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module 5 > 5.2 excretion > Flashcards

5.2 excretion Flashcards

1
Q

Excretion

A

The removal of metabolic waste from the body

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2
Q

Metabolic Waste

A

Substance that’s produced in excess by the metabolic processes in the cells
It may become toxic

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3
Q

What products must be excreted

A

Carbon dioxide
Nitrogenous compounds
Bile

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4
Q

name and explain the role of the excretory organs

A

Lungs - carbon dioxide produced by respiration diffuses into the alveoli to be excreted
Liver - converts excess amino acids to urea , substances produced are passed into the bile to be excreted
Kidneys - kidneys remove urea from the blood to be excreted by the urethra
Skin - sweat contains range of substances (urea, uric acid, ammonia)

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5
Q

Importance of excretion

A

products of metabolism if they are left to build up can become harmful
(CO2 and ammonia are toxic)
Interfere with cell processes by altering the pH - so metabolism is prevented
Other metabolic products - act as inhibitors reduce enzyme activity

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6
Q

Importance of removing CO2

A

CO2 is transported as hydrogencarbonate ions which dissociates into H+ (and HCO3-)
H+ = affect pH = interferes with bonds in the haemoglobin = changes tertiary structure = reduces affinity for oxygen
H+ can also bind to Hb = haemoglobinic acid
CO2 can bind to Hb = carbaminohaemoglobin acid
both reduces oxygen transport

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7
Q

Importance of removing nitrogenous compounds

A

Body can’t store excess amino acids
Transported to the liver and the potentially toxic amino acid group is removed (deamination )
Initially forms ammonia and keto acid (toxic)
Converted to less soluble and toxic urea - taken to kidneys to be excreted
Keto acid can be used in respiration or converted to fat/ carbohydrate

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8
Q

name the components of the liver

A

hepatic artery
hepatic portal vein
hepatic vein
hepatocyte cells
lobules
kupffer cells
sinusoid
bile canaliculas
bile duct

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9
Q

desribe the role of the hepatic artery and the hepatic portal vein

A

h. artery = oxygenated blood from the heart travels from the aorta via the hepatic artery into the liver - liver cells are very active so lots of oxygen used in respiration
h.p. vein = deoxygenated blood from the digestive system that contains lots of nutrients, may also contain toxic compounds which can be removed by liver

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10
Q

describe the role of the hepatic vein

A

blood is removed from the liver by the hepatic vein, it rejoins the vena cava and the blood returns the body to bodys normal circulation

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11
Q

describe the role of the bile duct and the bile canaliculus

A

bile is made in the liver, released into the bile canaliculus, this joins to the bile duct where it transports thebile to the ball bladder

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12
Q

what are liver cells called

A

hepatocytes

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13
Q

what is the liver made up of/ split into

A

hepatocytes
liver is spilt into lobes which is further split into hexagonal lobules

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14
Q

what are inter lobular vessels

A

the hepatic artery and hepatic portal vein splits into smaller vessels - which run between and parallel to the lobules

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15
Q

what is a sinosoid and the role

A

wide capillary that blood passes through large hepatocyte lined spaces
the blood from the h.a and h.p.v mixes and passes along - as blood passes through the oxygen and nutrients can be removed by the hepatocyte cells

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16
Q

what is a kupffer cell

A

macrophage that moves about within the sinusoid and breaksdown and recyles rbc

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17
Q

Main functions of the liver

A

Storage of glycogen
Detoxification
Deamination/ formation of urea

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18
Q

Other functions of the liver

A

Controls blood glucose levels/ amino acid levels / lipid levels
Synthesis of bile/ plasma proteins/ cholesterol
Synthesis of red blood cells in the foetus
Breakdown of hormones
Destruction of red blood cells

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19
Q

Explain the role of liver in storing glycogen

A

storage of glycogen makes up about 8% of the weight
Glycogen forms granules in the cytoplasm of the hepatocytes
Can be broken down into blood

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20
Q

Explain what detoxification is and how it works

A

Detoxification of substances that may cause harm
Toxins broken down by oxidation, reduction, methylation or combination with other molecules
Enzymes
- catalase breaks down hydrogen peroxide
- cytochrome P450 breaks down drugs

