i. Excretion - Objectives 9/6/10 2:11 PM

Section 2: Structure and functions in living organismsi) Excretion - humans

2.68 Recall that the lungs, kidneys and skin are organs of excretion (pg. 112).

2.69 Understand how the kidney carries out its roles of excretion and of osmoregulation (pg. 113)

2.70 Describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra (pg. 113)

2.71 Describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henle and collecting duct (not in book)

2.72 Describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate (not in book)

2.73 Understand that water is reabsorbed into the blood from the collecting duct (not in book)

2.74 Understand that selective reabsorption of glucose occurs at the proximal convoluted tubule (not in book).

2.75 Describe the role of ADH in regulating the water content of the blood (not in book)

2.76 Recall that urine contains water, urea and salts (not in book)

2.68 Organs of Excretion 9/6/10 2:11 PM

2.68 Recall that the lungs, kidneys and skin are organs of excretion.

Ref:Pg. 112 10.14Excretion if the removal of waste substances

To do: Discuss the difference between ‘excretion’ and ‘egestion’. Make a note about the difference between ‘excretion’ and ‘egestion’. Beside each organ of excretion, write down what is removed from the body. Read the section “The Importance of Waste Removal”Answer the question at the end of the page.

Excretion and Egestion

Organs of ExcretionThere are three important excretory organs in humans that you need to know about.

SkinLungsKidneys

The Importance of Waste RemovalAs long as homeostasis is maintained, body cells function efficiently and the body stays healthy. If homeostasis is not maintained a disease may occur, if the imbalance is great enough it may resulting death.

Nitrogenous waste products and carbon dioxide are poisons to the body and without their effective removal by the kidneys and lungs respectively, the body would very quickly begin to feel their effects. As soon as nitrogenous waste and carbon dioxide levels rise, the body’s homeostasis mechanisms ensure that the levels are returned to normal. If these systems fail to work then the levels of harmful waste products will rise and have detrimental effects on the individual.

Explain why the removal of urea from the body is an example of excretion. (2)

2.69 Kidneys, Excretion & Osmoregulation9/6/10 2:11 PM

2.69 Understand how the kidney carries out its roles of excretion and of osmoregulation

Ref:Pg. 113 10.16Urine is made by filtration and reabsorption

To do: Read the section belowAnswer the five questions which follow

The kidneys remove urea and other toxic wastes from the blood, forming a dilute solution called urine in the process. The two kidneys have a very extensive blood supply and the whole blood supply passes through the kidneys every 5 minutes, ensuring that waste materials do not build up.

The kidney acts as a filtering system. As blood flows through the kidney, harmful waste products, such as urea are filtered out. Useful substances such as glucose must remain in the blood. So the kidney must be able to filter out some substances but ensure at the same time that other substances remain in the blood.

Osmoregulation is the control of water levels within the body and the kidneys play a vital role in regulating the water content of the blood.

Questions 1 The diagram shows a water balance for a girl who spends most of the day working at a desk. It is not complete.

a. Complete the diagram by writing in the volume of sweat produced. (1)

The next day she spent much of the day training, doing many different types of exercise.b. State how each of the following would change and why it would be different from the previous day.i. The amount of water given off as sweat. (2)

ii. The amount of water breathed out. (2)

iii. The amount of urine passed, if she had the same water intake as on the previous day. (2)

c. Which organ controls the amount of water in the body? (1)

2 The table is about waste products which are removed from the student’s body. Complete the table by using the correct words from the box. (4)

amino acids breath circulation digestion fatty acidsglucose respiration sweat urine

Waste product

How it is produced

How it leaves the body

carbon dioxide

by .....................................

in .........................................

urea from ..................................

in .........................................

3 The table shows four ways in which water leaves the body, and the amounts lost on a cool day.

a. Fill in the table to show whether on a hot day the amount of water lost would be. The first answer has been done for you. (3)

less more the same

b. Name the process by which we lose water from the skin. (1)

c. On a cool day the body gained 2550 cm3 of water. 1500 cm3 came directly from drinking. Give two other ways in which the body may gain water. (2)

4 A runner might drink a special ‘sports drink’ at intervals during a marathon race. The table shows the substances present in a sports drink.

Substance

Percentage

WaterSugar 5.0Ions 0.2

a. Complete table to show the percentage of water in the sports drink. (1).

b. The runner sweats and also breathes heavily during the race.i. Why does the runner need to sweat? (1)

ii. Which two substances in the table are lost from the body in sweat? (1)

iii. Which substance in the table is lost from the body during breathing? (1)

c. How does the sugar in the sports drink help the athlete during the marathon? (2)

5 Each week, an athlete trains on 5 days (training days) but does not train on the other 2 days (rest days).The table shows how water losses from the athlete’s body are different on a rest day from those on a training day.

