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By the end of this section, you will be able to:
  • List specific transport mechanisms occurring in different parts of the nephron, including active transport, osmosis, facilitated diffusion, and passive electrochemical gradients
  • List the different membrane proteins of the nephron, including channels, transporters, and ATPase pumps
  • Compare and contrast passive and active tubular reabsorption
  • Explain why the differential permeability or impermeability of specific sections of the nephron tubules is necessary for urine formation
  • Describe how and where water, organic compounds, and ions are reabsorbed in the nephron
  • Explain the role of the loop of Henle, the vasa recta, and the countercurrent multiplication mechanisms in the concentration of urine
  • List the locations in the nephron where tubular secretion occurs

With up to 180 liters per day passing through the nephrons of the kidney, it is quite obvious that most of that fluid and its contents must be reabsorbed. That recovery occurs in the PCT, loop of Henle, DCT, and the collecting ducts ( [link] and [link] ). Various portions of the nephron differ in their capacity to reabsorb water and specific solutes. While much of the reabsorption and secretion occur passively based on concentration gradients, the amount of water that is reabsorbed or lost is tightly regulated. This control is exerted directly by ADH and aldosterone, and indirectly by renin. Most water is recovered in the PCT, loop of Henle, and DCT. About 10 percent (about 18 L) reaches the collecting ducts. The collecting ducts, under the influence of ADH, can recover almost all of the water passing through them, in cases of dehydration, or almost none of the water, in cases of over-hydration.

Locations of secretion and reabsorption in the nephron

This diagram shows the different ions and chemicals that are secreted and reabsorbed along the nephron. Arrows show the direction of the movement of the substance.
Substances Secreted or Reabsorbed in the Nephron and Their Locations
Substance PCT Loop of Henle DCT Collecting ducts
Glucose Almost 100 percent reabsorbed; secondary active transport with Na +
Oligopeptides, proteins, amino acids Almost 100 percent reabsorbed; symport with Na +
Vitamins Reabsorbed
Lactate Reabsorbed
Creatinine Secreted
Urea 50 percent reabsorbed by diffusion; also secreted Secretion, diffusion in descending limb Reabsorption in medullary collecting ducts; diffusion
Sodium 65 percent actively reabsorbed 25 percent reabsorbed in thick ascending limb; active transport 5 percent reabsorbed; active 5 percent reabsorbed, stimulated by aldosterone; active
Chloride Reabsorbed, symport with Na + , diffusion Reabsorbed in thin and thick ascending limb; diffusion in ascending limb Reabsorbed; diffusion Reabsorbed; symport
Water 67 percent reabsorbed osmotically with solutes 15 percent reabsorbed in descending limb; osmosis 8 percent reabsorbed if ADH; osmosis Variable amounts reabsorbed, controlled by ADH, osmosis
Bicarbonate 80–90 percent symport reabsorption with Na + Reabsorbed, symport with Na + and antiport with Cl ; in ascending limb Reabsorbed antiport with Cl
H + Secreted; diffusion Secreted; active Secreted; active
NH 4 + Secreted; diffusion Secreted; diffusion Secreted; diffusion
HCO 3 Reabsorbed; diffusion Reabsorbed; diffusion in ascending limb Reabsorbed; diffusion Reabsorbed; antiport with Na +
Some drugs Secreted Secreted; active Secreted; active
Potassium 65 percent reabsorbed; diffusion 20 percent reabsorbed in thick ascending limb; symport Secreted; active Secretion controlled by aldosterone; active
Calcium Reabsorbed; diffusion Reabsorbed in thick ascending limb; diffusion Reabsorbed if parathyroid hormone present; active
Magnesium Reabsorbed; diffusion Reabsorbed in thick ascending limb; diffusion Reabsorbed
Phosphate 85 percent reabsorbed, inhibited by parathyroid hormone, diffusion Reabsorbed; diffusion

Questions & Answers

Which of the following is generally called a Sprain?
Raneem Reply
sprain is also called torn ligament.. it is the streching Or tearing of ligament.. with in a joint
Khawaja
a long boin between your nick and pelvic
Marie
sprain is also known as" moch"
Sneha
sprain is also known as 'moch' it's a type of injury affect on ligaments..(sprain)
Sanjith
sprain and strain both called as 'moch'
Sanjith
moc
Mulumbwe
body, muscle and regional of structures in the body
Harmony Reply
when the heart beats, blood pumps through the body and making the body function
Harmony
what is vagina
Hausa Reply
what is ventricular circulation
Maryam Reply
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In a four-chambered heart, such as that in humans, there are two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, and the left ventricle pumps blood into the systemic circulation through the aorta.
yes
anjali
hi
A 23-year-old basketball player mentally rehearses free throw shots while lying in bed. Which option best describesthe area of the brain that is involved in generating a motor image of this action in the absence of actual movement?
Rai
hapothalamus
Prashant
a 67-year-old man has a stroke. one week later, he experiences sudden and uncontrolled flailing, ballistic movements of his limbs. which part of the man’s brain is most likely to have been damaged by the stroke?
Rai
primary motor cortex.. (principal area of cerebrum)
Khawaja
what factors that affect the rate diffusion
Gift Reply
the mass of the solute the temperature of theenvironment the solvent density and the distance traveled
Sulaiman
ok.
Thobok
sorry what are the common meaning of haemostatis
Juma Reply
homeostasis is the steady internal physical and chemical conditions maintaining by living systems
Sulaiman
what are the negatives feedback regulation of ADH
Nansi Reply
what is the the differences between DNA and RNA?
Mustapha
The major differences between the DNA and RNA are contain of double stranded and single stranded which the DNA contain duoble stranded and RNA contain single stranded.
Juma
what are the negatives feedback regulation of ADH before this we confused just verify long term of ADH firstly
Juma
How many genes consist of DNA?
Omaryare
omaryare muhyadiin when you talk about genes, is the material formed in a DNA genes have form like plasma have many genes round there
Juma
aldosterone, renin
Conan
DNA contains the sugar deoxyribone while RNA contains the sugar ribose the only difference between ribose and deoxyribone is that ribose has one more- OH group than deoxyribone which has -H attached to the second carbon in the ring DNA is a double stranded molecules RNA is a single strnded molecul
Sulaiman
yes
Thobok
in human genes very in size from a few hundred DNA based to more than 2million bases
Sulaiman
to know the different structures of the body To know how the body works To know more about our body parts
Deitdre Reply
hi Deitdre you tock about knowledge or you ask the question
Juma
do you need any explanation when reading this book?
janet Reply
Its Good
Hashir
yes
Balogun
Yes
Mariam
yes
Sale
yes
Mustapha
if have many ability just do it!!
Juma
we all waiting for it
Sulaiman
compare and contrast the operation of homeostasis
Dinelle Reply
what is the difference between an ionic, polar covalent and nonpolar covalent bond?
Dinelle
In summary, the bond has different in electronegativity.
Balogun
sorry help me to get the definition of hemostasis or the meaning
Juma
the definition of distal
Dinelle Reply
farthest away from the attachment point.
felix
Distal, is the farthest possition from the origin or midle point
Juma
exercise physiologist how ?
Noor Reply
hi noorr. when you talk about physiologist its a person who study physiology but exercise physiologist is what an exercise doing by physiologist in physiologican
Juma
can I get the questions of human physiology that is present in HSC 2nd semester
Rafiullah Reply
in my lerning the question com like for example ni eassy qustion must understand the the part of the body and how it work or mechanisms of each part learned
Juma
how can I memorize
mukhtaar Reply
which part of the body produces blood
aadil
give me answer
aadil
Red blood cells are formed in the red bone marrow ofbones. Stem cells in the red bone marrow called hemocytoblasts give rise to all of the formed element
mukhtaar
what is hemocytoblasts
Fatima
hemocytoblasts are stem cells in red bone marrow which give rise the all of formed elements
Khawaja
Discuss clonal theory in physiology and its application in measles infection in a 6yr child? Can anyone help me
Isaac Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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