The Excretory System

The Excretory System

- All the tissues and organs that are involved in the removal of waste products from the body.

I. Parts of the Human Excretory System:

A. The Urinary System- Excretes water, nitrogenous wastes and salts as urine from the body.

B. The Digestive System- Eliminates water, some salts and bile in addition to indigestible food matter. These materials combine to make feces.

Components of the Excretory System

C. Respiratory System- Eliminates carbon dioxide and water (as a vapor).

D. Integumentary System- (the Skin) Excretes water, salts and small amounts of nitrogenous wastes (urea), all in the form of perspiration.

II. The Urinary System in Detail

1. The Kidneys- extract wastes from the blood, balance the fluids of the body and form urine.

- Location- The body’s two kidneys are against the back wall of the abdominal cavity.

- The kidneys are separated into two regions, the outer Cortex and the inner Medulla.

II. The Urinary System in Detail

- The functional unit of the kidney is called the Nephron, a microscopic, coiled set of tubes with a tiny capillary filled bulb at one end.

II. The Urinary System in Detail

2.The kidneys are involved in the following processes: -Excretion of unwanted substances.-Metabolic breakdown of excess salts and toxins.-When Amino Acids are broken down in the body they leave behind nitrogen containing waste in the blood. This process is called deamination.-The liver turns these wastes into urea, which is filtered back out of the blood by the kidneys.

II. The Urinary System in Detail

3. Maintaining Water Balance.

-The kidneys are responsible for maintaining a steady level of water in the body, even when the amount of water entering the body varies from day to day.

II. The Urinary System in Detail

4. Excretion of unwanted substances:

- Urea (dissolved in water) is filtered out of the blood by the bulb end of the Nephron. This structure is called the Glomerulus.

II. The Urinary System in Detail

- Next, the tubule and the Loop of Henle reabsorb water from the filtrate and put it back in the blood stream.

- This concentrates the waste filtrate into a fluid called Urine.

- Urine is collected by the Ureter and carried to the urinary bladder where it is stored until urination.

- During urination, urine passes into the urethra and out of the body.

II. The Urinary System in Detail

C. Urine usually contains the following substances:

- Nitrogenous wastes like urea, uric acid and creatinine.

- Salts, also known as electrolytes, like sodium or potassium chloride.

-Pigments from bile compounds in the blood or from food or drug dyes.

II. The Urinary System in Detail

D. Urine does not usually contain the following:1. Glucose

-If present this indicates the cells are not absorbing or metabolizing sugars, usually as a result of diabetes. Having glucose in the blood is called glycosuria.

2. Blood-If present this indicates kidney damage or urinary system disease, like nephritis. This condition is called hematuria.

III. Disorders of the Urinary System:

A. Kidney Disorders: 1. Kidney stones are formed when calcium salts or uric

acid does not stay dissolved in urine. -The stones that form may arise in the kidneys, after filtration, or in the bladder. - Kidney stones can be the size of small grains of sand or the size of pebbles.

-Surgery is usually required to remove larger stones while some of the smaller ones can be passed through the ureters and urethra out of the body.

III. Disorders of the Urinary System:

2. Kidney Failure (Renal System Failure) results when nephrons are no longer able to perform their normal functions.

- Renal failure may cause dehydration, a build-up of nitrogen wastes in the blood, salt imbalances, anemia and hypertension.

- Renal dialysis- the artificial filtering of waste materials out of the blood.

- A kidney transplant is the final treatment for renal failure. Kidneys contain extra functioning tissue so that individuals can live normally with just one intact.

III. Disorders of the Urinary System:

3. Gout- results when the body makes uric acid crystals instead of urea.

-the crystals collect in the joints in the legs, causing pain and swelling.