HL IB-Biology 2011/12
#33 EXCRETION AND THE KIDNEY
11.3 The Kidney
Assessment Statements Addressed:
11.3.1 Define excretion.
11.3.2 Draw and label a diagram of the kidney.
11.3.3 Annotate a diagram of a glomerulus and associated nephron to show the function of
each part.
11.3.4 Explain the process of ultrafiltration, including blood pressure, fenestrated
blood capillaries and basement membrane.
11.3.5 Define osmoregulation.
11.3.6 Explain the reabsorption of glucose, water and salts in the proximal convoluted
tubule, including the roles of microvilli, osmosis and active transport.
11.3.7 Explain the roles of the loop of Henle, medulla, collecting duct and ADH
(vasopressin) in maintaining the water balance of the blood.
11.3.8 Explain the differences in the concentration of proteins, glucose and urea between
blood plasma, glomerular filtrate and urine.
11.3.9 Explain the presence of glucose in the urine of untreated diabetic patients.
The two key functions of the kidney are OSMOREGULATION and EXCRETION.
1. Define excretion.
2. Define osmoregulation.
3. Explain the need for excretion in animals.
4. Explain the need for osmoregulation in animals.
Labudda, CHS, 33 Excretion Kidney.pages
5. Discuss the challenges of nitrogen waste and how it relates to water conversation.
6. All excretory systems in the animal kingdom are a variation on a basic theme. Figure 1 shows
the basic processes shared by all excretory systems. Complete the figure by adding labels,
then complete table 1, which explains each process.
Figure 1: THE FOUR COMPONENTS OF A BASIC EXCRETORY SYSTEM
Table 1: DESCRIPTION OF THE FOUR BASIC PROCESSES IN EXCRETION
Name of
Process
FILTRATION
REABSORPTION
SECRETION
EXCRETION
Brief description of what is
taking place
Role in
excretion
Molecules
involved
Type of
transport and
source of
energy for
transport
Analogy
KIDNEY:
7. Draw a copy of a kidney on the left side of a big poster paper. Label your drawings with the
following terms:
Renal Artery
Renal Vein
Pelvis
Cortex
Medulla
Ureter
NEPHRON:
The nephron is the functioning unit of the kidney. You will need to know all the parts and molecular
processes taking place in each part.
8. Add the location of one nephron to your drawing of the kidney.
9. Add the label ‘nephron’ to your drawing. Keep in mind, that even though you are showing only
one nephron, the kidney is composed of many.
10. Draw a nephron in the center but closer to the right side of your poster. Leave enough space
around your drawing to add more details of molecular processes later.
11. Label your drawing of the nephron with the following parts:
Afferent Arteriole,
Efferent Arteriole
Glomerulus
Bowman’s Capsule
Proximal Convoluted Tubule
Loop of Henle
Descending
Ascending Limp
Distal Convoluted Tubule
Collecting Duct
Cortex-Medulla Divide
As stated above, the nephron is the functioning unit of the kidney. It consists of the four basic
functions of mammalian excretory organs see figure 1 above.
12. Complete table 2 by identifying which structure of the nephron serves one of the four
functions, and provide an overview of the basic molecular events (type of molecules involved
and direction of movement[in or out of blood]).
Table 1: OVERVIEW OF BASIC PROCESSES TAKING PLACE IN DIFFERENT PARTS OF NEPHRON
Basic
Function
Structure of Nephron
Overview of Events (Molecules involved and
direction of movement)
You now need to study the process in more detail and relate the structures of the nephron to its
function and the overall function of the kidney. You will look at different sections of the nephron
and study its anatomy and movement of molecules. In your drawing of a nephron add boxes
around the section discussed and provide a more detailed labeled drawing in an empty space next
to the nephron drawing. Connect the two with a line. Title all drawings of sections with the basic
function of secretion (see table 2). Some processes require the detail of cellular structures (i.e.
ultrafiltration).
Here are the sections of the nephron you need to study in more detail. For each provide a
drawing labeled with the listed terms.
Cross section of Glomerulus with Bowman’s capsule
• Indicate afferent arteriole and efferent show relative diameter. Label Bowman’s capsule.
Structure of part of Glomerulus
• Show a cross section of one capillary with blood plasma and red blood cell, fenestrated wall
of capillary, .podocytes, and basement membrane (indicate molecular composition)
• Next to your detailed drawings of glomerulus provide the following information:
✴ Describe the force for ultrafiltration.
✴ Determine the structure(s) that support the function of ultrafiltration.
✴ Outline the role of Bowman’s capsule.
Proximal Convoluted Tubule
• Show cross section with single cell layer, microvilli, mitochondria, invagination of outer
membrane, basement membrane, lumen, filtrate
• Next to your detailed drawing provide the following information:
✴ Determine the structure(s), that reflect/explain the role of the Proximal Convoluted
Tubule.
✴ Explain the increased numbers of mitochondria.
✴ Show the net movement of solutes and water and indicate which molecules are
transported actively and passively.
✴ State the molecules that are highly represented in the membrane of the cells.
Loop of Henle with Descending and Ascending Limp, Distal convoluted tubule and collecting
duct.
• Label all the parts
• Indicate the molecules each arm is permeable for
• Indicate which molecules are actively and passively transported.
• Indicate the solute gradient inside the limbs, tubule, and duct by shading more concentrated
areas darker. Provide a key. (High solute concentration compared to normal solute
concentration in blood.)
• Role of loop is to create an area of high solute concentration in the cells and tissue fluid of
the medulla. Explain and add to your drawing what processes are responsible. (What effect
does the loop of Henle have to the overall solute concentration in the medulla?)
• In your drawing of the kidney indicate the concentration gradient as well.
Distal Convoluted Tubule
Show a cross section and indicate the net movement of molecules. Explain in your drawing why
molecules move in the indicated direction.
Collecting Duct
• The major role is osmoregulation. Aquaporins are pores in the membrane permeable for
water, the expression of aquaporins is regulated by the hormone ADH (secreted by pituitary
gland).
• Study the feed back of water content of blood, secretion of ADH, expression of aquaporins,
and urine concentration. Decide on how to present this information on your poster.
• Make sure to explain what provides the force for water absorption.
13. The two functions of the kidney are excretion and osmoregulation. For each function outline
the part and process that serves the function. In other words, how does kidney balance
blood composition?
14. Table 3 compares the composition of different fluids involved in excretion.
Table 3: COMPOSITION OF FLUIDS IN KIDNEY
Molecule
Amount in
blood plasma
in mg 100 ml-1
Amount in
glomerular filtrate
in mg 100 ml-1
Amount in urine
in mg 100 ml-1
Proteins
> 700
0
0
Glucose
> 90
> 90
0
Urea
30
30
> 1800
Explain the difference in the concentration of protein, glucose, and urea between blood
plasma, glomerular filtrate and urine.
15. Explain the presence of glucose in the urine of untreated diabetic patients
16. Explain if an animal living in the desert would have a long or short loop of Henle.
17. Identify all the cell and molecular layers that a molecule would have to pass through in order
to be ultrafiltered and then reabsorbed into the bloodstream within a single nephron.
18. Predict the relative amount of ADH produced in a person who has been drinking lots of water
and has not been exercising recently. JUSTIFY your prediction.