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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 organelles controls protein synthesis?
Katie Reply
Ribosome
AMEL
hmm...the ribosomes?
Fatukasi
ribosome
adam
Ribosome
Opara
Ribosome
Saifkhan
ribosome
DR
ribosome
ELIZABETH
are ribisomes made in the rRNA?
Lola
nop they are produced by cells of Nucleolus
adam
Is there anything about nerve and muscle physiology?
AMEL Reply
how many types of epithelial tissues do we have
Benedicta Reply
Epithelial tissues are grouped in two ways.. ●Based on the number of layers.(Simple and stratified ) ●Based of their shapes(Squamous,Cuboidal and columnar) Also we can have a combination of the two,say,simple Squamous
Prince
awww thanks dearie😊😊😊💖
Benedicta
describe the function and structure of blood
Belindah Reply
It has four main components: plasma, red blood cells, white blood cells, and platelets. Blood has many different functions, including: transporting oxygen and nutrients to the lungs and tissues.
Arlena
well answered arlena.. #thumbs up#
Fatukasi
have u some prepared MCQs on CNS and Special senses physiology?
dr
Anyone got the human heart labelled diagram
Sawmtei
you can download from Google... I don't think it's possible to share docs or files here
Fatukasi
ok thanks
Sawmtei
you're welcome..
Fatukasi
thanks
dr
Thank you
Drs
what's an easy way of knowing the different structures of tissues what they do and where their found
Lola
are you know function of the blood?
Drs
to carry nutrients to parts of the body
Lola
well Lola the easiest way is to attributes the tissues based on their funcs(especially those with similar funcs)..you can create your own mnemonics that will help you rmba em..and the a random reading.. it helps you retain em better
Fatukasi
and try random reading*
Fatukasi
ok thanks
Lola
funtction of WBCs
DR
bone tissue
Waqar
identy the vein and arteries of coronary circulation
abdifatah Reply
to be a nurse a doctor or just to understand the body
Drew Reply
what is the basic part of life
Drew
cell remains the basic unit of life...
Fatukasi
The coronary arteries branches off of what
Ada Reply
gh
Asad
rephrase your question
Fatukasi
Discuss Active Myosin contraction theory
Xavier Reply
What is dissected?
Jc Reply
It is a minute and detailed analysis.."dissection"rather..
Kabwe
what is the net charge on both atoms of hydrogen and helium?
Brianna Reply
hii
Shubham
hii
Maddy
Muche kuch bhi samaz me nhi aa rha he
Shubham
kya samaj nahii Aa raha hai
Maddy
What is homeostasis?
Xavier Reply
it is tha condition of equilibrium in body is internal invorment
Ravi
it is a dynamic condition
Ravi
it is the tendency towards a relatively stable equilibrium between interdependent elements.
Kyekyelle
what is connective tissue
sourav Reply
it is tissue that connects, binds, supports and separates
Brenda
Just as it name it Connects and helps to attach parts
Xavier
tissue in a connects to tha bones
naime
who many days does the sperm stays before fertilizing
Ferlin Reply
72hours
Opara
you mean the durability of sperm In the oviduct?
Fatukasi
What is the meddle cranial fossa?
Margret Reply
What is the meddle cranial fossa.
Margret 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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