Slides in this set
· Liquid waste product of the body
Contains water, electrolytes and other waste metabolites
· Filtered out of blood by kidneys
· Excreted through the urethra
1-2 litres / 24 hours per normal adult
Amount per day varies considerably.
· Quantity of water excreted per person per day is
affected by factors such as:
recent fluid intake (water, and other food/drinks that
general health (some disease states may affect urine
· Colour: yellow/amber but varies according to recent diet and the
concentration of the urine.
Drinking more water reduces the concentration of urine, and causes it to have a
· Smell: Can be used to diagnose conditions
e.g. diabetics may have urine with a sweet or fruity odour due to the presence
of ketones (organic molecules of a particular structure).
Generally fresh urine has a mild smell but aged urine has a stronger odour,
similar to that of ammonia.
· Acidity: The real significance of pH in terms of physical chemistry is that pH
is a measure of the activity of hydrogen ions (H+) in a solution.
The pH of normal urine is generally in the range 4.6 - 8, a typical average being
Much of the variation is due to diet. For example, high protein diets result in
more acidic urine, but vegetarian diets generally result in more alkaline urine
(both within the typical range 4.6 - 8).
· Density: The density of normal urine is in the range 0.001 to 0.035.…read more
What is in urine?
· 95% of the volume of normal urine is due to water.
· 5% consists of solutes (chemicals that are dissolved in the water)
· These solutes can be divided into two categories according to their chemical structure (e.g. size and electrical
Some of these solutes are the results of normal biochemical activity within the cells of the body.
· Urea, uric acid, creatine
Other solutes may be due to chemicals that originated outside of the body, such as pharmaceutical
· Solutes found in urine may be classified as:
Ions (i.e. single elements that are positively or negatively charged due to loss or acquisition of one or
more electrons from/to the outer-levels of the atom)
· Sodium (Na+) : Amount in urine varies with diet and the amount of aldosterone (a steroid hormone) in the body.
· Potassium (K+) : Amount in urine varies with diet and the amount of aldosterone (a steroid hormone) in the body.
· Chloride (Cl-) : Amount in urine varies with diet (chloride is a part of common salt, NaCl).
· Magnesium (Mg2+) : Amount in urine varies with diet and the amount of parathyroid hormone in the body.
(Parathyroid hormone increases the reabsorption of magnesium by the body, which therefore decreases the
quantity of magnesium in urine.)
· Calcium (Ca2+) : Amount in urine varies with diet and the amount of parathyroid hormone in the body.
Organic molecules (i.e. several, sometimes many, atoms that have joined together to form a group of
atoms called a "molecule"; "organic" molecules are formed from groups, rings, or chains of carbon
atoms and are the "building blocks" of the living things on the earth - i.e. plants and animals).…read more