Summary
Summary Module 5.2: Excretion
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- Module 5.2: Excretion
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- OCR
OCR A level biology A Key concepts of liver and kidney function, and the control of water potential and kidney failure
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EXCRETION Supplied by renalarteries, renal vein
Excretion maintains homeostasis (inferior VC)
1) CO2 – cellular respiration + excreted in lungs Blader full, sphincter
2) Nitrogenous waste (excess aa) = urea, ammonia, uric opens, urine out urethra
3) Bile pigments – haemoglobin breakdown in liver Nephrons
- Blood filtered, remove
Liver structure nitrogenous, ions, H2O
- Bowmans cap =
ultrafiltration
Loop of Henle
- Concentrates urine, ATP transports
ions
- Different parts have different permeabilities, ↑
solute
PCT proximal convoluted tubule
- Reabsorption
- Hepatic artery = oxygenated blood from heart - Glucose, aa, vitamins, hormones, Na+ out by AT
- Hepatic vein = deoxygenated blood away from liver - Chloride ions + water passively down gradient
- HPV = 75% of blood, nutrients from intestines (toxic) - Cell lining = microvilli (SA), mitochondria for ATP
- HA + HPV mixed in sinusoid (↑ O2) to intralobular - Diffuse into capillary, constant flow = conc grad
(HV) - Filtrate at end of PCT = isotonic (same as blood)
- Kupffer cell in sinusoid (macrophage) break RBC
- BD = bile from liver (canaliculi), stored in gall bladder, DCT distal convoluted tubule
released via bile duct to small intestine (bilirubin) - permeability of walls varied with ADH
- Bilirubin (Hb product) excreted in bile - cells have mitochondria for AT
- Hepatocytes remove substances – large nuclei, mito - if lacks salt, sodium ions pumped out
- DCT balances pH of blood
Liver function
Carbohydrate metabolism Collecting duct
- Convert glucose to glycogen for storage (insulin) - Water moves out down conc due to ADH levels
- Convert glycogen to glucose due to glucagon - Urine more concentrated (hypertonic)
- Na+ in surroundings ↑ down = water removed
Detoxification
- Hepatocyte contain catalase H peroxide to O2 + H2O Kidney function
- Contain alcohol dehydrogenase = ethanol to ethanal, Ultrafiltration
converted to ethanoate (build fatty acids) - Specialised form of tissue fluid process, glomerulus
- Wide afferent arteriole (↑hp), out narrow efferent
Deamination of excess amino acids - Blood thru 3 layers: capillary, basement mem, podo
- Hepatocytes synth plasma proteins (collagen mesh stops > 69,000)
- Transamination = convert aa to aa - Filtrate = plasma, gluc, salt, urea (no blood, proteins)
- Deamination = remove amine
group, to ammonia then urea Selective reabsorption
(ornithine cycle) - Descending limb = water out, NaCl diffuse in, concen
- Used in - Ascending limb = permeable to sodium/chloride, out
respiration/lipids down conc, in second half of limb AT
- Not store proteins - Impermeable to water = filtrate dilute (hypo)
1) Na+ AT out tubule lining to blood
2) Na+ diffuse in by cotransport gluc/aa, water in by os
3) Glucose + aa diffuse into blood + water follows
Kidney structure
Cortex – outer layer, dense capillaries, filters blood
Medulla – nephron tubules
Pelvis – center where urine collects
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