Excretion Flashcards
Define the term metabolism
all the chemical reactions with take place in the body
Define the term excretion
the removal of waste products of metabolism from the body
Why do metabolic wastes like CO2 and nitrogenous waste need to be removed from the body
they are toxic so would cause damage if left to build up in the body
Describe the gross structure of the liver
hepatic artery supplies oxygenated blood to the liver
for respiration (narrow compared to others)
hepatic vein- takes deoxygenated blood away fro the liver
hepatic portal vein- brings blood from small intestine so its rich of products from digestion
bile duct takes bile to gall bladder to be stored
what is the role of bile
emulsify fats
what is the liver made up of and describe them
lobules- cylinders made up of cells called hepatocytes, each lobule has a central vein connecting it to the hepatic vein
how are the hepatic artery and the hepatic portal vein connected to the central vein
siusiuds
what are Kupffer cells
attached to walls of the sinusoids and remove bacteria/ old red blood cells
hepatocytes produce bile, where does this go
bile canilliculi which draining the bile duct
describe how amino acids are broken down in the liver
the amine group is removed from the main acids, forming ammonia and organic acids in a process called deamination
organic acids can be repaired or converted to carbohydrate and stored as glycogen
ammonia is too toxic to be directly excreted so is combined with CO2 in the ornithine cycle to create urea and water
urea is released into blood and filtered in the kidneys to remove urea in form of urine
draw the ornithine cycle
ammonia-> carbamoyl phosphate
-> citrulline
(AMP and water produced)
-> argininosuccinate
-> argenine
(urea produced)
-> ornithine
what is is the process of breaking down harmful substances so they can be excreted in the liver and give three examples of substances that may undergo this process
detoxification- alcohol, paracetamol and insulin
what is alcohol broken down into in the liver
ethanal then acetic acid
how does the liver store glucose
converts excess glucose in the blood to glycogen in process called glycogensis
draw the structure of a nephron
describe the process of ultrafiltration
the afferent brings blood to the glomerulus
the efferent arteriole takes blood away, as it is smaller in diameter it creates high hydrostatic pressure which forces liquid and small molecules out of the capillary into the Bowman’s capsule
the liquid and small molecules pass through three layers to get to the Bowman’s capsule: the capillary endothelium, the basement membrane and podocytes
the liquid and small molecules are now called filtrate and pass along rest of nephron where useful substances are reabsorbed and the rest of filtrate flows through collecting duct and is excreted
describe the process of selective reabsorption
Selective reabsorption is the process whereby certain molecules (e.g. ions, glucose and amino acids), after being filtered out of the capillaries along with nitrogenous waste products (i.e. urea) and water in the glomerulus, are reabsorbed from the filtrate as they pass through the nephron.
describe gross structure of the kidney
dark outer area (the cortex) and an inner lighter-coloured area (the medulla)
Each kidney is roughly 10 cm long and 5 cm wide, and is encased in a fibrous outer capsule called the renal capsule.
describe the histology of the kidneys
The kidney is organised into many lobes, organised in a pyramidal structure, where the outer portion is made up of cortex
how would you dissect a kidney to examine
Carefully make a lateral, longitudinal cut through the kidney and lay the 2 halves on the dissecting tray
where does ultrafiltration take place
glomerulus
what is urine made up of and why
water, dissolved salts and urea doesn’t usually contain proteins or blood cells and too big to be filtered out of blood
if water potential of blood is low (dehydrated)…
more water is reabsorbed by osmosis into the blood from the tubules of the nephrons, urine is more concentrated so less water is lost
if water potential of blood is high (too hydrated)
less water is reabsorbed by osmosis in the blood from the tubules of the nephrons so urine is more dilute and more water is lost during excretion
describe the countercurrent system present in the loop of Henle
at the top of the ascending limb, NA+ and Cl- ions are actively pumped out into the medulla, ascending limb is impermeable to water so water remains inside tubule, creating low w.p in the medulla
water moves into medulla from descending limb by osmosis, the filtrate is then more conc. (as ions cannot diffuse out cause descending limb is impermeable to ions) water in medulla is reabsorbed by blood
at bottom of ascending limb Na+ and Cl-ions diffuse out into the medulla further lowering the w.p of the medlla
these stages cause water to move out of the collecting duct via osmosis
describe how different lengths of loop of henles in animals affect their loss of water
the longer the animals loop of Henle the more water can be reabsorbed from the filtrate, a longer ascending limb more ions are actively pumped out into medulla creating lower w.p, therefore more water moves out of collecting duct to be reabsorbed by capillaries, animals in hot conditions usually have a long loop of henle to conserve water
what is water potential monitored by
osmoreceptors
what gland releases ADH
posterior pituitary
how does ADH control water potential
binds to receptors on plasma membranes
protein channels called aquaporins are inserted into membrane
this allows water to pass through via osmosis making walls of DCT and collecting duct more permeable
more water is reabsorbed by the blood so a small amount of conc. urine is produced
what happens in terms of ADH release when we are dehydrated
water content of blood drops so its w.p drops
this is detected by osmoreceptors in the hypothalamus
posterior pituitary gland is stimulated to release more ADH
DCT and collecting duct become more permeable so more water reabsorbed by blood via osmosis
small amount of high conc urine is produced
what happens in terms of ADH release when we are too hydrated
water content of blood rises so w.p rises
this is detected by osmoreceptors in the hypothalamus
posterior pituitary gland releases less ADH
less ADH means the DCT and collecting duct are less permeable so less water is absorbed ny blood via osmosis
large amount of dilute urine is produced
how can kidney failure be detected
glomerular filtration rate
how does kidney infections affect kidneys
causes inflammation which can interfere with filtering in Bowman’s capsule
how does high blood pressure affect kidneys
can damage glomeruli then larger molecules like proteins can get through capillary walls
what problems arise from kidney failure
waste products begin to build up
fluid accumulates in tissues so swelling occurs
imblance of ions
anaemia (long term)
what are the two types of dialysis used to treat renal dialysis
haemodialysis and peritoneal dialysis
how does haemeodialysis work
blood flows one side of the partially permeable membrane and dialysis fluid flows on the other
they flow in opposite directions to maintain a steep conc. gradient to increase rate of diffusion
waste products, excess water and ions diffuse into dialysis fluid removing them from th3 blood
what are the problems with haemodialysis
patients can feel increasingly unwell as waste products build up between sessions, expensive, time consuming,
how does peritoneal dialysis work
a tube is inserted that goes from the outside of the patents body to their abdominal cavity
dialysis fluid is put through the tube into the abdominal cavity
fluid remains in the body while waste products from the patients blood diffuse out of the capillaries into dialysis fluid, fluid is drained out and fresh fluid is put in
what are the problems with peritoneal dialysis
risk of infection, no dialysis free days
what are the advantages and disadvantages of a kidney transplant
+ cheaper, convenient, patients don’t feel unwell between sessions
- undergo major operation, risky, risk that the immune system will reject the transplant so immunosuppressant drugs will have to be taken
how do pregnancy tests work
stick contains monoclonal antibodies for HCG which are identical to each other
when urine is applied the antibodies will bind to antibody on beads
urine moves up carrying beads with it
test strip has antibodies to hCG stuck in place
if hCG is present the test strip turns blue because immobilised antibodies bind to any hCG attached to blue beads, if no hCG is present beads will pass through so no blue colour present
