Chapter 38:Excretory System

Functions of the Excretory System

a. Collect water and filter body fluidsb. Remove and concentrate waste products from body fluids and

return other substances to body fluids as necessary for homeostasis

c. Eliminate excretory products from the body- Include the kidneys (removes the most metabolic waste via urine),liver, lungs, and skin

*** Responsible for regulating water balance in various body fluids- Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too dilute or too concentrated (balance b/w sodium & water)

ANIMAL EXCRETORY STRUCTURES • PROTOZOA: CELL MEMBRANE

(DIFFUSION) CONTRACTILE VACUOLE (EXCESS WATER)

• FLATWORM(PLANARIA): FLAME CELLS

• EARTHWORM: NEPHRIDIA, SKIN• GRASSHOPPER: MALPHIGIAN

TUBULES, TRACHEAE• CRAYFISH: KIDNEYS, GILLS• HUMAN: LUNGS, SKIN, LIVER,

KIDNEYS• SNAKE: KIDNEYS

ANIMAL EXCRETORY STRUCTURES

• Made-up of the kidneys, ureters, bladder, and urethra.• Nephron, an evolutionary modification of the nephridium the kidney's functional unit • Waste is filtered from the blood and collected as urine in each kidney• Urine leaves the kidneys by ureters, and collects in the bladder can distend to store urine that eventually leaves through the urethra

• Renal artery brings blood into kidneys• Renal vein takes blood back to heart

Nephron- Urine ProductionUrine Production

1. Filtration in the glomerulus and nephron capsule2. Reabsorption in the proximal tubule3. Tubular secretion in the Loop of Henle

Components of The Nephrona. Glomerulus: mechanically filters bloodb. Bowman's Capsule: mechanically filters bloodc. Proximal Convoluted Tubule: reabsorbs 75% of the water, salts, glucose, and amino acidsd. Loop of Henle: countercurrent exchange, which maintains the concentration gradiente. Distal Convoluted Tubule: tubular secretion of H ions, potassium, and certain drugs

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

Structure of the KidneysSection 38-3

FiltrationMost 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.

ReabsorptionAs 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.

The NephronSection 38-3

KANGAROO RAT – LIVE IN HYPERTONIC ENVIRONMENT

ADAPTATIONS

• VERY EFFICIENT KIDNEYS, WHICH ALLOW IT TO LIVE WITHOUT DRINKING!

• HAVE A LONGER LOOP OF HENLE IN THEIR NEPHRONS, CAUSING THEM TO PRODUCE URINE THAT IS 5 TIMES MORE CONCENTRATED THAN HUMANS

• DON’T SWEAT, AND LOSE WATER ONLY THROUGH EVAPORATION DURING GAS EXCHANGE

• RETAIN 90% OF THEIR WATER, AND 10% COMES FROM THEIR DIET