Session 3 Flashcards
What are the 2 different types of nephrons?
Cortical nephrons
Juxtamedullary nephrons
What is the arrangement of capillaries around the cortical nephrons?
Randomly arranged
What is the arrangement of capillaries around the juxtamedullary nephrons?
Vasa Recta (Made of descending and ascending branches)
Where is the Glomerulus always?
In the cortex of the Kidney regardless of which type of nephron it is
What substances are filtered from the blood in the Glomerulus?
H2O
Salts
Small molecules
What are the 3 layers that make the filtration barrier?
Capillary endothelium
Basement membrane
Podocyte layer
What is the capillary endothelium permeable to?
Water
Salts
Glucose
Filtrate moves between cells
What are the properties of the Basement membrane?
Acellular gelatinous layer of collagen/glycoproteins (Repel protein movement because they are negatively charged.)
Permeable to small proteins
What are the properties of the Podocyte layer?
Pseudopodia interdigitate forms filtration slits (So big molecules cannot fit through)
What are the 3 forces involved in plasma filtration?
Hydrostatic pressure in the capillary (Favours filtration) Hydrostatic pressure in the Bowman's capsule (Opposes filtration) Osmotic pressure (Difference between the capillary & tubular lumen. Slight Oncotic pressure too. Opposes filtration)
Define tubular reabsorption
Solutes and H2O are removed from the tubular fluid and transported into the blood. (Reabsorption as these have already been absorbed once in GI tract)
Define tubuar secretion
Transfer of materials from peritubular capillaries to renal tubular lumen. (Mainly caused by active transport.)
Usually a small amount are secreted and are either in excess or natural posions
Define Transcellular movement
The substance transports through the cell
Define Paracellular movement
The substance transports through the intracellular space (i.e. Parallel to the cell)
What is reabsorbed in the Proximal Convoluted Tubule?
99% H2O
99.5% Na+
100% Glucose
50% Urea
What drives the unregulated reabsorption in the Proximal Convoluted Tubule?
Osmotic and driven by Na+ uptake
What are the Na+ transporters in the PCT?
Na/H antiporter
Na/Glucose symporter
What are the Na+ transporters in the Loop of Henle?
Na/K/2Cl symporter
What are the Na+ transporters in the early DCT?
Na/Cl Symporter
What are the Na+ transporters in the later DCT & Collecting ducts?
Epithelial Na+ channels
What does SGLUT do?
It is in the PCT and moves 2Na+/1 Glucose into the blood against the concentration gradient for Glucose
What is the renal threshold for Glucose?
200mg/100ml
How are molecules secreted into the PCT?
Passive carrier mediated diffusion across the Basolateral membrane down favourable concentration/electrical gradients created by the Na+/K+ pump
Define filtration fraction
Proportion of substance that is actually filtered
FF = GFR/RPF
How can GFR (Glomerular filtrate rate) give you an indication of how well the kidneys are working?
Measures the substance as its filtered so use a substance that is not reabsorbed or secreted as it passes through the kidney to get an indication of how well its working
Define clearance rate
The volume of plasma from which any substance is completely removed by the kidney in a given amount of time
Clearance rate = (Urine conc of substance x urine flow rate) / plasma conc of substrate
How is GFR autoregulated?
Myogenic response of the smooth muscle cells in the walls of the Afferent arteriole
What is the myogenic response when blood pressure increases?
The afferent arteriole constricts
What is the myogenic response when blood pressure decreases?
The afferent arteriole dilates
What is TGF?
Tubular glomerular feedback
How does TGF work?
A change in tubular flow rate as a result of changes in GFR cause a change in the concentration of NaCl that reaches the DCT
What cells in the DCT detect changes in NaCl concentration?
The Macula densa cells (TGF response works via a concentration dependent salt uptake through NaK2Cl co transporters in the apical membrane of the MD cells)
What is the response if NaCl is high?
Adenosine is released (Vasoconstriction occurs to drop GFR)
What is the response if NaCl is low?
Prostaglandins released (Vasodilation occurs to increase GFR)
