Excretory System

Excretory System: Poison Protection If you knew there was poison hidden in your house, you would surely do everything possible to find and remove that poison. If you didn't, you and your family would slowly die. How would you find it? How would you remove it? You would probably figure out a system of searching and removing. That would be an excretory system.

Functions of the Excretory System Remove toxic nitrogen wastes (urea) from the body Helps maintain homeostasis by eliminating or conserving water and salts In humans, the organs used for excretion are the kidneys

Kidneys Kidneys are located near the lower back on either side of the spinal column Blood enters the kidneys through the renal artery and exits through the renal vein

The kidneys remove wastes from the blood and produce liquid waste called urine Kidneys maintain blood pH and regulate the water content of the blood

Blood Purification The mechanism of blood purification involves two distinct processes: –Filtration –Reabsorption

Filtration Nephrons are the sites of filtration Takes place in the glomerulus (small network of capillaries encased in the upper end of the nephron by a hollow, cup shaped structure called Bowman’s Capsule) The filtrate contains water, urea, glucose, salts amino acids & some vitamins

Reabsorption The process in which liquid is taken back into a vessel Materials including amino acids, fats & glucose are removed from the filtrate by active transport & reabsorbed into the capillaries (water is returned by osmosis)

The clean blood returns through the renal vein and into circulation Urine is collected in the urinary bladder Urine is released from the bladder through a tube called the urethra

Parts of the Excretory System The wastes follow this path: Kidneys  Ureter  Bladder  Urethra –The ureter and urethra are transport tubes –The bladder is a collection point

The Excretory System Kidney Artery Vein Ureter Urinary Bladder Urethra

Kidney failure can cause toxic chemicals to build up to lethal levels in the blood Dialysis machines can perform the function of the kidneys Kidney transplants have become routine transplant surgeries The kidneys were the first organs to be successfully transplanted in 1954

Interesting Facts Your blood passes through the kidneys 300 times a day. The nephrons clean all your blood in 45 minutes. Every day the nephrons send about six cups of urine to the bladder.

Here is a graph on dialysis and transplant survival from : Kidney disease causes the build up of wastes in your system. Some cases of kidney disease can be treated with medication. But if the disease is more severe, then the patient might be put on a dialysis machine. Blood is pumped through a dialysis machine that filters the waste from the blood and returns the clean blood. Some patients have to spend near 60 hours/month on a dialysis machine.