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Biology 30S

THE EXCRETORY SYSTEM

(This workbook adapted from Manitoba Blackboard)

Student: ______________________

Instructor: _____________________

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Lesson 1: Excretory Organs

What goes in, must come out… This applies to living things. We started

our study of the human body with the digestive system. The digestive

system deals with the processes that involves taking in nutrients into the body and simplifying them so that they can enter the cells.

Whatever is left over, would be waste and need to be eliminated,

exhaled/expired, or excreted.

This unit deals with the excretion of the wastes from the circulatory

system. The liquid wastes are excreted through the excretory organs.

Every metabolic process in the human body uses energy and generates

wastes. If these waste products are not removed, they would quickly

accumulate in harmful proportions. In fact, some wastes are poisonous

and pose a serious threat to health if they are not removed promptly.

The process of getting rid of metabolic wastes is called excretion.

There are many organs and systems responsible for excretion. For

example, the skin removes salts and nitrogen-based wastes, the lungs remove carbon dioxide and the liver converts poisons and toxins to a

form that can be eliminated by the kidneys.

In the last unit, we studied the body’s blood and immune system and

the vital importance of these systems to your health. In this unit, we will

study the structure and function of the excretory system.

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Introduction

The human body is about 60% water. Two thirds of the water is in the

cells while the rest is in the fluid around the cells. The chemical

composition of this intercellular fluid must be carefully balanced. If it becomes too salty, the cells can become dehydrated. If it gets too

watery the cells can bloat. If too much acid or base accumulates, the

cells' enzymes can stop working. If metabolic wastes collect, the cells

can die of poisoning. Homeostatic mechanisms within the body keep

the chemical composition of the intercellular fluid constant when

conditions change.

Excretory systems regulate the chemical composition of these body

fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Components of the excretory system in

humans include the kidneys, liver, lungs, and skin.

How does excretion differ from the elimination of wastes from the digestive system?

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Outcomes

In this lesson, you will study the excretory organs and their importance in maintaining homeostasis in the body. By the end of this lesson, you

should be able to:

Define the term excretion.

Describe how excretion aids in maintaining homeostasis in the

body.

List the primary metabolic wastes produced in human body (i.e.,

carbon dioxide, water, ammonia, mineral salts) and the source of

each. Compare the role of the major excretory organs (kidneys, lungs,

skin, liver) in the excretory process.

Excretion and Homeostasis

Cells produce water and carbon dioxide as by-products of metabolic

breakdown of sugars, fats, and proteins. Chemical groups such as

nitrogen, sulfur, and phosphorous must be stripped, from the large

molecules to which they were formerly attached, as part of preparing

them for energy conversion. The continuous production of metabolic

wastes establishes a steep concentration gradient across the plasma membrane, causing wastes to diffuse out of cells and into

the extracellular fluid.

Multicellular organisms such as humans must have a specialized

organ system to concentrate and remove wastes from the interstitial

fluid and eventually from the body. The process of getting rid of

metabolic wastes is called excretion.

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Excretion aids homeostasis by removing metabolic wastes and

regulating the salt and water balance. The blood picks up carbon

dioxide, excess salts, nitrogen compounds, and any excess water that may be present in the interstitial fluid and carries them to the

excretory organs, which channel the wastes out of the body.

Therefore, the excretory system regulates volume of internal body

fluids as well as eliminates metabolic wastes from the internal

environment.

Fortunately, atoms and molecules do not wear out, but may be

changed or rearranged and used over and over again. Many of the

end products of various cell activities can be recycled and used in other processes. As a result, the amount of waste that actually

needs to be discharged from the body is very small in relation to the

amount of work done by all the cells of the human body.

Several organs take part in human excretion. The skin, lungs, liver,

and the transport system play very important roles. However, the

main excretory organs are the kidneys.

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The metabolic wastes produced and the organs that excrete them

are summarized in the table below.

Wastes Formed From Organ of

Excretion

1. Carbon Dioxide Cellular Respiration lungs

2. Water Cellular Respiration &

Dehydration Synthesis

kidneys, skin,

lungs

3. Nitrogenous

Wastes

Metabolism of Proteins (Amino

Acids)

kidneys, liver,

skin

a) Ammonia

(extremely toxic)

deamination of amino acids by

the liver

liver

b) Urea ammonia combined with

carbon dioxide

kidneys, skin

c) Uric Acid product of the breakdown of

nucleic acids, such as DNA

liver

4. Mineral Salts (NaCl, KSO4)

Metabolism of Various Food Substances

kidneys, skin

Table 7.1.1 Metabolic Wastes

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Lesson 1 Overview

Following is a list of topics covered in this lesson.

Excretion and Homeostasis

Skin and Homeostasis

Excretion in the Lungs

Role of Liver in Excretion

Kidneys: Major Organs of Excretion

Skin and Homeostasis

The skin has many functions in the body. These include protection, regulation of body temperature, sensory reception, water balance,

excretion, synthesis of vitamins and hormones, and absorption of

materials. The skin's primary functions are to serve as a barrier to

the entry of microbes and viruses, and to prevent water and

extracellular fluid loss.

Your skin has approximately 2 million sweat glands. These tiny,

coiled tubules are found in the dermis layer of skin, below the

surface layer or epidermis. See the diagram below.

http://www.nigms.nih.gov/news/features/artificial_skin.html

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These glands secrete sweat continuously, even when you are not

exercising. Sweat consists primarily of water, along with salts, and

some urea (nitrogen-based waste). These materials pass from the blood vessels in the skin into the sweat glands. The wastes travel up

the tubules and onto the surface of the skin through tiny openings

called pores. The wastes form perspiration on the skin, which

eventually evaporates. The solid wastes in the perspiration remain

on the surface of the skin or on clothing. Perspiration itself has no

odour. However, bacteria living on the skin decompose the urea in

perspiration, producing new compounds that do have odours.

Did you know that the skin and kidneys excrete the similar waste products? The composition of sweat and urine are very

similar (except urine is much more concentrated)!

Heat and cold receptors are also located in the skin. When the body

temperature rises, the hypothalamus, the region of the brain

responsible for coordinating many nerve and hormone functions,

sends a nerve signal to the sweat-producing skin glands, causing

them to release about 1-2 liters of water per hour, cooling the body

through evaporation. The hypothalamus also causes dilation of the blood vessels of the skin, allowing more blood to flow into those

areas, causing heat to be dissipated from the skin surface.

When body temperature falls, the sweat glands constrict and sweat

production decreases. If the body temperature continues to fall, the

hypothalamus will trigger the body to engage in thermiogenesis, or

heat generation, by raising the body's metabolic rate and by

shivering.

This is an excellent example of negative feedback mechanisms in

action.

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Excretion in the Lungs

Carbon dioxide and water are produced by all cells during cellular

respiration. The blood carries these to the lungs. Carbon dioxide

diffuses into the alveoli and is removed from the body when we exhale.

