Topic: ExcretionAIM: How does the process of

Excretion aid in the maintenance of Homeostasis?

• Do Now: Define & write an Acrostic Poem for the word EXCRETION

Homework: TEXT BOOK

Read Pages 595-599 Page 599

Questions 1-5

What is the Function or Purpose of the Excretory System?

• To Rid the body of METABOLIC WASTES!!

• Alternate wording: To Rid the body of CELLULAR WASTES!!

What are METABOLIC WASTES?

Metabolic wastes are chemical products which are of no use to the body.

In fact, some of them may prove detrimental to health, and accumulation of these waste products can even be fatal.

They are produced by different cellular activities.• Can you name some Metabolic wastes?

Metabolic Wastes

• Carbon Dioxide

• Sweat

• Ammonia

• Urine

What are the Components of the EXCRETORY SYSTEM

Kidneys Skin Lungs Liver

Explain the processes that produce these Metabolic Wastes.• CO2: Produced from the process of

Cellular Respiration

• Ammonia: The breakdown of excess Amino Acids in the Liver. (DEAMINATION)

• Urea: The breakdown of excess of Amino Acids in the Liver. (DEAMINATION)

• Sweat: Diffusion of excess urea, salts, and water.

How Do the Lungs function in Excretion?

• By removing Carbon Dioxide from the body

Explain the processHOW?

How Does the liver function in Excretion?

• Liver DETOXIFIES THE BLOOD

How Does the Skin function in Excretion?

• Sweat is excreted through tiny openings called pores.

SWEAT GLANDS There are approximately 2 million sweat glands

all over the skin. They are tiny, coil shaped tubes. They extend from the deepest layer of the skin to

the surface. These glands help to regulate the body

temperature and also contribute to the excretion of water and salt from the body.

Sweat contains about 98-99% of water. Certain inorganic salts – specially sodium

chloride along with small make up the remaining 1-2%.

SKIN STRUCTURE

SWEAT GLAND

How do the Kidneys function in Excretion?

• FILTER the blood

• Kidneys are part of the Urinary System

• Functional unit of Kidneys is the Nephron.

• Kidneys and the urinary system including Nephrons

URINARY SYSTEM

URINARY SYSTEM

KIDNEY

1. The Glomerulus is a ball of capillaries found inside Bowmans Capsule.

2. The blood is filtered in Bowmans Capsule.

3. The Filtrate moves down into the loop of Henle where the reabsorption of some substances occurs.

4. Whatever is not reabsorbed is now urine and goes to a collecting tubule.

5. Collecting tubules empty into the ureters which lead to the bladder.

6. Urine exits through the urethra.

URETERS There are 2 muscular tubes, 25 to 30 cm in

length, with a very small inner diameter of about 3 mm.

They convey urine from the kidneys to the bladder.

URINARY BLADDER Pear shaped organ, which lies in the pelvis. Though the 2 ureters, the bladder receives waste

products, including urea from the kidneys. The average capacity of the bladder is up to 400

or 500 mL. The need to pass urine is usually felt when the

bladder is filled to about 280 mL. Sometimes up to 500 mL can be tolerated. Filling above 500 mL leads to pain.

URETHRA Is a passage way through which urine is

discharged from the bladder. In men the urethra is longer than in females. It passes through the penis, and also has a

passage for the discharge of semen. In women the shorter urethra opens immediately

in front of the vagina. It serves solely for the discharge of urine.

URINEThe average daily output of urine is 1.0 to 1.5

liters/day.Apart from excess water, urine contains

nitrogenous substances (chiefly urea) – approximately 32 g and mineral salts containing sodium, chloride, phosphorus, and potassium.

Urea and other nitrogen containing substances are derived from protein.

These compounds undergo further changes in the liver before passing to the kidneys to be excreted in the urine.