The Kidneys
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- Created by: Willow
- Created on: 12-05-19 12:18
Kidney Function
- Excretory organ
- Excrete waste products of metabolism
- Produces urine by filtering blood
- Osmoregulation
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Osmoregulation
- The regulation of water potential in the blood
- too high = water enters cells and they burst
- too low= water leaves cells and cell shrinks
- reduces function of cells if not regulated
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Urea
- Product of the breakdown of excess amino acids
- toxic
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Nephron
- Long tubules which make up the main functional structures of the kidney
- Site of blood filtration
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Structure and location of Kidneys
- Located behind abdomen
- outer layer - Cortex (lighter colour observed)
- inner layer - medulla (darker colour observed)
- renal pelvis
- fibrous capsule - provides stability and protection, thin outer layer
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Blood moving through Kidneys
- oxygenated blood enters through renal artery (blood from aorta)
- deoxygenated blood leaves via renal vein
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Glomerulus
- located in cortex
- mesh of capillaries
- surrounded by bowmans capsule
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Journey of filtrate
- filtered out of blood in glomerulus
- into bowmans capsule
- PCT (proximal convouted tubule)
- Loop of henle
- DCT (distal convoluted tubule)
- collecting tube to renal pelvis
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Ultrafiltration definition
- process of filtering blood
- at molecular level
- under high pressure
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Ultrafiltration process
- blood enters glomerulus via afferent artiriole
- afferent artiriole has wide lumen
- blood leaves glomerulus via efferent artiriole
- efferent has small lumen
- high hydrostatic pressure inside glomerulus
- fluid pushed against walls of glomerulus and forced into bowmans capsule
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Glomerulus to bowmans capsule
- three layers between glomerulus and bowmans capsule
- glomerular endothelium
- basement membrane
- podocytes (epithilium cells of bowmans capsule)
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Glomerular endothelium
- single sheet of cells
- pores between cells allows movement of fluid
- also specialised to have holes called fenestrations
- allows everything but red blood cells and large proteins to move out
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Basement membrane
- mesh of collagen fibres and other glycoprotein fibres
- doesnt allow RBC, large proteins, platelets
- does allow glucose, urea, amino acids, small proteins
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Podocytes (epithelial of bowmans capsule)
- specialised shape
- finger like projections called major processes/ pedicels
- allow gaps for filtrate to exit
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selective reabsorption definition
- the reabsorbtion of only some molecules from the glomerular filtrate into the blood
- important substances reabsorbed
- glucose
- amino acids
- water
- mineral ions
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reabsorption where and how
- mostly in the PCT (85% fluid reabsorbed in PCT)
- also small amount occours in the collecting duct
- required active transport
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adaptations for reabsorption
- epitihluim lining PCT has two sides
- apical side= side of tubules
- basil side= side of blood
- apical side has microvilli, increase SA, more transport pumps/proteins, more reabsorption
- basil side slightly folded, increase SA
- PCT is tangled, increase distance for reabsorbtion to occour over
- many mitochondria, supply ATP for active transport
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Active transport of sodium
- sodium important for membrane electrical gradient and protein function
- needs to be reabsorbed into blood
- sodium potassium pump on basil side actively pumps Na into blood
- creates low conc of Na inside PCT cell and high conc in blood
- transports against conc gradient
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Cotransport
- cotransport occours on apical side
- secondary active transport
- glucose and amino acids transported with Na on apical side
- low conc generated inside PCT by basil side active transport
- causes Na from tubules to diffuse in, carrying glucose or amino acids with it
- amino acids and glucose then diffuse passively into blood due to constant supply of blood maintaining conc gradient
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water reabsorption
- reduce the loss of water from the body
- apical side
- movement of glucose, amino acids and sodium out of the tubules into the PCT cells creates low water potential inside PCT cells and high water potential in tubules
- water moves by osmosis down the gradient into the PCT cells
- moves via osmosis into blood
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loop of hence structure and function
- reduces water potential of the medulla
- uses counter current multiplication
- loop has a descending limb which desends into the medulla from the cortex
- has an ascending limb which ascends from the medulla back to the cortex
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descending limb
- thin
- permeable to water
- permeable to ions
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ascending limb
- thick
- permeable to ions
- also contains ion pumps to pump ions out
- not permeable to water
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counter current multiplication
- fluid flows in opposite directions to maximise diffusion
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DCT structure and function
- helps balance mineral concentrations
- regulates pH
- many mitochondria for active transport
- microvilli increase SA for active transport
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