1. Aim #49: Why is it important that waste material be excreted from the body?

2. Think Questions
1. The muscular nature of the walls of ventricles is most closely associated with their function of a. storing blood from the body b. producing red blood cells c. maintaining pressure lower than that in the atria d. forcing blood to the lungs and body 2. Which statement most accurately describes the human heart? a. It has two atria and one ventricle, and it pumps blood directly into veins. b. It has one atrium and one ventricle, and it is composed of cardiac muscle. c. It has one atrium and two ventricles, and it is composed of visceral muscle. d. It has two atria and two ventricles, and it pumps blood directly into arteries. 3. Although the digestive system is primarily responsible for the breakdown of food, this process can be disrupted if the circulatory system malfunctions. The best explanation for this disruption is that a. human body systems interact with each other to perform life functions b. the circulatory system is the control center of the body c. the digestive system and the circulatory system have many organs in common d. the circulatory system is responsible for the coordination of life functions, including the breakdown of food

3. I. Excretion is NOT egestion!
*Q: What are some wastes that the body produces? Think outside the box!
Egestion is part of the digestive system, and includes partially digested food (feces)
Excretion is part of the excretory system, and only includes the removal of waste
Includes the lungs, the skin, and the kidneys
*Q: How do you think the lungs and the skin help to eliminate wastes?
*Q: Why is it important that waste material be excreted from the body?

4. II. Kidneys: Structure and function
2 kidneys filter the blood to remove wastes from it
Just above the waist, in the back, by the spine
Functions:
They remove waste from the blood
Maintain blood pH
Regulate the water content of the blood (and also blood volume)
*Q: How do the kidneys work together with another body system to maintain homeostasis?

5. *Q: What on Earth is “a solution of wastes”?
Each kidney is connected to the ureter, a tube which then leads to the urinary bladder
Urinary bladder – a smooth muscle bag that stores “a solution of wastes”
*Q: What on Earth is “a solution of wastes”?
*Q: Based on this picture, summarize what the kidneys do.

7. III. Nephron: the main unit of the kidney
Each kidney is made up of ~1 million tiny filters
*Q: What is the purpose of a filter?
Nephron – the filtering unit of the kidney
*Q: What might be one reason so many nephrons are needed in the kidneys?

8. Blood entering a nephron carries wastes
*Q: Where is the waste coming from?
Water, ions, glucose, and amino acids from the blood get cleaned up and reabsorbed into the body
Almost 99% of the water that gets filtered gets reabsorbed into the blood.
*Q: How does this contribute to homeostasis?

9. IV. Urine - Waste molecules and excess water and ions Ureter 
*Q: Based on this information, why might your urine be darker if you are dehydrated?
Urine comes from the kidneys 
Ureter 
Urinary bladder 
Urethra (another tube) 
Toilet (hopefully!)