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21
Q

Detoxification of alcohol

A

Broken down in hepatocytes by enzymes
Ethanol - ethanol dehydrogenase -> forms ethanal + H+
NAD takes H away
Ethanol - ethanal dehydrogenase -> ethanoic acid + H+
NAD takes H away
bonds with coenzyme A = acetyl coenzyme A used in respiration

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22
Q

Explain how urea is formed

A

Excess amino acids need to be converted and excreted
1. Deamination - amine group is removed from the amino acid, produces ammonia (rest of amino acid is a keto group - used in respiration)
2. The ornithine cycle - ammonia broken down to urea

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23
Q

Explain what happens in the orinthine cycle

A

Ammonia + CO2 = citrulline + H20
Citrulline + ammonia = arginine + H20
Arginine + H20 = urea + ornithine (recycled and used again)

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24
Q

overall word equation of ornithine cycle

A

ammonia + CO2 -> urea + H20

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25
Q

name the structures of the kidney

A

capsule
cortex
medulla
pelvis
ureter
renal artery
renal vein
nephrons

26
Q

what are nephrons

A

functional unit of the kidney and is tiny tubules

27
Q

name the features of a nephron (in order)

A

bowmans capsule
glomerulus
proximal convoluted tubule
loop of henle
-descending limb
-ascending limb
distal convoluted tubule
collecting duct
pelvis

28
Q

what is the bowmans capsules and glomerulus

A

surround the glomerulus and fluid is pushed into this by ultrafiltration
a knot of capillaries formed from the renal artery

29
Q

define ultrafiltration

A

filtration of the blood under pressure and fluid gets pushed and filtered into the bowmans capsule

30
Q

name the 3 layers of ultrafiltration

A

the endothelium of the capillary
the basement membrane
the epithelial cells of the bowmans capsule

31
Q

desribe the role of the endothelium of the capillary

A

narrow gaps between cells of the endothelium of the capillary walls
gaps/pores
allow blood plasma and dissolved substances to pass out of the capillary

32
Q

describe the role of the basement membrane

A

fine mesh of collagen fibres and glycoproteins
acts as a filter to prevent the passage of molecules with mass greater then 69000 or large molecules
proteins get held in the capillaries

33
Q

describe the role of the epithelial cells of the bowmans capsule

A

cells called podocytes that have specialised shape - finger like projections
creates gaps between cells so fluid from the blood in the glomerulus can pass between the cells

34
Q

what is filtered out of the blood

A

water
amino acids
glucose
urea
ions

35
Q

what is left in the capillary during ultrafiltration

A

blood cells and proteins

36
Q

define selective reabsorbtion

A

reabsorbing molecules using active transport and cotransport

37
Q

function of a nephron

A

to reabsorb about 85% of fluid in selective reabsorption
leaves product of urine which has low water potential and a high concentration of solutes

38
Q

what part of the nephron is used for selective reabsorption

A

proximal convoluted tubule

39
Q

specialised features of the PCT cells for selective reabsorption

A

cell surface membrane is highly folded = microvilli = increases surface area for reabsorption
contains cotransporter proteins that transport glucose or amino acids from the tubule into the cell
Na K pumps in membrane
many mitochondria = produce lots of ATP

40
Q

mechanism of reabsorption

A
  1. Na ions are actively pumped out of the cells lining tubule into the blood
  2. concentration of Na decreases inside
  3. creates conc. gradient and Na ions diffuse back into cell by a cotransport protein bringing glucose or an amino acid
  4. causes water to move in by osmosis
  5. glucose and amino acids diffuse into the blood
41
Q

role of the loop of henle

A

reabsorption of water
decreases water potential in the tissue fluid of the medulla (make more salty)
descending limb is permeable to water
ascending limb is not permeable to water and uses active transport to remove ions from filtrate
water potential surrounding collecting duct is lower so water removed from collecting duct

42
Q

name the components of the loop of henle

A

proximal convoluted tubule
descending limb
ascending limb
distal convoluted tubule
collecting duct

