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Unit 4: Homeostasis. Chapter 10: Excretion and the Interaction of Systems. Chapter 10: Excretion and the Interaction of Systems. Overview The excretory system Functions Organs Urine formation in the nephron Other functions and disorders of the excretory system

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unit 4 homeostasis

Unit 4: Homeostasis

Chapter 10: Excretion and the Interaction of Systems

chapter 10 excretion and the interaction of systems
Chapter 10: Excretion and the Interaction of Systems
  • Overview
    • The excretory system
      • Functions
      • Organs
    • Urine formation in the nephron
    • Other functions and disorders of the excretory system
      • Regulating water-salt balance
      • Maintaining blood pH
      • Disorders
section 10 1 overview of the excretory system
Section 10.1: Overview of the Excretory System
  • Excretion is the process of separating wastes from body fluids, then eliminating the wastes from the body
  • Several body systems perform this function
    • The respiratory system excretes carbon dioxide and small amounts of other gases, including water vapour
    • The skin excretes water, salts, and some urea in perspiration
    • The digestive system excretes water, salts, lipids, and a variety of chemical compounds
      • Note that the elimination of food residue (feces) is not considered to be a process of excretion
section 10 1 overview of the excretory system1
Section 10.1: Overview of the Excretory System
  • Most metabolic wastes are dissolved or suspended in solution and are excreted by the excretory system (also called the urinary system)
  • The excretory system produces urine and conducts it outside the body
  • As the kidneys produce urine, they carry out four functions that contribute to homeostasis
functions of the excretory system
Functions of the Excretory System
  • Excretion of metabolic wastes
    • The kidneys excrete metabolic wastes, notably nitrogenous (nitrogen-containing) wastes
      • Include ammonia, urea, and uric acid
    • Ammonia is highly toxic, but it converted in the liver to the less toxic compound urea
    • Urea makes up the majority of nitrogenous waste in the body
      • About half of it is eliminated in urine
    • Uric acid is present in much lower concentrations, and is contained in urine
functions of the excretory system1
Functions of the Excretory System
  • Maintenance of water-salt balance
    • Kidneys maintain the appropriate balance of water and salt in the blood
    • Blood volume is closely tied to the salt balance of the body
      • By regulating salts in the blood, the kidneys are closely involved in regulating blood pressure
    • Kidneys also help maintain the appropriate level of potassium (K+), bicarbonate (HCO3-) and calcium (Ca2+) in the blood
functions of the excretory system2
Functions of the Excretory System
  • Maintenance of acid-base balance
    • Kidneys monitor and help keep the blood pH at about 7.4, mainly by excreting hydrogen ions (H+) and reabsorbing bicarbonate ions (HCO3-) as needed
    • Human urine usually has a pH of 6 or lower because our diet often contains acidic foods
functions of the excretory system3
Functions of the Excretory System
  • Secretion of hormones
    • Kidneys secrete two hormones:
    • Calcitriol
      • Active form of Vitamin D
      • Promotes calcium absorption from the digestive tract
    • Erythropoietin
      • Stimulates the production of red blood cells
      • Released in response to increased oxygen demand or reduced oxygen-carrying capacity of the blood
    • Kidneys also secrete renin
      • Leads to the secretion of the hormone aldosterone from the adrenal cortex
the organs of the excretory system
The Organs of the Excretory System
  • The human excretory system consists of:
    • Two kidneys
    • Two ureters
    • The urinary bladder
    • The urethra
the organs of the excretory system1
The Organs of the Excretory System
  • Two fist-sized kidneys are located in the area of the lower back on each side of the spine
  • A large cushion of fat usually surrounds them
    • Offers protection
  • Although most people have two kidneys, humans are capable of functioning with only one
    • If one kidney ceases to work, or one is removed due to disease, the remaining kidney will increase in size to handle the increased workload
the organs of the excretory system2
The Organs of the Excretory System
  • The kidneys release urine into two muscular, 28-cm-long tubes called ureters
  • From the ureters, urine is moved by the peristaltic actions of smooth muscle tissue to the muscular urinary bladder where it is temporarily stored
  • Drainage from the bladder is controlled by two rings of muscles called sphincters
    • Both sphincters must relax before urine can drain from the bladder
    • The innermost sphincter is involuntarily controlled by the brain
    • During childhood we learn to voluntarily control relaxation of the other sphincter
the organs of the excretory system3
The Organs of the Excretory System
  • Urine exits the bladder and the body through a tube called the urethra
    • In males, the urethra is approximately 20cm long and merges with the ductus deferens of the reproductive tract to form a single passageway to the external environment
    • In females, the urethra is about 4 cm long and the reproductive and urinary tracts have separate openings
the kidneys
The Kidneys
  • The kidneys are bean shaped and reddish-brown in colour
  • The concave side of each kidney has a depression where a renal artery enters and a renal vein and a ureter exit the kidney
