anatomy and physiology test 3 - urinary system
Terms
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- Kidney Functions
-
Filter 200 liters of blood daily to eliminate:
􀂃 Toxins
􀂃 Metabolic wastes
􀂃 Excess ions
Regulate blood volume
􀂃 5 liters
Regulate chemical makeup of the blood
􀂃 300 mmol concentration of solutes (i.e. sodium, potassium,
zinc)
Maintain the proper balance between water and salts, and
acids and bases
􀂃 Gluconeogenesis during prolonged fasting
􀂃 Production of renin to help regulate blood pressure
􀂃 Production of erythropoietin to stimulate red blood
cell production in bone marrow
􀂃 Activation of vitamin D - other urinary system organs
-
urinary bladder
paired ureters
urethra - Urinary Bladder funct
-
provides a temporary storage
reservoir for urine - paired ureters funct
-
transport urine from the kidneys to
the urinary bladder - urethra funct
-
transports urine from the urinary bladder
out of the body - urinary system anatomy (lect 1 pg 2)
- check slides
- kidney location/reason
-
􀂃 The bean-shaped kidneys extend from the twelfth
thoracic to the third lumbar vertebrae
􀂃 The right kidney is lower than the left because it is
crowded by the liver - Layers of Tissue Supporting the Kidney
-
Renal capsule
adipose capsule
renal fascia - Renal capsule
-
fibrous capsule surrounding kidneys
that prevents kidney infection - adipose capsule
-
fatty mass that cushions the
kidney and helps attach it to the body wall - renal fascia
-
outer layer of dense fibrous
connective tissue that anchors the kidney - Kidney Location and External Anatomy
- check slides
- three distinct regions of kidney
-
renal cortex
renal medulla
renal pyramid - cortex
-
the light colored, granular superficial
region - renal medulla
-
exhibits cone-shaped medullary (renal)
pyramids
􀂃 Pyramids are made up of parallel bundles of
urine-collecting tubules
􀂃 Renal columns are inward extensions of cortical
tissue that separate the pyramids
􀂃 Pyramid plus its surrounding capsule constitute a
lobe - Blood and Nerve Supply (pg5 lec 1 - fig)
-
Large blood flow to kidney:
􀂃 Approximately 25% (1200 ml) of blood flow from
heart to systemic circulation,flows through the
kidneys each minute
Arterial flow into and venous flow out of the
kidneys follow similar paths - Nephron function/units
-
functional units of kidney that form urine
-glomerulus
-Bowman’s capsule
-renal corpuscle
-Glomerular endothelium - glomerulus
-
a tuft of capillaries associated with a
renal tubule - Bowman’s capsule
-
cup-shaped end of a renal
tubule that completely surrounds the glomerulus - renal corpuscle
-
the glomerulus and its Bowman’s
capsule - Glomerular endothelium
-
epithelium that allows
solute-rich, virtually protein-free filtrate to pass
from the blood into the glomerular capsule - Renal Tubule parts
-
Proximal convoluted tubule (PCT)
Loop of Henle
Distal convoluted tubule (DCT) - Proximal convoluted tubule (PCT)
-
composed of
cuboidal cells with numerous microvilli and
mitochondria
-Reabsorbs water and solutes from filtrate and
secretes substances into it - Loop of Henle
-
a hairpin-shaped loop of the renal
tubule - Distal convoluted tubule (DCT)
-
cuboidal cells
without microvilli that function more in secretion
than reabsorption - Types of Nephrons
-
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 - Capillary Beds of the Nephron
-
Every nephron has two capillary beds
-Glomerulus
-Peritubular capillaries - Glomerulus Bed (characteristics)
-
-Fed by an afferent arteriole
-Drained by an efferent arteriole - Blood pressure in the glomerulus
-
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 - Nephron #'s/function
-
-1,000,000 per kidney
-Regulates the amount of
water, salts, glucose, urea,
and minerals are in the
body
-Filtration system - Juxtaglomerular Apparatus (JGA) diagram (lect 2 pg2)
- see slides
- Juxtaglomerular Apparatus (JGA)location / fact
-
􀂃 Where the distal tubule lies against the afferent
(sometimes efferent) arteriole
􀂃 Arteriole walls have juxtaglomerular (JG) cells
--Enlarged, smooth muscle cells
--Have secretory granules containing renin
--Act as mechanoreceptors - Juxtaglomerular Apparatus (JGA)function
-
Function as chemoreceptors or osmoreceptors
Influence capillary filtration - Filtration Membrane (diagram lect 2 pg 3)
-
Filter that lies between the blood and the interior of
the glomerular capsule - Mechanisms of Urine Formation
-
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 -
Urine formation
and adjustment of
blood composition - 3 majore processes -
-Glomerular
filtration
-Tubular
reabsorption
-Secretion - Glomerular Filtration
-
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) - Glomerulus Efficiency
-
-Its filtration membrane is more permeable
-Glomerular blood pressure is higher
-It has a higher net filtration pressure - Net Filtration Pressure (NFP)
-
-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 - Factors governing GlomerularFiltration Rate (GFR)
-
-Total surface area available for filtration
-Filtration membrane permeability
-Net filtration pressure - Diagram of GFR
- lect 21 pg 6
- Regulation of Glomerular Filtration
-
-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 - Mechanisms that control the GFR
-
-Renal autoregulation(intrinsic system)
-Neural controls
-Hormonal mechanism (the renin-angiotensin
system) - Intrinsic Controls
-
Under normal conditions, renal autoregulation
maintains a nearly constant glomerularfiltration
rate - Extrinsic Controls
-
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 - Renin-Angiotensin Mechanism
-
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 - Renin release
-
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 - Other Factors Affecting Glomerular Filtration
-
-Prostaglandins (PGEand PGI)
-Nitric Oxide
-Adenosine
-Endothelin - -Prostaglandins (PGEand PGI)
-
-Vasodilators produced in response to sympathetic
stimulation and angiotensinII
-Are thought to prevent renal damage when peripheral resistance is increased - Nitric Oxide
- vasodilator produced by the vascular endothelium
- Adenosine
- vasoconstrictor of renal vasculature
- Endothelin
- a powerful vasoconstrictor secreted by tubule cells
- Tubular Reabsorption
-
-A process whereby most tubule contents are
returned to the blood
-Transported substances move through three
membranes - things reabsorbed by Tubular Reabsorption / details
-
-All organic nutrients are reabsorbed
-Water and ion reabsorptionis hormonally
controlled
-Reabsorptionmay be an active (requiring ATP) or
passive process -
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 - reason for Nonreabsorbed Substances
-
-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 - Tubular Secretion
-
