) Loop of Henle Distal convoluted tubule (DCT)
how the renal arteries get to the kidney
Renal artery Segmental artery Interlobar artery Arcuate artery Interlobular artery Afferent arterioles (veins follow a different pattern leaving) interlobular vein arcuate veins interlobar vein renal vein
what is the function of the vasa recta?
This balances solute reabsorption and osmosis in the medulla without disturbing the concentration gradient.
what are people with CHF, kidney disease, or excessive ADH secretion at risk for?
overhydration!!! -this can occur by accident too if people are treated for dehydration
secretion
blood --> tubules
vasa recta
long loops of capillaries that bring nutrients to the medullary cells -these capillary networks are only associated with juxtameduallary nephrons
what makes up the juxtaglomerular apparatus?
macula densa and juxtaglomerular cells
Cl-
most negative ions in the body
Na+
most positively charged ion in the body
crenation
occurs when a blood cell is placed in a hypertonic solution
what is excretion?
the removal of organic waste products from body fluids and their discharge from the body
in the ascending loop of henle, what is the transport at the luminal membrane dependent on?
transport at the basolateral membrane
reaborbtion
tubules --> blood
