Structure and function of the renal tubule Flashcards
What happens in the renal tubule?
→ Filtered fluid is converted to urine
What is the composition of glomerular filtrate?
→Same composition as plasma except that there are no cells and very little protein
When does urine formation begin?
→ large amounts of fluid that is free of protein is filtered from the glomerular capillaries into the Bowman’s Capsule.
What is the glomerular filtrate?
→ An ultrafiltrate of plasma
What is reabsorption?
→moving from the tubular lumen into the peritubular capillary
→ returning wanted substances into the blood
What is secretion?
→ moving from the peritubular capillary plasma into the tubular lumen
What is excretion?
→ how unwanted substances are cleared into the urine
What is the pathway substances have to take to be reabsorbed?
→cross the luminal membrane
→ diffuse through the cytosol
→ across the basolateral membrane
→ into the blood
What is active transport?
→ Moving a molecule against its concentration gradient
→ requires energy
What is passive transfer?
→ Passive movement down the concentration gradient
What is co-transport?
→ Movement of one substance down its concentration gradient
→ allows the transport of another substance against its concentration gradient
What is a symport transporter?
→ transported species move in the same direction
What is an antiport transporter?
→ transported species move in opposite directions
What is the sodium-glucose transporter called in the kidney?
→ SGLT-2
What is the effect of SGLT-2 inhibitors?
→ don’t allow glucose to be carried across with sodium into the peritubular capillaries
What are the techniques used to investigate tubular functions in humans?
→ Clearance studies
What are the techniques used to investigate tubular functions in animals?
→ Micropuncture & isolated perfuse tubule
→ Electrophysiological analysis
How is micropuncturing done?
→ isolate the nephron
→ sample tubular fluid in different parts of the nephron
How is the electrical potential measured?
→ Micropipettes are inserted into the cell
→PD is measured across the whole cell epithelium
What is patch clamping for?
→The current flow through an individual ion channel is measured
How is patch clamping done?
→ A blunt tip pipette is pressed against the cell membrane
What cells is the nephron made from?
→ a single layer of epithelial cells resting on a basement membrane
What are the 7 parts of the nephron?
→ PCT →Thin Descending limb → Thin ascending limb → Thick ascending limb → DCT → Collecting duct → Medullary collecting duct
What are the two types of nephron?
→ Cortical nephron
→Juxta-medullary nephron
What do juxta medullary loops do?
→ they have a long loop of Henle
→ They are better at concentrating urine
What percentage of each type of nephron do humans have?
→ 85% cortical
→ 15% juxta medullary
What are the efferent arterioles in the juxtamedullary nephrons divided into?
→ Specialized capillaries (vasa recta)
→ they extend downward into the medulla and lie side by side with loops of Henle
Where is the PCT?
→ Adjacent to the Bowmans capsule
What are the adaptations of the PCT for transport?
→ Mitochondria for active transport
→ Brush border on the luminal side which gives a large surface area for rapid exchange
→Enzymatic proteins and carriers
→ the PCT has a high permeability