    • Many branches of the renal artery renal vein reach inside the kidney
the kidneys1
The Kidneys
  • A kidney has 3 regions
    • The renal cortex is an outer layer that dips down into an inner layer called the renal medulla
    • The renal medulla contains cone-shaped tissue masses
    • The renal pelvis is a central space, or cavity, that is continuous with the ureter
the kidneys2
The Kidneys
  • Embedded within the renal cortex and extending into the renal medulla are more than a million microscopic structures called nephrons
  • A network of blood vessels is closely associated with these nephrons
  • Nephrons are responsible for filtering various substances from blood, transforming it into urine
  • To perform this function, each nephron is organized into 3 main regions:
    • A filter
    • A tubule
    • A collecting duct
the nephron
The Nephron
  • A Filter
    • The filter structure at the top of each nephron is a cap-like formation called the Bowman’s capsule
    • Within each capsule, the renal artery enters and splits into a find network of capillaries called a glomerulus(means “little ball” in Latin)
    • The walls of the glomerulus act as a filtration device
      • Impermeable to proteins, other large molecules, and red blood cells, so these remain within the blood
      • Water, small molecules, ions, and urea (the main waste products of metabolism) pass through the walls and proceed further into the nephron
    • The filtered fluid that proceeds from the glomerulus into the Bowman’s capsule of the nephron is referred to as filtrate
the nephron1
The Nephron
  • A Tubule
    • The Bowman’s capsule is connected is connected to a small, long, narrow tubule that is twisted back on itself to form a loop
      • This long hairpin loop is a reabsorption device
    • The tubule has 3 sections:
      • The proximal tubule
      • The loop of Henle
      • The distal tubule
    • The tubule absorbs substances that are useful to the body, such as glucose and a variety of ions, from the filtrate passing through it
    • Also secretes substances into the tissues surrounding it
the nephron2
The Nephron
  • A Duct
    • The tubule empties into a larger pipe-like channel called a collecting duct
      • Functions as a water-conservation device, reclaiming water from the filtrate passing through it so that very little water is lost from the body
    • The filtrate that remains in the collecting duct is a suspension of water and various solutes and particles
      • It is now called urine
      • Its composition is distinctly different from the fluid that entered the Bowman’s capsule
    • The solutes and water reclaimed during reabsorption are returned to the body via the renal vein
section 10 2 urine formation in the nephron
Section 10.2: Urine Formation in the Nephron
  • Nephrons are surrounded by the tissues of the renal cortex and the renal medulla
  • Also closely associated with a network of blood vessels that spreads throughout the surrounding tissue
  • Thus, any substances secreted by the nephrons enter the surrounding tissue of the kidney
    • Most of these substances return to the bloodstream through the network of blood vessels
    • The remainder leave the body in the form of urine
how urine forms
How Urine Forms
  • 4 processes are crucial to the formation of urine
  • Glomerular filtration
    • Moves water and solutes, except proteins, from blood plasma into the nephron (recall this filtered fluid is called filtrate)
  • Tubular reabsorption
    • Removes useful substances such as sodium from the filtrate and returns them into the blood for reuse by body systems
  • Tubular secretion
    • Moves additional wastes and excess substances from the blood into the filtrate
  • Water reabsorption
    • Removes water from the filtrate and returns it to the blood for reuse by body systems
glomerular filtration filters blood
Glomerular Filtration Filters Blood
  • The formation of urine starts with glomerular filtration
    • This process forces some of the water and dissolved substances in blood plasma from the glomerulus into the Bowman’s capsule
    • This occurs in millions of nephrons at the same time
glomerular filtration filters blood1
Glomerular Filtration Filters Blood
  • Two factors contribute to filtration
  • The first factor is the permeability of the capillaries of the glomerulus
    • Capillaries of the glomerulus have many pores in their tissue walls
    • The pores are large enough to allow water and most dissolved substances in the blood plasma to pass easily through the capillaries and into the Bowman’s capsule
    • The pores are small enough to prevent proteins and blood cells from entering
  • The second factor is blood pressure
    • Blood pressure within the glomerulus is about 4X greater than it is in capillaries elsewhere in the body
    • The great rush of blood through the golmerulus provides the force for filtration
glomerular filtration filters blood2
Glomerular Filtration Filters Blood
  • Each day, 1600L – 2000L of blood pass through the kidneys, producing about 180L of glomerular filtrate
  • This filtrate is almost chemically identical to blood plasma, minus proteins and blood cells
  • If the composition of urine were the same as that of glomerular filtrate, the body would continually lose water, salts, and nutrients
    • Therefore, the composition of the filtrate must change as this fluid passes through the remainder of the tubule
tubular reabsorption recovery of substances in the proximal tubule
Tubular Reabsorption: Recovery of Substances in the Proximal Tubule
