9 Urine characteristics and composition and Microution

Urine

A liquid waste produced by the kidneys, stored in the bladder and is expelled from the body through the urethra

Physical characteristics

Characteristics of the urine change, depending on influences such as water intake, exercise, environmental temperature, nutrient intake, and other factors

Color

freshly voided urine is clear and pale to deep yellow due to urochrome/urobilin, a

pigment resulting from the destruction of

hemoglobin

color may vary with diet, presence of bile pigments or blood, drugs and vitamin

supplements in urine

cloudy urine may indicate a UTI

Odor

fresh urine is slightly aromatic, but develops an ammonia odor if allowed to stand, due to bacterial metabolism of urea

some drugs and vegetables alter the usual odor of urine

some diseases may alter the smell of urine eg urine of diabetics may have a sweet or fruity odor because of its ketone content

pH

normal pH is around 6.0

changes in body metabolism or diet may cause the pH to vary from 4.6 – 8, eg high protein diets result in more acidic urine, but vegetarian diets generally result in more alkaline urine

Specific gravity

This is the ratio of the mass of a substance to the mass of the same volume of distilled water

the specific gravity of normal urine ranges from 1.001 to 1.035

Turbidity

it is gauged subjectively and reported as clear, slightly cloudy, cloudy, opaque or flocculant

fresh urine is normally either clear or slightly cloudy

excess turbidity results from the presence of suspended particles in the urine

common causes of abnormal turbidity include : increased blood cells, numerous crystals, bacteria, lipiduria, mucus, semen or fecal contamination

Chemical composition

about 95% of urine is water

the remaining 5% consists of solutes

normal solute constituents in order of decreasing concentration are

urea 9.3 g/L

chloride 1.87 g/L

sodium 1.17 g/L

potassium 0.750 g/L

creatinine 0.670 g/L and

other dissolved ions, inorganic and organic compounds (proteins, hormones, metabolites)

unusually high concentrations of any solute, or the presence of abnormal substances such as blood proteins, WBC (pus), or bile pigments may indicate pathology

Micturition

It is the act of emptying the urinary bladder

Urinary bladder

the bladder is a hollow, distensible, muscular organ

it consists of 4 layers:

serosa- a thin connective tissue layer which covers the bladder dome and is continuous with the peritoneal layer of the abdominal wall.

adventitia- a loose connective tissue layer which serves as the bladder’s outer layer in

areas of the bladder where there is no

serosa

muscular layer - the detrusor muscle of the urinary bladder wall, which consists of inner and outer longitudinal smooth muscle layers, with a circular layer sandwiched between

sub-mucous layer - a thin layer of areolar

tissue loosely connecting the muscular layer

with the mucous layer

mucous layer - the innermost layer with transitional epithelium

when empty, the inner wall retracts into many folds called rugae, that disappear as it fills

the neck of the bladder forms an internal urethral sphincter, which controls excretion of urine

a skeletal muscle that encircles the urethra where it goes through the pelvic floor (pelvic diaphragm) opening to the outside forms the external urethral sphincter