The human urinary system to Address nys standard

LESSON II:

THE HUMAN URINARY SYSTEM

To Address NYS Standard:

5 (Living things maintain a dynamic equilibrium which sustains life)

Behavioural Objective:

The students will be able to understand how the concepts of diffusion, WTSGTWF, and concentration gradients related to how urine is created in the human. Students will also be able to understand the anatomy and physiology of the human kidney.

Explanation of Lesson Plan:

This lesson will allow students to see how the human kidney functions, and how it is similar to and differs from other modes of waste concentration.

Hook: (3 minutes)

So we know that all organisms have to get rid of waste, which includes humans. In general, the more complex an organism is, the more complex its individual structures have to be. The human urinary system performs the same functions as nephridia and Malpighian tubules, but it does it in a much more elegant and controlled way. Let us examine it now.

Test of Prior Learning: (5 minutes)

1. What is the purpose of a nephridrium or a Malpighian tubule?

2. How do you think concentration gradients are going to come into play here?
New Learning: (30 minutes)

1. The human kidney is the organ most involved in creating urine.

2. As we said before, humans are complex machines, and so waste is created in many different ways all over the body.

3. Just as it would not make sense for everyone to have their own individual dump in their backyard, it doesn’t make sense for each cell to have to worry about getting rid of its own waste. We centralize.

4. The waste is transported how? Through the blood! So yes, we take nutrients and gasses out of the blood, then put the waste and waste gasses right back in. AMAZING!

5. So now we have our wastes in the blood. We need to get them back out, though.

6. The kidney is the organ that we use. It’s like the central processing plant. It’s job is to make urine from wastes in the blood.
[hand out diagram of kidney and nephron]
7. The kidney is a collection of functional units called nephrons. Recall that a functional unit is the smallest bit of an organ that does the organ’s job. The functional unit of the lungs is the alveoli.

8. The nephron is comprised of several different parts. The first is the “Scotty” Bowman’s capsule. (Scotty bowman is the winningest coach in the NHL, and coached the Sabers for a while) The capsule is actually not named after him. It’s named after Sir William Bowman, a surgon and anatomist who lived in the 1800s.

9. The Bowman’s capsule collects stuff that is pushed out of the blood by positive pressure. Small proteins, sugars, water, plasma, wastes, etc. are pushed out. Cells, large proteins and other very charged molecules cannot move out because the pore sizes are too small.

10. The Bowman’s capsule collects what is now known as filtrate, from the glomerulus. This is a tightly wound ball of capillaries that fit inside the Bowman’s capsule.

11. The proximal convoluted tubule leads away from the Bowman’s capsule. This is where much sugar, vitamins, etc. that are needed by the body are reabsorbed. Water is also reabsorbed here, but not in as much volume as in a later structure.

12. The filtrate then passes into the Loop of Henle (Don Henley’s loop. Don Henley was the lead singer of the band “The Eagles”) the loop is not named after him, but after Friedrich Gustav Jakob Henle, a German pathologist and anatomist who lived in the 1800s.

13. The loop of Henle is very exciting! It has a descending leg, and an ascending leg. The descending leg is permeable only to water, but not to salt.

14. The ascending leg is permeable to salt, but not to water. This creates CONCENTRATION GRADIENTS!!!! The water moves out on the descending leg, because of the salt that is moving out on the ascending leg.

15. This can be used to moderate salt concentrations in the blood and in the interstitial fluid. If the kidney malfunctions, salt concentrations in the body are thrown off.

16. The distal convoluted tubule is next. This is where more water or salts are absorbed, to fine tune the balance of salt in the urine and blood.

17. Finally, the filtrate, now properly called urine, is moved into the collecting duct, and is further concentrated on its way to the renal pelvis.

18. Recall that the cortex is the outermost portion of the kidney. This is where the convoluted tubules are. The medulla is the innermost section, where the loop of Henle goes to.

19. The medulla has a higher salt concentration than the cortex, so it pulls out more water.

20. Many problems can arise with the kidney; too much sugar in the urine might indicate diabetes, too much protein could be a problem, and blood is a definite problem.

Test of New Learning: (5 minutes)

1. Explain the use of concentration gradients in the kidney.

2. What would happen if you didn’t eat enough salt? If you ate too much?

Assignment: