Clarity – transparent when freshly voided; becomes turbid (cloudy) on standing.
Color – yellow to amber; varies with urine concentration and diet.
Odour – mildly aromatic; becomes ammonia-like on standing.
Chemical composition of Urine
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Percentage of water – 95%.
Three most abundant organic solutes – urea, creatinine, amylase.
Four most abundant inorganic solutes – calcium, chloride, potassium, sodium.
Specific Gravity Of Urine
Ratio of weight of volume of substance to weight of equal volume of distilled water
The normal laboratory value – 1.001 – 1.035
Micturition
Discharge of urine from the urinary bladder
Mechanism Of Micturition
1.
Volume of urine that initiates the process –
200-400 ml
2.
Receptors involved –
Stretch receptors in the wall of the urinary bladder
3.
Location and function of the micturition reflex centre –
Sacral spinal cord segments s2 and s3.
Receives impulses from the stretch receptors and transmits parasympathetic impulses to the urinary bladder wall and internal urethral
sphincter
4.
Nature of the motor pathway to the detrusor muscle and internal sphincter and their responses – parasympathetic; cause contraction of
the detrusor muscle and relaxation of the internal urethral sphincter muscle
5.
Nature of the motor pathway to the external sphincter and its response – somatic (inhibitory); somatic motor neurons that innervate
skeletal muscle in the external urethral sphincter are inhibited, sphincter relaxes
6.
Role of the cerebral cortex – can initiate micturition or delay its occurrence for a limited period
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