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Glomerular filtration

Glomerular filtration filters out most of the solutes due to high blood pressure and specialized membranes in the afferent arteriole. The blood pressure in the glomerulus is maintained independent of factors that affect systemic blood pressure. The “leaky” connections between the endothelial cells of the glomerular capillary network allow solutes to pass through easily. All solutes in the glomerular capillaries, except for macromolecules like proteins, pass through by passive diffusion. There is no energy requirement at this stage of the filtration process. Glomerular filtration rate (GFR) is the volume of glomerular filtrate formed per minute by the kidneys. GFR is regulated by multiple mechanisms and is an important indicator of kidney function.

To learn more about the vascular system of kidneys, click through this review and the steps of blood flow.

Tubular reabsorption and secretion

Tubular reabsorption occurs in the PCT part of the renal tubule. Almost all nutrients are reabsorbed, and this occurs either by passive or active transport. Reabsorption of water and some key electrolytes are regulated and can be influenced by hormones. Sodium (Na + ) is the most abundant ion and most of it is reabsorbed by active transport and then transported to the peritubular capillaries. Because Na + is actively transported out of the tubule, water follows it to even out the osmotic pressure. Water is also independently reabsorbed into the peritubular capillaries due to the presence of aquaporins, or water channels, in the PCT. This occurs due to the low blood pressure and high osmotic pressure in the peritubular capillaries. However, every solute has a transport maximum    and the excess is not reabsorbed.

In the loop of Henle, the permeability of the membrane changes. The descending limb is permeable to water, not solutes; the opposite is true for the ascending limb. Additionally, the loop of Henle invades the renal medulla, which is naturally high in salt concentration and tends to absorb water from the renal tubule and concentrate the filtrate. The osmotic gradient increases as it moves deeper into the medulla. Because two sides of the loop of Henle perform opposing functions, as illustrated in [link] , it acts as a countercurrent multiplier    . The vasa recta around it acts as the countercurrent exchanger    .

Art connection

A U-shaped tube represents the loop of Henle. Filtrate enters the descending limb, and exits the ascending limb. The descending limb is water-permeable, and water travels from the limb to the interstitial space. As a consequence, the osmolality of the filtrate inside the limb increases from 300 milliosmoles per liter at the top to 1200 milliosmoles per liter at the bottom. The ascending limb is permeable to sodium and chloride ions. Because the osmolality inside bottom part of the limb is higher than the interstitial fluid, these ions diffuse out of the ascending limb. Higher up, sodium is actively transported out of the limb, and chloride follows.
The loop of Henle acts as a countercurrent multiplier that uses energy to create concentration gradients. The descending limb is water permeable. Water flows from the filtrate to the interstitial fluid, so osmolality inside the limb increases as it descends into the renal medulla. At the bottom, the osmolality is higher inside the loop than in the interstitial fluid. Thus, as filtrate enters the ascending limb, Na + and Cl - ions exit through ion channels present in the cell membrane. Further up, Na + is actively transported out of the filtrate and Cl - follows. Osmolarity is given in units of milliosmoles per liter (mOsm/L).

Loop diuretics are drugs sometimes used to treat hypertension. These drugs inhibit the reabsorption of Na + and Cl - ions by the ascending limb of the loop of Henle. A side effect is that they increase urination. Why do you think this is the case?

Questions & Answers

phenotype is your big head
Amagiya Reply
what is a dichotomous key
Moses Reply
explain the role of
Moses
Dichotomous key : Is the key that is use to classify or group an organism base on their common features
Alale
an amoeba is what kind of cellular organism?
Mercy Reply
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AFANU Reply
daigram of connective tissue
Yunusa Reply
what is polarization
Finda Reply
What is appendicular
GLORIA Reply
relating to or denoting an appendage or appendages.
Eric
Homeostasis definition
Ben Reply
can be defined as a steady of internal environment
Aliyu
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Kaole
🙄
Aliyu
:-)
Kaole
wat is active transport
Roster Reply
The movement of molecules from the region of lower concentration to the region of higher concentration
gerard
what are derived quantities
Esther Reply
Derived quantities are quantities that are calculated from two or more measurements. Derived quantities cannot be measured directly. They can only be computed.
Stanley
name two types of acid
Grace Reply
Hydrochloric acid and tetraoxoshulphate(VI) acid
Mercy
melic acid and aspartic acid
dilip
sulphuric acid, hydrochloride acid
Greig
describe the effect of smoking on the respiratory surface
Castro Reply
Tar which causes lung cancer
Castro
what is osmosis
Tinashe Reply
explanation of osmosis
Finda
what is respiration
Favour Reply
organisms and their respiratory organs
Favour
Osmosis.. An example of Osmosis is when red blood cells, which have a high concentration of protein and salt, are plaeed in a lower concentration fluid like water the water will rush into the red blood cells.
boafo Reply
You're asked for the Definition, not yet an example. Definition first,before example, o.k?
Tseyina
osimosis is the movement of watermolecules from they region of high concetration to the region of lower concertation
Grace

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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