Kidney Revision

 

Kidney Revision 1.2 1)

Excretion

1.2 2)

The liver

1.2 3)

Functions of the liver

1.2 4)

The kidney

 

 The nephron

 

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About one million nephrons in ech !idney.

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glomerulus.. "n the cortex the cpillries form  !not clled the glomerulus

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capsule. #urrounded #urr ounded by the Bowman's capsule.

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Fluid from the blood is pushed into the $o%mn&s cpsule by by   ultrafiltration. ultrafiltration. As the fluid moves lon' substnces re rebsorbed by selective reabsorption.  This psses into the the pelvis nd do%n the uter uterer er..

 

1.2 5) Form Formti tion on o off (ri (rine ne (ltrfiltrtion

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ydrosttic pressure of the blood filters out %ter* mino cids* ydrosttic 'lucose* ure* nd inor'nic ions +,-/l0K-). roteins re left in the cpillry %hich cuses  lo% %ter potentil 0 roteins some %ter remins in the blood.

#elective Rebsorption

+t promixl convoluted

tubule)

 

 

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4 of filtrte is rebsorbed. /ell surfce membrne is hi'hly folded to form microilli 5 increse surfce re. 6embrne lso contins co!transporter contins co!transporter proteins tht trnsport 'lucose or mino cids %ith ,- ions from tubule to cell 5  5  facilitated diffusion diffusion..

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7pposite membrne +close to blood cpillries) is lso folded to increse surfce re. /ontins sodium!potassium pumps +pump ,- ions into cell). mitochondria 5 ener'y re8uired process /ell cytoplsm hs many mitochondria 5 5 involves AT.

1) #odium0potssium #odium0potssium pum pumps ps rremove emove sodium ions fr from om the cells linin' the proximl convoluted tubule. /oncentrtion of ,- ions in cell reduces. 2) ,- ions r re e trnsp trnsporte orted d into cell by fcilitt fcilitted ed diffusi diffusion. on. 3) 9lucose : mino cid concentrtions rise inside cells 5 diffus diffuse e out o off opposite side of cell into tissue fluid. ;iffuse into blood n dre crried %y. <) Rebsorption Rebsorption of slts* 'lucose nd mino mino cids rreduces educes the %ter potentil in cells nd increses the %ter potentil in the tubule fluid. 6ens %ter %ill enter the cells then be rebsorbed into the blood by osmosis. ) =r'er molecules* e.'. smll pr proteins oteins m my y hve ent entered ered ttubule ubule %il be rebsorbed by endocytosis.

 

1.2 ") #ater reabsorption

 

$%& (& *+,T-*,-T ,/T&(/&- #>#TE6?  To  To increse the co concentrtion ncentrtion of slts in the the tubule fluid* cusin' them to to diffuse out to the surroundin' medull tissue 5 very lo% %ter potentil.  The removl removl of ions from the scendin' limb m mens ens tht t the top o off the scendin' limb the urine is dilute. @ter my then be rebsorbed in the osmoregulation.. distl tubules nd collectin' ducts 5 osmoregulation Fluid psses lon' distl convoluted tubule 5 ctive trnsport is used to salts.  dust concentrtions of vrious salts.  Collecting duct has very high

 

water potential 5 potential 5 it contins  lot of %ter s it trvels do%n the duct* diffuses by osmosis into medull since tht hs  very lo% %ter potentil. Amount of %ter rebsorbed depends rebsorbed depends on the permeability  of  of the %lls of the collectin' duct.

1.2 0) +smoregulation •

/ontrol of %ter levels : slt levels in the body. body.

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Water balance:

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Gain = food/drink, metabolism

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Loss = rine, sweat, water vapour, faeces

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A; 5 hormone +ntidiuretic) B ;ehydrted

1) 7sm 7smore orecepto ceptors rs de detect tect chn chn'e 'e ++increse incresedecrese decrese of %ter potentil in blood) 2) =ess A; =ess A;6ore 6ore A;  A; relesed from posterior pituitry 'lnd lessmore permeble more permeble 3) /ollec /ollectin tin' ' duc ductt %l %lls ls less <) =ess =ess more %ter rebsorbed into blood +mor +moreless eless urine produced) +smoreceptors in hypothalamus of the brain @hen the %ter potentil of the blood is lo% 5 osmorecetpor cells lose %ter by osmosis* %hich cuses them to shrin! nd stimulte neurosecretory cells.

 

,eurosecretory cells re specilised neurones tht produce nd relese ,eurosecretory A; 5 A; flo%s do%n the xon to the terminl bulb in the posterior pituitry 'lnd. Action potentil B relese of A;.