Some water also leaves the lungs as water vapour.

The lungs can also eliminate alcohol, which, since it is made up of small molecules, can be rapidly passed from the bloodstream into the alveoli

of the lungs and exhaled. This is why the breathalyzer test is an

effective and simple way of determining the amount of alcohol that

people have taken into their systems.

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Role of Liver in Excretion

Although, we obtain most of our energy from carbohydrates and fats,

we sometimes use proteins for energy. Some proteins and other

nitrogenous compounds are broken down in the liver by a process called deamination. The extraction of energy from proteins

produces ammonia (NH3), a highly toxic substance. The liver converts

ammonia to a non-toxic substance called urea by combining it with

carbon dioxide. The blood then delivers urea to the kidneys, where it is

excreted.

The liver also breaks down red blood cells. About 120 days after they

are formed, erythrocytes are destroyed by special cells in the liver.

These cells engulf the red blood cells and break down their hemoglobin. Iron released from the hemoglobin is carried by the blood to various

parts of the body. In the bone marrow the iron is used in the

manufacture of new hemoglobin. Another part of the broken down

hemoglobin is the yellow pigment bilirubin. This pigment enters the bile,

passes into the small intestine, and is eventually removed from the

body with the feces.

The liver is also responsible for removing potentially hazardous

chemicals from the blood. It "detoxifies" the blood. For this reason, alcoholics and other types of drug addicts have a higher incidence of

liver disease. The liver breaks down harmful and foreign substances,

such as many ingested poisons and drugs after they are absorbed by

the digestive system and before they reach the rest of the body. Since

the liver has the enzymes to break down the natural materials, it is also

able to destroy certain drugs. This function can be life-saving, because it makes destructive substances harmless, and prevents hormones,

medications, and other chemicals from accumulating to harmful levels.

Cortisone and sulfur-containing medicines are examples of drugs that

the liver breaks down.

The liver's ability to make substances harmless has limits. Materials can

accumulate in the liver and destroy its tissues. For example, alcohol

taken in excess over a period of time can deteriorate the liver.

Pollutants, such as PCBs (polychlorinated biphenyls) and pesticides, such as DDT, can also harm the liver.

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Kidneys: Major Organs of Excretion

The kidneys are the major organs of excretion in the human body. They

form part of the urinary system and function primarily in filtering wastes

from the blood. The kidneys also play a key role in fluid balance in the

body.

In the next lesson, you will study the urinary system and the function of

the kidneys in detail.

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Lesson 1 Questions

Please answer the following six questions.

1. Define the term excretion.

2. Describe two ways that excretion contributes to homeostasis?

3. Complete the following table.

Wastes Formed From Organ of Excretion

1. Cellular Respiration lungs

2. Water Cellular Respiration &

Dehydration Synthesis

3. Nitrogenous

Wastes

Metabolism of Proteins (Amino

Acids)

kidneys, liver,

skin

a) Ammonia

(extremely toxic)

liver

b) ammonia combined with carbon dioxide

kidneys, skin

c) Uric Acid product of the breakdown of

nucleic acids, such as DNA

4. Mineral Salts

(NaCl, KSO4)

Metabolism of Various Food

Substances

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4. Describe the role of the skin in temperature regulation of the

human body.

5. How does the formation of urea prevent poisoning?

6. Why is it said that the liver "detoxifies" the body?

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Activity - Mammalian Diving Reflex

What happens to the heart rate when a person falls into cold water?

Test the mammalian diving reflex with this activity and see how your

body responds.

Materials: pan filled with about 8 cm of cold water, stopwatch or clock

with second hand, towel, partner

1. Have your partner measure your resting pulse for 15 seconds and

calculate your beats per minute.

2. Hold your breath and submerge your face in the pan of cold water

for 15 seconds. Before you start, predict what will happen to your pulse rate. Have your partner measure your pulse rate for the 15

seconds that your face is submerged. Calculate your beats per

minute.

3. Switch roles and repeat the procedure.

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Answer the following questions:

1. What happens to your pulse rate when your face

is submerged in water?

2. Why do you think this happens?

3. How might this help someone who has fallen

into very cold water?

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Lesson 1 Summary

In this lesson, you have studied that excretory systems regulate the

chemical composition of body fluids by removing metabolic wastes and

retaining the proper amounts of water, salts, and nutrients. You have also learned about the role of the liver, lungs, and skin in excretion. In

the next lesson, you learn about the role of the urinary system in

maintaining homeostasis.

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Lesson 2: The Urinary System

The kidneys remove metabolic wastes from the body by filtering the

blood. The entire blood volume is filtered through the kidneys about 65

times per day by way of the renal arteries. After the blood is cleaned, it flows back into the body through the renal veins. The kidneys work

continuously, processing all of the blood in the body every 20 minutes.

At this rate, every 24 hours the kidneys filter approximately 325 litres of

blood. Of these 325 litres, only 1 to 2 litres of fluid are excreted as urine.

In the last lesson, you studied the function of the skin, lungs and liver in

excretion. In this lesson, you will study the role of the urinary system in

excreting wastes and balancing fluids in your body.

Outcomes

When you have completed this lesson, you will be able to:

Identify on a diagram or model and describe the function of the

following structures of the human urinary system:

o kidneys

o renal cortex o renal medulla

o renal pelvis

o renal arteries and veins

o ureters

o urinary bladder

o urethra

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Identify from a diagram or model and describe the function of the

following structures of the nephron:

o afferent and efferent arterioles

o glomerulus o Bowman's capsule

o proximal convoluted tubule

o peritubular capillaries

o Loop of Henle

o distal convoluted tubule

o collecting duct

Differentiate between the terms filtration, reabsorption, and

secretion as they relate to nephron function.

Analyze and compare water and solute concentrations in various

parts of the nephron and urine.

Describe the role of antidiuretic hormone (ADH) in maintaining

water balance in the body.

Describe the role of aldosterone in maintaining blood pressure in

the body.

Explain the effect of diuretics such as caffeine and alcohol on

water loss.

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Lesson 2 Overview

Following is a list of topics covered in this lesson.

The Urinary System

Importance of Kidneys

Structure of Kidneys

Nephron Kidney Function

Kidneys and Water Balance

Kidneys and Blood Pressure

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The Urinary System

The human urinary system consists of two kidneys, two ureters, the

urinary bladder, and the urethra. Normally, there are two of kidneys,

one on either side of the spine under the lower ribs. The ureters lead from the kidneys to the urinary bladder, which lies low in the abdominal

cavity. The urethra extends from the bladder to the exterior of the body,

carrying urine through the urogenital organs, either the penis or vagina.

Refer to the diagram below.

Figure 7.2.1 Urinary System

http://www.kidney.ca/publications-eng.htm

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Importance of Kidneys

Your kidneys are important because they do these essential things.

1. Regulate water

For your body to work properly, it must contain just the right

amount of water. One of the important jobs of the kidneys is to

remove excess water from the body or to retain water when the

body needs more.

