Aim: How does excretion maintain homeostasis ?

DO NOW:

Summarize each page with 3 sentences

HW #17

Text – read pages 985-989

Ans ques. 2 and 4 on page 989

Digestive wastes (undigested food) is the elimination of feces. It moves into the large intestine for compaction.

Wastes of metabolism are..

..products of cell processes that must be removed from the organism or they will become toxic.

nitrogenous wastes - urea

excess salt and water

Carbon dioxide

Your Body’s Filter

Have you ever seen a water-purification system attached to a faucet?This system removes impurities from the water such as arsenic or other chemicals that can be harmful to people. As water passes through the filters contained in the system, the impurities are trapped on the surface of the filters. Eventually, the water that comes out of this purifier is free of the impurities.

Pg 985 work in groups and answer the questions

• 1. Your body has its own system for filtering blood. Why might the blood in your body need to be filtered?

• 2. What organ(s) do you think filters your blood?

• 3. How do you think the filtered materials leave your body?

Excretory System

The Kidneys

1. Kidney Structure

2. Filtration

3. Reabsorption

The Skin (Integument)

Respiratory System (carbon dioxide)

Renal ArteryRenal Vein

Kidney

Ureter

Bladder

Urethra

Cortex

Medulla

Kidney Nephron

Cortex

Medulla Renal artery

Renal vein

Ureter

To the bladder

Bowman’s capsule

Glomerulus

Capillaries

Collecting duct

To the ureter

Loop of Henle

Artery

Vein

Figure 38–17 Structure of the Kidneys

Section 38-3

Filtration

Most filtration occurs in the glomerulus. Blood pressure forces water, salt, glucose, amino acids, and urea into Bowman’s capsule. Proteins and blood cells are too large to cross the membrane; they remain in the blood. The fluid that enters the renal tubules is called the filtrate.

Reabsorption

As the filtrate flows through the renal tubule, most of the water and nutrients are reabsorbed into the blood. The concentrated fluid that remains is called urine.

Secretion

Substances such as hydrogen ions are transferred from the blood to the filtrate.

Figure 38–18 The NephronSection 38-3

Vein

Artery

Shunt

Air detector Dialysis machine

Blood pump

Blood in tubing flows through dialysis fluid

Used dialysis fluid

Compressed air

Fresh dialysis

fluid

Figure 38–19 Kidney DialysisSection 38-3