What is the major function of the urinary system?
Keeps chemicals and water in balance by removing urea (waste) from the blood
What is urea produced from?
Foods containing protein, such as meat, poultry, and certain vegetables
Where is urea carried?
In the bloodstream to the kidneys
How many kidneys does a mammal contain? Where are they found?
- Two kidneys
- Located below the ribs towards the middle of the back
Which hormone is produced by the kidneys? What is its function?
- Erythropoietin
- Aids in the formation of RBCs
What are the filtering units of the kidneys?
Nephrons
What does each nephron consist of?
- Glomerulus: ball formed of small blood capillaries
- Renal tubule: small tube
What forms the urine?
- Urea
- Water
- Other waste substances
What does urine pass through?
Nephrons, and down the renal tubules of the kidney
What is the function of ureters? How many do we have?
- Two ureters
- Carry urine from the kidneys to the bladder
Which muscles continually tighten and relax to force urine downward?
Muscles in the ureter
How often are small amounts of urine emptied into the bladder from the ureters?
About every 10 to 15 seconds
Where is the bladder located?
Located in the lower abdomen
How is the bladder held in place?
By ligaments that are attached to other organs and the pelvic bones
What function does the bladder exert during relaxation and during contraction?
- Relax and expand to store urine
- Contract and flatten to empty urine through the urethra
How much urine can the typical adult healthy bladder store?
Up to 2 cups for 2 to 5 hours
What are the functions of the two sphincter muscles?
- Circular muscles that help keep urine from leaking
- Close tightly like a rubber band around the opening of the bladder
What is the function of the nerves in the bladder?
Alert a person when it is time to urinate, or empty the bladder
What is the function of the urethra?
The tube that allows the urine to pass outside of the body
How does normal urination occur through nervous signalling?
- The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder
- The brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra
What is the volume and composition of urine adjusted by? Why?
- Neural and hormonal mechanisms
- To maintain constancy of volume and electrolyte concentrations in the body fluids
What is usually accompanied by sodium reabsorption in the renal tubules? Why?
- Chloride
- To maintain electrostatic neutrality
How can the amount of sodium excreted be approximately determined?
By the estimation of chloride concentration
The number of drops of silver nitrate is equal to what in this experiment?
The number of grams of sodium chloride per liter of solution
How is specific gravity (or density) determined?
With a urinometer
What is the specific gravity of pure water?
1.000
What is the definition of specific gravity?
The ratio of the density (compactness) of a substance (urine) to that of distilled water at a specific temperature
What does a higher specific gravity infer?
A higher composition of dissolved solids (urea, sodium chloride, etc.)
How may a rough approximation of the total dissolved substances in urine may be obtained?
By multiplying the final two figures of the specific gravity reading by 2.66 (Long’s coefficient)
What is the normal specific gravity of a 24-hour specimen of urine?
1.020 (range: 1.016 to 1.025)
What does a specific gravity of 1.001 indicate?
Following ingestion of a large amount of fluids
What does a specific gravity of 1.040 indicate?
Heavy perspiration
What are the major components of urine?
- 95% water
- 2% urea
- 0.18% sulphate
- 0.12% phosphate
- 0.1% creatine and sodium
- 0.6% potassium and chloride
What type of instrument is a urinometer?
Hydrometer
What does each line of a urinometer represent?
0.001
What is specific gravity a function of?
- Number
- Density
- And weight of the solute particles present
Specific gravity is used as a measure of the power of what?
Concentration power of the kidney
What is the indicator in the chloride concentration procedure?
K2CrO4 (potassium chromate)
What is the function of silver nitrate (AgNO3)?
- Reacts with the chloride in urine to precipitate AgCl (silver chloride)
- Any excess AgNO3 reacts with potassium chromate to form a reddish precipitate of silver chromate (Ag2CrO4), which indicates the endpoint
Is specific gravity a physical or chemical characteristic?
Physical characteristic of urine measured through a chemical test
When would a urine sample be recommended if a lab technician is looking for a very small amount of protein?
- In the morning
- A concentrated morning urine specimen is superior to a diluted specimen
What is the normal range of sodium in a random urine sample?
25 to 100 mEq
How do you determined the number of mg from the mEq of sodium?
mg = mEq x 35.4
What is the normal urine sodium value over a day?
40 to 220 mEq/L per day