THE NEPHRON THE TUBES AND BALANCE

The Human Body
The Urinary System Part IIa
Water balance and waste disposal

VOLUME OF URINE Water balance and controlled reabsorb ion
The two kidneys have about 2.4 million nephrons.
All the nephrons filter 125 ml/min or about 170 lit/24 hrs.
Most of this filtered fluid is reabsorbed
800 to 2500 ml. of urine is passed out in a day depending on body needs.


If you drink more water more urine is formed and you pass out more urine.
If you drink less you will form less urine which is deep coloured since most of the filtered fluid in the nephrons is reabsorbed
The other substance reabsorbed, by the tubules are
sodium,
glucose,
amino acids and
bicarbonate.

There is no re-absorbtion of
Urea
Creatinine and
Potassium.

The colour of normal urine is yellow.
Dilute urine (when a large amount of water is drunk) is light yellow.
In a healthy person it is germ free (sterile)

PASSING OF URINE Water holding - control

Urine is stored in the bladder,
The sensation that there is urine in the bladder, comes from the stretch receptors, and nerves in the wall of the bladder,
Starts usually when you have 150 cc. collected.

You can hold upto 400 cc without discomfort
Beyond that volume causes discomfort, signals go up your spinal cord and from there to your brain.
You now need to pass urine, you go to a convenient place (urinal) hold your breath and relax, a muscle at the neck of the bladder relaxes.

The bladder wall and the abdominal muscle contract the pressure rises, and urine is passed out.

Older man, with enlargement of prostate that can compress the urethra, may have difficulty in passing urine.

Any question should be addressed to: drmmkapur@gmail.com you will receive further information regarding your question.
All earlier posts are stored in archives for your access and review.
Visitors that follow the site may post contributions to the site.
Click on image to see details.