5.1.2- Excretion Flashcards
what is excretion?
the removal of metabolic waste (unwanted by-products of normal cell processes) from the body
what are the three major metabolic wastes removed via excretion?
-carbon dioxide
-urea/nitrogenous waste
-bile pigments (bilirubin)
where is carbon dioxide removed from the body
from the lungs
why is excess carbon dioxide toxic?
-excess carbon dioxide lowers blood pH, causing respiratory acidosis (breathing difficulties, headaches, confusion).
-CO2 reduced the amount of haemoglobin available to carry oxygen
why is excretion important?
-is a key process in homeostasis
-is important in maintaining metabolism, as metabolic waste can have serious negative consequences on the body if allowed to accumulate
what is the equation that occurs in the blood if there is excess carbon dioxide?
carbon dioxide + water —> carbonic acid —> hydrogen ions + hydrogen carbonate ions
CO2 + H2O —> H2CO —> H+ + HCO3-
what is urea?
a nitrogenous waste, made up of excess amino acids
why is urea toxic?
-the body cannot store excess amino acids as they contain an amine group
-it diffuses into cells and causes a decrease in water potential and so water is absorbed by osmosis until cell bursts
where is urea created?
in the liver, from the excess amino acids into the toxic amine group
-the useful parts of the molecule are used in respiration
what are the names of the two processes that are used to create urea, and what do these mean?
-deamination= the removal of the amine group from an amino acid to produce ammonia
-ornithene cycle= conversion of ammonia to urea
what occurs in deamination?
amino acid + oxygen —-> (deamination) ketoacid + ammonia
what occurs in the ornithene cycle?
ornithene
+NH3 (ammonia) + CO2
-H2O
citrulline
+NH3
-H2O
arginine
-H2O
-UREA
what is the function of the liver?
to carry out hundreds of metabolic processes
-production of urea, bile and glycogen
-detoxification of drugs, hydrogen peroxide and ethanol
-disposal of old red blood cells and removal of hormones from circulation
-carbohydrate metabolism (when insulin rises, hepatocytes convert glucose to storage carbohydrates glycogen)
describe the external structure of the liver?
-hepatic vein
-hepatic artery
-hepatic portal vein
-bile duct
describe the internal structure of the liver?
-made up of cells known as hepatocytes
-divided into many lobules, which are separated from each other by connective tissue
-branches of the hepatic artery and the hepatic portal vein supply each lobule with blood
-blood is carried in wide capillaries known as sinusoids
-each lobule is also connected to a branch of the hepatic vein that drains blood away from the lobule
what is detoxification?
the conversion of toxic molecules to less toxic or non-toxic molecules.
what is the detoxification of ammonia?
-ammonia is produced in the liver from excess amino acids
-converted to urea during the ornithene cycle
what is the detoxification of drugs?
-medical or recreational, that are ingested or injected
-converted to less harmful molecules by liver enzymes, in a variety of chemical reactions
what is the detoxification of hydrogen peroxide?
-hydrogen peroxide is a toxic product of metabolism, and is produced throughout the body
-converted to oxygen and water by catalase
what is the detoxification of ethanol?
-ethanol is a toxic molecule but contains a lot of energy which the body can use
-hepatocytes break down ethanol using alcohol dehydrogenase to products that are used in respiration
-ethanol —- ethanal —- ethanoic acid —– acetylcoA
—-2H, NAD —> REDUCED NAD
what happens in the livers of alcoholics that causes ‘fatty liver’ which can further lead to hepatitis and cirrhosis?
the liver uses up so much NAD in removing ethanol that they don’t have enough NAD to metabolise fatty acids. Instead of breaking these fatty acids down, the liver converts them to lipids, which are stored in hepatocytes, leading to fatty liver.
what is hepatitis?
inflammation of the liver
what is cirrhosis?
the scarring,. destruction of hepatocytes and loss of liver function
what are the two major functions of the kidney?
-excretion of urea from the body
-osmoregulation (control of water and salt levels in the body)
what type of vein and artery enter and leave the kidney?
-renal vein
-renal artery
how much blood passes through the kidneys every minute?
about 90-120 cm^3
what small structures make up the kidneys?
nephrons
what are the 3 layers of the cross section of a kidney?
-cortex (dark outer layer)
-medulla (lighter in colour)
-pelvis ( basin/central chamber)
what leaves the kidneys and via what?
urine (produced by liver tubules) via the ureters and then out of the body via the urethra
what happens in the cortex of the kidney?
where the filtering of the blood takes place
-dense capillary network carrying the blood from the renal artery to the nephrons
what happens at the medulla of the kidneys?
contains the tubules of the nephrons that form the pyramids of the kidney and the collecting ducts
what happens at the pelvis of the kidney?
the central chamber where the urine collects before passing down the ureter
what are the 5 ways in which the liver maintains an internal environment?
