MODULE 1.2 EXCRETION Flashcards
Define excretion
the removal of metabolic waste substances from the body
What are the two main substances to be excreted from the body
co2 from respiration and urea from the liver made by deamination of amino acids
Why is excess co2 bad
- hydrogen carbonate ions form hydrogen ions which competes with 02 for haeomglobin = lack of 02 transport
- carbaminohaemoglobin = lower affinity for o2 than normal haem
- respiratory acidosis
what enzyme forms hydrogen ions from hydrogencarbonate ions
under the influence of the enzyme carbonic anhydrase
what is respiratory acidosis
- co2 dissolves in blood plasma
- combines with h2o to produce carbonic acid
- h2co3 dissolves to release h+ and hco3- ions
- h+ ions change ph of blood and proteins in blood act as buffers to stop this
- little h+ ions detected by medulla oblongata and breathing increases to expel it but + h+ ions causes blood ph to drop below 7.35 and breathing slow/diff, headaches and drowsiness
What is the hepatic portal vein
has two capillaries one at either end and takes blood from digestive system to liver
where does the liver get oxygenated blood and what is it used for
from the aorta via the hepatic artery- used for aerobic respiration as the liver carries out many metabolic processes that need energy in the form of ATP
where does the liver get deoxygenated blood
the digestive system via the hepatic portal vein and this blood is rich in digestion products
how does blood leave the liver
hepatic vein where it returns to normal circulation via the vena cava
what does the bile duct do
takes bile from the liver to the gall bladder where it is stored until it is needed in the digestion of fats in the small intestine
describe the arrangement of cells inside the liver
- split into lobes and then further into cylindrical lobules
- hepatic portal vein + artery enter liver and split into smaller vessels and run between lobules= inter lobular vessels
- blood mixes at intervals in a sinusoid which is lined by liver cells so exchange can take place between molecules
- blood empties from sinusoid into a branch of the hepatic vein
how is the bile duct formed
bile released into bile canaliculli which join together to form bile duct
what are kupffer cells
specialised macrophages involved in breakdown and recycling of old red blood cells - produces bilirubin which is removed in bile and faeces
function and shape of liver cells
cuboidal shape with many microvilli
-protein synthesis, synthesis of cholesterol and bile salts, trans and storage of carbs
what are the by products of de amination in the liver
ammonia and keto acid which goes straight into respirationto release its energy
what are the functions of the liver
- make rbc for fetus, bile,
- destroy rbc
- breakdown hormones
- detoxification of alcohol
describe the ornithine cycle
converting ammonia into a less toxic form called urea bu combining the ammonia with co2
water is also produced
how does urea get to the bladder
passed back into the blood from the liver where it passes into the kidneys where urea is filtered out of the blood and concentrated in the urine
urine is stored in the bladder until it is expelled
define detoxification
the conversion of toxic molecules into less toxic or non toxic molecules
how is alcohol` broken down
- taken to the liver where it is broken down using ethanol dehydrogenase into ethanal
- ethanal further dehydrogenated into ethanoate by ethanal dehydrogenase
- ethanoate combines with co enzyme a to form acetyl co enzyme a which enters respiration
what happens to the hydrogen ions during the breakdown of alchohol
combine with another co enzyme called NAD to form reduced NAD
What is NAD used for and what is a problem with insuffiecient NAD
used to break down fatty acids in the liver to be used in respiration
too many fatty acids = not enough NAD which means they build up in the liver as lipids and are stored in liver cells
this can cause alcohol hepatitis or cirrhosis
what are the 4 main parts of the nephron
collecting duct
distal convoluted tubule
proximal convoluted tubule
loop of henle
where does the kidney get its blood supply and how is it drained
renal artery
renal vein
what are the three regions of the kidney and where are they located
outer region is called the cortex
inner region is the medulla
centre is the pelvis
what is the nephron
microscopic tubule that recieves fluid from the blood capillaries in the cortex and turns in into urine which drains into the ureter
what is the glomerulus
a fine network of capillaries that increases the local bp to squeeze fluid out of the blood, the bowman capsule collects the fluid and leads it to the nephron
what is the difference between an afferent vessel and an efferent vessel
afferent carries blood into the organ and efferent carries it away
what are podocytes
specialised cells that make up the lining of the bowmans capsule
what is ultrafiltration
the filtration of substances on a molecular level
what are the 3 sections in the barrier between the blood in the capillary and the fluid in the lumen of the bowmans capsule and how are they adapted
- endothelium; small pores that allow blood plasma and substances in it to dissolve through
- basement membrane; mesh network of collagen fibres and glycoproteins- main part of ultrafiltration (most proteins and all blood cells remain in glomerelus)
- podocytes which have major processes that ensure there are gaps between the cells so fluid can pass through into the bowmans capsule
what is filtered out of the blood
urea, water, small inorganic ions, glucose, amino acids and a small amount of protein
what is left in the capillary during ultrafiltration and why
almost all proteins and blood cells
proteins keep very negative water potential to allow for necessary water re absorption
define osmoregulation
the regulation and control of water potential in the bloody and bodily fluids
how does the levels of ADH make the collecting duct wall more permeable
- cells in the wall contains membrane bound receptors for ADH
- adh binds and sends of enzyme contolled chain reactions in cell
- this inserts vesicles containing aquaporins in cell
- more ADH means more aquap which means wall is more permeable to water so more water moves out collecting duct via osmosis; less pee that is more concentrated
how are the walls of the collecting duct made less permeable
plasma membrane folds inwards making new vesicles that remove aquaporins from membrane which makes wall less permeable which means more pee that is more dilute
what are osmoreceptors
receptors that monitor the water potential of the blood; when low they lose water by osmosis and shrink which causes stimulation of neurosecretory cells
what are neurosecretory cells
cells that act like nerve cells but manufacture and release ADH
ADH made in cells body but pass down the axon and are stored in the terminal bulb; if an action potential passes down then ADH is released
how is the level of ADH adjusted in blood
- osmoreceptors in hypothalamus
- low wp causes osmoreceptors to shrink and trigger neurosecretory cells in hp
- these produce and release ADH from the terminal bulb in the posterior pituitary gland when stimulated
- ADH runs through blood capillaries to the rest of the body and acts on cells of the collecting ducts
- when wp of blood rises less adh released
what 3 things can cause kidney failure
diabetes mellitus
hypertension
infection
what is dialysis
the use of a partially permeable mebrane to filter the blood
what is haemodialysis
- blood from a vein passed into the dialysis machine
- heparin added to avoid clotting
- any substances in excess are removed through the membrane into the dialysis fluid and any substances low in conc diffuse into blood
what is peritonal dialysis
- bodies own abdominal membrane is filter
- permanent tube inserted into abdomen
- dialysis fluid in tube and fills space between abdominal walls and organs
- after the used solution is drained from the abdomen
what happens to amino acids so that they are not wasted from the body
go to liver where potentially dangerous amine group is removed
amino group forms ammonia
can be converted into urea + water when combined with co2
any keto acid that is made can be used in respiration
how are the cells lining the proximal convoluted tubule specialised for re absorption
- many microvilli for increased surface area of readsorption
- special co transporter proteins that transport glucose or amino acids from the tubule into the cell aka facilitated diffusion
- sodium pottasium pumps
- many mitochondria to produce a lot of ATP
how does reabsorption occur
- na/k pumps na out of cell reducing conc of na ions in cell
- na ions enter cell with glucose/amino acids from pt lumen
- as level of glucose and amino acids rise in cell can be transported back out of the cell into the blood plasma
- all this decreases water potential of cells and increases in PT fluid so water will enter the cells and be put back into the blood via osmosis