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 - Tubular secretion important for:
-
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 -
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 - Diuretics
-
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 - Osmotic diuretics include:
-
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 - Renal Clearance
- The volume of plasma that is cleared of a particular substance in a given time
- Renal Clearance tests: USE:
-
Determine the GFR
Detect glomerular damage
Follow the progress of diagnosed renal disease - Renal Clearance equation
-
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 -
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 -
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 -
Physical Characteristics of Urine
pH -
Slightly acidic (pH 6) with a range of 4.5 to 8.0
Diet can alter pH -
Physical Characteristics of Urine
Specific gravity -
Ranges from 1.001 to 1.035
Is dependent on solute concentration - Chemical Composition of Urine
-
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 - Ureters function / structure and related function
-
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 - Ureter muscle structure
-
Uretershave a trilayered wall
Ureters actively propel urine to the bladder via
response to smooth muscle stretch - Urinary Bladder
-
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 - Urinary Bladder wall
-
has three layers
The bladder is distensible and collapses when empty
As urine accumulates, the bladder expands without
significant rise in internal pressure - Urethra
-
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 - Micturition(Voiding or Urination)
-
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 - Micturition cont.
-
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 - Diagnosis of Urinary Tract Problems
-
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 - Urinary Tract Infections
-
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 -
Urinary Tract Infection
Cystitis -
Bladder inflammation
-Increased urination,frequency and urgency
-Pain
-Cloudy urine
-Blood in urine
Treatment: antibiotics - Kidney Infection
-
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 - Urinary Disorders
-
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 - Abnormal Appearance of Urine
-
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 - Urinary Incontinence
-
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 - Use of Diuretics to Treat Urinary System Disorders
-
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 - Treatment of Renal Failure
-
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 - Treatment of Renal Failure (cont)
-
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 - Bladder Cancer
-
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 - Trauma, Ischemia and Kidney Damage
-
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 - Scenario
-
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 - Diabetic Nephropathy Cause
-
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 - Kidney Stones features
-
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 - Kidney Stones treatment
-
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 - Focal Glomerulosclerosis(FSGS)
-
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 - Focal Glomerulosclerosis(FSGS) symptoms
-
Serum creatinine and blood urea nitrogen (BUN) are
elevated
Protein in urine
Fatigue
Anemia (why??????)
Nausea
Headaches
Swollen joints and abdomen (fluid retention) - Polycystic Kidney Disease
-
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 -
Stages of Renal Failure
diagram lect 23 pg 9 - see slides
- Acquired Cystic Kidney Disease
-
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 - Tissue engineering: Bladder
-
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 - Prostate Gland characteristics/function
-
Size of walnut
Surrounds neck of urinary bladder and urethra
Secretes fluid that forms part of semen - Benign Prostate Disorders
-
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 - Prostate Cancer
-
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% - Other Considerations for Prostate Cancer
-
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 - Body Water Content
-
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 - Fluid Compartments
-
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 - Composition of Body Fluids
-
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 - Extracellularand Intracellular Fluids
-
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 - Extracellular and Intracellular Fluids composition
-
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 - Fluid Movement Among Compartments
-
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 - Extracellularand Intracellular Fluids movement
-
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 - Water Balance and ECF Osmolality
-
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) - Regulation of Water Intake
-
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 - Regulation of Water Output
-
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 - Influence and Regulation of ADH
-
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 - Dehydration
-
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 - Hypotonic Hydration
-
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 - Edema
-
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 - Electrolyte Balance
-
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 - Sodium in Fluid and Electrolyte Balance
-
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 - Results of Changes in Plasma Sodium
-
affect:
-Plasma volume, blood pressure
-ICF and interstitial fluid volumes
Renal acid-base control mechanisms are coupled to
sodium ion transport - Regulation of Sodium Balance: Aldosterone
-
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 - Cardiovascular System Baroreceptors
-
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†- Substances which affect renal function
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Renin
Angiotensin
Aldosterone
ADH -
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 -
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 -
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 -
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 - 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 - 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 - 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 - What counteracts body's production of acids
-
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 - Acidosis
-
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 - 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)