1. Mrs. Legro’s Science Class 2017-2018
The Excretory System
Mrs. Legro’s Science Class

2. Learning Objectives
Distinguish between the excretory and urinary systems.
Describe the functions of the excretory system
Know the organs/other body systems of the excretory system
Describe how the kidneys work
Learn important vocabulary related to lesson

3. Functions of the Excretory System
The excretory system is responsible for eliminating wastes from the body.
Homeostasis is the body’s way of keeping the internal environment stable despite the changes that are happening outside of the body.
If wastes aren’t eliminated, toxic substances build up and damage organs, which can result in serious illness or death.
This system includes other body systems:
Digestive System, Respiratory System, Skin, Urinary System
Body parts that make up the excretory system: liver, lungs, skin, kidneys, ureters, urinary bladder, urethra

4. Objective 1
Describe the functions of the excretory system

5. Body Systems Within the Excretory System

6. Objective 2
Know the organs/other body systems of the excretory system

7. The Urinary System Rids the blood of wastes produced by the cells.
Controls blood volume by removing excess water produced by body cells during respiration.
Regulates fluid levels
The hypothalamus constantly monitors the amount of water in the blood.
When brain detects too much water in the blood, the hypothalamus releases a lesser amount of a specific hormone.
This signals the kidneys to return less water to the blood and increase the amount of wastewater, called urine, that is excreted.
Also balances amounts of certain salts and water that must be present for all cell activities to take place.

8. Organs of the Urinary System
Kidneys:
Located on the back wall of abdomen, at about waist level.
They filter blood that contains wastes collected from cells.
In about 5 minutes, all of the blood in your body passes through your kidneys
Acts as a 2-stage filtration system
Made up of about 1 million tiny filtering units called nephrons, which are tiny filtering units of the kidney.

9. Objective 3
Distinguish between the excretory and urinary systems.

10. Filtration in the Kidney (How the Kidneys Work)
An average-sized person produces about 1L of urine per day.
Each nephron has a cuplike structure and a tube-like structure, called a duct.
In the cuplike structure, blood moves from a renal artery to capillaries
The 1st filtration occurs when water, sugar, salt, and wastes from the blood pass into the cuplike structure.
Left behind in the blood are red blood cells and proteins.
Liquid in the cuplike structure is squeezed into a narrow tubule.
Capillaries that surround the tubule perform the 2nd filtration
Most of the water, sugar, and salt are reabsorbed an returned to the blood.
The collection capillaries merge to form small veins, which merge to form a renal vein in each kidney.
Purified blood is returned to the main circulatory system.
The liquid left behind flows into collecting tubules in each kidney.
This wastewater, or urine, contains excess water, salts, and other wastes that are not reabsorbed by the body.

11. Objective 4
Describe how the kidneys work

12. Urine Collection and Release
Ureters: tubes that lead from each kidney to the bladder.
Bladder: is an elastic, muscular organ that holds urine until it leaves the body. It can stretch to hold up to .5L of urine.
Urethra: carries urine from the bladder to the outside of the body.

13. Urinary Diseases and Disorders
What happens when someone’s kidneys don’t work properly or stop working?
Waste products not removed act like poisons in body cells.
Water that normally is removed from body tissues accumulates and causes swelling of the ankles and feet.
Sometimes these fluids build up around the heart, causing it to work harder to move blood to the lungs.
Imbalance of salt occurs and if the body can’t restore this balance, the kidneys and other organs can be damaged.
Infections caused by microorganisms
Ureters and Urethra are narrow tubes, which means they can become blocked easily in some disorders.
A blockage of one of these tubes can cause serious problems because urine cannot flow out of the body properly.
If the blockage is not corrected, the kidneys can be damaged.

14. Detecting Urinary Diseases
Urine can be tested for signs of a urinary tract disease
Change in urine’s color can suggest kidney or liver problems
High levels of glucose can be a sign of diabetes
Increased amounts of a protein called albumin can indicate kidney disease or heart failure
Dialysis: is a process that allows a person’s blood to be filtered by an artificial machine (because their kidneys have failed).
When kidneys are damaged, albumin can get into the urine, just as a leaky water pipe allows water to drip.

15. Objective 5 Learn important vocabulary related to lesson
Do you know the meaning of these words?
excretory system, homeostasis, kidneys, nephrons, urine, ureter, urethra, bladder and dialysis