Excretion Flashcards
Excretion-
removal of metabolic waste from the body eg. lungs excrete CO2
Excretory organs
Lungs- excrete CO2
Liver- deamination of amino acids producing NH3 which is converted to urea
Skin- excrete sweat which contains salts, urea, water, amino acids, ammonia
Kidney- excrete urea via urine
CO2 excretion
-reacts with water producing carbonic acid
-dissociates to H+ and HCO3-
-this is then transported to lungs
Nitrogenous compounds storage
-body can’t store proteins or amino acids
-amino acids contain energy so instead are deaminated in the liver
-this produces ammonia which is converted to urea
Deamination and formation of urea equation
amino acid + oxygen -> keto acid + ammonia
ammonia + CO2 -> urea + water
Blood flow to and from the liver
-hepatic artery- oxygenated blood travels from aorta via hepatic artery to the liver for aerobic respiration as very metabolically active
-hepatic portal vein- deoxygenated blood from digestive system enters via HPV. Blood is rich in products of digestion. blood from HA mixes with blood from HPV
-hepatic vein- blood leaves via HV and joins to vena cava
-bile duct- secretes bile for digestion and excretion. carries bile from liver to gall bladder, where it is stored
Structure of liver
-cells, blood vessels, chambers are arranged to ensure greatest contact between blood and cells
-divided to lobes, which further divide to cylindrical lobules
-HA and HPV split into smaller vessels which run parallel to lobules- inter lobule vessels
-blood from HA and HPV are mixed and pass along sinusoid (chamber), this allows close contact between cells and blood
-when blood reaches end of sinusoid, conc. of many components have been altered
-sinusoid empties into the intra-lobule vessel, which is a branch or the hepatic vein
Kupffer cells
-specialised macrophagea
-move within sinusoids
-breakdown and recycle old RBCs
Liver cells
-called hepatocytes
-cuboid shape, with microvilli on surface
-dense cytoplasm for metabolic processes
Liver function
-control of blood glucose, amino acid and lipid levels
-synthesis of bile, plasma proteins, cholesterol
-synthesis of RBC in fetus
-storage of vitamins A, D, B12, iron, glycogen
-detoxification
-break down of hormones
-destruction of RBCs
Detoxification enzymes
-catalase- converts H2O2 to water and oxygen
-cytochrome P450- group of enzymes that break down drugs eg. cocaine
Detoxification of alcohol
-ethanol dehydrogenated via ethanol dehydrogenase producing ethanal- this reduces NAD in the process
-ethanal is dehydrogenated via ethanal dehydrogenase producing ethanoate- this reduces NAD in the process
-ethanoate can convert to acetyl CoA for respiration
Formation of urea
- deamination
- ornithine cycle
amino acid -> NH3 + keto acid -> urea
Deamination
-removal of amine
-this produces ammonia and keto acid
-ammonia is highly soluble and toxic so quickly converted to urea via ornithine cycle
Ornithine cycle
-NH3, CO2 and ornithine react to produce citrulline and water
- citrulline reacts with NH3 to produce arginine and water
-arginine reacts with water to produce urea and ornithine for the cycle to continue
Problems of drinking too much alcohol
-detoxification of alcohol uses up NAD stores
-therefore they can’t be used to deal with fatty acids
-fatty acids convert to lipids to be stored as fat
-this causes the the liver to become enlarged
kidney structure
have to revise in textbook as need diagrams
Ultrafiltration
-blood enters glomerula knot through afferent arteriole
-this knot increases the pressure
-small molecules leave arteriole through gaps between cells
-basement membrane prevents larger molecules eg. plasma proteins leaving
-podocytes have finger like projections to ensure there’s gaps
Selective reabsorption
-start with ultrafiltration where everything is removed from blood
-selective reabsorption which is where kidney takes back what it requires and occurs in the proximal convoluted tubule
-finally regulation where the kidney controls how much substance is reabsorbed
Proximal convoluted tubule adaptations
-microvilli for large SA for absorption
-lots mitochondria for active transport
-membrane has co transporter proteins (Na and glucose/ amino acids)
-opposite membrane, close to capillary, folded to increase SA
-membrane has Na/K pumps
How reabsorption occurs
-Na+ actively pumped out of cells lining the tubule into the blood
-conc Na+ decreases inside cell
-Na+ diffuse in from proximal tubule through co transporter protein with glucose/ amino acids
- decreases WP inside cell, so water moves in via osmosis
-glucose and amino acids diffuse into blood
Water reabsorption and loop of henle
-after selective reabsorption, 45cm3 fluid left in PCT
-function of loop is to create a salt bath in surrounding medullary fluid
-later this results in water reabsorption from collecting duct
-this decreases filtrate volume
Descending limb
-permeable to water and salt
-water moves out via osmosis and enters capillary
-filtrate volume decreases so filtrate salt conc increases
-base of loop is impermeable
Ascending limb
-filtrate moves up ascending limb and is impermeable to water
-permeable to salt
-at base Na+ and Cl- diffuse into tissue fluid
-decreases WP fluid, so water leaves descending via osmosis
Loop of henle collecting duct
-conc of medullary fluid causes water to be removed from collecting duct via osmosis
-water then enters capillaries by osmosis
Osmoregulation-
control of water potential in the body
Dehydrated
-osmoreceptors in hypothalamus shrink and detect change
-sends impulse to pituitary gland
-this causes it to secrete ADH
-ADH travels in blood to target cells= cells in wall of collecting duct
-causes a chain of enzyme controlled reactions
-this causes aquaporins to fuse with the membrane, increasing its permeability to water
-therefore water moves into the capillary as it has a lower WP via osmosis
-therefore, more water is reabsorbed and less urine is produced
Hydrated
-detected by osmoregulatory cells in hypothalamus
-sends impulse to pituitary gland
-secretes less ADH
-collecting duct walls less permeable
-less water reabsorbed
Assessing kidney function
-assess glomerular filtration rate=volume of fluid that passes into the nephrons each minute
-analyse uribe for substances eg proteins
Causes of kidney failure
-diabetes
-heart disease
-hypertension
-infection
Treatment of kidney failure
-haemodialysis
-peritoneal dialysis (both types renal dialysis)
-kidney transplant
Haemodialysis
-blood passes into machine containing an artificial membrane
-surrounded by dialysis fluid which flows opposite direction
-heparin added to avoid clotting
-dialysis fluid contents are monitored
Peritoneal dialysis
-dialysis membrane in the body’s abdominal membrane
-surgeon implants permanent tube into abdomen
-dialysis solution poured through thins and fills space between abdominal wall and organs
-after few hours solution is drained
What happens if kidneys fail
-urea, water, salts and toxins aren’t excreted
-less blood filtered by glomerulus, lower glomerular filtration rate
-build up of toxins in the blood
Kidney transplant advantages and disadvantages
+free from dialysis
feeling fitter
improved QoL
-immunosuppressants
major surgery
regular checks for rejection
Urine analysis
can be tested for:
-glucose in diagnosis of diabetes
-alcohol to determine blood alcohol in drivers
-recreational drugs
-hCG in pregnancy testing
Pregnancy testing
-urine poured onto test stick
-hCG binds to mobile antibodies attached to blue bead
-mobile antibodies move down test stick
-if hCG present it binds to fixed antibodies holding the bead in place showing a blue line
-mobile antibodies with no hCG attached binge to another fixed site to show the test is working
Testing for anabolic steroids
-increase protein synthesis so increase the build up of muscles
-banned in many sports
-tested by analysing urine sample using gas chromatography