  • About 65% of the filtrate that passes through the entire length of the proximal tubule (including the loop of Henle) is reabsorbed and returned to the body
  • This process of reabsorption involves both active and passive transport mechanisms
    • The cells of the proximal tubule contain many mitochondria, which use the energy-releasing power of ATP to drive the active transport of sodium ions, glucose, and other solutes back into the blood
    • Negatively charged ions tag along passively, attracted by the electrical charge on the transported substances
    • Water follows the ions by osmosis, so it, too, is reabsorbed into the blood flowing through the capillaries
focusing on the loop of henle in the proximal tubule
Focusing on the Loop of Henle in the Proximal Tubule
  • The function of the loop of Henleis to reabsorb water and ions from the glomerular filtrate
  • As the descending limb of the loop of Henle plunges deeper into the medulla region, it encounters an increasingly salty environment
  • The cells of the descending limb are permeable to water and only slightly permeable to ions
  • As a result of the salty environment of the medulla, and the permeability of the descending limb, water diffuses from the filtrate to the capillaries by osmosis
  • As water moving through the descending limb leaves the filtrate, the concentration of sodium ions inside the tubule increases, reaching its maximum concentration at the bottom of the loop
focusing on the loop of henle in the proximal tubule2
Focusing on the Loop of Henle in the Proximal Tubule
  • As the filtrate continues around the bend of the loop of Henle and into the ascending limb, the permeability of the nephron tubule changes
  • Near the bend, the thin portion of the ascending tubule is now impermeable to water and slightly permeable to solutes
  • Sodium ions diffuse from the filtrate along their concentration gradient and pass into nearby blood vessels
focusing on the loop of henle in the proximal tubule4
Focusing on the Loop of Henle in the Proximal Tubule
  • At the thick-walled portion of the ascending limb of the loop of Henle, sodium ions are moved out of the filtrate by active transport
  • This transport of Na+ out of the filtrate has 2 consequences:
    • It helps replenish the salty environment of the medulla, which aids in the absorption of water from filtrate in the descending limb
    • The removal of sodium ions from the filtrate in the thick-walled portion of the tubule makes the filtrate less concentrated than the tissues and blood in the surrounding cortex tissue
  • By now, about two thirds of the Na+ and water from the filtrate has been reabsorbed
tubular reabsorption and secretion in the distal tubule
Tubular Reabsorption and Secretion in the Distal Tubule
  • The active reabsorption of sodium ions from the filtrate into the capillaries depends on the needs of the body
  • Passive reabsorption of negative ions such as chloride occurs by electrical attraction
  • The reabsorption of ions decreases the concentration of the filtrate, which causes water to be reabsorbed by osmosis
tubular reabsorption and secretion in the distal tubule1
Tubular Reabsorption and Secretion in the Distal Tubule
  • Potassium ions (K+) are actively secreted into the distal tubule from the bloodstream in the capillaries
  • Hydrogen ions (H+) are also actively secreted from the blood into the distal tubule as necessary in order to maintain the pH of the blood
  • Other substances that are not normally part of the body, such as penicillin and other medications, are secreted from the blood into the distal tubule
  • Reabsorption and secretion in the distal tubule are under the control of hormones, as you will see in the next section
reabsorption from the collecting duct
Reabsorption from the Collecting Duct
  • The filtrate entering the collecting duct still contains a lot of water
  • Because the collecting duct extends deep into the medulla, the concentration of ions along its length increases
    • This concentration of ions is the result of active transport of ions from the ascending limb of the loop of Henle
    • This causes the passive reabsorption of water from the filtrate in the collecting duct by osmosis
reabsorption from the collecting duct1
Reabsorption from the Collecting Duct
  • If blood plasma is too concentrated (for example, if a person is dehydrated) the permeability to water in the distal tubule and the collecting duct is increased
    • This causes more water to be reabsorbed into the surrounding capillaries in order to conserve water in the body
  • In the collecting duct, as in the distal tubule, hormones control reabsorption and secretion
  • The reabsorption of water in the collecting duct causes the filtrate to become about 4X as concentrated by the time it exits the duct
    • This filtrate, which is approximately 1% of the original filtrate volume, is now called urine
section 10 3 other functions and disorders of the excretory system
Section 10.3: Other Functions and Disorders of the Excretory System
  • Kidneys not only filter wastes from the blood, but also carry out several other important homeostatic functions including:
    • Maintaining the water-salt balance of the blood
    • Regulating blood pH
    • Secreting some hormones
  • Kidneys also play an important role in maintaining blood pressure
    • They can be damaged if blood pressure gets too high
    • Blood pressure tests, blood tests, and urinalysis are used to determine whether the kidneys are functioning properly
regulating water salt balance
Regulating Water-Salt Balance

