Workbook3 Excretion Answers

Wellsway School Science Team Curriculum 2006 Triple Science - Biology workbook

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EXCRETION

WORKBOOK

Name:_________________

Tutor Group:____________


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Transport and Water Relations 3. (WASTE PRODUCTS OF BODY FUNCTIONS ARE REMOVED BY) THE KIDNEYS

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OBJECTIVES: Why do animals need an excretory system? What parts make up the excretory system? How does a kidney work? What can be done if the system does not function? By the end of this topic you should: (a) Know that the kidneys regulate the water content of the blood and remove waste products from the blood. (b) Recognise and label a given diagram of the human excretory system to show: kidneys, renal artery, renal vein, ureters, urethra, and bladder. (c) Know that the waste, a solution containing urea and excess salts called urine, passes from the kidneys in the ureters to the bladder where it is stored before being passed out of the body. Interpret data about the level of substances present in urine and during passage through the kidney. (d) Observe gross structure of a section through a kidney (e) Recognise and label a given diagram of a section through a kidney to include: cortex, medulla, pelvis, ureter and position of nephrons. (f) Recognise and label a given simplified diagram of a nephron and its associated blood supply to show: capillary knot, Bowman's caps ule, tubule, collecting duct, capillary network. (g) Understand the process of filtration under pressure and know that selective reabsorption of glucose, some salts, and much of th e water takes place in the tubule. (h) Know that the kidneys regulate the water content of the blood by producing dilute urine if there is too much water in the blood or concentrated urine if there is a shortage of water in the blood. (i) Know that kidney failure may be treated by a transplant or by a dialysis machine and compare the advantages and disadvantages of the use of these methods. (j) Know that a diseased kidney may be replaced by a he althy one by transplant from a donor of a similar 'tissue type' to the recipient . The donor kidney may be rejected, attacked by the immune system, unless anti-rejectio n drugs are taken. (k) Understand that in a dialysis machine a person's bl ood flows between selectively permeable membranes. It is important that useful su bstances in the blood, such as glucose and salts, are not lost. To prevent this, t he dialysis fluid contains the same concentration of these substances as blood plasma. This ensures that only urea and excess salts and water diffuse into the dialysis fl uid. This treatment has to be carried out at regular intervals.

2. Look at the video, OR MSS presentation OR PowerPoint presentation, OR read your textbook on THE KIDNEYS. Discuss the kidneys & excretory system with your teacher. If possible, examine a sheep or pig’s kidney, OR a kidney model, OR computer images of a kidney. Use the labels to complete the diagrams below showing the position of the kidneys in the body, gross structure of the kidney and fine structure of a nephron:


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1. Position of kidneys in the body. Labels: aorta, bladder, kidneys, renal artery, renal vein, ureters, urethra, vena cava.

2. Gross structure of the Kidney.

Labels: cortex, medulla, pelvis, (position of) nephrons, renal artery, renal pyramids, renal vein, ureter.


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3. Fine structure of a nephron.

Labels:, Bowman's capsule, capillary knot (glomerulus), capillary network (x2), collecting duct, renal artery (branch of), renal vein (branch of), tubules (x2).

3. Functions of the kidney. Answer the following questions:

a. What are the 2 main functions of the kidneys?

Excretion (urea) Osmoregulation (regulating water levels) b. What are the 3 main components of urine?

Water Mineral ions Urea c. What is the source of urea?

Breakdown of XS amino acids in the liver d. Which blood vessel carries blood into the kidney under high pressure?

Renal Artery

e. Blood enters each glomerulus under high pressure. What happens to most of the small molecules in the blood?

Filtered into the Bowman’s Capsule


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f. LIST the main small molecules filtered out of the blood from the glomerulus into the kidney tubules.

Water, glucose, amino acids, fatty acids, mineral ions, urea.

g. Why are red & white blood cells, platelets and large plasma proteins NOT filtered out of the blood from the glomerulus?

Too large to be filtered

h. What happens to useful materials (i.e. glucose, most water & most salts) in the tubules?

All selectively reabsorbed into the blood

i. Useful materials are reabsorbed into the blood by ACTIVE TRANSPORT, which needs energy from respiration in tubule cells. Why is it necessary to use this process, rather than just diffusion, which requires no energy?

Diffusion alone would cause the loss of about ½ the useful molecules, e.g. glucose. Active transport is needed to pump the remaining ½ back into the blood against the concentration gradient.

j. What happens to the urea, water and salts NOT reabsorbed back into the blood?

Forms urine, passes to bladder, removed at intervals through the urethra. i.e. It is EXCRETED!

