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141 Cards in this Set
- Front
- Back
Kidney Functions
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Filter 200 liters of blood daily to eliminate:
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other urinary system organs
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urinary bladder
paired ureters urethra |
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Urinary Bladder funct
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provides a temporary storage
reservoir for urine |
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paired ureters funct
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transport urine from the kidneys to
the urinary bladder |
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urethra funct
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transports urine from the urinary bladder
out of the body |
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urinary system anatomy (lect 1 pg 2)
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check slides
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kidney location/reason
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Layers of Tissue Supporting the Kidney
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Renal capsule
adipose capsule renal fascia |
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Renal capsule
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fibrous capsule surrounding kidneys
that prevents kidney infection |
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adipose capsule
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fatty mass that cushions the
kidney and helps attach it to the body wall |
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renal fascia
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outer layer of dense fibrous
connective tissue that anchors the kidney |
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Kidney Location and External Anatomy
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check slides
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three distinct regions of kidney
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renal cortex
renal medulla renal pyramid |
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cortex
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the light colored, granular superficial
region |
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renal medulla
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exhibits cone-shaped medullary (renal)
pyramids |
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Blood and Nerve Supply (pg5 lec 1 - fig)
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Large blood flow to kidney:
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Nephron function/units
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functional units of kidney that form urine
-glomerulus -Bowman’s capsule -renal corpuscle -Glomerular endothelium |
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glomerulus
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a tuft of capillaries associated with a
renal tubule |
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Bowman’s capsule
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cup-shaped end of a renal
tubule that completely surrounds the glomerulus |
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renal corpuscle
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the glomerulus and its Bowman’s
capsule |
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Glomerular endothelium
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epithelium that allows
solute-rich, virtually protein-free filtrate to pass from the blood into the glomerular capsule |
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Renal Tubule parts
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Proximal convoluted tubule (PCT)
Loop of Henle Distal convoluted tubule (DCT) |
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Proximal convoluted tubule (PCT)
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composed of
cuboidal cells with numerous microvilli and mitochondria -Reabsorbs water and solutes from filtrate and secretes substances into it |
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Loop of Henle
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a hairpin-shaped loop of the renal
tubule |
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Distal convoluted tubule (DCT)
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cuboidal cells
without microvilli that function more in secretion than reabsorption |
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Types of Nephrons
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Cortical nephrons
-85% of nephrons; located in thecortex Juxtamedullary nephrons: -Are located at the cortex-medulla junction -Have loops of Henle that deeply invade the medulla -Have extensive thin segments -Are involved in the production of concentrated urine |
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Capillary Beds of the Nephron
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Every nephron has two capillary beds
-Glomerulus -Peritubular capillaries |
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Glomerulus Bed (characteristics)
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-Fed by an afferent arteriole
-Drained by an efferent arteriole |
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Blood pressure in the glomerulus
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high because:
-Arterioles are high-resistance vessels -Afferent arterioles have larger diameters than efferent arterioles Fluids and solutes are forced out of the blood throughout the entire length of the glomerulus |
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Nephron #'s/function
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-1,000,000 per kidney
-Regulates the amount of water, salts, glucose, urea, and minerals are in the body -Filtration system |
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Glomerulus
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Main filtering system in kidney
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Juxtaglomerular Apparatus (JGA) diagram (lect 2 pg2)
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see slides
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Juxtaglomerular Apparatus (JGA)location / fact
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Juxtaglomerular Apparatus (JGA)function
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Function as chemoreceptors or osmoreceptors
Influence capillary filtration |
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Filtration Membrane (diagram lect 2 pg 3)