Volume of water lost in cm3Method Rest day Training dayUrine 1500 900Sweating 625 2400Breathing 450 1500Faeces 125 120Total 2700

a.Complete the table to show the total volume of water lost by the athlete on a training day. (1)

b.Explain why the athlete sweats more on a training day. (2)

c. On a training day, the athlete needs to take in more water. Explain why the athlete needs to take in more water on a training day. (2)

2.70 Urinary System 9/6/10 2:11 PM

2.70 Describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra

Ref:Pg. 113 10.16The Kidneys are part of the excretory systemPg. 114 10.18The Bladder stores urine

To do: Label the diagram below. Visit the website: http://msjensen.cehd.umn.edu/WEBANATOMY/timed/39.htm Some of these labels might be difficult but you should recognise most of them.Answer the 2 questions

1. To find out if a person has kidney disease, a radioactive substance is injected into the blood going to the kidneys. A special camera is then used to take pictures that show the radioactive substance in the kidneys and in the bladder.

The drawings show some of these pictures, taken from the front, at various times after the injection of the radioactive substance.

a. After how many minutes did the injected radioactive substance appear in the bladder? (1)

b. After how many minutes did the injected radioactive substance appear in the bladder? (1)

c. Use the information in the drawings and your own knowledge to describe the route of excretion of the radioactive substance. (2)

2. The diagram shows a kidney with a ureter and two blood vessels.

a. Name artery A. (1)

b. What evidence from the diagram shows that A is an artery and not a vein? (1)

2.71 Nephron 9/6/10 2:11 PM

2.71 Describe the structure of a nephron, to include Bowman’s capsule and glomerulus, convoluted tubules, loop of Henle and collecting duct

To do: Watch the animation on the whiteboard about nephron structure. Use the words from the learning objective to help you label the two diagrams below of kidney structure.

2.72 Ultrafiltration 9/6/10 2:11 PM

2.72 Describe ultrafiltration in the Bowman’s capsule and the composition of the glomerular filtrate

To do: Watch the animation on the whiteboard about ultrafiltration. Read the paragraph on ultrafiltration. Visit the website: http://www.biologymad.com/resources/kidney.swf From the website, for each of the following substances, follow what happens to it as it enters the nephron. Make a note of what happens to the substances. Visit the website: Target Practice.http://www.zerobio.com/target_practice_quiz/target_practice_quiz_kidney_htm Answer the 3 questions

UltrafiltrationThe blood vessel entering the glomerulus is wider than the one that leaves. This raises the pressure inside the vessel to such an extent that some of the liquid in the blood passes out between the cells of the capillary wall. Small soluble molecules and ions are taken with it. The larger substances, such as blood cells and proteins, are too big to leave the blood capillary. The glomerular filtrate formed consists mainly of water, glucose, amino acids, salts and urea. This drains from the Bowman’s capsule into the proximal convoluted tubule.

Notes from WebsiteUrea

Glucose

Water

Protein

Sodium

Questions1. The diagram shows part of the urinary system.

a. Underline the correct words to complete the following sentences.i. Waste urea is taken out of the body by the … renal artery /

kidney / renal vein (1)

ii. Urine is carried away from the kidney by the … renal artery / renal vein / ureter (1)

iii. Urine is stored in the … renal vein / ureter / bladder. (1)

b. Choose the correct word from the box to complete the following sentence. (1)

liver lungs stomachUrea is made in the ……………………………………………

2. The table gives the amounts of some substances in blood plasma and in urine.

Substance Blood plasma(g/100 cm3)

Urine(g/100 cm3)

water 92.0 95.0proteins 7.3 0.0urea 0.1 2.0sodium ions 0.3 0.6chloride ions

0.4 0.6

glucose 0.1 0.0

a. Which TWO substances in the table are not excreted in urine? (1)

b. Which organ makes urine? (1)

c. Suggest what happens to the blood plasma if this organ stops working.Use the information in the table to help you. (2)

3. The diagram shows part of the human urinary system and its blood supply.

a. Name one useful substance carried by the blood into the kidney. (1)

b. Blood entering the kidney contains more urea than blood leaving the kidney.

i. Describe, in order, the route by which urea passes from the kidney to outside the body. (3)

ii. Name liquid Y. (1)

iii. Put an X on the diagram in the part which contains the greatest concentration of urea. (1)

c. If a kidney no longer works, urea can still be removed from the body. How is this possible? (1)

2.73 Water Reabsorption 9/6/10 2:11 PM

2.73 Understand that water is reabsorbed into the blood from the collecting duct

To do: Discuss the role of the collecting duct in water reabsorption Notes to be taken in class

2.74 Selective Reabsorption 9/6/10 2:11 PM

2.74 Understand that selective reabsorption of glucose occurs at the proximal convoluted tubule.

To do: Read the section belowAnswer the 4 questions which follow

Glucose is essential for the process of respiration. This means that every cell in the body needs to be continually supplied with glucose. As blood undergoes ultrafiltartion in the glomerulus, glucose is small enough to be squeezed out through the capillaries during due to the high pressure.

The body cannot afford to lose this glucose in the urine and so it must be reabsorbed into the capillaries. Glucose is reabsorbed in the proximal convoluted tubule. All of the glucose will be absorbed before the end of the proximal convoluted tubule in a healthy person.