-filters the blood
-re-absorbs all the sugar
-re-absorbs the dissolved ions needed for the body
-re-absorbing as much water as the body needs
-releasing urea, excess salts and excess water as urea
-
what key words appear in the structure of a nephron?
-Bowman’s Capsule
-Proximal Convoluted Tubule
-Loop of Henle
-Distal Convoluted Tubule
-Collecting Duct
-afferent arteriole
-efferent arteriole
-glomerulus
what is ultrafiltration?
the filtration of small molecules and ions out of the blood in the glomerulus into the Bowman’s Capsule.
what pressure does ultrafiltration occur under?
high pressure, because the presssure in the glomerulus is unusually high due to the after ent arteriole being wider than the efferent arteriole
what are the 3 layers that fluid is forced out of during ultrafiltration?
-endothelium of capillary walls, pores are present
-basement membrane
-podocytes
what are pores in the 3 layers of bowman’s capsule?
pores (holes) in the capillary walls that allow blood and plasma and dissolved solutes to pass through
what is the basement membrane?
-made up of collagen and glycoproteins
-this forms a fine mesh, which acts as a filter
-blood cells, platelets and molecules, with >69,000 RMM cant get through.
what are podocytes?
-epithelium of bowman’s capsule
-specialised epithelial cells with finger like projections called ‘foot processes’, which are separated by gaps
which small molecules can pass through the basement membrane?
-vitamins
-amino acids
-glucose
-ions
-nitrogenous waste
-water
what blood cells and large molecule are too big to pass through the basement, so stay in the blood?
-red blood cells
-platelets
-white blood cells
-blood proteins
what does the kidney reabsorb?
-all vitamins, amino acids and glucose
-most (85%) of water and ions
-some nitrogenous waste
how are epithelial cells that line the proximal convulsant tubule specialised for reabsorption?
-folded basement membrane which has a large surface area and a Na+-K+ pump
-many mitochondria which provide ATP for Na+-K+ pumps for active transport
-microvilli which provides a large SA and co-transporter proteins for facilitated diffusion
how are glucose and amino acids re absorbed from filtrate in the PCT?
by sodium cotransport
how is water re absorbed in the PCT?
-removal of Na+ ions, glucose and amino acids filtrate in PCT increase the WP of the tubule fluid and reduced WP of PCT cells
-water leaves the fluid and enters the cells by osmosis
-by re absorbing water, the PCT reduces the volume of fluid which enters it by ~60%
what is the role of the Loop of Henle?
-to create a very low water potential in the tissue surrounding the medulla tissue
-so that water can be re absorbed from fluid im the collecting duct and distal convoluted tubule further along the nephron
what are the names of the two limbs of the loop of henle?
-descending limb
-ascending limb
what is the loop of henle arranged in and what does this mean?
hairpin countercurrent multiplier
-hairpin= two limbs lie close together in a tight bend
-countercurrent= fluid flows in opposite directions
-multiplier= produces high conc of sodium chloride in surrounding medulla tissue
what do hepatocytes of the liver contain?
-large nuclei
-prominent Golgi Apparatus
-lots if mitochondria (metabolically active cells)
what is transamination, which occurs in the liver?
the conversion if one amino acid into another
-it overcomes the problems if having a diet that does not always contain the required balance of amino acids
what has happened to the concentration of blood when entering and leaving the kidney?
-reduced levels of urea
-levels of glucose/other substances has remained the sake
-mineral ion concentration has been restored to ideal levels
what is the main function if the nephron after ultrafiltration at the bowman’s capsule?
to return most of the filtered substances back to the blood
what occurs at the loop if henle?
-water diffuses out of descending limb
-NaCl ions diffuse and actively transport out of ascending limb
-solution = isotonic to hypertonic to hypotonic
where does the balancing of water that the body needs occur in the kidney?
the distal convoluted tubule and collecting duct
what effects the permeability of the DCT and CD walls?
the presence of ADH
what does the cells lining the DCT contain and what does this do?
have many mitochondria so are adapted to carry out active transport
what waste substances are secreted into the fluid inside the DCT?
-when the body lacks salt, Na+ is actively transported out and Cl- follows down a electrochemical gradient
-H+ ions are secreted to regulate blood pH
-NH4+ ions form nitrogenous waste
-K+ ions added to remove excess K+ from blood
-drugs are removed from blood and secreted
what is determined at the collecting duct?
concentration and volume of the urine produced
why can water be removed from the whole length of the collecting duct?
because the level of sodium irons in the surrounding fluid increases through the medulla the cortex to the pelvis
how does water leave the fluid in the CD?