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Filter that lies between the blood and the interior of
the glomerular capsule |
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Mechanisms of Urine Formation
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The kidneys filter the body’s entire plasma volume
60 times each day The filtrate: -Contains all plasma components except protein ----Loses water, nutrients, and essential ions to become urine -The urine contains metabolic wastes and unneeded substances |
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Urine formation
and adjustment of blood composition - 3 majore processes |
-Glomerular
filtration -Tubular reabsorption -Secretion |
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Glomerular Filtration
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Principles of fluid dynamics that account for tissue
fluid in all capillary beds apply to the glomerulus -Plasma proteins are not filtered |
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Glomerulus Efficiency
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-Its filtration membrane is more permeable
-Glomerular blood pressure is higher -It has a higher net filtration pressure |
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Net Filtration Pressure (NFP)
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-The pressure responsible for filtrate formation
NFP = HPg–(OPg+HPc) HPg= glomerularhydrostatic pressure OPg= oncoticpressure of glomerular blood HPc= capsular hydrostatic pressure -GFR is directly proportional to the NFP -Changes in GFR normally result from changes in glomerularblood pressure |
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Factors governing GlomerularFiltration Rate (GFR)
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-Total surface area available for filtration
-Filtration membrane permeability -Net filtration pressure |
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Diagram of GFR
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lect 21 pg 6
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Regulation of Glomerular Filtration
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-If the GFR is too high:
--Needed substances cannot be reabsorbed quickly enough and are lost in the urine -If the GFR is too low: --Everything is reabsorbed, including wastes that are normally disposed of |
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Mechanisms that control the GFR
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-Renal autoregulation(intrinsic system)
-Neural controls -Hormonal mechanism (the renin-angiotensin system) |
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Intrinsic Controls
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Under normal conditions, renal autoregulation
maintains a nearly constant glomerularfiltration rate |
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Extrinsic Controls
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When the sympathetic nervous system is at rest:
-Renal blood vessels are maximally dilated -Autoregulationmechanisms prevail Under stress: -Norepinephrineis released by the sympathetic nervous system -Epinephrine is released by the adrenal medulla -Afferent arterioles constrict and filtration is inhibited The sympathetic nervous system also stimulates the renin-angiotensin mechanism |
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Renin-Angiotensin Mechanism
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Is triggered when the JG cells release renin
-Reninacts on angiotensinogen to release angiotensinI --AngiotensinI is converted to angiotensinII ---Causes mean arterial pressure to rise ----Stimulates the adrenal cortex to release aldosterone =As a result, both systemic and glomerular hydrostatic pressure rise |
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Renin release
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Renin release is triggered by:
-Reduced stretch of the granular JG cells -Stimulation of the JG cells -Direct stimulation of the JG cells by renal nerves -AngiotensinII |
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Other Factors Affecting Glomerular Filtration
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-Prostaglandins (PGEand PGI)
-Nitric Oxide -Adenosine -Endothelin |
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-Prostaglandins (PGEand PGI)
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-Vasodilators produced in response to sympathetic
stimulation and angiotensinII -Are thought to prevent renal damage when peripheral resistance is increased |
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Nitric Oxide
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vasodilator produced by the vascular endothelium
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Adenosine
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vasoconstrictor of renal vasculature
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Endothelin
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a powerful vasoconstrictor secreted by tubule cells
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Tubular Reabsorption
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-A process whereby most tubule contents are
returned to the blood -Transported substances move through three membranes |
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things reabsorbed by Tubular Reabsorption / details
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-All organic nutrients are reabsorbed
-Water and ion reabsorptionis hormonally controlled -Reabsorptionmay be an active (requiring ATP) or passive process |
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Sodium Reabsorption:
Primary Active Transport |
-Sodium reabsorption is almost always by active transport
-Na+ reabsorption provides the energy and the means for reabsorbing most other solutes |
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reason for Nonreabsorbed Substances
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-A transport maximum (Tm):
Reflects the number of carriers in the renal tubules available -Exists for nearly every substance that is actively reabsorbed When the carriers are saturated, excess of that substance is excreted Substances are not reabsorbed if they: --Lack carriers --Are not lipid soluble --Are too large to pass through membrane pores --Urea, creatinine, and uric acid are the most important nonreabsorbed substances |
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Tubular Secretion
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=reabsorption in reverse
--substances move from capillarire or tubule cells into filtrate |
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Tubular secretion important for:
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Disposing of substances not already in the filtrate
