Lecture 2 : Filtration at the Renal Corpuscle Flashcards
Renal Corpuscle:
Glomerulus
Glomerular Capsule
Glomerulus
Capillary bed
Glomerular Capsule
cup surrounding glomerulus
Renal Tubule:
Proximal Convoluted Tubule
Nephron Loop (Loop of Henle)
Distal Convoluted Tubule
Proximal Convoluted Tubule
leads out of glomerular capsule
Nephron Loop (Loop of Henle)
Descending limb into medulla
Ascending limb back to cortex
Distal Convoluted Tubule
leads to collecting duct
____ collects from many nephrons and completes modification of urine
Collecting duct
The cortex contains:
renal corpuscles
proximal convoluted tubules
distal convoluted tubules
The medulla contains the straight structures:
loops of Henle
collecting ducts
vasa recta blood vessels
Renal cortex histology
Glomeruli stand out visually
Renal medulla histology
Lots of tubes running in parallel
Renal corpuscle histology:
- squamous epithelium of parietal layer of glomerular capsule
- glomerular capsular space
- glomerulus
Proximal convoluted tubule histology:
fuzzy lumen due to long microvilli
Distal convoluted tubule histology:
clear lumen
Two types of nephrons distinguished by location:
Cortical & Juxtamedullary nephrons
Both types of nephrons filter ___ and process filtrate to make ____.
blood
urine
Cortical nephrons
85% of all nephrons
Located primarily in the cortex; only part of the loop of Henle dips into medulla
Juxtamedullary nephrons
Renal corpuscle located near the cortex-medulla junction
Loop of Henle dips deep into the medulla
Primary role is to establish osmotic gradient in kidney to make it possible to concentrate urine
____ carries blood into the glomerulus
Afferent arteriole
___ leads out of the glomerulus and drains into ____ capillary bed surrounding proximal and distal convoluted tubules
Efferent arteriole
peritubular
In juxtamedullary nephrons, efferent arteriole drains into _____ associated with the nephron loop.
vasa recta
Blood vessels of the Nephron
These are low pressure capillary beds which favor exchange of substances from interstitial spaces around tubules
Urine formation and blood adjustment relies on:
FILTRATION, REABSORPTION
SECRETION
Glomerular filtration
dumps cell-free and protein-free blood filtrate into the container (glomerular capsule or Bowman’s capsule)
Tubular reabsorption
reclaims what the body needs to keep (from tubule to the blood)
Tubular secretion
selectively adds to the filtrate (from blood to tubule)
Excretion
the term used to describe elimination of finished urine from body
The kidneys will process 180 L (47 gallons) of blood derived fluid (filtrate) a day, BUT, only ___ leaves the body as urine
1.5 L
Filtrate ≠ Urine
We only call it urine after ALL processing is complete
structure of typical capillary bed
Small holes within and between endothelial cells allow solutes and water to move across capillary wall
Blood moves from arteriole across the capillary bed
to a ___
venule
Exchange with interstitial space occurs across the ___
capillary wall
Forces in Capillary Exchange:
Filtration
Reabsorption
Filtration:
Water and small solutes squeezed out of the capillary into the interstitial fluid
Reabsorption:
Water drawn back into the capillary from the interstitial fluid
Filtration is driven by blood pressure _____
capillary hydrostatic pressure
(CHP)
Reabsorption is pulled by ____ exerted by large plasma proteins trapped in blood
osmotic pressure
______ of arteriole increases blood flow into capillary bed
= ___ filtration pressure
Vasodilation
increases
_____ of arteriole decreases blood flow into capillary bed
= ____ filtration pressure
Vasoconstriction
Decreases
Glomerulus
A coiled capillary bed between two arterioles
The _____brings blood into the glomerulus
afferent arteriole
Capillaries of the glomerular tuft are ____, and capillary hydrostatic fluid pushes fluid and solutes out of the capillary
fenestrated
Blood leaves the capillary through the ______
efferent arteriole
Note that we can adjust ____ (and affect pressure) from either side of the glomerulus!
flow
The glomerular capsule has a ____ and a ______:
parietal layer
visceral layer
Parietal layer
simple squamous epithelium
outer part of capsule
Visceral layer
inner visceral layer
special cells called PODOCYTES with “foot processes”
High pressure blood entering glomerular capillary bed is filtered a filtration membrane and the filtered material is collected in the _____
glomerular capsular space
The Filtration Membrane has three (3) layers:
1) Fenestrated endothelium of glomerular capillary
2) Basement Membrane
3)Filtration slits between the foot processes of podocytes (visceral layer of glomerular capsule)
Fenestrated endothelium of glomerular capillary
Allows passage of everything but blood cells
Basement Membrane
Repels negatively charged macromolecules (plasma proteins)
Filtration slits between foot processes of podocytes (visceral layer of glomerular capsule)
Slit diaphragm cover filtration slits adding a final barrier to macromolecules
Glomerular mesangial cells phagocytize debris caught between layers
“Ultrafiltrate of Blood Plasma”
In healthy nephrons, filtrate contains anything that is in blood plasma, except cells and proteins
Anything smaller than 3nm easily passes through membrane:
water, glucose, amino acids, drugs
Anything larger than 5nm stays in the capillary :
maintains the osmotic pressure of blood, preventing loss of all water to capsular space
The presence of cells or proteins in the urine can indicate problems with the ______
filtration membrane
Two types of pressure affect fluid flow:
Hydrostatic pressure
Osmotic (oncotic) pressure
Hydrostatic pressure
pressure of fluid against walls of a vessel
Can be:
blood in the capillary pushing toward the capsular space (HPgc)
fluid in the capsular space pushing toward the blood vessel (HPcs)
Osmotic (oncotic) pressure
pressure exerted by particles (proteins) in the blood (or a fluid) which tend to “pull” water into the vessel or space (OPgc)
Pressures in the glomerular and capsular space can be pulling water in:
opposite directions and therefore oppose each other
The sum of all opposing forces determines the ___ pressure in a system.
NET
____ is the most important force determining net pressure in a healthy kidney, and can be regulated
Glomerular Capillary Hydrostatic pressure
Glomerular capillary hydrostatic pressure can be adjusted by altering ___
arteriole diameter
Efferent arteriole vasodilation
Modify the amount of blood LEAVING the glomerulus
Afferent arteriole vasoconstriction
Modify the amount of blood ENTERING the glomerulus
Osmolarity
the number of particles or solutes in a given volume of water
Blood plasma has a normal osmotic concentration of ___
~280-300mOsm
The goal of the kidneys is to keep the osmolarity of body fluids constant by regulating _____
urine concentration and volume
Maintaining constant osmolality of extracellular fluids is crucial for preventing cells, particularly in the brain, from :
shrinking or swelling from osmotic movement of water.
Filtrate is ___ with Blood
Isosmotic = same osmotic pressure
Osmolarity of blood entering kidney =
300
Osmolarity of blood in afferent arteriole =
300
Osmolarity of blood in efferent arteriole =
300
Osmolarity of filtrate =
300
Filtrate is a pre-urine, produced at the ___ by filtering blood through the filtration membrane
glomerulus
Filtrate contains waste products we want to eliminate from blood and :
water
ions
glucose
amino acids
How do we prevent loss of water, ions and nutrients
from body if we put it into the filtrate?
The long tubule system of the nephron
