objective 7 pt 2 Flashcards by Kaitlyn Dominie

basically blood plasma except the proteins

filtrate

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what are the 3 processes that are involved in urine formation and adjustment of blood composition?

glomerular filtration
tubular reabsorption
tubular secretion

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passive process, no metabolic energy required
hydrostatic pressure forces fluid and solutes through filtration membrane into glomerular capsule
no reabsorption into capillaries of glomerulus occurs

glomerular filtration

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porous membrane between blood and interior of glomerular capsule
allows water and solutes smaller than plasma proteins to pass

filtration membrane

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what are the 3 layers of the filtration membrane

fenestrated endothelium
basement membrane
foot processes of podocytes

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allows all blood components except blood cells to pass through

fenestrated endothelium

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physical barrier that blocks all but smallest proteins while still allowing other solutes to pass

basement membrane

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contain filtration slits which repel macromolecules

foot processes of podocytes

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blood enters the glomerulus
filterable blood components, such as water and nitrogenous waste, will move towards the inside of the glomerulus
non-filterable conponents, such as RBCs and plasma proteins, will exit via the efferent arteriole
the filterable components accumulate in the glomerulus to form the glomerular filtrate

filtration

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forces that promote filtrate formation

outward pressure

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essentially glomerular blood pressure
chief force pushing water, solutes out of blood

hydrostatic pressure in glomerular capillaries

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forces inhibiting filtrate formation

inward pressure

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filtrate pressure in capsule; 15 mm Hg

hydrostatic pressure in capsular space

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“pull” of proteins in blood; 30 mm Hg

colloid osmotic pressure in capillaries

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sum of forces
pressure responsible for filtrate formation

net filtration pressure

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volume of filtrate formed per min by both kidneys

glomerular filtration rate

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what is GFR directly proportional to?

net filtration pressure
total surface area
filtration membrane permeability

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primarily pressure is glomerular hydrostatic pressure

net filtration pressure

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available for filtration

total surface area

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much more permeable than capillaries

filtration membrane permeability

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renal autoregulation
enables kidneys to maintain constant blood flow and GFR

intrinsic controls and GFR

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what are the two types of renal autoregulation?

myogenic mechanism
tubuloglomerular feedback mechanism

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local smooth muscle
increased BP causes muscle to stretch, leading to constriction of afferent arterioles
restricts blood flow into glomerulus
protects glomeruli from damaging high BP
decreased systemic BP causes dilation of afferent arterioles and raises glomerular hydrostatic pressure

myogenic mechanism

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with an increased concentration of NaCl in filtrate in the distal tubules, it causes a release of adenosine from the macula densa
cells
initiates a cascade of events that brings GFR to an appropriate level

tubuloglomerular feedback mechanism

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neural and hormonal mechanisms regulate GFR to maintain systemic blood pressure override renal intrinsic controls if blood volume needs to be increased

extrinsic controls

renal blood vessels dilated renal autoregulation mechanisms prevail

sympathetic nervous system under normal conditions at rest

* Norepinephrine released by sympathetic nervous system and epinephrine is released by adrenal medulla, causing: * Systemic vasoconstriction, which increases blood pressure * Constriction of afferent arterioles, which decreases GFR * Blood volume and pressure increases

sympathetic nervous system under abnormal conditions

main mechanism for increasing BP. low BP causes the release of renin from granular cells of the juxtaglomerular complex

renin-angiotensin-aldosterone mechanism

what are the 3 pathways that stimulate granular cells?