Eliminating undesirable substances such as urea and uric acid Ridding the body of excess potassium ions Controlling blood pH |
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Regulation of Urine Concentration and
Volume |
Osmolality
--The number of solute particles dissolved in 1L of water Body fluids are measured in milliosmols(mOsm) The kidneys keep the solute load of body fluids constant at about 300 mOsm This is accomplished by the countercurrent mechanism |
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Diuretics
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Chemicals that enhance the urinary output include:
Any substance not reabsorbed Substances that exceed the ability of the renal tubules to reabsorb it Substances that inhibit Na+reabsorption |
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Osmotic diuretics include:
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High glucose levels –carries water out with the glucose
Alcohol –inhibits the release of ADH Caffeine and most diuretic drugs –inhibit sodium ion reabsorption Lasix and Diuril |
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Renal Clearance
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The volume of plasma that is cleared of a particular substance in a given time
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Renal Clearance tests: USE:
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Determine the GFR
Detect glomerular damage Follow the progress of diagnosed renal disease |
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Renal Clearance equation
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RC = UV/P
RC = renal clearance rate U = concentration (mg/ml) of the substance in urine V = flow rate of urine formation (ml/min) P = concentration of the same substance in plasma |
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Physical Characteristics of Urine
Color and transparency |
Clear, pale to deep yellow (due to urochrome)
Concentrated urine has a deeper yellow color Drugs, vitamin supplements, and diet can change the color of urine Cloudy urine may indicate infection of the urinary tract |
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Physical Characteristics of Urine
Odor |
Fresh urine is slightly aromatic
Standing urine develops an ammonia odor Some drugs and vegetables (asparagus) alter the usual odor |
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Physical Characteristics of Urine
pH |
Slightly acidic (pH 6) with a range of 4.5 to 8.0
Diet can alter pH |
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Physical Characteristics of Urine
Specific gravity |
Ranges from 1.001 to 1.035
Is dependent on solute concentration |
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Chemical Composition of Urine
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Urine is 95% water and 5% solutes
Nitrogenous wastes: urea, uric acid, and creatinine Other normal solutes include: -Sodium, potassium, phosphate, and sulfate ions -Calcium, magnesium, and bicarbonate ions Abnormally high concentrations of any urinary constituents may indicate pathology |
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Ureters function / structure and related function
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Slender tubes that convey urine from the kidneys
to the bladder Ureters enter the base of the bladder through the posterior wall --This closes their distal ends as bladder pressure increases and prevents backflow of urine into the ureters |
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Ureter muscle structure
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Uretershave a trilayered wall
Ureters actively propel urine to the bladder via response to smooth muscle stretch |
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Urinary Bladder
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Smooth, collapsible, muscular sac that stores urine
It lies on the pelvic floor posterior to the pubic symphysis -Males –prostate gland surrounds the neck inferiorly -Females –anterior to the vagina and uterus Trigone–triangular area outlined by the openings for the uretersand the urethra -Clinically important because infections tend to persist in this region |
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Urinary Bladder wall
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has three layers
The bladder is distensible and collapses when empty As urine accumulates, the bladder expands without significant rise in internal pressure |
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Urethra
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Muscular tube that:
-Drains urine from the bladder -Conveys it out of the body Sphincters keep the urethra closed when urine is not being passed Internal urethral sphincter -–involuntary sphincter External urethral sphincter –-voluntary sphincter Levatoranimuscle –voluntary urethral sphincter |
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Ureter muscle structure
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Uretershave a trilayered wall
Ureters actively propel urine to the bladder via response to smooth muscle stretch |
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Urinary Bladder
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Smooth, collapsible, muscular sac that stores urine
It lies on the pelvic floor posterior to the pubic symphysis -Males –prostate gland surrounds the neck inferiorly -Females –anterior to the vagina and uterus Trigone–triangular area outlined by the openings for the uretersand the urethra -Clinically important because infections tend to persist in this region |
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Urinary Bladder wall
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has three layers
The bladder is distensible and collapses when empty As urine accumulates, the bladder expands without significant rise in internal pressure |
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Urethra
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Muscular tube that:
-Drains urine from the bladder -Conveys it out of the body Sphincters keep the urethra closed when urine is not being passed Internal urethral sphincter -–involuntary sphincter External urethral sphincter –-voluntary sphincter Levatoranimuscle –voluntary urethral sphincter |
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Micturition(Voiding or Urination)
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The act of emptying the bladder
Distension of bladder walls initiates spinal reflexes that: -Stimulate contraction of the external urethral sphincter -Inhibit internal sphincter (temporarily) Voiding reflexes: -Inhibit the internal and external sphincters |
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Micturition cont.
