4 Practical 2
Investigating the structure of the kidney
Safety
Hydrogen peroxide is an irritant. Eye protection must be worn.
At the end of the practical, the kidneys and any material cut from them should be wrapped up and
disposed of safely. Students should wash their hands thoroughly with soap and hot water. Dissection
instruments and boards should be washed with disinfectant.
Apparatus and materials
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fresh whole lamb’s kidney with vessels and
ureter attached
dissecting scissors
forceps
blunt seeker
scalpel
surgical gloves
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dissecting board
10 cm3 of 20 volume hydrogen peroxide in
labelled container
dropping pipette
hand lens
eye protection
Introduction
You are provided with a lamb’s kidney. Note that it does not have quite the same structure as a human
kidney, nor is it quite like the rodent kidneys that are normally used to make prepared microscope
slides (Practical 3).
In this practical, you will:
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examine the structure of the kidney and relationships between its different parts.
Procedure
1 Look at a diagram showing the position of the kidneys in the body of a mammal (Figure 4.9, page
47 of Biology 2).
2 Examine a whole kidney. This should have parts of the blood vessels and ureter still attached. See
if you can find and identify these structures – you will probably have to remove some fat to locate
them. The concave part of the kidney where they are attached is called the hilum. Note the overall
shape of the kidney and place it on a board with the hilum to the left.
3 Remove all of the fat surrounding the kidney and make a labelled drawing of the kidney to show
its shape and external features. If the ureter and blood vessels are very short, use dotted lines on
your drawing to show where they would be. Measure the length of the kidney and include a scale
on your drawing.
4 Use a scalpel to make a cut along the edge of the kidney on the convex side opposite the hilum.
This should follow the line you drew to show the outer edge of the kidney. Do not cut all the way
through the kidney yet.
COAS Biology 2 Teacher Resources
Original material © Cambridge University Press 2009
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4 Practical 2
5 You should now be able to see into the slit that you have cut. Inside there should be some white
tissue visible. This is the pelvis. On each side of the slit you will see pink tissue, partly covering
the pelvis (see Figure 4.10 on page 47 of Biology 2). This is the medulla. The darker tissue towards
the outside of the kidney is the cortex.
6 Look for a hole in the pelvis. Push a blunt seeker through the hole and see where it emerges.
If you are successful, you should find that it comes out through the ureter at the hilum.
7 Now continue to cut all the way through the kidney to produce two longitudinal sections. Note the
colours of the pelvis, medulla and cortex. As far as possible, trace the path of the renal artery from
the hilum into the cortex. The renal vein follows the same path, but is much more difficult to see –
try using a hand lens. In the cortex, the artery branches to supply the glomeruli and kidney tubules.
8 Use a hand lens to examine the cut surface of one section. In the cortex, you will see tiny red spots.
These are glomeruli. In the medulla, you should be able to see striations that run from the cortex
towards the pelvis. These are loops of Henle and collecting ducts. Compare what you see with
Figure 4.11 on page 47 of Biology 2.
9 Use a pipette to add some hydrogen peroxide to one of the cut surfaces. After the vigorous
effervescence has cleared, you should be able to see the structures within the cortex and the
medulla more clearly.
10 Make a labelled drawing of one of the cut surfaces of the kidney, to the same scale as your first
drawing. Annotate the drawing to show the functions of the structures that you have labelled.
Add a scale to the drawing.
11 When you have finished, dispose of the dissected material and board as instructed, and place the
dissecting instruments into disinfectant. Wash your hands thoroughly.
12 a
Describe the differences in appearance of the cortex, medulla and pelvis in the kidney that you
dissected.
b Why was there vigorous effervescence when you added hydrogen peroxide to the cut surface
of the kidney?
c The kidneys make up about 0.5 to 1.0% of the total mass of the body, but they receive about
25% of the output of the heart. Explain why the kidney has such a large blood supply.
COAS Biology 2 Teacher Resources
Original material © Cambridge University Press 2009
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