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A Biology > 5.1.2 Excretion > Flashcards

5.1.2 Excretion Flashcards

1
Q

excretion

A

removal of metabolic waste products from the body.

important in maintaining metabolism as they may be toxic if they build up and homeostasis as it maintains constant levels of stuff in blood

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2
Q

examples of metabolic waste products

A
  • CO2 (from resp, excreted by lungs)
  • bile products (breakdown of Hb, excreted from liver into small intestine)
  • nitrogenous waste products (breakdown of excess a.as by liver –> urea/uric acid which are excreted by kidney)
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3
Q

what are the 2 main organs involved in excretion?

A

kidney and liver

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4
Q

what makes up the portal triads in the liver? (at the edges of hexagonal lobules)

A

hepatic portal vein (blood loaded w/ products of digestion from intestines)
hepatic artery
bile duct

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5
Q

what is the central vein in the liver?

A

hepatic vein

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6
Q

sinusoids

A

blood from hepatic artery and hepatic portal vein mixes, increasing O2 content of blood from portal vein so hepatocytes can be supplied with enough O2 for needs

surrounded by hepatocytes
contain Kupffer cells

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7
Q

canaliculi

A

bile is secreted into canaliculi and drains into bile ductules, which take it to gall bladder

bile flows in opposite direction to blood

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8
Q

function of Kupffer cells

A

ingest foreign particles and act as resident macrophages of liver

help protect against disease

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9
Q

function of hepatocytes

A

secrete bile into bile canaliculi from breakdown of Hb

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10
Q

function of hepatocytes

A

secrete bile into bile canaliculi from breakdown of Hb

convert a.as to NH3 and then to urea in ornithine cycle

detoxification

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11
Q

functions of the liver (outline)

A
  • carbohydrate metabolism (glycogen storage in granules)
  • deamination of excess amino acids
  • transamination
  • detoxification
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12
Q

carbohydrate metabolism

A

when blood glucose levels rise, insulin is produced and stimulates hepatocytes to convert glucose into glycogen for storage (glucogenesis)

when blood glucose levels fall, glucagon allows glycogen –> glucose (glycogenolysis)

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13
Q

deamination and ornithine cycle

A

body can’t store a.a.s so hepatocytes have to remove amine group of excess a.as and convert a.a –> NH3 (deamination)

NH3 is toxic so enters the ornithine cycle where it is converted to urea (less toxic). Urea is excreted in the kidneys and remaining a.as are used in respiration or converted to lipids for storage

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14
Q

detoxification

A

toxic things detoxified
eg. Alcohol (ethanol)
alcohol dehydrogenase breaks down
ethanol -> ethanal -> ethanoate

eg. Hydrogen peroxide (H2O2)
hepatocytes contain catalase that breaks down H2O2 -> H2O +1/2O2

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15
Q

glycogenolysis

A

glycogen –> glucose

stimulated by glucagon

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16
Q

stages of the ornithine cycle

A

Ornithine + NH3 + CO2 –> Citrulline + H20
Citrulline + NH3 –> Arginine + H2O
Arginine + H2O –> Urea + Ornithine

total 
2NH3 in
1CO2 in
1H2O in, 2H2O out
1Urea out
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17
Q

transamination

A

conversion of one a.a to another to correct dietary imbalance

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18
Q

function of the kidney

A

excretion of urea

osmoregulation

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19
Q

ureter

A

TWO - one from each kidney. Urine passes down

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20
Q

ureter

A

TWO - one from each kidney pelvis. Urine passes down into bladder

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21
Q

urethra

A

ONE- urine passes out of body from bladder via urethra

22
Q

What are the layers of filtration blood goes through to form glomerular filtrate?

A

Capillary wall
Basement membrane
- network of collagen fibres
- rbcs and plasma proteins don’t pass through
Bowman’s capsule
- podocyte cells have finger like pedicel projections that wrap around capillaries

23
Q

ultrafiltration

A

glomerulus is supplied with blood from wide afferent arteriole and it leaves via a narrow efferent arteriole so creates a pressure in the glomerulus.

this forces blood through capillary wall and through basement membrane. (network of collagen fibres that make up 2nd sieve). Red blood cells and plasma proteins don’t pass through.