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Infants have small bladders and the kidneys cannot
concentrate urine, resulting in frequent micturition Control of the voluntary urethral sphincter develops with the nervous system E. coli bacteria account for 80% of all urinary tract infections Sexually transmitted diseases can also inflame the urinary tract Kidney function declines with age, with many elderly becoming incontinent |
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Diagnosis of Urinary Tract Problems
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Urinalysis
-Test general health of urinary system -Drug testing Measure protein, glucose, ketones, nitrates, hydrogen ions, metabolites of drugs Proteinuria -Glomerular damage Ketonuria -Diabetes or starvation Glucosuria -Diabetes Solids in urine -Sediment examined under microscope --Types of cells: red blood cells, white blood cells Ability of kidneys to concentrate urine -Administer ADH -Urine should become more concentrated since more fluid should beretained |
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Urinary Tract Infections
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Occurs in any portion of urinary tract
10-20% of all women in US have lower urinary tract infections at some time Limited occurrence -Effects of urea (kill bacteria) -Acidic pH of urine -Washing out of bacteria during voiding -Minimize urine reflux |
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Urinary Tract Infection
Cystitis |
Bladder inflammation
-Increased urination,frequency and urgency -Pain -Cloudy urine -Blood in urine Treatment: antibiotics |
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Kidney Infection
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Bacterial or viral
Urinary obstruction causes backflow of urine from bladder to kidneys From blood infection Most cases in women Symptoms -Pain -Fever -Increased urinary frequency Treatment -Longer use of antibiotics |
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Urinary Disorders
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Changes in urinary frequency
Changes in urinary volume Dark urine Pain with urination Kidneys unable to regulate body water and sodium ion balance -Edema (fluid retention) -High blood pressure |
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Abnormal Appearance of Urine
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Color: deep amber to very pale yellow
If myoglobin, hemoglobin or red blood cells in urine: red or brown urine If pus, bacteria, lipids, or alkaline (higher pH): white cloudy urine Foamy urine: excessive protein in urine |
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Urinary Incontinence
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Normal effect of aging or pathology
Stretching of pelvic floor during childbirth -Incontinence during sneezing and coughing (stress incontinence) Prostate removal Neurogenicbladder dysfunction Treatment -Kegelexercises: tightening pelvic muscles as if trying to stop urination |
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Use of Diuretics to Treat Urinary System Disorders
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Diuretics: increase urine volume
-Aldosteroneantagonists: block sodium retaining effect of aldosterone --More sodium remains in renal tubule ---More sodium excreted ---Where sodium goes, water goes (increased fluid elimination Sodium and chloride reabsorptioninhibitors (thiazides) -Work in Loop of Henleto block reabsorptionof sodium, potassium and chloride --Increased salt and water elimination |
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Treatment of Renal Failure
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Will not develop unless both kidneys are damaged
-Restrict water, salt and protein intake ---Minimizes volume of urine produced ---Prevention of production of large amount of nitrogenous waste Hemodialysis -Uses artificial membrane (replaces glomerularfiltration)tofilter blood ---Diffusion of small ions ---Minimal loss of blood protein Dialysis fluid --Potassium ions, phosphate ions, sulfate ions, urea, creatinine, uric acid go into dialysis fluid |
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Treatment of Renal Failure (cont)
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Dialysis
--15 hrs per week --Performed in dialysis centers by rained staff Transplantation --15000 transplants in 2003 --1 yr success rate is 85-95% --Immunosupressive drugs to reduce transplant rejection |
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Bladder Cancer
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60,000 cases a year in the US
13,000 deaths per year 4 times more likely to occur in men Occurs most frequently between at 60-70 yrs of age Causes -Environmental exposures ---High rates in employees in chemical and rubber plants Prognosis for metatastic bladder cancer is poor -Spreads to bone, lymphatic system |
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Trauma, Ischemia and Kidney Damage
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Kidney is well vascularized