2. Remove wastes

Many of the substances in the blood and body fluid must be kept

at the correct level for the body to function properly. For example,

sodium and potassium are minerals which come from food. These

minerals are needed by the body for good health, but they must

be kept at specific levels. When the kidneys are working properly,

excess minerals, such as sodium and potassium, are excreted

from the body in the urine. The kidneys also help to regulate the

levels of other minerals, such as calcium and phosphate, which

are important for the formation of bone.

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3. Wastes, such as urea and creatinine, must also be removed from

the body. Urea and other wastes are made when the body breaks

down protein, such as meat. Creatinine is a waste product of the

muscles. As kidney function decreases, the levels of urea and

creatinine in the blood increase. Many waste products are toxic

(poisonous) if they are not removed from the body fluids. For

example, when certain drugs are taken, chemical wastes are

produced which must be removed from the body by the kidneys.

4. Produce hormones

Normal kidneys also make important chemical messengers called

hormones. These hormones circulate in the bloodstream and

regulate some body functions such as blood pressure, the making

of red blood cells, and the uptake of calcium from the intestine.

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Structure of Kidneys

Kidneys are reddish brown in colour and shaped like kidney beans.

Each kidney is about the size of your clenched fist. If you were to cut a

kidney in half, you would see the following parts:

renal capsule - a thin, outer membrane that helps protect the

kidney

cortex - a lightly colored outer region

medulla - a darker, reddish-brown, inner region

renal pelvis - a flat, funnel shaped cavity that collects the urine

into the ureters

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Figure 7.2.2 Kidney Structure

Image from Purves et al., Life: The Science of Biology, 4th Edition, by

Sinauer Associates

(www.sinauer.com) and WH Freeman (www.whfreeman.com)

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Nephron

The working units of the kidney are microscopic structures

called nephrons. Each kidney contains about one million nephrons. A nephron contains a network of capillaries called the glomerulus, which

filters blood into a cup-shaped structure known as the Bowman's

capsule. The filtrate then passes into a series of tubules. Water and

waste products are separated from the blood by the filtering process

and the flow into and out of the tubules. Much of the water is

reabsorbed by the tubules and the wastes are concentrated into urine.

Figure 7.2.3 Nephron Location

http://www.kidney.ca/publications-eng.htm

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The main parts of the nephron are as follows:

Glomerulus - coiled capillaries inside the Bowman's capsule.

Bowman's (Glomerular) capsule - closed end at the beginning of

the nephron. It is located in the cortex.

Proximal convoluted tubule - first twisted region after the

Bowman's capsule. It is also in the cortex.

Loop of Henle - long, loop after the proximal tubule. It extends

from the cortex down into the medulla and back.

Distal convoluted tubule - second twisted portion of the nephron

after the loop of Henle. It is also in the cortex.

Collecting duct - long straight portion after the distal tubule that is

the open end of the nephron. It extends from the cortex down

through the medulla.

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Figure 7.2.4 Nephron Structure

http://botany.indstate.edu/hughes/endo/412pics/

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The nephron also has a unique and rich blood supply compared to

other organs. They are listed below.

Renal artery - supplies blood to the kidney from the circulatory

system

Renal vein - returns blood from the kidney to the circulatory

system

Afferent arteriole - connects the renal artery with the glomerular

capillaries.

Efferent arteriole - connects the glomerular capillaries with the

peritubular capillaries.

Peritubular capillaries - located after the glomerular capillaries and

surrounding the proximal tubule, loop of Henle, and distal tubule.

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Draw the nephron and label the parts. Identify what happens in each

part.

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Kidney Function

Many of the substances in the blood and body fluids must be kept at the

correct level for the body to function properly. Regulating the

composition of these fluids involves the following:

Keeping the concentrations of various ions and other important

substances constant.

Keeping the volume of water in your body constant.

Removing wastes from your body.

Keeping the acid/base concentration of your blood constant.

The kidney performs these functions by a combination of:

Filtration - the passage of substances through the capillaries of

the glomerulus into Bowman's capsule. Reabsorption - the transfer of essential solutes and water from

the nephron back into the blood

Secretion - the movement of materials from the blood back into

the nephron.

Anything (fluid, ions, small molecules) that has not been reabsorbed

from the nephron gets swept away to form the urine, which ultimately

leaves the body. Through these processes, the blood is maintained with

the proper composition, and excess or unwanted substances are

removed from the blood into the urine. See diagram below.

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Figure 7.2.5 Filtration, Reabsorption and Secretion

http://www.sirinet.net/~jgjohnso/urinary.html

Filtration

The blood supply to the kidneys is carried by the large renal arteries

(right and left). These large vessels divide into many smaller vessels as

soon as they enter the kidneys. The result of the decrease in diameter

of the artery is to produce an increase in the pressure of the blood. In

addition, the efferent arterioleleaving the Bowman's capsule is considerably smaller than the afferent arteriole which delivers blood to

Bowman's capsule. This increases the blood pressure within the

glomerulus. In the kidney, blood pressure in the capillaries is 60 to 70

mm Hg, whereas elsewhere in the body capillary blood pressure is only

25 mm Hg or less. As a result of this high pressure in the glomerulus,

about 20% of the blood plasma entering the kidneys is passed rapidly

and easily into Bowman's capsule, creating a filtering effect.

The substances that pass from the glomerulus into Bowman’s capsule comprise what is called the filtrate. Blood cells and large protein

molecules are too large to pass through the tiny pores in the capsule

capillaries. Other substances such as, salts, sugars, water, and wastes

are composed of smaller molecules and can pass easily through the

pores to enter the capsule. About 80% of the plasma component of the

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blood entering the kidney is left behind and does not become part of the

filtrate, but re-enters the bloodstream.

Reabsorption

The filtrate that enters Bowman's capsule contains metabolic waste

products and other materials not needed by the body. It also however, contains salts, water, amino acids, and other useful substances which

must be retained and recycled back into the blood.

Sometimes it is necessary to move molecules from an area of low

concentration to an area of high concentration. Such movement is

known as active transport. It requires energy and the presence of

special carrier molecules, which temporarily associate with the

substance to help it pass through a membrane.

As the filtrate passes through the proximal tubule of the nephron,

glucose, amino acids, and some salts are reabsorbed back out of the

tubules into the bloodstream by active transport. The efferent arteriole, which leaves the glomerulus, branches out into a network of capillaries

called the peritubular capillaries which surround the tubules. It is this

bed of capillaries that is constantly reabsorbing the needed products

from the filtrate and enabling them to re-enter the bloodstream. The

waste substances remain in the tubules, becoming gradually more

concentrated until they are formed into urine.

The cells of the proximal tubule are filled with mitochondria which

produce energy for active transport to take place. The cells of the proximal tubules also contain microvilli which increase the efficiency of

absorption by increasing the surface area of the tubule.

