Anatomy Test 4: Urinary & Electrolytes

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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


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