--High density of blood vessels --Blood flow within nephroncontrolled by afferent arteriole Ischemia –decreased oxygen supply to nephron because there is decrease in blood flow Decreased blood flow to nephronwhich is chronic --Anything that causes afferent arteriole prolonged constriction |
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Scenario
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Young Jason ClumSee runs into door that punctures his femoral artery
which bleeds profusely Decreases blood volume and decreases blood pressure Body responds by trying to bring blood pressure back to normal Massive vasoconstriction Afferent arterioles to kidney vasoconstrict Decreased blood flow and decreased oxygen supply to kidneys If prolonged ischemia to kidneys this will lead to kidney tissue death Kidney damage; temporary or permanent kidney failure |
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Diabetic Nephropathy Cause
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CAUSE:
Diabetes -Abnormally high blood glucose -Causes major problems with blood chemistry including osmotic balance -Kidneys normally remove all extra glucose from blood --Kidneys must work extra hard to do this -Larger urine volume as kidneys must excrete excess glucose Prolonged high blood glucose causes nephropathy -Damage to the glomerulus and the filtering system Proteins and blood cells that would normally not be filtered appear in the urine Kidney function is compromised Diabetic nephropathy is leading cause of kidney failure in United States |
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Kidney Stones features
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Proteins and blood cells that would normally not be
filtered appear in the urine Kidney function is compromised Diabetic nephropathy is leading cause of kidney failure in United States Stones in the kidney Substances in the urine crystallize in renal tubule --Why does substance crystallize???? --Stones are calcium or uric acid or caused by kidney infection Once you have stone, you are more susceptible to kidney stones in the future Many stones in kidney pass unnoticed Larger stones may lodge in kidney tubules Obstruction and irritation Very painful (lower back pain) and blood in urine |
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Kidney Stones treatment
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Treated for pain and sent home and told to drink a lot
--wait for stone to pass Lithotripsy which uses shock waves applied outside of body to break up stone Surgery |
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Focal Glomerulosclerosis(FSGS)
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Prevalence of disease is increasing
--Do not realize they have disease until advanced stage of condition --Autoimmune disease???? African-Americans at greater risk --Increased risk of high blood pressure --Increased risk for diabetes Effects --Impurities build up in blood |
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Focal Glomerulosclerosis(FSGS) symptoms
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Serum creatinine and blood urea nitrogen (BUN) are
elevated Protein in urine Fatigue Anemia (why??????) Nausea Headaches Swollen joints and abdomen (fluid retention) |
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Polycystic Kidney Disease
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Genetic disorder
Large cysts form in the kidneys Over time, decreasing kidney function as nephrons are replaced by cysts Kidney hypertrophy 500,000 cases in US No cure except kidney transplant Kidney failure Dialysis or transplant 50% with PKD progress to kidney failure (end stage renal disease) 500,000 cases in US 4thleading cause of kidney failure |
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Stages of Renal Failure
diagram lect 23 pg 9 |
see slides
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Acquired Cystic Kidney Disease
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From long-term kidney dialysis and end-stage renal
disease --90% of people on dialysis for 5 yrs develop ACKD Cysts may bleed Increased risk of kidney cancer (very rare) --2 times as likely with ACKD |
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Tissue engineering: Bladder
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Bladder disease
--Increased pressure in poorly functioning bladder leads to kidney damage --Reconstruction with tissue from small intestine Grow own bladder cells in culture for 7-8 weeks Attached ‘new bladder’to old bladder in 7, 4-19 yr old children --2-5 yrs later: improved bladder function in all subjects |
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Prostate Gland characteristics/function
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Size of walnut
Surrounds neck of urinary bladder and urethra Secretes fluid that forms part of semen |
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Benign Prostate Disorders
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Infection
Inflammation Enlarged prostate --High blood levels of PSA (prostate specific antigen) --Impotence --Incontinence Symptoms of all prostate disorders --Interference of flow of urine from bladder --Frequent or infrequent urination --Pain |