As salts (and ions) are forced out of the proximal tubule, the

concentration of the filtrate changes. Eventually, there are more salts

outside the tubule and more water inside the tubules. This establishes

the condition under which normal diffusion takes place; water then flows

out of the tubules by osmosis and is reabsorbed into the capillaries.

Water continues to diffuse out of the top portion of the descending loop

of Henle. However, water does not pass out of the remainder of Henle's

loop. Sodium ions (Na+) are moved out of the ascending portion of the loop by active transport, into the intercellular fluid. The walls of the

ascending loop of Henle are impermeable to water, so no water leaves

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the loop as it would if the membrane did not block it. Sodium ions

diffuse into the descending loop and increase the concentration of the

filtrate there, so that a point is reached when the concentration of dissolved materials in the filtrate is equal to or greater than the

concentration of the blood in the nearby capillaries and water ceases to

diffuse out. The diagram below summarizes this process.

Figure 7.2.6 Reabsorption

www.columbia.edu/cu/biology/courses/w2501/kidney_notes.html

Secretion

Secretion is the movement of wastes from the blood into the nephron.

Nitrogen-containing wastes, excess hydrogen ions, and other minerals

are balanced by secretion. Even drugs such as penicillin can be

secreted. Cells loaded with mitochondria line the distal tubule. Like reabsorption, tubular secretion occurs by active transport, but unlike

reabsorption, molecules are transferred from the blood into the

nephron.

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Kidneys and Water Balance

As mentioned earlier in the lesson, for your body to work properly, it

must contain just the right amount of water. One of the important jobs of

the kidneys is to remove excess water from the body or to retain water

when the body needs more.

Water conservation by the kidney is controlled by a hormone called antidiuretic hormone or ADH. ADH is produced in the pituitary

gland in the brain. Low water levels in the blood signals the pituitary to

release more ADH. The blood carries the ADH to the kidneys and

increases the permeability of the tubule cell membranes to water

causing more water to be reabsorbed from the tubule into the blood,

producing more concentrated urine. If, on the other hand, a person has too much water, less ADH is released. Then the cell membranes of the

tubules become impermeable to water. As a result, they do not allow

water to return to the blood and the urine is very dilute.

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Kidneys and Blood Pressure

The kidneys play a role in the regulation of blood pressure by adjusting

for blood volumes. A hormone called aldosterone acts on the nephrons

to increase sodium ion reabsorption. This hormone is produced in the cortex region of the adrenal glands that lie on the upper surface of the

kidneys. As Na+ reabsorption increases, the osmotic gradient increases

and more water moves out of the nephron by osmosis.

Low blood pressure through the body (resulting perhaps from loss of

blood through a wound or loss of water and salts in diarrhea) is

reflected in a lowering of the blood pressure in each glomerulus of the

kidneys. This decreases the amount of plasma that leaves the

glomerulus and enters the Bowman's capsule. Accordingly, this lowered blood pressure decreases the amount of water and salts filtered into the

kidney tubules, helping to conserve them.

High blood pressure results in an increase in the volume of filtrate in the

glomeruli (plural form of glomerulus) and the excretion of more water

and salts from the body. However, the activities of the tubule cells

increase in an attempt to cause more water and salts to be reabsorbed

into the bloodstream.

While we think of the kidney as an organ of excretion, it is more than

that. It does remove wastes, but it also removes normal components of

the blood that are present in greater-than-normal concentrations. When excess water, sodium ions, calcium ions, etc. are present, the excess

quickly passes out in the urine. On the other hand, the kidneys can step

up their reclamation of these same substances when they are present

in the blood in less-than-normal amounts. Thus the kidney continuously

regulates the chemical composition of the blood within narrow limits.

The kidney is one of the major homeostatic devices of the body.

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Lesson 2 Questions

1. Label the following diagram.

2. Describe the three main functions of the kidneys.

3. What are the functional units of the kidney?

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4. List the function of the following structures:

a. Glomerulus

b. Bowman's (Glomerular) capsule

c. Proximal convoluted tubule d. Loop of Henle

e. Distal convoluted tubule

f. Collecting duct

g. Renal artery

h. Renal vein

i. Afferent arteriole j. Efferent arteriole

k. Peritubular capillaries

5. Label the following diagram. Also, indicate the processes associated with the green, blue and red arrows..

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6. List and explain the three main processes that are involved in

urine formation.

7. Place the following processes in the correct order.

a. urine is stored in the bladder.

b. blood enters the afferent arteriole c. fluids pass from the glomerulus into Bowman’s capsule

d. urine is excreted by the urethra

e. sodium ions, glucose and amino acids are actively

transported from the nephron to the bloodstream

f. water is diffused from the nephron to the bloodstream

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8. How do the blood vessels in the glomerulus contribute to

filtration?

9. Explain the role of ADH in water balance.

10. How does the kidney contribute to the maintenance of blood

pressure?

11. A micropipette was used to extract fluids from various structures within the kidney. The data in the following table is an

analysis of the substances collected. All quantities are in g/mL.

Answer the following questions providing an explanation for each.

Substance

found in body

fluid

Blood plasma

from afferent

arteriole

Glomerular filtrate

from Bowman’s

capsule

Urine

protein 7.00 0.00 0.00

urea 0.04 0.04 2.00

glucose 0.10 0.10 0.00

sodium ions 0.32 0.32 0.35

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12. a. Which substance is not filtered from the blood into

Bowman’s capsule?

b. Which substance provides evidence of secretion?

c. Which substance provides evidence of reabsorption?

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Research Assignment

Investigate the effects of caffeine and alcohol on water loss. Can you relate these findings to the so-called "hangover"?

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Lesson 2 Summary

In this lesson, you have studied the role of the urinary system in

excreting wastes and balancing fluids in your body. In the next lesson,

you will study some of the major disorders that effect the urinary system. You will also examine some of the treatments available for

these disorders and consider the issues surrounding kidney transplants.

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Lesson 3: Diseases and Disorders

Did you know?

Kidney disease can strike anyone at any age.

Every day an average of 10 Canadians learn that their kidneys

have failed and that their survival depends on dialysis or a kidney

transplant.

Kidney diseases rank 6th among diseases causing death in

Canada.

Leading causes of kidney failure are diabetes, renal vascular

disease (including high blood pressure), and glomerulonephritis

(inflammation of the tiny filters in the kidney which clean the

blood).

People aged 65 to 74 are the fastest growing group newly

diagnosed with kidney failure.

At the end of 2001, 3,500 Canadians were on a waiting list for an

organ transplant. Of those, 80 % were waiting for a kidney.

In 2002 there were 25,000 Canadians with kidney failure who are

living with dialysis or a kidney transplant.

In the last lesson, you studied the function of the urinary system in

maintaining homeostasis in the body. In this lesson, you will study some

common disorders and diseases that can upset the homeostatic

balance of the urinary system.