-the fluid contains a lot of water
-the CD runs through the medulla tissue, which has a high salt conc
-therefore, water leaves the fluid in the CD by osmosis, and enters the cells if the collecting duct wall, and then enters the blood capillaries
what is osmoregulation?
the controlling of the water potential of the blood within narrow boundaries regardless of activities of the body
-it is ESSENTIAL FOR SURVIVAL
what is the volume of water lost in the urine controlled by?
ADH in a negative feedback system
what happens to cells is the water potential of tissue fluid is too high?
cells gain too much water and burst/lysis
what happens to cells is the water potential of tissue fluid is too low?
cells lose too much water by osmosis and cremate/shrink
where in the brain are osmoreceptors?
in the hypothalamus of the brain
where is ADH stored?
the posterior pituitary gland of the brain
what is the mechanism of ADH action?
-ADH is released from the pituitary gland and carried in the blood to the cells of the CD
-ADH binds to receptors on the cell membrane and triggers the formation of cyclic AMP
-cAMP acts as a second messenger and so causes a cascade of events
-vesicles in the cells lining the CD fuse with the cell surface membranes on the side of the cells in contact with the tissue fluid in the medulla
-the membranes of these vesicles contain aquaporins and when inserted into the CSM, they make it permeable to water
-this provides a route for water to move out of the tubule cells into the tissue fluid of the medulla and the blood capillaries by osmosis
what happens when blood WO falls?
-Osmo receptors lose water and shrink
-they send nerve impulses to the posterior pituitary which release stored ADH into the blood
-The increased ADH level makes CD walls more permeable to water, so more is reabsorbed
-this means that urine is more concentrated, a darker colour and is released in smaller volumes
what happens when blood WP rises?
-change detected by osmoreceptor where they gain water and swell
-Osmo receptors don’t send a nerve impulse
-so pituitary gland releases less ADH
-decreased ADH levels make the CD less permeable to water so urine is dilute and is in larger volumes
what is kidney failure?
the damage of the kidney, and so it can no longer work effectively
what are the three causes of kidney failure?
-diabetes
-hypertension/high blood pressure
-infection
what are the two types of kidney failure?
-acute
-chronic
what are the three treatments for kidney failure?
-haemodialysis
-peritoneal dialysis
-kidney transplant
what happens in haemodialysis?
-
what happens in peritoneal dialysis?
-
what are the advantages and disadvantages of haemodialysis?
-
what are the advantages and disadvantages of peritoneal dialysis?
-
what is glomerular filtration rate?
the measure of the rate at which the blood is filtered in the Bowman’s Capsule
-blood test measures the level of creatine in the blood
-it can be used to indicate kidney disease, if it is too high
what factors effect the GFR?
age, it decreases steadily with age
gender, men have more muscle mass and so more creatine
what measurement of GFR indicates kidney failure?
15 or below
what does loss of electrolyte balance in kidney failure mean?
if the kidney fails, the body cannot excrete excess sodium, potassium and chloride ions, and so this causes osmotic imbalances in the tissue and eventual death
what is urine known as in terms of diagnosis?
a diagnostic tool
what are the 7 things found in urine that can show a condition/disease?
-glucose= diabetes
-protein=hypertension
-creatine= muscle damage
-nitrites= urinary tract infection
-white blood cells= urinary tract infection, inflammation of kidney
-ketones= starvation, excessive vomiting
-human chorionic gonadotrophin (hCG)= pregnancy
how to pregnancy tests work in terms of showing a positive pregnancy result?
-pregnancy hormone hCG is present in a woman’s urine, which will travel up the test
-hcg binds to place monoclonal anti-hcg antibodies that have enzymes that trigger a colour change
-already placed anti-hcg ma bind to already binded hcg which triggers a colour change
-already placed monoclonal antibodies compatible to anti-hcg antibodies, and bind, to trigger a second colour change, not for the presence of hcg
what are the anti-hcg antibodies known as?
mobile
what are the monoclonal antibodies known as?
immobile
what are monoclonal antibodies?
antibodies from a single clone of cells that is produced to target particular cells/chemicals in the body
how are monoclonal antibodies created?
-mouse is injected with hcg to create appropriate antibody
-b-cells that create the antibody are removed from the mouse, and fused with myeloma/tumor
-this new cell is known as a hybridoma
-these reproduce rapidly and result in clones of ‘living factories’ to make the desired antibody
-these monoclonal antibodies are collected, purified and used in a variety of ways
what are anabolic steroids?
-athletes and body builders try to cheat using these
-they mimic the action of testosterone, stimulating the growth of muscles
what are the negative side effects?
-hypertension
-heart attack
-aggression
-infertility
what is the test for anabolic steroids?
gas chromatography
-urine sample vaporised with a known solvent
-passed along tube
-lining of tube absorbs the gases
-analysed to give a chromatogram