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Prostate Cancer
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Increased liklihood with enlarged prostate
60% of prostate cancers discovered remain localized 5 yr survival = 100% 10 yr survival = 68% 15 yr survival = 52% In past 20 yrs survival has increased from 67-93% |
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Other Considerations for Prostate Cancer
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PSA check annually after age 50
High risk males should begin screening earlier RISK FACTORS Age Race --African Americans are 61% more likely to get prostate cancer and 2.5 times more likely to die from disease Diet: high fat, low fiber Obesity Environmental exposures Family history |
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Body Water Content
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Infants are made up of over 70% water
Total water content declines throughout life Healthy males are about 60% water; healthy females are around 50% This difference reflects females: -Higher body fat -Smaller amount of skeletal muscle In old age, only about 45% of body weight is water |
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Fluid Compartments
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Water occupies two main fluid compartments
Intracellular fluid (ICF) –about two thirds by volume, contained in cells Extracellularfluid (ECF) –consists of two major subdivisions --Plasma –the fluid portion of the blood --Interstitial fluid (IF) –fluid in spaces between cells Other ECF –lymph, cerebrospinal fluid, eye humors, synovialfluid, serous fluid, and gastrointestinal secretions |
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Composition of Body Fluids
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Water is the universal solvent
Solutes are broadly classified into: -Electrolytes –inorganic salts, all acids and bases, and some proteins -Nonelectrolytes–examples include glucose, lipids, creatinine, and urea Electrolytes have greater osmotic power than nonelectrolytes Water moves according to osmotic gradients |
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Extracellularand Intracellular Fluids
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Each fluid compartment of the body has a distinctive pattern of electrolytes
Extracellularfluids are similar (except for the high protein content of plasma) -Sodium -Chloride Intracellular fluids have low sodium and chloride -Potassium -Phosphate Sodium and potassium concentrations in extra-and intracellular fluids are nearly opposites This reflects the activity of cellular ATP-dependent sodium-potassium pumps Electrolytes determine the chemical and physical reactions of fluids |
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Extracellular and Intracellular Fluids composition
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Proteins, phospholipids, cholesterol, and neutral fats
account for: -90% of the mass of solutes in plasma -60% of the mass of solutes in interstitial fluid -97% of the mass of solutes in the intracellular compartment |
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Fluid Movement Among Compartments
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Compartmental exchange is regulated by osmotic
and hydrostatic pressures Net leakage of fluid from the blood is picked up by lymphatic vessels and returned to the bloodstream Exchanges between interstitial and intracellular fluids are complex due to the selective permeability of the cellular membranes Two-way water flow is substantial |
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Extracellularand Intracellular Fluids movement
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Ion fluxes are restricted and move selectively by active transport
Nutrients, respiratory gases, and wastes move unidirectionally Plasma is the only fluid that circulates throughout the body and links external and internal environments |
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Water Balance and ECF Osmolality
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To remain properly hydrated, water intake must equal water output
Water intake sources -Ingested fluid (60%) and solid food (30%) -Metabolic water or water of oxidation (10%) Water output -Urine (60%) and feces (4%) -Insensible losses (28%), sweat (8%) Increases in plasma osmolality trigger thirst and release of antidiuretichormone (ADH) |
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Regulation of Water Intake
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The hypothalamic thirst center is stimulated:
-By a decline in plasma volume of 10%–15% -By increases in plasma osmolalityof 1–2% -Via baroreceptorinput, angiotensinII, and other stimuli |
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Regulation of Water Intake
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Thirst is quenched as soon as we begin to drink water
Feedback signals that inhibit the thirst centers include: -Moistening of the mucosa of the mouth and throat -Activation of stomach and intestinal stretch receptors |
