The kidney Flashcards
How is urine produced?
Filtration of plasma which is then reabsorbed
What are nephrons?
Basic functional unit of a kidney
What do nephrons include?
Afferent and efferent arterioles
What are afferent arterioles made from?
Small vessels
What is the function of afferent arterioles?
One supplies each nephron to deliver blood to glomerular capillaries
What are efferent arterioles made from?
Glomerular capillaries
What is the function of efferent arterioles?
Carry unfiltered blood to tubules and supply renal tissue with blood
What are tubular components?
Hollow tubes formed by epithelial cells
What are Bowman’s capsule, loop of Henle and distal and proximal tubules?
Tubular components
Function of Bowman’s capsule
Collects fluid around glomerulus
Function of proximal tubule
Reabsorbs sugar, amino acids, water, urea and chlorine
Function of loop of Henle
Establishes osmotic gradient for urine and reabsorbs chlorine
Function of distal tubule
Empties into collecting duct under hormonal control
What are glomerular filtration, tubular reabsorption and tubular secretion?
Renal processes
What is glomerular filtration?
Removal of 15-25% of water and solutes from the blood
What does glomerular filtration rate depend on?
Hydrostatic and osmotic pressure of blood plasma and permeability of membranes
What is the function of the glomerular membrane?
Retains blood cells and plasma proteins but permits water and small molecules
What is renal clearance?
Various substances are removed from plasma and excreted in urine
If plasma clearance < glomerular filtration rate what has occurred?
Substance has been reabsorbed
What is the clearance rate of glucose and urea?
0ml and 62.5ml
If plasma clearance = glomerular filtration rate…
Substance is not reabsorbed
What is the clearance rate of inulin?
125ml/min
If a substance is secreted and not reabsorbed then…
Clearance rate > glomerular filtration rate
How do you measure renal plasma flow?
PAH (acid)
What is glomerular filtration rate driven by?
Arterial blood pressure
What mechanisms cause auto regulation?
Myogenic, tubuloglomercular feedback and neural mechanisms
What is tubular reabsorption?
Recovery of useful products filtered out during glomerular filtration
What must occur to a substance before epithelial transport?
Cross the luminal membrane of tubule cell
Pass through cytosol and cross basolateral membrane to interstitial fluid
Diffuse through interstitial fluid and penetrate capillary wall to blood plasma
What is the only tubular component not involved in sodium reabsorption?
Bowman’s capsule
When is glucose reabsorbed?
When it has been filtered by the glomerulus
Do the kidneys regulate blood plasma?
No, unless diabetic
Where does phosphate reabsorption occur?
Tubules
Where is excess phosphate excreted?
Urine
What does the proximal convoluted tubule remove?
75% sodium and water to the loop of Henle
What is the loop of Henle made up of?
Descending, thin ascending and thick ascending limb
What is the descending limb’s permeability?
Highly permeable to water but impermeable to salts
What is the permeability of the thin ascending limb?
Permeable to sodium and chlorine ions but low permeability to water
What is the permeability of the thick ascending limb?
Low permeability of water but active transport of sodium and chlorine
What is the role of the distal convoluted tubule?
Transport of potassium, hydrogen and NH3 into lumen but sodium chlorine and HCO3 out of lumen
What is the role of the collecting duct?
Reabsorbs NaCl by active transport
What is the permeability of the collecting duct?
Permeable to water and urea
How does urea contribute to urine?
Urea is impermeable in early collecting tubule but becomes more concentrated as it passes to medulla
