BPK 105 Study Guide - Final Guide: Oncotic Pressure, Capillary Pressure, Colloid
27 Apr 2018
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● Module 12—Do question 3, and 10.
3. Illustrate and describe the pressures that influence filtration pressure at the Bowman capsule. [5 marks]
Filtration pressure allows for filtrate to form. Filtration pressure is a pressure gradient and its calculation involves the
subtraction of the forces that move fluid into the glomerular capillary from the Bowman capsule from the forces that
move fluid into the Bowman capsule from the glomerular capillary (glomerular capillary pressure - capsular pressure -
colloid osmotic pressure = filtration pressure). The blood pressure that is in the glomerular capillary is called
glomerular capillary pressure. Glomerular capillary pressure is a significant force that moves fluid into the Bowman
capsule from the glomerular capillary via the filtration membrane (into the Bowman capsule from the blood). Capsular
pressure and colloid osmotic pressure are significant forces that go against the pressure that causes the fluid to move
into the Bowman capsule’s lumen (into the blood from the Bowman capsule). While the capsular pressure results
from the pressure due to the filtrate that is located inside the Bowman capsule, the colloid osmotic pressure results
from the pressure due to filtrate that is located in the glomerular capillary. Colloid osmotic pressure results from blood
protein pressure uses osmosis to move fluid. The majority of plasma membranes are unable to go through the
filtration membrane and so, establishes a pressure - called an osmotic pressure - in which the movement from the
Bowman capsule into the glomerular capillary preferred. Because the combination of the colloid osmotic pressure and
the capsular pressure are smaller than the glomerular capillary pressure, the filtration fluid causes fluid to move into
the Bowman capsule from the glomerulus.
The filtration pressure does not vary very much in most cases, but urine volume and filtrate volume both lower with
the decrease of filtration pressure. Conversely, urine volume and filtrate volume both rise with a rise in filtration
pressure. Blood pressure in the glomerular capillaries also impacts filtration pressure. Typically, the blood pressure in
the majority of capillaries is lower than in the glomerular capillaries. When the blood pressure in the glomerular
capillaries decreases, so does the filtration pressure. When the blood pressure in the glomerular capillaries
increases, so does the filtration pressure. With a higher concentration in proteins in the blood, more water moves into
the glomerular capillaries by osmosis; this lowers filtration pressure. When the concentration in blood protein lowers,
so does the filtration pressure, because this prevents water from going into the glomerular capillaries by osmosis.
(Van Putte et al., 507).
Document Summary
Module 12 do question 3, and 10: illustrate and describe the pressures that influence filtration pressure at the bowman capsule. The blood pressure that is in the glomerular capillary is called glomerular capillary pressure. Glomerular capillary pressure is a significant force that moves fluid into the bowman capsule from the glomerular capillary via the filtration membrane (into the bowman capsule from the blood). Capsular pressure and colloid osmotic pressure are significant forces that go against the pressure that causes the fluid to move into the bowman capsule"s lumen (into the blood from the bowman capsule). While the capsular pressure results from the pressure due to the filtrate that is located inside the bowman capsule, the colloid osmotic pressure results from the pressure due to filtrate that is located in the glomerular capillary. Colloid osmotic pressure results from blood protein pressure uses osmosis to move fluid.
