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THE KIDNEY. Organ of osmoregulation and excretion. © 2008 Paul Billiet ODWS. Aorta. Renal vein. Kidney. Renal artery. Vena cava. Ureter. Bladder. Urethra. The urinary system. © 2008 Paul Billiet ODWS. Outer membrane. Renal artery. Nephrons (2 million). Renal Vein. Pelvis.
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THE KIDNEY Organ of osmoregulation and excretion © 2008 Paul Billiet ODWS
Aorta Renal vein Kidney Renal artery Vena cava Ureter Bladder Urethra The urinary system © 2008 Paul Billiet ODWS
Outer membrane Renal artery Nephrons (2 million) Renal Vein Pelvis Cortex Medulla organised in pyramids Ureter Urine The Kidney © 2008 Paul Billiet ODWS
The blood supply © 2008 Paul Billiet ODWS
The cortex (view x100) Tubule Malpighian or renal corpuscles © 2008 Paul Billiet ODWS
The Malpighian corpuscle (view x400) Glomerulus – a ball of capillaries Bowman’s capsule © 2008 Paul Billiet ODWS
Medulla (view x400) Tubules Capillaries © 2008 Paul Billiet ODWS
The nephron In the cortex In the medulla © 2008 Paul Billiet ODWS
Bowman’s capsule Branch of renal artery Glomerulus Branch of renal vein Proximal convoluted tubule Distil convoluted tubule Capillary Collecting duct Loop of Henlé The nephron © 2008 Paul Billiet ODWS
Southern Illinois School of Medicine Filtration in the glomerulus • Blood enters the glomerulus from a branch of the renal artery • This blood is under high pressure • The capillary walls are one cell thick • They are pierced with openings (fenestrations) • The plasma filters though the membrane under pressure • Proteins do not pass © 2008 Paul Billiet ODWS
Southern Illinois School of Medicine Filtration in the glomerulus • A membrane surrounds each capillary of the glomerulus • The blood plasma is filtered at about 150 litres per day © 2008 Paul Billiet ODWS
Southern Illinois School of Medicine Auer Lab Life Sci Div Lawrence Berkley National Lab Filtration in the glomerulus The filtration membrane is held in place by specialised podocytes © 2008 Paul Billiet ODWS
Blood plasma v Filtrate © 2008 Paul Billiet ODWS
The nephron functions Impermeable to water Variable permeability to water Freely permeable to water © 2008 Paul Billiet ODWS
Impermeable to water Variable permeability to water Freely permeable to water The nephron osmoregulation Active reabsorption Na+ Na+ Na+ H2O H2O Passive osmosis Ultrafiltration under pressure 80% of water reabsorbed © 2008 Paul Billiet ODWS
More and more salty Na+ H2O Na+ H2O H2O Na+ H2O H2O H2O H2O H2O Impermeable to water Variable permeability to water Freely permeable to water The nephron osmoregulation Collecting duct Loop of Henlé © 2008 Paul Billiet ODWS
The nephron osmoregulation • The blood concentration is monitored by osmoreceptors in the hypothalamus • If the concentration rises the hypothalamus releases ADH • ADH makes the collecting duct walls more permeable • More water is reabsorbed from the filtrate as the ducts pass through the salty tissues of the medulla © 2008 Paul Billiet ODWS
The nephron osmoregulation • The urine released into the pelvis is more or less concentrated depending upon the blood concentration • Excessive sweating and eating salty food will produce concentrated urine • Drinking and cold weather will produce dilute urine © 2008 Paul Billiet ODWS
Kidney reabsorption © 2008 Paul Billiet ODWS
Dr Millet USC Med schooll Reabsorption Microvilli on cuboidal epithelial cells Kidney tubule with brush border © 2008 Paul Billiet ODWS
The proximal tubules reabsorb: • 80% of water • All of the glucose • All of the amino acids • Blood pH is regulated • Blood salt levels are regulated • Urea is left behind and even secreted into the tubules Reabsorbed molecules pass into the surrounding capillaries © 2008 Paul Billiet ODWS