1. Excretion

2. Excretion

3. Excretion
Excretion = the process by which wastes are eliminated from the body
The excretory system includes:
Lungs: excrete gaseous carbon dioxide from cellular respiration
Rectum: excrete solid undigested remains from food
Skin: excretes excess water, salts, urea
Kidneys and accessory organs

4. The Urinary System
The urinary system rids the blood of wastes produced by the metabolism of nutrients and controls blood volume by removing excess water produced by body cells.
The urinary system includes:
Kidneys
Urinary bladder
Connecting tubules:
Ureter
Urethra

5. The Urinary System Section 38-3 Artery Vein Kidney (Cross Section)
Cortex
Medulla
Ureter
Urinary bladder
Urethra

6. Kidneys
Most people have 2 kidneys located on either side of the spinal column on your lower back
Ureters = tubes that carry urine from each kidney to the urinary bladder
Urinary bladder = saclike organ that stores urine until it can be excreted
The kidneys filter blood by removing urea, excess water and other wastes collected as urine and the clean filtered blood returns to circulation

7. Kidney Structure Inner part = renal medulla Outer part = renal cortex
Functional units of the kidney = nephrons
About 1 million nephrons in each kidney
Each nephron has its own arteriole (small artery), venule (small vein), and network of capillaries to filter blood

8. Figure 38–17 Structure of the Kidneys
Section 38-3
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
FILTRATION…REABSORBTION…SECRETION

9. Urine
The material that remains = urine containing urea, salts, water and other substances
The loop of Henle conserves water and minimizes the volume of urine
Urine is stored in the urinary bladder until it can be released from the body through a tube = urethra

10. Kidney Function The kidneys maintain homeostasis by:
Regulating the water content of the blood (blood volume)
Maintaining blood pH
Removing waste products from the blood