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GFR is influenced by the hydrostatic pressure and colloid osmotic pressure on either side of the capillary membrane of the glomerulus. Recall that filtration occurs as pressure forces fluid and solutes through a semipermeable barrier with the solute movement constrained by particle size. Hydrostatic pressure is the pressure produced by a fluid against a surface. If you have a fluid on both sides of a barrier, both fluids exert a pressure in opposing directions. Net fluid movement will be in the direction of the lower pressure. Osmosis is the movement of solvent (water) across a membrane that is impermeable to a solute in the solution. This creates a pressure, osmotic pressure, which will exist until the solute concentration is the same on both sides of a semipermeable membrane. As long as the concentration differs, water will move. Glomerular filtration occurs when glomerular hydrostatic pressure exceeds the luminal hydrostatic pressure of Bowman’s capsule. There is also an opposing force, the osmotic pressure, which is typically higher in the glomerular capillary.

To understand why this is so, look more closely at the microenvironment on either side of the filtration membrane. You will find osmotic pressure exerted by the solutes inside the lumen of the capillary as well as inside of Bowman’s capsule. Since the filtration membrane limits the size of particles crossing the membrane, the osmotic pressure inside the glomerular capillary is higher than the osmotic pressure in Bowman’s capsule. Recall that cells and the medium-to-large proteins cannot pass between the podocyte processes or through the fenestrations of the capillary endothelial cells. This means that red and white blood cells, platelets, albumins, and other proteins too large to pass through the filter remain in the capillary, creating an average colloid osmotic pressure of 30 mm Hg within the capillary. The absence of proteins in Bowman’s space (the lumen within Bowman’s capsule) results in an osmotic pressure near zero. Thus, the only pressure moving fluid across the capillary wall into the lumen of Bowman’s space is hydrostatic pressure. Hydrostatic (fluid) pressure is sufficient to push water through the membrane despite the osmotic pressure working against it. The sum of all of the influences, both osmotic and hydrostatic, results in a net filtration pressure (NFP)    of about 10 mm Hg ( [link] ).

Net filtration pressure

This figure shows the different pressures acting across the glomerulus.
The NFP is the sum of osmotic and hydrostatic pressures.

A proper concentration of solutes in the blood is important in maintaining osmotic pressure both in the glomerulus and systemically. There are disorders in which too much protein passes through the filtration slits into the kidney filtrate. This excess protein in the filtrate leads to a deficiency of circulating plasma proteins. In turn, the presence of protein in the urine increases its osmolarity; this holds more water in the filtrate and results in an increase in urine volume. Because there is less circulating protein, principally albumin, the osmotic pressure of the blood falls. Less osmotic pressure pulling water into the capillaries tips the balance towards hydrostatic pressure, which tends to push it out of the capillaries. The net effect is that water is lost from the circulation to interstitial tissues and cells. This “plumps up” the tissues and cells, a condition termed systemic edema    .

Questions & Answers

what are the three types of adrenocorticoids hormones
Lubega Reply
glucocorticoids mineralocorticoid and catecholamines
Kartik
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Jackson Reply
polar unequal share of electron while non polar is equal share
Quran
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Jackson Reply
Bocz of unpaired elections
Javid
because of unpaired electrons
ABDULLAH
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Jackson Reply
Amphipathic molecules are molecules with both polar and non polar regions
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MADUBULA Reply
Hw does the male organ develop
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it is an imagency condition resulting from abnormal and immediate alagic response to a substance to which the body has become intensively sensitized
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ado Reply
drugs have no medical application (cocaine, heroin, crystal meth). medicine have medical purpose (fentanyl, albuterol, aspirin, ect ect)
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medicine is a substance or preparation used in treating disease,drug is chemical compound medicine are drugs but all drugs are not medicines
Wafa
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Sidra
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stomach
Sidra
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saba
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saba
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O-olfactory O-optic O-occumulator T-trochlear T-trigemenal A-abducent F-facial A-auditory G-glossopharyngeal V-vagus A-acessory
Aniee
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Shahab
out patient department
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Read KD Tripathi book of Pharmacology.
mayank
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mayank
CT Scan means
Sintung
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Sintung
CT means - computerized tomography
Vivek
connective tissue
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they link some body organs
Sintung
Difference between drug and medicine
Javid
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saba
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tomography ☝
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how hemolytic anemia cause due to gas gangrene?
Huma Reply
what's gangrene?
Sidra
why retro abdominal region called or named "flank "?
Huma Reply
list types epithelial tissue
Sangu Reply
Squeamus epithelial tissu Cubidal Columna Cilliated columna
Aliyu
squamous cuboidal columnar ciliated stratified
Ken
psuedostratified ciliated columnar stratified squamous transitional epithelium
Espinoza
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shahid
electrical conduction ... sa node
Dee
squamous epithelial tissue.
Tariq
squamous, stratified epithelial tissue
Sintung
explain how hormonal control aids in homeostasis regarding fluids and electrolytes, internal organs, clinical application, edema electrolyte imbalance?
Hensheal Reply
someone to help me explain those
Hensheal
parathyroid hormone : Calcium uptake, H+ and PO-4 wasting thyroid hormone, cortisol for temperature regulation by acting on B.V
Kartik
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Kartik
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Hensheal
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Huma
it is just Anatomical terminology
Kartik
meaning side of body b/w rib cage and hip bone
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list down all the hormones secreted by adrenal gland
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adrenaline hormones
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adrenaline and noradrenaline
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adrenocorticotrophic hormone
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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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