4. Controlling body water. In the spaces below, explain how the kidneys control the level of water in the blood,

a. when the blood is too dilute:

Less water is reabsorbed from the kidneys & so more is lost in urine – you produce a larger VOLUME of more DILUTE urine. b. when the blood is too concentrated:


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More water is reabsorbed into the blood in the kidneys, so you produce a smaller VOLUME of more CONCENTRATED urine.

5. If you have finished…. Explain the role of ADH in controlling the level of water in the blood:

Less ADH is secreted, less water is reabsorbed from the kidneys & so more is lost in urine – you produce a larger VOLUME of more DILUTE urine.

MORE ADH is secreted, so more water is reabsorbed into the blood in the kidneys, so you produce a smaller VOLUME of more CONCENTRATED urine.

6. Look at the video, OR MSS presentation OR PowerPoint presentation, OR read your textbook on KIDNEY FAILURE. Discuss kidney failure & treatment with your teacher. If possible, examine kidney dialysis units.

a. Describe how a kidney transplant takes place:


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b. Complete the diagram showing how kidney dialysis works:


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c. Complete the table comparing the advantages & disadvantages of transplant & dialysis:

Treatment ADVANTAGES DISADVANTAGES Transplant

No need to spend hours on dialysis machine. Can lead a normal life. Much improved quality of life.

Need a donor – either a relative donating one kidney, or from someone who has died. Need to suppress immune system, which can make patient vulnerable to other infections, e.g. pneumonia, MRSA. Operation is not always successful; it is a major operation, which always has risks associated with it.

Dialysis Reliable technique. Relatively low risk to health. Improves quality of life – even saves lives! Prolongs life while waiting for a transplant.

Very time-consuming; 5-6 hours, 2-3 times per week causes a great deal of disruption to a normal life. Eventually, places to take blood from run out! (Tissue becomes blocked by scar tissue). Need to have a careful diet, to avoid large excesses of protein.

7. Well done! You have now completed the Excretion topic. Now you need to revise your work in preparation for the Excretion test.

8. Useful web links: http://www.bbc.co.uk/schools/gcsebitesize/biology/humansasorganisms/6homeostasisrev5.shtml http://www.biotopics.co.uk/human2/homkid.html


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http://www.s-cool.co.uk/topic_quicklearn.asp?subject_id=17&Topic_ID=8&Quicklearn_ID=4&loc=ql http://www.purchon.com/biology/kidney.htm http://www.squashedfrogs.co.uk/resources/2006/1/the_kidney_-_how_it_works.ppt http://www.revisionworld.co.uk/gcse/biology?q=category/export/html/18 (general revision site)

9. Glossary. (Muddled – sort them out!) 1 ADH First part of tubule system; collects filtrate from capillary knot 4 2 Aorta Surrounds tubules; useful substances reabsorbed into blood here 6 3 bladder Hormone from pituitary gland which controls water content of blood 1 4 Bowman's capsule Large artery; carries blood under high pressure to renal arteries 2 5 capillary knot

(glomerulus) Stores urine before it is removed from the body

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6 capillary network Where high pressure filtration of small molecules takes place 5 7 collecting duct Process where small molecules are forced from blood plasma into the

Bowman’s capsule 11

8 cortex Machine in which urea is artificially removed from the blood and other molecules are regulated

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9 dialysis fluid Outer region of the kidneys where filtration takes place 8 10 dialysis machine Last part of tubule which carries urine to the pelvis of the ureter 7 11 filtration Contains the same concentration of the substances in blood plasma. 9 12 kidney Inner region of the kidney which connects to the ureter 15 13 medulla Tubule system; about 1 million in each kidney 14 14 nephron Main organ for urea excretion and water regulation 12 15 pelvis Carries high pressure blood from aorta to each kidney 16 16 renal artery Inner region of kidney, where most reabsorption takes place 13 17 renal vein Produce large surface area for filtration in dialysis machines 18 18 selectively

permeable membranes

Replacing a damaged kidney with a healthy one from a donor 20

19 selective reabsorption

Carries deoxygenated blood from each kidney to the vena cava 17

20 transplant Process where useful molecules are actively absorbed into the blood 19 21 tubule Carries deoxygenated blood from renal veins to the heart 26 22 urea Liquid made in kidneys containing urea, water and mineral ions 25 23 ureter Carries urine from the bladder to the outside of the body 24 24 urethra Main excretory waste made in liver from breakdown of amino acids 22 25 urine Microscopic tubes in the nephron in which urine is formed 21 26. Vena cava Carries urine from the kidney pelvis to the bladder 23 10. Additional Notes:


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11. QUESTIONS ON EXCRETION


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1. 2.


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GCSE - WJEC

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Workbook3 Excretion Answers