(MOS) Excretion Lesson

Excretion Lesson

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No one likes to have garbage pile up, least of all cells. Why are the cells of the human body continuously cleaning house? What types of metabolic activities cause waste products to accumulate? How do skin, lungs and kidneys help to remove waste from the body? What would happen if cells could not remove waste products? To discover the answer to these and other questions, read through the following learning object about the Excretory System.

 

Excretion helps the body maintain homeostasis by collecting and removing wastes produced by cells from the body. The major organs of the excretory system are the kidneys, ureter, urinary bladder, and urethra. The excretory system removes excess water and urea, a harmful toxin produced by the breakdown of proteins, from the blood. Have you ever used a strainer to separate spaghetti from a pot of water? The kidneys act as a filtration system to remove urea and other waste materials from your blood. These watery waste materials and urea are known as urine as they accumulate in millions of tiny structures within the kidney called nephrons. A small cluster of capillaries are enclosed within a capsule located inside the nephron. This arrangement of blood vessels or the glomerulus is responsible for the filtration of your blood.

 

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The urine travels through the ureters to the urinary bladder. Urine is stored in the urinary bladder until it is ready to exit the body through a small tube called the urethra. The kidneys help maintain homeostasis by not only regulating the amount of water in your body but also removing proteins and glucose from your blood. The presence of the sugary substance glucose in a urine sample may indicate that a person may have diabetes. Their cells are not able to absorb enough glucose from their blood.

The learning object below (adapted from a resource created by the University of Alberta) explores heat exchange between the human circulatory system and the environment and illustrates how our body adapts its blood flow under different conditions. Animations show how peripheral heat loss, counter-current heat exchange, and selective vasoconstriction help maintain a healthy core body temperature. Use the interactive to see how blood flow is controlled by the skin and kidneys to maintain body temperature.

 

Review the information presented in the following presentation.

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