Once it is reabsorbed from the proximal convoluted tubule it will enter the capillaries which eventually return the blood to the renal vein.

Questions1. The diagram shows a nephron from the human kidney.

A molecule of glucose may leave the blood in the glomerulus but then be present again in the blood in the renal vein. Explain how the molecule of glucose returns to the blood. (2)

2. The diagram shows a kidney nephron.

a. Name the process taking place:

i. in the glomerulus. (1)

ii. between points ‘A’ and ‘B’ (1)

b. In kidney dialysis, blood from the patient is passed into the dialyser.The diagram shows how urea is removed from the blood in a dialyser.

i. Why must the dialysate be continually replaced? (1)

i. Darren has been receiving dialysis since 1996. He is waiting for a kidney transplant. Explain how Darren’s quality of life would be improved by a kidney transplant. (3)

3. The diagram shows a kidney nephron.

a. Label A and B. (2)

b. Place X on the diagram where ultrafilteration takes place. (1) c. Blood is filtered as it passes through a kidney. Complete the table by putting YES or NO in boxes to show where each substance can be found in a healthy person. (4)

Found in

Substance

bloodfiltrate in first convoluted tubule

filtrate in second convoluted tubule

urine

proteinwaterureaglucose

B.

A.

4. The diagram shows a kidney nephron and its blood supply.

a. Label parts P, Q and R. (3)

b. Put an X on the diagram to show where ultrafiltration takes place. (1)c. Samples were taken from positions A, B, C, D and E. The samples were analysed and the results are shown in the table.

i. Why were there no proteins in the glomerular filtrate? (2)

ii. Explain why there was glucose in the glomerular filtrate but not in the urine. (2)

P.

Q.

R.

iii. Explain why the percentage of urea increased as the filtrate passed from ‘B’ to ‘C’ along the tubule. (2)

2.75 ADH 9/6/10 2:11 PM

2.75 Describe the role of ADH in regulating the water content of the blood

To do: Discuss the role of ADH in regulating water content of blood. Take notes in class on the role of ADH and water regulation Answer the 6 questions

Questions1. The diagram shows a nephron from the human kidney.

a. A molecule of glucose may leave the blood in the glomerulus but then be present again in the blood in the renal vein. Explain how the molecule of glucose returns to the blood. (2)

b. Describe how the hormone ADH acts to reduce the volume of the urine.(2)

2. Read the passage and answer the questions that follow.

Young people who go clubbing lose a lot of water as sweat while they dance.This makes them very thirsty, so they drink a lot of water. Some of them alsotake tablets called Ecstasy. Ecstasy stimulates release of the hormone ADH.Young people who dance a lot and take Ecstasy have very dilute blood plasma.When blood passes through the brain, the brain cells swell and press against the inside of the skull. The pressure on the brain cells causes damage, which can be fatal.

a. Explain why it is important that young people sweat when dancing. (2)

b. Name the organ that releases ADH. (1)

c. Which organ does ADH target? (1)

d. How does ADH travel from where it is releases to the organ it targets?(1)

3. The graph shows how the mass of urea in the urine depends on the mass of protein in the diet.

a. Which organ in the body makes urea? (1)

b. Explain the results shown in the graph. (3)

c. Urine volume is controlled by the hormone ADH. ADH acts in the kidney on the second coiled tubule and on one other part. Name this part. (1)

d. In hot weather we tend to produce less urine than in cold weather. Explain how ADH acts to decrease the volume of urine produced. (2)

4. The diagram shows a kidney nephron and its blood vessels.

Samples were taken from each of the positions A, B, C, D and E, shown in the diagram. Data showing the relative proportions of some substances found in the samples are shown in the table. The samples were all of equal volume.

A B C D E% in blood

% in glomerular filtrate

% in tubule

% in blood

% in urine

protein 6.8 0.0 0.0 6.95 0.0glucose

0.65 0.2 0.0 0.65 0.0

water 89.0 97.0 95.5 90.0 97.5urea 0.04 0.07 1.4 0.03 2.1

a. Put an X on the diagram to show where ultrafiltration takes place. (1)

b. Name two structures, shown in the diagram, which must be in close contact to help reabsorption. (2)

c. Explain why there is no protein in the liquid in part B. (2)

d. Explain the changes in percentages in glucose AND urea from part B to part C.(4)

e. When a person is in a very warm room, how does ADH regulate the water content of the blood? (2)

5. Dave is training for a marathon.He does not drink enough to replace the water he loses as sweat.This has an effect on his body.

a. Name hormone A. (1)

b. What effect will hormone A have on the kidney tubules? (1)

c. How will this affect the urine that is produced? (1)

6. A doctor injected a radioactive substance into a patient’s blood.Its progress through the body was followed using a radiation detector.As it passed through the urinary system, the level of radiation was recorded.The radioactive substance was excreted in the patient’s urine.

The data were plotted on the graph.

The table shows the missing labels for the curves.Write the most suitable letter, X, Y or Z, in each box. (2)

bladderright kidneyblood

2.76 Urine 9/6/10 2:11 PM

Recall that urine contains water, urea and salts

To do:Easy one – learn the objective