Unit D

Module 8 ~ Lesson 3

Structures of the Excretory System

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.

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

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.

The nephron has three functional regions: a filter, a tubule, and a duct.


Read "The Organs of the Excretory System", "The Kidneys: The Body's Blood Cleansers", and "An Overview of the Nephron and its Three Functional Regions" on pages 306 to 308 of your textbook.