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Outcomes

When you have completed this lesson, you will be able to:

Describe how the following diseases/disorders affect the urinary

system:

o diabetes (Type I and II)

o nephritis o kidney stones

o urinary tract infection

o high blood pressure

Explain the function of the kidney dialysis machine.

Identify urinary system disorders through urinalysis results.

Discuss patient options when kidney failure occurs (i.e. kidney

dialysis technology, organ transplant).

Lesson Overview

Following is a list of topics covered in this lesson.

Kidney Disease

Diabetes

Nephritis

Kidney Stones

Urinary Tract Infections

High Blood Pressure

Kidney Failure

Dialysis

Kidney Transplant

Testing for Healthy Kidney Function

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Kidney Disease

Proper urinary and kidney function is essential for maintaining

homeostasis in the body. Kidney disease usually progresses silently,

often destroying most of the kidney function before causing any symptoms. Therefore, people at risk of developing kidney disease

should be evaluated regularly. These people include those with

diabetes, high blood pressure or blood vessel diseases, and close

relatives of people with hereditary kidney disease. Sometimes even

people with serious kidney disease may not have any symptoms. That

is why a blood or urine test may be necessary to check for kidney

problems.

Some of the Signs and Symptoms That May Indicate Kidney Disease

High blood pressure (hypertension)

Puffiness of the eyes, hands and feet Passage of bloody, cloudy or tea-coloured urine

Presence of protein in the urine

Excessive foaming of the urine

Frequent passing of urine during the night

Passing less urine or difficulty passing urine

Fatigue Loss of appetite or weight

Persistent generalized itching

When the kidneys fail, wastes and fluids accumulate in your body. As a

result, you need dialysis treatments or a kidney transplant.

We will now explore some of the most common disorders of the urinary

system.

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Diabetes

Diabetes is the most common cause of kidney failure, accounting for

more than 40 percent of new cases. Diabetes is a disease which is caused by the lack of insulin in the body or the body's inability to

properly use normal amounts of insulin. The body converts the food we

eat into sugar (glucose). The body needs this sugar, in the form of

energy, to perform its functions. The hormone insulin, produced by the

pancreas, regulates the amount of glucose (sugar) in the blood. If the

body lacks insulin or does not use the insulin properly, then this imbalance results in high blood sugar. Eventually, many unhealthy

changes can occur in different body organs, including the kidneys.

Even with the use of injected insulin, people who have had diabetes for

some time often suffer from damage to the small blood vessels of the

body. This may cause damage to the retina of the eye and result in loss

of vision. Also, the delicate blood vessels in the nephrons of the kidney

may be damaged. At the early stage, this damage is shown by finding

protein in the urine.

Sometimes at a later stage, so much protein is lost from the blood that

water from the blood moves into the body tissues and causes swelling (edema). After a number of years, the kidneys' nephrons can become

so damaged by diabetes that the kidneys fail. Because smoking also

damages the blood vessels, it worsens the complications of diabetes.

People with diabetes should try to stop smoking completely.

Diabetes can also damage the nerves in many parts of the body. When

the bladder is affected, it may be difficult to pass urine. If urine builds up

in the bladder, the pressure can cause it to back up to the kidneys

causing damage there.

The urine of people with diabetes has high sugar content. This

encourages the growth of bacteria and kidney infections may occur. People with diabetes must take special care to avoid infections and

have them treated immediately.

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There are different types of diabetes. The most common ones are Type

1 and Type 2.

Type 1 - Juvenile Onset Diabetes

Occurs mainly in young people

Is caused by an inability of the pancreas to produce enough

insulin

Requires regular insulin injections

Type 2 - Adult Onset Diabetes

Usually develops in people over the age of forty (usually

overweight people)

The pancreas produces close to normal amounts of insulin, but

the body is unable to use it properly

Making proper food choices and/or taking oral medication can

control the abnormal blood sugar level

About 40% of people with Type 1 diabetes (juvenile onset) and 10% of

people with Type 2 diabetes (adult onset) will eventually develop kidney disease which will lead to permanent chronic renal insufficiency (kidney

failure).

A person could have serious kidney damage without being aware of it.

There are usually no specific symptoms of diabetic kidney disease until

the kidneys fail completely. However, there are certain early signs or

risk factors to watch for:

High blood pressure (over 130/85 mm Hg*) or a family history of

high blood pressure

Protein in the urine

Burning or difficulty during urination

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Nephritis

Nephritis, also called Glomerulonephritis (GN) is a disease of the

kidneys in which the glomeruli, the tiny filters in the kidneys that help to

clean the blood, become inflamed or damaged. This allows protein and

red blood cells to pass into the urine.

If glomerulonephritis does not respond to treatment, the glomeruli may slowly be destroyed and the kidneys may lose their ability to clean your

blood.

As we studied in the last lesson, each kidney consists of about a million

tiny units called nephrons. Each nephron is made up of a very small

filter called a glomerulus which is attached to a tubule. The glomeruli

clean the blood by filtering out excess water and waste products. In a

normal kidney, the glomeruli allow small-sized waste products to be

filtered out of the blood, while at the same time preventing protein and

red blood cells from passing into the urine.

Glomerulonephritis has many different causes. These include infection, certain drugs, and in rare cases, even cancer. However, in the great

majority of cases, the cause is unknown. Most cases of

glomerulonephritis are sporadic. This means the disease arises

spontaneously and is not inherited.

There is some evidence that GN may be caused by a problem in the

body's immune system. This system protects the body against invasion

by foreign materials such as viruses and bacteria. However, if the

immune system is not working properly, it may harm the kidneys. The immune system may mistakenly attack the kidneys' filters (glomeruli)

and cause them to become inflamed.

There are many types of glomerulonephritis. These may be grouped as

primary and secondary. In primary GN, only the kidneys are affected. In

secondary GN, the kidneys are damaged as part of a more generalized

disease that can affect other parts of the body.

The exact diagnosis can be made by a test called a kidney biopsy. This

is a medical procedure in which a very tiny tissue sample from one

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kidney is removed using a special needle. This tissue sample is

examined to determine the pattern of kidney damage, and to give more

information about the type of GN. A kidney biopsy is not required for

every patient so a kidney specialist will decide whether one is needed.

Unfortunately, the presence of glomerulonephritis is difficult to detect. In early stages, there may be no symptoms or signs of the disease. A test

to measure the protein and red blood cells in the urine will confirm

whether or not a person has GN.

As the disease progresses, the following symptoms may become

evident:

high blood pressure

excessive foaming of the urine

change in the colour of the urine (to red or dark brown)

puffiness of the eyes, hands and feet

nausea and vomiting difficulty breathing

headaches

In mild cases, kidneys may recover on their own, or following specific

treatment. Even if the disease is more advanced, it may be slowed by

lowering blood pressure with medication and by making changes in diet.