Reabsorption of water

  • The force generated as water moves by osmosis is called osmotic pressure
    • Osmotic pressure affects many cellular activities, especially the exchange of materials between cells and blood
  • Osmoreceptors are cells that are sensitive to osmotic pressure
    • Most are located in the hypothalamus
    • Recall from Chap 8 that the hypothalamus regulates mechanisms that enable the body to maintain homeostasis
      • Ex: Hunger, thirst, blood pressure, body temperature, fluid balance, and salt balance
regulating water salt balance1
Regulating Water-Salt Balance
  • When blood plasma becomes too concentrated (ex: if you are dehydrated), osmotic pressure increases
  • Osmoreceptors in the hypothalamus send impulses to the pituitary gland which causes the release of antidiuretic hormone (ADH)
    • “Anti” means “against” or “opposed to” and “diuresis” means “increased excretion of urine”
  • So “antidiuresis” means “decreased excretion of urine”
  • ADH travels through the blood to the kidneys
    • It increases the permeability of the distal tubule and the collecting duct
    • Allows more water to be reabsorbed into the blood
  • This dilutes the blood and lowers osmotic pressure to normal
regulating water salt balance2
Regulating Water-Salt Balance
  • If blood plasma is too dilute (i.e. if osmotic pressure is too low) osmoreceptors in the hypothalamus stop or prevent the release of ADH
  • As a result, the distal tubule and the collecting duct become less permeable to water
    • Allows more water to be excreted in the urine, concentrating the solutes in the blood
  • The osmotic pressure of the plasma and tissue fluids rises to normal
regulating water salt balance4
Regulating Water-Salt Balance
  • In a condition called diabetes insipidus ADH activity is insufficient
    • Person urinates excessively (as much as 4L – 8L per day)
  • Thirst is intense, but water is excreted more quickly than it’s consumed, leading to severe dehydration and ion imbalances
  • People who have this condition may take synthetic ADH to restore the balance of water reabsorption
regulating water salt balance5
Regulating Water-Salt Balance
  • The ethanol in alcoholic beverages is a diuretic
    • Increases the volume of urine
  • Alcohol stimulates urine production partly by inhibiting the release of ADH
    • Decreases the permeability of the tubules and collecting ducts
  • Because it increases water loss to urine, drinking alcohol actually intensifies thirst and leads to dehydration
  • Caffeine, a substance in coffee and many carbonated drinks, is also a diuretic
regulating water salt balance6
Regulating Water-Salt Balance

