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141 Cards in this Set

  • Front
  • Back
Kidney Functions
Filter 200 liters of blood daily to eliminate:
other urinary system organs
urinary bladder
paired ureters
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
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
the light colored, granular superficial
renal medulla
exhibits cone-shaped medullary (renal)
Blood and Nerve Supply (pg5 lec 1 - fig)
Large blood flow to kidney:
Nephron function/units
functional units of kidney that form urine
-Bowman’s capsule
-renal corpuscle
-Glomerular endothelium
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
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
-Reabsorbs water and solutes from filtrate and
secretes substances into it
Loop of Henle
a hairpin-shaped loop of the renal
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
Capillary Beds of the Nephron
Every nephron has two capillary beds
-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
-Filtration system
Main filtering system in kidney
Juxtaglomerular Apparatus (JGA) diagram (lect 2 pg2)
see slides
Juxtaglomerular Apparatus (JGA)location / fact
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
Urine formation
and adjustment of
blood composition - 3 majore processes
Glomerular Filtration
Principles of fluid dynamics that account for tissue
fluid in all capillary beds apply to the glomerulus

-Plasma proteins are not filtered
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
Intrinsic Controls
Under normal conditions, renal autoregulation
maintains a nearly constant glomerularfiltration
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

Other Factors Affecting Glomerular Filtration
-Prostaglandins (PGEand PGI)
-Nitric Oxide
-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
vasoconstrictor of renal vasculature
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
things reabsorbed by Tubular Reabsorption / details
-All organic nutrients are reabsorbed

-Water and ion reabsorptionis hormonally

-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

-Exists for nearly every substance that is actively

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
=reabsorption in reverse
--substances move from capillarire or tubule cells into filtrate
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
--The number of solute particles dissolved in 1L of

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
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 = 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
Physical Characteristics of Urine

Fresh urine is slightly aromatic

Standing urine develops an ammonia odor

Some drugs and vegetables (asparagus) alter the
usual odor
Physical Characteristics of Urine

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
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
-Males –prostate gland surrounds the neck
-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
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
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
-Males –prostate gland surrounds the neck
-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
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
-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

Sexually transmitted diseases can also inflame the urinary

Kidney function declines with age, with many elderly
becoming incontinent
Diagnosis of Urinary Tract Problems
-Test general health of urinary system
-Drug testing

Measure protein, glucose, ketones, nitrates, hydrogen ions, metabolites of drugs

-Glomerular damage

-Diabetes or starvation


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

Bladder inflammation

-Increased urination,frequency and urgency
-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

-Increased urinary frequency

-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

-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

--More sodium remains in renal tubule

---More sodium excreted
---Where sodium goes, water goes (increased fluid

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

-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)

--15 hrs per week
--Performed in dialysis centers by rained staff

--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

-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

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
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
Kidney damage; temporary or permanent kidney failure
Diabetic Nephropathy Cause


-Abnormally high blood

-Causes major problems
with blood chemistry
including osmotic balance

-Kidneys normally remove
all extra glucose from
--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

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


--Impurities build up in blood
Focal Glomerulosclerosis(FSGS) symptoms
Serum creatinine and blood urea nitrogen (BUN) are

Protein in urine


Anemia (why??????)



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

--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
Prostate Gland characteristics/function
Size of walnut

Surrounds neck of urinary bladder and urethra

Secretes fluid that forms part of semen
Benign Prostate Disorders


Enlarged prostate
--High blood levels of PSA (prostate specific antigen)

Symptoms of all prostate disorders
--Interference of flow of urine from bladder
--Frequent or infrequent urination
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



--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


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

--Plasma –the fluid portion of the blood
--Interstitial fluid (IF) –fluid in spaces between

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

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)


Intracellular fluids have low sodium and chloride


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
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
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
Regulation of Water Intake
Thirst is quenched as soon as we begin to drink water

Feedback signals that inhibit the thirst centers

-Moistening of the mucosa of the mouth and throat

-Activation of stomach and intestinal stretch
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
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

Factors that specifically trigger ADH release include
prolonged fever; excessive sweating, vomiting, or diarrhea;
severe blood loss; and traumatic burns
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
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

-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

-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

-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
-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

-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
renin-angiotensin mechanism
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
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
Substances which affect renal function:

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:

What is it: protein in blood

When: activated by renin

Action: constriction of blood vessels to increase blood
pressure; stimulates release of aldosteronefrom adrenal
Substances which affect renal function:

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:

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
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)
Tubular resorption
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
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
Transport maximum
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

--Transport maximum

---Tm for glucose = 375 mg/min

---When blood glucose is greater than 180 mg/dl –renal

----Glucose spills into urine
Acid-base Balance
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


-Short term pH regulation

Kidney function

-Reabsorb or eliminate H ions

-Long term pH regulation
Drop in body fluid pH to less than 7.35

-Depresses nervous system


---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
pH exceeds 7.45

Excites nervous system

-Tingling sensations, muscle twitches, paralysis

From hyperventilation, excess antacid ingestion, prolonged vomiting (elimination of stomach acids)