43
Q

how are water and ions reabsorbed in the loop of henle

A

filtrate passes from PCT to the descending limb of loop of henle
water moves out of the d.l by osmosis into the tissue fluid/medulla
at the bottom of the limb = high concentration of urea + ions as water has left
enters ascending limb = impermeable to water left in, permeable to ions
ions move out by facilitated diffusion and active transport as cotransport proteins become saturated/ conc will even out but ions still need to be removed
urea is left in the filtrate
filtrate enters collecting duct
water moves out of collecting duct
urine passes down c.d to the pelvis

44
Q

what happens to the water potential as you travel down the loop of henle

A

decreases more as you go deeper (down collecting duct and descending limb)

45
Q

explain the concentration changes in the tubule fluid

A

glucose decreases in conc. as its selectively reabsorbed from the PCT
Na+ actively transported out of the ascending limb = conc falls
urea conc increases as water moves out adn urea actively moved in
conc of Na+ increases as water removed in collecting duct

46
Q

define osmoregulation

A

the control of water potential in the body and salt levels

47
Q

when does osmoregulation happen

A

kidneys alter the volume of urine produced
walls of collectind duct can be made more or less permeable
conserve less water - walls of CD become less permeable = less water is reabsorbed = more urine produced
conserve more water - walls of CD become more permeable = more water is reabsorbed = smaller volume of urine

48
Q

how does ADH alter the permeabilitly of the collecting duct

A

ADH level increases in the blood = detected by receptors in DCT and CD = causes aquaporins to be inserted/ water permeable channels = allows more water to be reabsorbed
ADH level decreases in the blood = cell surface membrane folds inwards = creates new vesicles that remove water permeable channels from membrane = more water passes down CD = more urine which is more dilute

49
Q

ADH

A

antidiuretic hormone that controls the permeability of the CD

50
Q

how is the concentration of ADH adjusted in the blood

A

osmoreceptors in the hypothalamus - detect water potential in the blood
stimulates neurosecretory cells in the hypothalamus - release ADH store it in the postierior pituitary where it then gets secreted into the blood

51
Q

negative feedback to control water potential

A

increase in water potential
detected by osmoreceptors in the hypothalamus
less ADH released from posterior pituitary
CD walls less permeable
less water reabsorbed into blood / more urine produced
decrease in water potential
detected by osmoreceptors in the hypothalamus
more ADH released from posterioir pituitary
CD walls are more permeable
more water reabsorbed into blood/ less urine produced

52
Q

what will kidney failure cause

A

death as watse products accumlate (urea)

53
Q

how can kidney failure be assessed

A

glomerular filtration rate - the rate at which fluid enters the nephron
analysing the urine for substances eg. proteins

54
Q

causes of kidney failure

A

diabetes
heart disease
hypertension
infection

55
Q

name the treatments for kidney failure

A

dialysis
- haemodialysis
- peritoneal dialysis
transplant

56
Q

describe how dialysis works

A

wate products and excess fluids are removed by passing it over a partially permeable membrane
dialysis fluid contains the correct amount of substances
countercurrent flow allows the substances to move down the concentration gradients

57
Q

describe the difference between haemogdialysis and peritonal dialysis

A

haemogdialysis - blood from an artery and passed into a machine, contaons dialysis fluid, heparin added to prevent blood clotting, air bubbles removed before returned to the blood, performed 2-3 times a week - has countercurrent flow
peritoneal - dialysis membrane is the bodys abdominal perionel membrane, tube implanted into abdomen, dialysis fluid fills membrane that surrounds the organs, solution drained after several hours - no countercurrent flow

58
Q

adavnatges of kidney transplant

A

freedom from time consuming dialysis
feel physically fitter
improved quality of life
improved self image
no longer chronically ill

59
Q

disadvantages of kidney transplant

A

need to take immunosuppressants
need for surgery/ general anaesthetic
need for regualr checks for signs of rejection
side effects of immunosuppressants

60
Q

how does a pregnancy test work

A

Hormone (HCG) binds to free monoclonal antibodies
complementary shape
forms antigen antibody complex
this attaches to immobilised monoclonal antibody
so coloured pattern form a line
test zone and control zone

61
Q

testing for anabolic steroids

A

anabolic steriods increase protein synthesis
gas chromotography can be used
sample vapourised and passed down tube with absorbant lining
substances dissolve differently in the gas and have a different retention time
creates chromatogram
compared to normal chromatograms

module 5 (7 decks)

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