Reabsorption of salt

  • The kidneys regulate salt balance in the blood by controlling the excretion and reabsorption of various ions
  • The sodium ion (Na+) is the most abundant ion in blood plasma
    • Its concentration can fluctuate dramatically depending on diet and the consumption of beverages with diuretic effects
regulating water salt balance7
Regulating Water-Salt Balance
  • Hormones regulate the reabsorption of sodium at the distal tubule
  • Recall from Chap 9 that aldosterone is a hormone secreted by the adrenal cortex
    • Stimulates the excretion of potassium ions (K+) and the reabsorption of sodium ions (Na+)
  • The release of aldosterone is set in motion by the kidneys themselves
regulating water salt balance8
Regulating Water-Salt Balance
  • When blood volume, and therefore blood pressure, is too low to promote glomerular filtration, the kidneys secrete renin
    • Renin, an enzyme, starts a reaction that eventually triggers the release of aldosterone from the adrenal cortex
  • Aldosterone stimulates the distal tubules and collecting ducts to reabsorb Na+
    • The reabsorption of Na+ is followed passively by chloride ions and water
  • Aldosterone has the net effect of retaining both salt and water
    • As a result, blood volume and blood pressure increases
maintaining blood ph
Maintaining Blood pH
  • The normal pH of body fluids is about 7.4
    • pH at which our enzymes function optimally
  • If homeostasis is not maintained and blood pH goes above or below 7.4, serious medical conditions can result
  • Many processes can alter blood pH, such as
    • Eating a meal
    • Drinking liquids
    • Metabolic processes (ex: cellular respiration)
  • Three mechanisms maintain blood pH at 7.4
    • Acid-base buffer system
    • Respiratory center
    • The kidneys
acid base buffer system
Acid-Base Buffer System
  • This system buffers the blood
    • Prevents changes in pH by taking up excess hydrogen ions (H+) or excess hydroxide ions (OH-) that enter the blood
  • On of the key buffering reactions in the blood involves carbonic acid (H2CO3) and bicarbonate ions (HCO3-)
  • When hydrogen ions are added to the blood:

H+ + HCO3- H2CO3

  • When hydroxide ions are added to the blood:

OH- + H2CO3 HCO3- + H2O

  • These reactions temporarily prevent changes in blood pH
    • A blood buffer can be overwhelmed unless some more permanent adjustment is made
    • The next adjustment to maintain blood pH occurs in the lungs
respiratory system
Respiratory System
  • If the hydrogen ion concentration of the blood rises, the respiratory center in the medulla oblongata increases the breathing rate
  • Increasing the breathing rate rids the body of hydrogen ions because the following reaction takes place in the lung capillaries:

H+ + HCO3- H2CO3 H2O + CO2

 Blood pH decreases  Blood pH increases

  • Increased breathing rate pulls the reaction to the right to generate CO2 more quickly
    • When CO2 is exhaled, the number of hydrogen ions is reduced
  • It’s important to have the correct proportion of carbonic acid and bicarbonate ions in the blood
    • Breathing readjusts this proportion so that this particular acid-base buffer system can continue to absorb both H+ and OH- as needed
the kidneys3
The Kidneys
  • The acid-base buffer system and respiration are aided by the more powerful actions of the kidneys to control the acid-base balance of the blood
    • Only the kidneys can rid the body of a wide range of acidic and basic substances
    • The kidneys are slower acting than the other two mechanisms, but they have a more powerful effect on pH
the kidneys4
The Kidneys
  • Think of the kidneys as excreting H+ and reabsorbing HCO3- as needed to maintain normal blood pH
    • If the blood is too acidic, H+ is excreted and HCO3- is reabsorbed
    • If the blood is too basic, H+ is not excreted and HCO3- is not reabsorbed
  • Urine is acidic, so H+ is being excreted
the kidneys5
The Kidneys
  • Ammonia (NH3) provides another means of buffering and removing the hydrogen ions in urine (NH3 + H+ NH4+)
    • Ammonia is produced in tubule cells by the breakdown of amino acids
  • The ability of the kidneys to control blood pH is crucial to maintaining an internal environment in which cell enzymes continue to function properly
releasing hormones
Releasing Hormones
  • In addition to being part of the feedback loop for aldosterone, the kidneys release two hormones of their own
    • Erythropoietin
    • Calcitriol
releasing hormones1
Releasing Hormones
  • If the oxygen-carrying capacity of the blood is reduced, or oxygen demand increases, sensors in the kidneys stimulate kidney cells to release erythropoietin
    • Stimulates the production of red blood cells in bone marrow
  • As the number of red blood cells in the blood increases, the oxygen-carrying capacity of the blood increases
  • When oxygen delivery to the kidneys returns to normal, the kidneys stop releasing erythropoietin
releasing hormones2
Releasing Hormones
  • The kidneys also play a role in calcium regulation in the blood
  • If the level of calcium in the blood falls below normal, parathyroid hormone (PTH) is released by the parathyroid gland
    • Stimulates the release of calcitriol by the kidneys
  • Calcitriol (the active form of vitamin D) promotes calcium absorption from the digestive tract
disorders of the excretory system
Disorders of the Excretory System
  • The excretory system is vital to maintaining homeostasis
  • When it’s affected by a disorder, the proper functioning of other body systems may be jeopardized
urinary tract infection
Urinary Tract Infection
  • One of the most common disorders of the excretory system
    • If the bladder is infected, it is called cystitis
    • If only the urethra is infected, it is called urethritis
  • Urinary tract infections are more common in females than in males
    • Primarily due to difference in anatomy
    • In females, the urethra and anal openings are closer together, making it easier for bacteria to enter the urinary tract
urinary tract infection1
Urinary Tract Infection
  • Symptoms include:
    • A painful burning sensation during urination
    • A need to urinate frequently even when no urine is present
    • Bloody or brown urine
    • The upper abdomen or lower back may be tender
    • Chills, fever, nausea, and vomiting may occur
  • Have the potential to become serious
    • Can result in permanent damage to kidneys and possible kidney failure
  • Treatment is usually an antibiotic
    • In serious cases, surgery may be needed
kidney stones
Kidney Stones
  • Fairly common disorder involving the development of crystalline formations called kidney stones
  • Most kidney stones form due to excess calcium in the urine
    • About 85% of stones are made up of calcium compounds
kidney stones1
Kidney Stones
  • The following factors contribute to kidney stone formation:
    • Recurrent urinary tract infections
    • Insufficient water consumption
    • Low activity levels
  • Treatment varies depending on the size of the stones
    • Many stones pass through the urinary tract on their own
    • Depending on the cause of the stone formation, medications may be able to break down the crystals
    • If the stones are less then 20mm in diameter, ultrasound shock waves can be used to disintegrate the stones so they can be passed naturally in the urine
    • For larger stones, surgery may be needed to remove them
renal insufficiency
Renal Insufficiency
  • Renal insufficiency describes the state in which the kidneys cannot maintain homeostasis due to damage to their nephrons
  • Some causes of nephron damage include:
    • Kidney infection
    • High blood pressure
    • Diabetes mellitus
    • Polycystic kidney disease (PKD)
      • A genetic disorder in which cysts grow in the kidneys, impairing proper functioning)
    • Trauma from a blow to the lower back or constant vibration from machinery
    • Poisoning (either from skin contact, inhalation of fumes, or ingestion of contaminated food) by heavy metals such as mercury and lead or solvents such as paint thinners
    • Atherosclerosis (which reduces blood flow to the kidneys)
    • Blockage of the tubules
renal insufficiency1
Renal Insufficiency
  • Nephrons can regenerate and restore kidney function after short-term injuries
    • Even when some of the nephrons are irreversibly damaged, others can compensate for their lost function
    • A person can survive on as little as one third of one kidney
  • If 75% or more of the nephrons are destroyed, however, urine output is inadequate to maintain homeostasis
    • Under these circumstances, a person requires a means for replacing kidney function
    • This is achieved either with a kidney transplanted from a donor, is one is available, or with an artificial kidney that performs a blood-cleansing process called dialysis