A kidney specialist may recommend other specific treatments as well. In

rare cases, temporary dialysis treatments (to clean your blood) may be

needed until the kidneys respond. However, in some cases when the damage is severe, the kidneys become unable to perform their usual

functions adequately, and eventually regular dialysis treatments or a

kidney transplant may be required.

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Kidney Stones

A kidney stone can develop when certain chemicals in urine form

crystals that stick together. The crystals may grow into a stone ranging

in size from a grain of sand to a golf ball. Small stones can pass through the urinary system without causing problems. However, larger

stones might block the flow of urine or irritate the lining of the urinary

tract.

Most stones form in the kidney and some travel to the ureter or bladder.

Most stones (70 to 80 percent) contain mainly calcium oxalate crystals.

A smaller number are uric acid stones or cystine stones.

One out of ten Canadians will have a kidney stone at some point in their

life. Kidney stones occur much more commonly in men than in women.

They tend to affect people in middle age, and occur more frequently hot

climates.

Normally, urine contains chemicals which prevent crystals from forming.

However, some people seem to be more prone to kidney stones than others. If you are prone to kidney stones, there are several factors

which contribute to their formation:

Recurrent urinary tract infections

Drinking too little fluid

Blockage of the urinary tract

Limited activity for several weeks or more

Consuming too much calcium oxalate or uric acid in your diet

Consuming too much Vitamin C or D Certain medications

Certain metabolic diseases

Symptoms of kidney stones include:

Severe pain that usually starts suddenly in the small of the back under the ribs or in the lower abdomen, and which may move to

the groin; the pain may last for minutes or hours, followed by

periods of relief.

Blood in the urine

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Nausea and vomiting

Sometimes, stones can also develop if a person has a persistent kidney

infection. If there is a urinary tract infection, symptoms may include:

Burning during urination and the urge to urinate frequently

Cloudy or foul-smelling urine

Fever, chills and weakness

Kidney stones are diagnosed by a complete medical examination, X-

rays and other tests. A doctor will usually start with a physical

examination and asking questions about past kidney illness, diet, use of medications, lifestyle and family background. An X-ray of the kidneys,

ureters and bladder can reveal the presence of most stones.

Sometimes, stones which are less common can be seen using dye

injections or an ultrasound test. Blood and urine tests may be needed to

find out what is causing the stones to form.

Most small stones pass through the body by themselves within hours or

a few days. To help this process, a doctor may advise the patient to

drink a lot of fluids and follow a special diet. Medication may also be prescribed. Certain types of stones can be dissolved using medication.

However, the most common stones (those containing calcium) cannot

be dissolved.

Stones that do not pass by themselves are treated with Extra-corporeal

Shock Wave Lithotripsy (ESWL). This treatment is a non-surgical

technique which uses high energy shock waves to break the stones into

small fragments (about the size of grains of sand). They can then be

passed during urination during the next few weeks. This treatment is successfully used in many cases where the stones are less than two

centimetres in size. When stones are larger than two centimetres, a

surgical procedure is often needed.

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Kidney stones recur in about 50 percent of cases. There are steps that

can be taken in consultation with a doctor and a dietitian, to help

prevent this from happening.

Drink a glass of water every hour during the day and whenever

you get up at night. Be sure to drink plenty after meals and exercise.

If you have calcium oxalate stones, do not consume very large

amounts of dairy products or foods high in oxalate content (such

as tea or chocolate). Do not take very large doses of Vitamin C (4

grams or more daily) and avoid heavy use of antacids.

If you have uric acid stones, cut down on the amount of red meat

you eat.

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Urinary Tract Infections

The urinary tract is made up of the kidneys, the ureters, the bladder and

the urethra. Each plays an important role in helping the body eliminate

waste products in the form of urine. The main job of the kidneys is to remove wastes from the blood and return the cleaned blood back to the

body. The ureters carry the waste products, as urine, from the kidneys

to the bladder. Urine is stored in the bladder until urination. It passes

out of the body through a tube called the urethra.

A urinary tract infection (UTI) is an inflammation usually caused by

bacteria attacking the kidneys, ureters, bladder or urethra. Under

normal circumstances the urinary tract is free of bacteria. A UTI most

often occurs when bacteria enter the urethra and travel to the bladder, causing a bladder infection. A kidney infection results if bacteria climb

further from the bladder to the kidneys. The bacteria that most often

cause UTIs sit on the skin in the genital area and are called Escherichia

coli (E. coli).

Although this is by far the most common cause, there are other ways

the body can get a UTI. Some people get an infection because the

normal flow of urine is blocked, or is backed up from the bladder into

the kidneys. Sometimes kidney or bladder stones can cause repeated infections. In rare cases, bacteria can reach the kidneys through the

bloodstream.

People are more inclined to get a UTI if they have an abnormal urinary

tract. People are also more susceptible to develop a UTI during

pregnancy, if they have diabetes or if they have an indwelling urinary

catheter (a tube placed in the bladder to help drain urine).

Women have a much greater tendency than men to get a UTI. In fact,

Canadian women make about 500,000 visits to doctors per year, due to

UTIs.

Women are more prone than men to develop UTIs because a woman's

urethra is much shorter than a man's, and bacteria have a shorter

distance to travel from the outside into the bladder. If a woman is prone to developing bladder infections she should avoid wiping her genitals

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from back to front as this might transport bacteria from the anus to the

vagina or urethra, causing infection.

Pregnant women are at increased risk of having a bladder infection

progress and develop into a kidney infection. The drainage system from

the kidney to the bladder dilates during pregnancy and does not empty as rapidly. This reduced flow of urine makes it easier for bacteria to

climb from the bladder to the kidney and for infection to set in. UTIs

during pregnancy may result in a smaller, premature baby.

After menopause, UTIs might increase due to a lack of certain

hormones. An increase in sexual activity might trigger symptoms of a

urinary tract infection in some women. Bladder and kidney infections

are generally not transmitted by sexual intercourse.

Bladder infection (cystitis) is the most common UTI. Symptoms include:

Feeling an urgent need to pass urine often, although the amount

of urine may be small

Burning during urination

Cloudy or foul-smelling urine

Pain in the lower abdomen

If a person also suffers from any of the following, they might have an

infection of the kidneys or prostate gland:

Blood or pus in the urine Fever, chills or vomiting

Diabetes or chronic illness

A history of kidney infection or disease

Pain on urination during pregnancy

Bad back pain

In some cases a person might have mild symptoms (e.g. urge to urinate

frequently), without having a UTI. Smoking, anxiety, drinking a lot of

coffee, food allergies or premenstrual syndrome may cause symptoms similar to a UTI. If mild symptoms have not disappeared within a day or

two, then a urine test is recommended. Infections are usually treated

with antibiotics.

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High Blood Pressure

Proper control of high blood pressure can prevent many of its

complications. If high blood pressure is not well-controlled, it can lead to

stroke, heart attack, heart failure, kidney failure (also called chronic renal insufficiency), and damage to the blood vessels of the legs

leading to amputation.

If a person has diabetes as well as high blood pressure, they must be

especially careful about blood pressure control. For people with kidney

disease, blood pressure control can slow down the decrease in kidney

function.

Some people who already have kidney disease can develop high blood

pressure. The opposite is also true: people with high blood pressure

can develop kidney disease. In fact, high blood pressure is the cause of

kidney failure in about 10% of new patients. High blood pressure

damages the blood vessels of the kidneys. This reduces the blood

supply to the kidneys so they are unable to remove fluids and waste products from the blood. This can lead to kidney failure. When the

kidneys fail, dialysis treatment or a kidney transplant is needed.

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Kidney Failure

Acute kidney failure occurs when kidneys fail suddenly. In this situation,

kidney function usually returns to normal, but dialysis may be needed

until the kidneys begin to work again. There are a number of reasons

why acute kidney failure happens.

Slow and progressive deterioration of kidney function is called chronic kidney failure or chronic renal insufficiency (CRI). It is usually

irreversible. Chronic kidney failure occurs when the tiny filters in the

kidney (nephrons) that remove wastes stop working. Damage to the

nephrons can be caused by conditions such as diabetes and high blood

pressure. In some cases, control of these conditions may slow or even

prevent the development of complete kidney failure.

There is no cure for chronic renal insufficiency. In the early stages,

proper food choices, medications and good blood pressure control may be all that is required to slow the damage to the kidneys. However,

once the kidneys are functioning at less than 10-20% of their normal

rate, either dialysis or transplantation is needed to keep on living. This

period is called end-stage renal disease or ESRD.

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Dialysis

Dialysis is a way to clean the blood by removing wastes and excess

water. There are two types: hemodialysis and peritoneal dialysis.

During hemodialysis, the blood is passed through an artificial kidney.

The artificial kidney cleans the blood in almost the same way that

healthy kidneys do. The treatment is performed usually three times a week. It can take between three and five hours each time and is called

a run.

Figure 7.3.1 Dialysis Machine

http://www.kidney.ca/publications-eng.htm

Hemodialysis can be done in a hospital dialysis unit, in a self-care

centre (with some assistance from the staff), or at home with the aid of

a partner. Special training is required for self-care or home dialysis.

Peritoneal dialysis works on the same principle as hemodialysis, but the blood is cleaned inside the body rather than through an artificial kidney.

Your abdomen or "belly" has a peritoneal cavity lined by a thin

membrane called the peritoneum that surrounds the intestines and

other internal organs.

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In peritoneal dialysis, your peritoneal cavity is filled with a special

dialysis fluid. Excess water and wastes pass through the peritoneum

into the dialysis fluid. This fluid is then drained from the body and discarded. The process is repeated between four to five times a day

(continuous ambulatory peritoneal dialysis, CAPD), or a machine called

an automatic cycler can perform exchanges while you sleep. In most

cases, this treatment can be performed without assistance, at home or

at work. Peritoneal dialysis is sometimes done in a hospital, but more

often, you are trained to do this independently at home.

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Kidney Transplant

A kidney transplant is a surgical procedure in which a healthy donated

kidney is transplanted into another body. A successful kidney transplant

will allow the person to return to a more normal lifestyle and will free them from dialysis treatments. However, a kidney transplant is not a

cure. It is the treatment of choice for chronic renal insufficiency for those

who are considered suitable candidates for a transplant.

There are two types of kidney transplants: a living donor transplant and

a cadaveric transplant.

In a living donor transplant, a kidney from a donor, usually a blood

relative is transplanted. The most suitable donors are usually members

of the immediate family. Sometimes a spouse, distant relative, or close

friend can also be a suitable donor.

The donor's blood group and tissue type must be compatible, and

extensive medical tests will be done to determine the health of the

donor. People who donate a kidney can live a normal life with one kidney and there are few risks to healthy donors. For this type of

transplant, there is a shorter waiting period and the transplant operation

is planned at a time convenient for you and your donor.

Living donor transplants have a 90 to 95% success rate. That means

that after one year, 90 to 95 of every 100 transplanted kidneys are still

working.

A transplant from a non-living donor is called a cadaveric transplant. In

this type of transplant, a healthy kidney from someone who has died

suddenly is transplanted. Before a cadaveric donor's organs can be

transplanted, a series of medical tests is done to determine if they are healthy. In addition, the family of the donor must consent to organ

donation.

After a series of tests, the person will be put on a transplant waiting list

until a kidney is found that is compatible. The length of time a person

will have to wait is hard to predict because it depends on how hard the

match is and how many kidneys become available. Unfortunately, the

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waiting time for a cadaveric organ transplant is getting longer.

Cadaveric transplants have an 80 to 85% success rate.

The transplant operation usually takes two to four hours. The new

kidney and ureter (the tube through which the urine flows into the

bladder) are placed in the lower abdomen near the groin. They are surgically attached to the blood vessels and bladder. The old kidneys

are not removed unless they are so large there is no room for the new

kidney, or they are chronically infected.

Figure 7.3.2 Kidney Transplant

http://www.kidney.ca/publications-eng.htm

A catheter is placed in the bladder for a few days to drain the urine

made by the new kidney. Sometimes a drainage tube is placed near the

transplanted kidney to remove fluids that build up. In some cases,

dialysis may be required following the transplant until the new kidney

starts to work. Fluids and medications are given through intravenous lines, often inserted in the arm and neck. After the transplant, the

person receives anti-rejection medication. Many tests are done to make

sure the new kidney is working properly and to watch for any signs of

rejection.

Rejection occurs when the body recognizes that the transplanted kidney

is not its own and mobilizes the immune system to fight against it.

Various anti-rejection medications (called immunosuppressives) are

used to prevent or treat rejection. They work by blocking the activity of the immune system. Some of these medications may cause side

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effects. Rejection is more common in the early months but can occur at

any time after the transplant. It may occur even when medications are

taken faithfully. Rejection episodes can usually be treated successfully. If the transplanted kidney stops working, the person will be able to go

back on dialysis. The transplanted kidney may not be removed. Many

factors influence its long term functioning. Some kidneys have lasted as

long as 25 years and more.

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Testing for Healthy Kidney Function

Healthy kidneys remove wastes and excess fluid from the blood. Blood

tests show whether the kidneys are failing to remove wastes. Urine

tests can show how quickly body wastes are being removed and

whether the kidneys are leaking abnormal amounts of protein.

Blood Tests

Serum creatinine - Creatinine is a waste product that comes from

meat protein in the diet and from the normal wear and tear on muscles of the body. Higher levels may be a sign that the kidneys

are not working properly. As kidney disease progresses, the level

of creatinine in the blood increases.

Blood urea nitrogen (BUN) - Urea nitrogen also is produced from

the breakdown of food protein. As kidney function decreases, the

BUN level increases.