sympathetic nervous system activated macula dens cells reduced stretch

part of baroreceptor reflex, renal sympathetic nerves activate receptors that cause granular cells to release renin

sympathetic nervous system

occurs when filtrate NaCl concentration is low. signal grandular cells to release renin

activated macula dens cells

grandular cells ac as mechanoreceptors. reduced MAP reduced tension in grandular cells plasma membranes stimulates them to release more renin

reduced stretch

quickly reclaims most of contents from filtrate and returns them to blood via a selective transepithelial process process that moves solutes and water out of the filtrate and back into your bloodstream

tubular reabsorption

* Na+ is most abundant cation in filtrate * Transport of Na+ out of the tubule cell via primary active transport by a Na+-K+ ATPase pump in the basolateral membrane * Na+ into the interstitial space * Na+ is then swept by bulk flow of water and solutes into peritubular capillaries. * Organic nutrients reabsorbed by secondary active transport are cotransported with Na+

sodium transport

* Movement of Na+ and other solutes creates osmotic gradient for water * Water is reabsorbed by osmosis into the peritubular capillaries, aided by transmembrane proteins called aquaporins (act as water channels)

reabsorption of water

* Aquaporins are always present in PCT * Forces body to reabsorb water regardless if over or under hydrated

obligatory water reabsorption

* Aquaporins are inserted in collecting ducts only if ADH is present

facultative water reabsorption

* Solute concentration in filtrate increases as water is reabsorbed * Creates a concentration gradient for solutes, which drive their entry into the tubule cell and peritubular capillaries * Fat-soluble substances, some ions, and urea will follow water into peritubular capillaries down their concentration gradients * For this reason, lipid-soluble drugs and environmental pollutants are reabsorbed even though it is not desirable

passive tubular reabsorption of solutes

Site of most reabsorption * All nutrients, such as glucose and amino acids, are reabsorbed * 65% of Na+ and water reabsorbed * Many ions/electrolytes * Almost all uric acid * About half of urea (later secreted back into filtrate)

proximal convoluted tubule

H2O can leave, solutes cannot (permeable to water)

descending limb

H2O cannot leave, solutes can (impermeable to water)

ascending limb

reabsorption is hormonally regulated in these areas

distal convoluted tubule and collecting duct

* Released by posterior pituitary gland * Causes formation of aquaporins in collecting ducts, increasing water reabsorption * Increased ADH levels cause an increase in water reabsorption

antidiuretic hormone

* Released by adrenal cortex in response to decreased blood volume/BP or hyperkalemia * Targets collecting ducts and DCT * Promotes Na+ reabsorption (water follows) * As a result, little Na+ leaves body * Without aldosterone, daily loss of filtered Na+ would be 2%, which is incompatible with life

aldosterone

what are the functions of aldosterone?

increase blood pressure and decrease K+ levels

* Reduces blood Na+, resulting in decreased blood volume and blood pressure * Released by cardiac atrial cells if blood volume or pressure elevated

atrial natriuretic peptide

* Acts on DCT to increase Ca2+ reabsorption

parathyroid hormone

is the opposite of reabsorption * Occurs almost completely in DCT * Selected substances are moved from peritubular capillaries through tubule cells out into filtrate * K+, H+, NH4+, creatinine, organic acids and bases * Substances synthesized in tubule cells also are secreted * Helps control blood pH and acid base balance of body by selectively secreting electrolytes

tubular secretion

what is tubular secretion important for?

* Disposing of substances, such as drugs or metabolites, that are bound to plasma proteins * Eliminating undesirable substances that were passively reabsorbed (example: urea and uric acid) * Ridding body of excess K+ (aldosterone effect) * Controlling blood pH by altering amounts of H+ or HCO3– in urine

substance not reabsorbed, so water remains in urine; for example, in diabetic patient, high glucose concentration pulls water from body

osmotic diuretics

inhibit medullary gradient formation

loop diuretics

urine is examined for signs of disease can also be used to test for illegal substances

urinalysis

volume of plasma the kidneys can clear of a particular substance in a given time used to determine GFR

renal clearance

what is the chemical composition of urine

95% water 5% solutes

largest solute component

urea

from nucleic acid metabolism

uric acid

metabolite of creatine phosphate found in skeletal muscle

creatinine

what are they physical characteristics of urine?