Wall of bowman’s capsule has podocyte cells that wrap around capillaries and stop platelets and plasma proteins from passing though

filtrate contains glucose, salts, urea, and water in same conc as in blood plasma

24
Q

GFR

A

glomerular filtration rate

volume of blood that is filtered through the kidneys in a given time (cm3min-1)

estimated by measuring creatinine levels in blood

low GFR indicates kidney disease (below 60 for 3 months)

GFR decreases with age and women have lower

25
what is reabsorbed at the PCT?
100% of glucose, a.as, hormones, vitamins | 85% of water and NaCl (Na+ by active transport, Cl- and water passively)
26
what does hypotonic mean when is the filtrate is hypotonic to blood
less concentrated than eg. filtrate is hypotonic to blood at start of PCT
27
adaptations of PCT
- microvilli (SA) | - mitochondria (provide ATP for AT of Na+)
28
permeability to water and ions of descending limb
PERMEABLE to water (apart from top bit) | IMPERMEABLE to ions
29
permeability to water and ionsof ascending limb
IMPERMEABLE to water | PERMEABLE to ions
30
where is most of water reabsorbed?
PCT
31
what does isotonic mean when is the filtrate is isotonic to tissue fluid and blood
same conc as eg. start of loop of henle
32
how does the loop of henle produce steep conc grads
acts as a countercurrent multiplier, using energy (active NaCl pumping) to produce conc grads that allow water to passively move out of descending limb of LOH and collecting duct
33
what happens in the descending limb of LOH
water is reabsorbed passively as it moves into the salty medulla down conc grad filtrate is very concentrated by the time it gets to bottom of LOH
34
what happens in the ascending limb of LOH
Na+, Cl-, K+ reabsorbed initially, NaCl moves out of tubules passively as filtrate is highly concentrated higher up ascending limb, NaCl is actively pumped out into medulla ascending limb is impermeable to water so it cannot move out
35
external examination of kidney
- renal capsule (layer of protective fat and connective tissue) - renal artery supplies blood and renal vein takes it away
36
what happens in collecting duct
due to countercurrent multiplication, water can diffuse out of CD passively all the way down as medulla gets increasingly salty so maintains conc grad
37
release and action of ADH
osmoreceptors in the hypothalamus are sensitive to the conc of inorganic ions in the blood and sends nerve impulses to the posterior pituitary gland if ψ is low, stimulating ADH to be released. Binds to receptors on csm of DCT and CD, triggering the formation of 2nd messenger molecule cAMP. Causes vesicles in cells to fuse w cell membrane, inserting aquaporins into csm and making it permeable to water.
38
the effects of kidney failure
- lowers GFR - measured indirectly by creatinine levels in blood - loss of electrolyte balance as body can't excrete extra Na+/K+/Cl- so there are osmotic imbalances in tissues --> eventual death also - build up of toxic urea in blood - high BP - weakened bones - pain and stiffness in joints - aneamia
39
potential treatments of kidney failure
- haemodialysis - peritoneal dialysis - transplant
40
what are three red flags of problems with kidney
protein in urine blood in urine low GFR (indicates kidney disease)
41
what is creatinine?
a breakdown product of muscles
42
process of haemodialysis
- carried out in hospital - blood leaves artery and flows between pp dialysis membrane that mimics basement membrane - dialysis fluid contains no urea, and normal plasma levels of glucose and mineral ions (so restores electrolyte balance) - blood and dialysis fluid flow in opposite directions to main a countercurrent exchange system that maximises exchage - only diffusion down conc grad (no AT)
43
process of peritoneal dialysis
- uses natural dialysis membranes in abdomen lining (peritoneum) - done at home - dialysis fluid introduced using catheter - left for a few hours then fluid is drained off and discarded
44
advantages and disadvantages of haemodialysis
+ no risk of infection - takes 8 hours and has to be repeated regularly - careful management of diet (can only eat or drink what they like at beginning and end of dialysis process) - have to be in hospital
45
advantages and disadvantages of peritoneal dialysis
+ done at home | - catheter infections
46
process of renal transplant
donor kidney is inserted into bladder and blood vessels are joined and ureter inserted.
47
advantages and disadvantages of renal transplant
+ no dialysis! + no diet control - high risk of rejection as antigens on csm of kidney differ from self - have to take immunosuppressant drugs for rest of life which increase risk of contracting infectious disease - only last for 9-10 years
48
how do pregnancy tests work?
hCG in urine binds mobile antibodies to form hCG antibody complex. in first window complex binds to immobilised monoclonal antibodies arranged in pattern that are specific to hCG/antibody complex in second window there is a line of immobilised monoclonal antibodies that bind to mobile antibodies, regardless of of they are bound to hCG or not. Line indicates test is working.
49
how can you test for anabolic steroids?
anabolic steroids mimic the action of testosterone and stimulate muscle growth they are excreted in the urine and you can use GCMS to test for it vaporise urine with solvent and pass along tube. Lining of tube absorbs gases and is analysed to give chromatogram that can be read to show presence of drugs
50
how can you test for drugs?
drugs and their metabolites are filtered through kidneys and stored in bladder so you can find drug traces in urine some time after initial use

A Biology (25 decks)

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