The document summarizes key components and functions of the distal convoluted tubule and collecting duct system in the kidney. It explains that thiazide diuretics inhibit sodium and chloride reabsorption in the distal convoluted tubule. It also describes how the collecting duct system, regulated by aldosterone and antidiuretic hormone, is responsible for 4-5% of sodium and 5% of water reabsorption on average, but can reabsorb over 24% of filtered water during extreme dehydration. Finally, it explains how antidiuretic hormone activates aquaporins in the collecting ducts to reabsorb water and inhibit diuresis.

1. Water reabsorption
Zac, Garrett,Murphy

2. DCT
• Distal convoluted tubule
• Thiazide diuretics inhibit Na+/Cl- reabsorption
from the DCT by blocking the thiazide-sensitive
Na-Cl cotransporter.
• By inhibiting the cotransporter, thiazide diuretics
increase the gradient potential for Na. This
increases the activity of the basolateral Na/Ca
antiport and causes the increase in calcium
reclamation associated with thiazide diuretics.

3. Collecting ducts
• The collecting duct system of the kidney consists
of a series of tubules and ducts that connect the
nephrons to the ureter. It participates in
electrolyte and fluid balance through
reabsorption and excretion, processes regulated
by the hormones aldosterone and antidiuretic
hormone.
• There are several components of the collecting
duct system, including the connecting
tubules, cortical collecting ducts, and medullary
collecting ducts.

4. • The collecting duct system is the final component of
the kidney to influence the body's electrolyte and fluid
balance. In humans, the system accounts for 4–5% of
the kidney's reabsorption of sodium and 5% of the
kidney's reabsorption of water. At times of extreme
dehydration, over 24% of the filtered water may be
reabsorbed in the collecting duct system.
• The wide variation in water reabsorption levels for the
collecting duct system reflects its dependence on
hormonal activation. The collecting ducts, in
particular, the outer medullary and cortical collecting
ducts, are largely impermeable to water without the
presence of antidiuretic hormone (ADH, or
vasopressin).

5. • In the absence of ADH, water in the renal filtrate
is left alone to enter the urine, promoting
diuresis.
• When ADH is present, aquaporins allow for the
reabsorption of this water, thereby inhibiting
diuresis.
• The collecting duct system participates in the
regulation of other electrolytes, including
chloride, potassium, hydrogen ions, and
bicarbonate.

6. Juxtaglomerular Apparatus
• microscopic structure in the kidney, which
regulates the function of each nephron The
juxtaglomerular apparatus is named for its
proximity to the glomerulus: it is found
between the vascular pole of the renal
corpuscle and the returning Distal Convoluted
Tublue of the same nephron.

7. Extracellular Fluid (ECF)
the extracellular fluid can be divided into two
major subcompartments, interstitial fluid
and blood plasma. The extracellular fluid also
includes the transcellular fluid; making up only
about 2.5 percent of the ECF.
In humans, the normal glucose concentration of
extracellular fluid that is regulated
by homeostasis is approximately 5 mM.
The pH of extracellular fluid is tightly regulated
by buffers around 7.4.

8. • The volume of ECF is typically 15L (of which
12L is interstitial fluid and 3L is plasma).
• Interstitial Fluid makes up 16% of your body
weight and blood plasma 4% of your body
weight.

9. Osmoregulation
• active regulation of the osmotic pressure of
anorganism's fluids to maintain
the homeostasis of the organism's water content
• Osmotic pressure is a measure of the tendency
of water to move into one solution from another
by osmosis. The higher the osmotic pressure of a
solution, the more water tends to move into it.
• Pressure must be exerted on the hypertonic side
of a selectively permeable membrane to
prevent diffusion of water by osmosis from the
side containing pure water.

10. Salt Water Reabsorption
• Renal blood flow is 25% of cardiac output (1200
ml/minute). Of this, renal plasma flow is about
660ml/minute, and 120ml/minute is filtered out of the
blood and into the nephron. Ultimately approximately
1.2ml of this fluid is excreted as urine (1% of filtered
load). The major determinants of GFR are
• 1. Renal blood flow and renal perfusion pressure.
• 2. The hydrostatic pressure difference between the
tubule and the capillaries.
• 3. The surface area available for ultrafiltration.
• The rate at which fluid is filtered by the glomerulus is
the glomerular filtration rate (GFR).

12. Work cited
• http://en.wikipedia.org/wiki/Osmoregulation
• http://www.ccmtutorials.com/renal/pathphys
/page_03.htm
• https://courses.stu.qmul.ac.uk/smd/kb/micro
anatomy/senior/metabolism/renal/distal.htm
• http://www.researchgate.net/publication/242
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