The Excretory System

Functions

• Excretion - Filtering metabolic wastes

• Wastes– Excess salts– Carbon Dioxide– Urea – produced when amino acids are

used for energy

Skin

• Sweat– Excess water,

salt, small amounts of urea

Lungs

• Excrete CO2 when energy is produced by the mitochondria

Liver

• Converts amino acids to useful compounds

• Produces urea as waste

Kidneys

• Remove waste products from the blood

• Maintain blood pH

• Regulate water content of blood

Urinary System

The Urinary Organs:

• Kidneys: filters that take waste out of the blood and make urine

The Urinary Organs:

• Ureters: tubes that carry urine to the bladder

The Urinary Organs:

• Bladder: a muscular bag that collects urine

The Urinary Organs:

• Urethra: a tube that carries urine out of the body

Kidneys

Kidney Regions

Renal Corte

xRenal Medull

aRenal Pelvis

Blood Flow

• Waste-laden blood enters kidneys through the renal artery

• Clean filtered blood leaves the kidney through the renal vein

Nephron

• Structural units of the kidney

• Over 1,000,000 in each kidney!– 3 cm long– 0.03 mm wide

• Filter the blood• Reabsorb water,

glucose, and salt

Glomerulus

NephronGlomerulus

Loop of Henle

Bowman’s Capsule

Filtration

• Blood pressure forces blood through the glomerulus– All blood is

filtered every 45 minutes

Filtration

• Filtrate– Water, urea,

glucose, salts, amino acids, and some vitamins• Proteins, cells, and

platelets are too large to pass through and remain in the blood

Reabsorption

• Most of the filtrate reenters the blood

• Active transport– Amino acids, fats,

glucose

• Osmosis – 99% of water reabsorbed

Urine

• Forms in Kidneys– Loop of Henle

• Made up of urea, excess salts, and water – Concentration

variation

• Kidney Ureter Bladder

Bladder

• Hollow muscular organ • Flexible cells• Nerves tell the brain

when the bladder is full. – After 200 ml have

accumulated– After 1 minute reflex

subsides

• Holds approximately 500 ml

Kidney Disease

Dialysis

• http://www.kidneypatientguide.org.uk/site/HDanim.php