Urine Tests

Some urine tests require only a few ounces of urine. But some tests

require collection of all urine produced for a full 24 hours. A 24-hour

urine test shows how much urine your kidneys produce in 1 day. The

test is sometimes used to measure how much protein leaks from the kidney into the urine in 1 day. However, protein leakage can also be

accurately determined in a small sample of urine by measuring its

protein and creatinine concentration. Following are some common

substances tested in urine.

Ketones - A urine test that uses a reagent strip to check for the

presence of ketones. Ketones spill into the urine when the body

metabolizes, or breaks down, fat for fuel in the absence of

glucose. They are often identifiable by their fruity odor. Presence in urine may indicate ketoacidosis (diabetic coma). This test may

also be performed as part of a routine urinalysis.

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Protein - Also known as the Proteinuria test or "dipstick" test, it

detects protein in the urine. Healthy kidneys filter and absorb

proteins; damaged or diseased kidneys are unable to properly

process proteins and instead excrete them into the urine. Presence may indicate renal or kidney disease. This test may also

be performed as part of a routine urinalysis. Proteinuria can also

signal other urinary tract disorders.

Microalbumin - Also known as the Microalbuminuria test, the

microalbumin test checks for albumin, a protein, in the urine over

a period of 24 hours. It is a more sensitive test than a "dipstick"

protein test. It may be performed along with a creatinine clearance

test. Presence may indicate deterioration of the kidneys due to

diabetes. Bladder infection and/or nephritis can also cause an

elevated microalbumin level.

Creatinine Clearance - A urine test that measures the kidney's

ability to filter creatinine from the blood. Creatinine is a metabolic byproduct of creatine, the acid that supplies energy for muscle

contractions. Normal kidneys should filter creatinine into the urine

at a constant rate. If kidney function is impaired, creatinine levels

will be low. Low levels indicate kidney disease (i.e., polycystic

kidney disease, glomerulonephritis, renal cancer), congestive

heart failure, or and/or severe dehydration.

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Glucose - Also known as the Glucosuria test or urinary sugar test,

it is a test for the presence of glucose in the urine. It measure

glucose levels from several hours earlier, and results vary depending on the concentration of the urine. This test may be

performed as part of a routine urinalysis. It generally is not used

as a standalone measure of glucose levels any more, as blood

glucose testing has replaced this function. Elevated levels of

glucose indicate the presence of sugar in the urine, which may

indicate diabetes.

Urine Culture - This is a test for the presence of bacteria in urine.

Under normal conditions, urine is sterile. The presence of bacteria

typically indicates a urinary tract infection (UTI).

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Homework Questions

1. List five symptoms that may indicate kidney disease.

2. Differentiate between Type I and Type II diabetes.

3. How does diabetes lead to kidney disease?

4. Why is nephritis such a potentially serious kidney disease?

5. Describe 3 treatments for kidney stones.

6. What is the most common cause of a urinary tract infection?

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7. What is chronic kidney failure and how is it treated?

8. Differentiate between hemodialysis and peritoneal dialysis.

9. Why would living donor transplants have higher success rate than

cadaveric transplants?

10. Describe three substances that are analyzed in urine

samples.

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Project Assignment

Debate: Xenotransplants

Statement: The government should allow xenotransplants in Canada.

Procedure:

1. Choose a partner to work with from your class.

2. Read the background information on the next page.

3. Research the issue of xenotransplants in newspapers, periodicals

and the Internet (some web references are provided on the

following page). 4. Discuss the issue with your partner and others in preparation for a

debate.

5. Prepare a joint report (you and your partner) with the information

in the points below.

6. Your teacher will give you specific instructions about how to post

or submit your report.

1. Write a list of points and counterpoints

that you and your partner considered.

2. Decide whether your group agrees or

disagrees with the statement.

3. Defend your group’s position. 4. What responsibility do governments have

to ensure that all groups have a voice in

the debate?

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Background Information

Canada but only 1,667 received one (including 378 kidneys donated by

living people). More than 3 out of 4 people on the waiting list needed a

kidney. The rest were waiting for livers, hearts, lungs or pancreases.

available. It appears that the number of people waiting for organs will

continue to grow as the number of people over the age of 60 grows.

transplants in Canada.

from one animal species to another for medical purposes. We use the

term here to refer to animal-to-human transplants. The transplanted

material is called a xenotransplant.

-to-human transplants

could potentially be treated by xenotransplantation. Organ

xenotransplants could include whole hearts, lungs, livers, kidneys or

pancreas of animals. Tissue xenotransplants could include skin grafts for burn victims, corneal transplants for the visually impaired or bone

transplants for limb reconstruction. Cellular xenotransplants may be a

way to treat people who have diabetes or Parkinson's disease.

transplants, is not new and the procedure has largely been

unsuccessful. The main scientific challenges to xenotransplantation are

immune rejection and infection. While drugs have been available for

some time to sufficiently suppress the immune system for human-to-human transplants, they have not been successful in animal-to-human

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transplants. To date, survival times for recipients of xenotransplants

have been poor although some cellular xenotransplants seem better

able to resist immune rejection.

genes to animal cells to make them more acceptable to a patient's immune system. Genetically modified animals are called "transgenic"

animals. Transgenic pigs have been developed in various countries and

shipped to researchers in Canada.

lot of questions. Is this a good way to save lives and cure people? Is it

safe? Who should pay for it? Should humans use animals in this way?

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Web References

Public Consultation on Xenotransplantation

(http://www.xeno.cpha.ca/english/index_e.htm) Information on the status of xenotransplantation in Canada and the

issues surrounding it can be found on this Canadian Public Health

Association Web site. The function of the site is to inform Canadians

about the government's Public Consultation on Xenotransplantation

program and to involve citizens in the decisions concerning the use of

this technology in our country. The results of this public consultation are published here. Also included is a list of links to Canadian documents

and Web sites on the topic.

Xenotransplantation

(http://www.hc-sc.gc.ca/dhp-mps/brgtherap/activit/fs-fi/xeno_fact-fait-

eng.php http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/01vol27/27s1/index.html)

This report published by Health Canada defines Xenotransplantation

and outlines some of the potential problems associated with it. The

main function of this report is to describe government plans to keep a

close watch on the effects of xenotransplantation on the population.

Background to the Current Regulatory Framework for

Xenotransplantation in Canada

(http://www.hc-sc.gc.ca/dhp-

mps/brgtherap/activit/consultation/xenotransplant/forum_rep-rap_xeno-

eng.php )

Background to the Current Regulatory Framework for Xenotransplantation in Canada is a long document that is part of the

Report of the Xenotransplantation Surveillance Workshop, Health

Canada. It outlines the current status of xenotransplantation in Canada,

and the issues and perceived risks associated with it.

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Organ Farm

(http://www.pbs.org/wgbh/pages/frontline/shows/organfarm/) Organ Farm is a PBS Frontline report on xenotransplantation. It

provides excellent coverage of the risks and business of

xenotransplants. Options for viewing include video excerpts, interviews,

and some historical background of the experiments.