Bio 4: Excretion Flashcards
Excretion
Removal of metabolic waste from the body
Metabolic waste
The waste substances that may be toxic or are produced in excess by the reactions inside cells. E.g. CO2 and urea
Carbon dioxide (as waste)
Passed from cells of respiring tissues. It is toxic in excess.
+Travels as hydorgencarbonate, this forms hydrogen ions that compete with oxygen for space on haemoglobin.
+Form carbaminohaemoglobin, reducing oxygen transport
+Respiratory acidosis, lower blood pH, blood becomes more acidic. Significant changes cause drowiness, headaches, confusion and even death.
Urea (as waste)
Produced by deamination. This makes ammonia, which converted into urea, which is taken to the kidney.
Keto acid is used in respiration or for storage.
Deamination
Removal of amine group from an amino acid to produce ammonia.
Hepatic artery
Takes the oxygenated blood from the aorta into the liver
Hepatic portal vein
Takes the deoxygenated blood from the digestive system to the liver.
Hepatic vein
Blood leaves the liver, joins the vena cava
Bile duct
Carries bile from the liver to the gall bladder
Kupffer cells
Specialised macrophages that move in sinusoids. They breakdown and recycle old red blood cells. One product is bilirubin.
Ornithine cycle
Process in which ammonia is converted to urea. It occurs partially in the cytosol and partly in mitochondria, as ATP is used.
Ammonia and carbon dioxide makes urea and water
Alcohol detoxification
Ethanol is dehydrogenated to ethanal, then again to ethanoic acid. The final compound is acetate. This is combined with coenzyme A forming acetyl coenzyme A.
Nephron
Functional unit of the kidney. Microscopic tubule that receives fluid from the blood capillaries in the cortex and converts this to urine, which drains into the ureter.
Glomerulus
Fine network of capillaries that increases the local blood pressure to squeeze fluid out of the blood. It is surrounded by a cup - or funnel-shaped capsule which collects the fluid and leads to the nephron.
Selective reabsorption
Useful substances are reabsorbed from the nephron into the bloodstream while other substances remain in the nephron.
Ultrafiltration
Filtration at a molecular level
Podocytes
Specialised cells that make up the inner lining of the Bowman’s capsule. They have finger like projections called foot processes. This ensures there are gaps between the cells.
Basement membrane
Fine mesh of collagen fibres and glycoproteins. This acts as a filter prevent large molecules getting through. Blood cells and proteins cannot get through. Water, amino acids, glucose, urea and inorganic ions can get through.
Co-transporter proteins
Proteins in the cell surface membrane that allow facilitated diffusion of simple ions to be accompanied by transport of a larger molecule such as glucose.
Osmoregulation
Control and regulation of the water potential of the blood and body fluids. This is the kidney in humans.
Loop of Henle
A descending limb into the medulla and an ascending limb into the cortex. This allows salts from the ascending limb into the descending. This increase the concentration in the tubule fluid, and causes them to diffuse out into the medulla.
Cortex has high water potential because…
+ at the base sodium and chloride ions diffuse out of tubule
+high up, they are transported out
+ascending wall is impermeable to water (no water loss here)
Distal convoluted tubule
In the cortex, between the loop of Henle and the collecting duct
Collecting duct
Tubule fluid has a high water potential, water is lost depending on the presence of aquaporins. This lost by osmosis. The duct goes back into the medulla.
ADH
Antidiuretic hormone, is released from neurosecretory cells in the pituitary gland and acts on the collecting ducts in the kidneys to increase their reabsorption of water. More ADH means more aquaporins are inserted into the collecting duct, this means more water is reabsorbed, and there is less urine.
Osmoreceptors
Receptor cells that monitor the water potential of the blood.
Haemodialysis
Blood is taken from a vein and passed through a dialysis machine so that exchange can occur across an artificially partially permeable membrane.
Heparin is added to avoid clotting.
Peritoneal dialysis
Dialysis fluid is pumped into the body cavity so that exchange can occur across the peritoneum..
Human chorionic gonadaotrophin
The hormone released by human embryos, it’s presence in the mothers urine as early as 6 days after conception confirms pregnancy.
Monoclonal antibodies
Identical because they have been produced by cells that are clones of one original cell.
Anabolic steroids
Drugs that mimic the action of steroid hormones that increase muscle growth.
