1. Module 8 Intro

1.42. Page 3

Lesson 7

Module 8—Circulation, Immunity, and Excretion

Structures of the Excretory System

 

So, what are the structures of the excretory system that will get rid of wastes and perform filtration?

 

kidneys:  two organs that filter wastes from the blood and adjust the concentration of salts in the blood


The waste is excreted in the urine.

 

bladder:  the organ where urine is stored before being discharged by the urethra

 

ureter:  in mammals, a pair of muscular tubes that carry urine from the kidneys to the bladder

 

urethra:  the tube through which urine exits the bladder and the body

The human excretory system is characterized by two kidneys located symmetrically in the lower abdominal region on either side of the spinal cord. The kidneys are the body’s blood cleaners.

 

The renal artery brings oxygenated blood to the kidney, while the renal vein removes deoxygenated blood. These two blood vessels deliver and move the large volume of blood necessary for efficient removal of the waste products. Each kidney is connected to the bladder by a long tube called the ureter.

 

The kidneys release urine through the ureters. The bladder stores urine and physically excretes urine to the external environment through another shorter tube called the urethra.

 

You may read pages 306 and 307 in the textbook and see visual diagrams.

 

Try This

 

TR 1. Investigation 9.A: Identifying Structures of the Excretory System

 

You now have the opportunity to either perform a real dissection of a sheep’s kidney or observe a virtual dissection of a sheep’s kidney.

 

If you have access to the materials listed on page 309 of the textbook, you can proceed to complete the dissection as outlined.

 

Or you may choose to watch a virtual dissection.

 

In either case, you will go to your Lesson 7 Assignment to complete two analysis questions based on your experiences with the sheep’s kidney.

 

Look at the top of page 307 of the textbook for a labelled diagram of the excretory system.

 

Read

 

Kidney Structure and General Function

 

nephron: a microscopic tube-like filtration unit found in the kidneys that filters and reabsorbs various substances with the blood and produces urine

The main function of the kidneys is to filter, reabsorb, and secrete hormones. Filtration and reabsorption take place in the nephron, while kidney secretions are a function of the hormone system.

 

This is a general graphic of the nephron, with no labelling.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007). 307, fig. 9.3. Reproduced by permission.

 

The nephron has three functional regions. Review these regions as described on page 308 of your textbook. Try the following Self–Check activity.

 

Self-Check

 

SC 1. Complete this Self-Check activity.

 

Module 8: Lesson 7 Assignment

 

Remember to submit the Assignment answers to your teacher as part of your Lesson 7 Assignment.