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Regulation of Water Output
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Obligatory water losses include:
-Water losses from lungs (expired air) and skin -Water that accompanies undigested food residues in feces Obligatory water loss reflects the fact that: -Kidneys excrete 900-1200 mOsmof solutes to maintain blood homeostasis -Urine solutes must be flushed out of the body in water |
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Influence and Regulation of ADH
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Water reabsorption in collecting ducts is proportional to ADH release
-Low ADH levels produce dilute urine and reduced volume of body fluids -High ADH levels produce concentrated urine Hypothalamic osmoreceptors trigger or inhibit ADH release Factors that specifically trigger ADH release include prolonged fever; excessive sweating, vomiting, or diarrhea; severe blood loss; and traumatic burns |
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Dehydration
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Water loss exceeds water intake and the body is in
negative fluid balance Causes include: hemorrhage, severe burns, prolonged vomiting or diarrhea, profuse sweating, water deprivation, and diuretic abuse Signs and symptoms: cottonmouth, thirst, dry flushed skin Prolonged dehydration may lead to weight loss, fever, and mental confusion, heat illness |
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Hypotonic Hydration
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Renal insufficiency or an extraordinary amount of
water ingested quickly can lead to cellular overhydration, or water intoxication ECF is diluted –sodium content is normal but excess water is present -The resulting hyponatremia promotes net osmosis into tissue cells, causing swelling -These events must be quickly reversed to prevent severe metabolic disturbances, particularly in neurons |
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Edema
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Atypical accumulation of fluid in the interstitial
space, leading to tissue swelling Caused by anything that increases flow of fluids out of the bloodstream or hinders their return Factors that accelerate fluid loss include: -Increased blood pressure, capillary permeability -Incompetent venous valves, localized blood vessel blockage -Congestive heart failure, high blood volume Hindered fluid return usually reflects an imbalance in colloid osmotic pressures Hypoproteinemia–low levels of plasma proteins -Forces fluids out of capillary beds at the arterial ends -Fluids fail to return at the venous ends -Results from protein malnutrition, liver disease, or glomerulonephritis Blocked (or surgically removed) lymph vessels/glands: -Cause leaked proteins to accumulate in interstitial fluid -Exert increasing colloid osmotic pressure, which draws fluid from the blood Interstitial fluid accumulation results in low blood pressure and severely impaired circulation |
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Electrolyte Balance
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Electrolytes are salts, acids, and bases, but electrolyte balance usually refers only to salt balance
Salts are important for: -Neuromuscular excitability -Secretoryactivity -Membrane permeability -Controlling fluid movements Salts enter the body by ingestion and are lost via perspiration, feces, and urine |
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Sodium in Fluid and Electrolyte Balance
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Sodium holds a central position in fluid and
electrolyte balance Sodium salts: -Account for 90-95% of all solutes in the ECF -Contribute 280 mOsmof the total 300 mOsmECF solute concentration Sodium exerts significant osmotic pressure |
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Results of Changes in Plasma Sodium
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affect:
-Plasma volume, blood pressure -ICF and interstitial fluid volumes Renal acid-base control mechanisms are coupled to sodium ion transport |
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Regulation of Sodium Balance: Aldosterone
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Sodium reabsorption
-65% of sodium in filtrate is reabsorbed in the proximal tubules -25% is reclaimed in the loops of Henle When aldosterone levels are high, all remaining Na+ is actively reabsorbed Water follows sodium if tubule permeability has been increased with ADH |
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renin-angiotensin mechanism
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triggers the release of aldosterone
mediated by the juxtaglomerular apparatus, which releases reninin response to: -Sympathetic nervous system stimulation -Decreased filtrate osmolality Decreased stretch (due to decreased blood pressure) Renin catalyzes the production of angiotensinII, which prompts aldosterone release Adrenal cortical cells are directly stimulated to release aldosteroneby elevated K+ levels in the ECF Aldosterone brings about its effects (diminished urine output and increased blood volume) slowly |
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Cardiovascular System Baroreceptors
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Baroreceptor salert the brain of increases in blood
volume (hence increased blood pressure) -Sympathetic nervous system impulses to the kidneys decline -Afferent arterioles dilate -Glomerularfiltration rate rises -Sodium and water output increase This phenomenon, called pressure diuresis, decreases blood pressure Drops in systemic blood pressure lead to opposite actions and systemic blood pressure increases Since sodium ion concentration determines fluid volume, baroreceptorscan be viewed as “sodium receptors” |
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Substances which affect renal function
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Renin
Angiotensin Aldosterone ADH |
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Substances which affect renal function:
Renin |
What is it: Enzyme produced by cells of kidney
When: BP is too low for effective filtration Action: activates angiotensin |
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Substances which affect renal function:
Angiotensin |
What is it: protein in blood
When: activated by renin Action: constriction of blood vessels to increase blood pressure; stimulates release of aldosteronefrom adrenal cortex |
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Substances which affect renal function:
Aldosterone |
What is it: Hormone released from adrenal cortex
When: release regulated by angiotensin Action: promotes reabsorption of sodium and water -Conserves water to increase blood pressure |
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Substances which affect renal function:
ADH |
What is it: Hormone synthesized in hypothalamus and released by posterior pituitary
When: When blood becomes to concentrated Action: Promotes reabsorption of water to concetrate urine and conserve water |
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Glomerular Filtration
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Walls of the capillaries of glomerulusare porous
and permit free flow of water and soluble materials -Capillaries are impermeable to blood cells and large proteins (blood cells and proteins therefore remain in the blood capillaries) -Diameter of afferent arteriole is larger than diameter of efferent arteriole ---Effect: BP in glomerulusis high and capillary fluid and solutes are pushed out of capillaries and into the renal capsule (filtration) |
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Tubular resorption
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160-180 liters of filtrate formed per day
1 –1.5 liters of urine formed per day Therefore most of the filtrate is returned to circulation --Most urea and other nitrogenous waste remain in tubule to be excreted |
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Tubular Secretion
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Before filtrate leaves the body as urine there is
final adjustment --Substances move from blood to the kidney to be excreted in urine --Potassium ions --Hydrogen ions |
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Transport maximum
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Carriers are needed to return substances from the filtrate to the blood
Limit to the amount a substance can be reabsorbed in a given amount of time because there is finite number of carriers --Transport maximum ---Tm for glucose = 375 mg/min ---When blood glucose is greater than 180 mg/dl –renal threshold ----Glucose spills into urine |
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Acid-base Balance
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Body fluids are slightly alkaline (pH = 7.35 –7.45)
Body is always producing acids challenging the normal pH -Acids being produced: fatty acids, pyruvicacid, lactic acid, carbonic acid Systems and processes to counteract effect of body producing acids |
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What counteracts body's production of acids
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Buffer systems (neutralize acids): accept or release
H ions as needed to keep pH steady -Bicarbonate and phosphate buffers, and proteins Respiration -Short term pH regulation Kidney function -Reabsorb or eliminate H ions -Long term pH regulation |
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Acidosis
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Drop in body fluid pH to less than 7.35
-Depresses nervous system -Coma ---Results from respiratory obstruction or other lung disease that inhibits carbon dioxide release ---Results from kidney failure or prolonged diarrhea (drains alkaline substances from intestine) Inadequate carbohydrate metabolism (diabetes), low carbohydrate diet, starvation ---Increased fat and protein metabolism leading to excess acid production |
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Alkalosis
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pH exceeds 7.45
Excites nervous system -Tingling sensations, muscle twitches, paralysis From hyperventilation, excess antacid ingestion, prolonged vomiting (elimination of stomach acids) |