hemodialysis and peritoneal dialysis
Hemodialysis and Peritoneal Dialysis
  • The diffusion of dissolved substances through a semipermeable membrane is referred to as dialysis
    • These substances more across a membrane from the area of high concentration to one of low concentration
    • Substances more concentrated in blood diffuse into the dialysis solution, called the dialysate
    • Substances more concentrated in the dialysate diffuse into the blood
  • Other substances can be added to the blood following this same principle
    • Ex: If the acid-base balance of the blood is off and the blood is too acidic, bicarbonate ions can be added to the dialysate where they will diffuse into the blood and reduce its acidity
hemodialysis and peritoneal dialysis1
Hemodialysis and Peritoneal Dialysis
  • There are two main types of renal (kidney) dialysis
  • Hemodialysis
    • Utilizes an artificial membrane in an external device (essentially an artificial kidney) that is connected to an artery and a vein in person’s arm
  • Peritoneal dialysis
    • Utilizes the lining of the intestines, called the peritoneum, as the dialysis membrane
    • Dialysate is introduced to the abdominal cavity, where the large surface area and rich supply of capillaries of the peritoneum slowly filter the blood
kidney transplants
Kidney Transplants
  • Dialysis enables people with kidney disease to continue many of their daily activities, such as going to a job or attending school
    • Dialysis is not a cure, and it’s not intended to be a long-term solution to the problem of kidney disease
  • Individuals with 10% or less kidney function will eventually have a replace their kidneys
    • The need for kidneys is much greater than the available supply
    • 75% of people waiting for in Canada are waiting for kidneys
kidney transplants1
Kidney Transplants
  • The success rate of organ transplantation, particularly of kidneys, is fairly high
    • Success rate of 95%-98%
  • Surgical techniques, such as the laproscopic surgery are constantly being improved
  • New medicines to prevent rejection of the new organ are constantly being developed and improved
the kidney coronary connection
The Kidney-Coronary Connection
  • High blood pressure is one of the main reasons that kidneys begin to fail
    • When blood pressure is high for a prolonged period of time, the heart must pump a greater volume of blood, and blood vessels can be damaged
  • The blood vessels in the kidneys are very sensitive to changes in blood pressure
    • If they become damaged by high blood pressure the amount of waste and extra fluid that can be filtered from the blood will be reduced
    • As the extra fluid accumulates in the body, it will increase the blood volume even more and cause the blood pressure to rise further
    • This cycle can continue until the kidney function is so reduced that symptoms become obvious
  • Unfortunately, both high blood pressure and kidney impairment don’t have obvious symptoms until the damage is well underway
the kidney coronary connection1
The Kidney-Coronary Connection
  • Maintaining a healthy lifestyle supports the overall health of all your body systems
  • None of these systems functions in isolation, so any activity that affects one of your systems will affect other systems as well
    • For example, ensuring that you have adequate physical exercise can help make your heart and circulatory system stronger and healthier
    • A stronger heart can pump more blood throughout the body with less effort
    • Reduced effort translates to less force on the arteries, keeping blood pressure low
    • High blood pressure has such an impact on kidney function that exercise to reduce blood pressure ultimately reduces the likelihood of kidney damage
evaluating kidney function
Evaluating Kidney Function
  • The composition of urine reflects the amounts of water and solutes that the kidneys must remove from or retain in the body to maintain homeostasis
  • Analyzing the physical and chemical composition of urine enables physicians to make reasoned inferences and hypotheses about a person’s health and kidney function
  • In fact, physicians have been using urinalysis as a tool for thousands of years
    • Examining the characteristics of urine, including colour, odour, and taste, gave clues as to the internal conditions of the person’s body
    • Ex: If the urine smelled sweet or fruity, it was usually a sign of diabetes (the overabundance of sugar in the blood led to an overabundance of sugar in the urine as your body attempted to expel the excess)
  • This table provides values for selected tests that are performed in a modern day urinalysis
  • These values are consistent with those of urine from a healthy adult
  • However, urine composition varies greatly over the course of a day due to factors such as:
    • Dietary intake
    • Physical activity
    • Emotional stress
    • Fatigue
  • Unhealthy constituents of urine may not necessarily indicate illness or disease
    • The presence of glucose in urine may result from a sugary meal
    • Proteins may appear in urine following vigorous exercise
    • Ketones (acids that result from the digestion of fats when the body lacks sufficient stores of carbohydrates) may result from a short-term fast or a specifically designed low-carbohydrate diet
  • Because so many factors can influence the presence and amounts of substances in urine, trained professionals must consider a wide variety of variable when evaluating a sample of urine
blood tests
Blood Tests
  • Blood tests can also reveal information about kidney function
  • For example, health professionals may screen the blood to measure the amount of urea nitrogen it contains
    • If levels are higher than normal, it can indicate that the kidneys are not working properly
    • When kidneys are functioning properly, urea is filtered from the blood
  • Another measurement that may be measured is the amount of creatinine in the blood
    • Creatinine is waste produced by muscles during metabolic processes
    • A high level indicates that the kidneys are not filtering it properly