How do plant and animal systems function?

Practical: Kidney Dissection

Outcome:

To dissect a mammalian kidney and observe the macroscopic structures

Respect for the specimen and safety are key for this activity

Engage

Learning Tasks

Aim

To dissect a sheep kidney and observe its macroscopic structures

Materials

1 x dissection board

1 x scalpel

1 x forceps

1 x ruler

1 x Garbage bag

Newspaper

Paper towel

Disinfectant

Plastic gloves

1 x Kidney

Method

1. Observe the outside of the kidney. It has a concave (inward bending) side and a convex (outward bending) side. The concave side has a white region in the middle, called the renal hilum. This is where three large tubes leading into and out of the kidney are located. These tubes are the ureter, renal artery and renal vein. The tubes may have been cut off, leaving behind three holes.

2. Lay the kidney flat on the table, so that the concave side is pointing towards you and the convex side is pointing away. Draw a diagram of the kidney, including the tubes if they are present. Label the features listed below. Next to the diagram, write down the colour of the kidney and its length in centimetres.

3. Describe the outside appearance of the kidney. Also, describe the hilum. In these descriptions, consider factors such as colour, size, shape and location. All observations and descriptions made in this investigation should be recorded.

4. Reposition the kidney so that the concave side is facing down into the dissection board and the convex side is facing upward towards the ceiling.

5. Using the scalpel, cut down the long side of the kidney, producing two equal halves. Do not cut all the way through: leave a few millimetres intact so the kidney can be folded open like a book. Try to make the cut clean and smooth. When the kidney is opened flat along the cut, it should look similar to a tomato slice, with a white centre, red outer rim and several red and pink lobes in-between. The kidney may be discoloured, depending on how it has been stored and preserved.

6. Identify the three main layers in the kidney and describe each layer. The outer layer is the renal cortex. It is striated, meaning it has many ridges or lines running along it. The white, inner-most layer is the renal pelvis. Everything in between is the renal medulla. Depending on how the kidney has been preserved, the medulla may be darker on the end closer to the cortex and lighter on the end closer to the pelvis.

7. Inside the medulla there are several triangular sections, called renal pyramids. Describe the renal pyramids.

8. There is a hole, or tube, at the centre of the renal pelvis leading to the outside of the kidney. This is the ureter. Insert the forceps through the ureter to see how it leads to the outside of the kidney. Describe the location and size of the ureter.

9. Make sure the kidney is laid flat on the table, like an open book. Draw a diagram of the inside of the kidney. The two halves should be identical, so it is only necessary to draw one of them. On the diagram, label the following structures: renal cortex, renal medulla, renal pelvis, renal pyramid, ureter

10. Using the forceps, investigate how the medulla attaches to the pelvis. It should be possible to lift the inner edge of the medulla up and look underneath. This should reveal small, white tubes, called minor calyces (singular: minor calyx). These join to form larger tubes, called major calyces (singular: major calyx) that drain into the pelvis. Urine produced in the medulla is transported to the pelvis via these tubes. It then travels out of the kidney via the ureter.

11. Use the scalpel to cut into the calyces and investigate how urine would flow from the minor calyces, to the major calyces, to the renal pelvis and ureter. Describe the calyces.

12. Double check that every feature has been identified and described. Two diagrams should also have been drawn: one of the outside of the kidney and one of the inside.

Results and observations

Include any observations or diagrams here

Discussion questions

1.) What did was observed throughout the practical (refer to the results section)? Did your observations align with the expectations (compare your drawings to the one provided)? Did any observation surprise you?

2.) Order the following kidney structures to show the path of urine formation and its departure from the body: renal pelvis, glomerulus, ureter, renal artery, bladder, renal tubules (Loop of Henle and collecting ducts), calyx, urethra, Bowman’s capsule. 

3.) What structure allows urine to move from the kidneys to the urinary bladder?

4.) What gives the renal pyramids their striped appearance?

5.) What are the calyces?