color and transparency odor pH specific gravity

Clear * Cloudy may indicate urinary tract infection * Pale to deep yellow from urochrome * Pigment from hemoglobin breakdown * Yellow color deepens with increased concentration * Abnormal color (pink, brown, smoky) * Can be caused by certain foods, bile pigments, blood, drugs

color and transparency of urine

* Slightly aromatic when fresh * Develops ammonia odor upon standing as bacteria metabolize urea * May be altered by some drugs or vegetables * Disease may alter smell * Patients with diabetes may have acetone smell to urine

odor of urine

* Urine is slightly acidic (~pH 6, with range of 4.5 to 8.0) * Acidic diet (protein, whole wheat) can cause drop in pH * Alkaline diet (vegetarian), prolonged vomiting, or urinary tract infections can cause an increase in pH

pH of urine

* Ratio of mass of substance to mass of equal volume of water (specific gravity of water = 1) * Ranges from 1.001 to 1.035 because urine is made up of water and solutes * Normally excrete approx. 450 ml in 24 hours (30 ml/hr)

specific gravity of urine

slender tubes that convey urine from kidneys to bladder retroperitoneal enter base of bladder through posterior wall

ureters

what are the 3 layers of the ureters?

mucosa muscularis adventitia

consists of transitional epithelium

mucosa

smooth muscle sheets contract in response to stretch

muscularis

gravity alone is not enough; must also be pushed by peristaltic wave action of smooth muscle

propels urine into bladder

outer fibrous connective tissue

adventitia

* Smooth, collapsible, Muscular sac for temporary storage of urine * Retroperitoneal, on pelvic floor posterior to pubic symphysis

urinary bladder

prostate inferior to bladder neck

males urinary bladder

anterior to vagina and uterus

females urinary bladder

* Smooth triangular area outlined by openings for ureters and urethra * Infections tend to persist in this region

trigone

what are the layers of the bladder wall?

mucosa muscular layer fibrous adventitia

transitional epithelial mucosa

mucosa

thick detrusor muscle that contains 3 layers of smooth muscle

muscular layer

except on superior surface where it is covered by peritoneum

fibrous adventitia

* Collapses when empty * Mucosa folds (Rugae) * Expands and rises superiorly during filling without significant rise in internal pressure * Moderately full bladder is ~12 cm long (5 in.) and can hold ~ 500 ml (1 pint) * Can hold twice that amount if necessary but can burst if over distended

urine storage capacity

* Muscular tube that drains urinary bladder * Mucosal lining consists mostly of pseudostratified columnar epithelium, except: * Transitional epithelium near bladder * Stratified squamous epithelium near external urethral orifice

urethra

* Involuntary (smooth muscle) at bladder-urethra junction * Controlled by autonomic nervous system to keep closed when urine not being passed. * Contracts to open

internal urethral sphincter

* Voluntary (skeletal) muscle surrounding urethra as it passes through pelvic floor

external urethral sphincter

tightly bound to anterior vaginal wall

female urethra

anterior to vaginal opening; posterior to clitoris

external opening

carries semen and urine

male urethra

what are the 3 named regions of the male urethra?

prostatic urethra intermediate part of the urethra spongy urethra

within prostate

prostatic urethra

passes through urogenital diaphragm from prostate to beginning of penis

intermediate part of the urethra

passes through penis; opens via external urethral orifice

spongy urethra

act of emptying the bladder

micturition also called urination or voiding

what are the 3 simultaneous events that must occur for micturition?

1. Contraction of detrusor muscle by ANS 2. Opening of internal urethral sphincter ANS 3. Opening of external urethral sphincter by somatic nervous system

* Distension of bladder activates stretch receptors * Causes excitation of parasympathetic neurons in reflex center in sacral region of spinal cord * Leads to contraction of detrusor and opening (contraction) of internal sphincter * Inhibition of somatic pathways to external sphincter allow its relaxation and opening

reflexive urination