Session 3 Flashcards
What is the sequence of arteries from the renal artery?
Renal artery > Segmental artery > Interlobar artery > Arcuate artery > Interlobular Artery
What are the 2 types of nephrons found in the kidney?
- Cortical nephrons
- Juxtamedullary nephrons
What are the features of the cortical nephrons?
- Short loop of henle which just enters the medulla
- Peritubular capillaries covering most of the nephron
- Rich sympathetic innervation
- High concentration of renin
- In the outer part of the cortex
- Small glomerulus
What are the features of the juxtamedullary nephrons?
- Glomerulus sits juxtaposed to the medullary boundary
- Loop of henle is very long and penetrates deep into medullary tissue
- Vasa recta runs in parallel to the loop of henle.
- Poor sympathetic innervation
- Almost no renin
- Glomerulus is large
What is renal plasma flow?
(1-haemotocrit) X renal blood flow
What is the renal blood flow?
About 1.1 L/min
Where is the glomerulus found?
Found in the cortex alone
How much of the blood is filtered at a time?
20%
What happens to 80% of the blood arriving at the glomerulus?
Leaves via the efferent arteriole
What is the function of the renal corpuscle?
To produce ultra filtrate of plasma
What is the renal corpuscle?
The glomerulus + bowman’s capsule
What produces the filtration barrier in the renal corpuscle?
- Capillary endothelium - permeable. Water, salts, glucose. Filtrate moves between cells
- Visceral layer of Bowman’s capsule - Acellllar gelatinous later of collagen/glycoproteins which is permeable to small proteins. Glyocproteins repel protein movement
- Podocyte layer - Pseudopodia interdigitate froms filtration slits
Which molecules cannot cross the filtration barrier?
Cells and large proteins
What is the effect as a result of the negative charge on the filtration barrier being lost?
-Proteins are more readily filtered and result in a condition called proteinuria
What are the 3 physical forces involved in filtering the plasma?
- Hydrostatic pressure in the capillary
- Hydrostatic pressure in the Bowman’s capsule
- Oncotic pressure difference between the capillary and tubular lumen
Why do we need Autoregulation of GFR?
Feedback mechanism intrinsic to the kidney to keep RBF and GFR constant. Without this a slight change in the blood pressure would cause a significant change in the GFR
What is the myogenic mechanism?
- Arterial smooth muscle response to decrease and increase in vascular tension
- Contribute to total auto-regulatory mechanism
- Occurs rapidly
- Property predominantly of the preglomerular resistance vessels
What is the myogenic response to an increase in blood pressure?
-Constriction of the afferent arteriole predomantly or dilation of the efferent arteriole to decrease the blood volume arriving to be filtered. This keep the GFR unchanged
What is the myogenic response to a decrease in blood pressure?
-Dilation of the afferent arteriole predominantly or constriction of the efferent arteriole in order to increase the blood volume arriving to be filtered. This keep the GFR unchanged.
How does the Tubular glomerular feedback mechanism work?
- Links the sodium and chloride concentration at the macula densa with control of renal arteriole resistance
- Acts in response to acute deviation in the delivery of fluid and solutes to the JGA.
- Control the distal solute delivery and hence tubular reabsorption
What are the 2 components of the tubular glomerular feedback mechanism?
- Afferent arterole resistance
- Efferent arteriole resistance
What is the action of the Tubular goloemrular feedback when the arterial pressure increases?
- Increase in renal plasma flow and increase in GFR leads to increase in NACl
- Macula densa cells responds to changes in NaCL arriving in the distal convoluted tubule
- Juxtaglomerular apparatus is stimulated to release adenosine which constricts the afferent arteriole by stimulating the Alpha 1 receptors. The efferent arteriole is dilated by stimulation of the Alpha 2 receptors
- This reduces the GFR
How do macula densa cells detect changes in NaCl?
-Macula densa senses the NaCl in the DCT via a concentration-dependant salt uptake through the NaKCC co-transporter in the apical membrane of the macula densa cells
What is the action of the Tubular goloemrular feedback when the arterial pressure decreases?
- Decrease in renal plasma flow and decrease in GFR leads to decrease in NACl
- Macula densa cells responds to changes in NaCL arriving in the distal convoluted tubule
- Juxtaglomerular apparatus is stimulated to release prostaglandins which dilates the afferent arteriole.
- This increases the GFR
Sympathetic innervation of the Afferent arteriole and efferent arteriole are high. True/False
False. They are low
When is the sympathetic innerveation of the renal vessels most active?
During haemorrhage, ischamia or the fight or flight response.
Vasoconstriction occurs in order to conserve blood volume and can cause a fall in GFR
How does the parasympathetic nervous system act on the blood vessels?
Release of nitrous oxide for endothelial cells and vasodilation
What is the glomerulotubular balance?
It blunts the sodium excretion in response than ant any GFR changes which occur do occur despite the Myogenic and TG feedback response.
