1. Unit Four Urinary System & Excretion
Lisa Michelek 1

2. Excretion Cellular activities, such as respiration, produce wastes.
Some of these wastes are harmful to the body and must be removed.
An upset in the balance of body chemicals can lead to serious health problems or death.
Excretion is the removal of the wastes of cell activities from the body.
Do not confuse excretion with egestion.
The wastes of excretion are liquids and gases.
Solid wastes are removed during egestion. 2

3. Metabolic Wastes
Wastes produced by life activities (metabolism) are called metabolic wastes.
Carbon dioxide, water, urea, and mineral salts are metabolic wastes.
Carbon dioxide is a gaseous waste formed during aerobic respiration.
Water is produced by aerobic respiration and other cellular activities.
Urea is a nitrogen waste resulting from the breakdown of amino acids produced during protein digestion.
The breakdown of various compounds in the cell form mineral salts. 3

4. The Role of Blood in Excretion
The wastes of excretion leave body cells and are secreted into intercellular fluid.
Wastes pass from intercellular fluid into the blood plasma by the process of diffusion.
The blood plasma transports these excretions to excretory organs that remove them from the body. 4

5. The Excretory System
The excretory system removes cellular wastes from the body.
By getting rid of wastes, the excretory system helps maintain proper balance of body chemicals.
The organs of the excretory system are:
skin,
lungs,
urinary system
liver 5

6. Skin
The skin is made up of an outer layer called the epidermis and an inner layer called the dermis.
The skin contains sweat glands that excrete perspiration through skin pores.
Perspiration is made up of nitrogenous wastes (urea), salts, and water. 6

7. Skin The skin is also involved in controlling body temperature.
When perspiration evaporates from the skin, heat is absorbed from skin cells.
This absorption of heat lowers body temperature, which results in cooling the body. 7

8. Lungs The lungs also play a role in excretion.
Lungs excrete carbon dioxide and water vapor by diffusion and exhalation. 8

9. Human Urinary System
Some of the body’s excretions leave by way of the urinary system.
The urinary system consists of the kidneys, ureters, urinary bladder and the urethra. 9

10. Human Urinary System
The kidneys are bean-shaped organs that lie along the back wall of the abdomen.
Each kidney is made up of masses of microscopic subunits called nephrons. 10

11. Human Urinary System
The kidneys act as filters in the removal of urea and excess water and salts from the blood.
Besides wastes, useful substances diffuse out of the blood into the kidney.
The useful substances are returned to the blood before the blood leaves the kidney. 11

12. Human Urinary System
Each kidney sends excretions, called urine, into a tube called the ureter.
Urine, made up of urea and water, flows through the ureters to the sac-like urinary bladder.
The bladder stores urine temporarily.
The urinary bladder opens into a single tube, the urethra, through which the urine leaves the body. 12

13. Liver The liver is the largest internal organ in the body.
The liver produces urea, a nitrogenous waste, by breaking down excess amino acids.
Other functions of the liver include the production of bile to aid the small intestines during digestion, the removal of poisons, such as alcohol, from the blood and the storage of extra sugar in the form of animal starch (glycogen).
The liver changes glycogen into glucose and secretes it back into the bloodstream when the body needs energy. 13

14. Excretory System Disorders
Kidney Stones
Kidney stones are collections of solid material that may block the kidneys, ureters, or bladder.
Gout
Gout is a disease associated with the production and deposition of uric acid crystals in joints.
It is very painful condition that produces symptoms similar to arthritis. 14

15. Excretory System Disorders
Uremia
During uremia, urea and other wastes are not filtered out of the blood.
The body cells become poisoned and there is urine in the blood.
Skin Problems
One cause of skin problems, such as blackheads and acne, is the clogging of skin pores. 15

16. Excretory System Disorders
Cirrhosis of the Liver
A disease of the liver caused by damage to the liver cells.
This leads to a type of high blood pressure, which can cause serious complications.
The most common cause is drinking large amounts of alcoholic beverages.
Hepatitis, an inflammation of the liver, can also lead to this disease. 16

17. Excretory System Disorders
Cirrhosis of the Liver
There may be no symptoms in the early stages of the disease.
It is usually discovered during routine medical examinations or blood tests.
Later symptoms are mild jaundice (yellow skin), edema (fluid collection in tissues), mental confusion and vomiting of blood.
In men, enlargement of breasts and loss of body hair can occur.
The treatment is to slow down the disease. This is done by eliminating alcoholic beverages.
Liver transplants are the only chance for long-term cures. 17

18. Urinary System Summary