Biology > Excretion > Flashcards

Excretion Flashcards

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1
Q

what is excretion?

A

the removal of toxic waste products of metabolism from the body

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2
Q

what is the kidney responsible for the excretion of?

A

nitrogenous waste products

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3
Q

what is ammonia converted into?

A

urea and then excreted as urine

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4
Q

how is the kidney responsible for osmoregulation?

A

it keeps the composition of the blood/body fluids in a steady state despite fluctuations in water and solutes due to for example excess drinking, water shortage, excess sweating, excess or shortage of salts

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5
Q

see IRL flashcard for diagram of nephron

A
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6
Q

what does the distal convoluted tubule do?

A

reabsorbs water and ions; influenced by ADH

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7
Q

what is the glomerulus?

A

a knot of capillaries in the Bowman’s/renal capsule

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8
Q

what is the collecting duct?

A

area of nephron where water is reabsorbed by osmosis. affected greatly by ADH hormone

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9
Q

what does the proximal convoluted tubule do?

A

reabsorbs 80/85% of filtrate entering renal tubule by selective reabsorption

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10
Q

what is the vasa recta?

A

blood capillaries surrounding the nephron

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11
Q

what does the loop of henle do?

A

creates and maintains negative water potential in the medulla

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12
Q

what is the afferent arteriole?

A

artery taking blood into the glomerulus

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13
Q

what is the efferent arteriole?

A

artery leaving the glomerulus/taking blood to vasa recta

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14
Q

what is the branch of renal artery?

A

artery carrying blood needed for cleaning the kidneys

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15
Q

see IRL flashcard for diagram of inside the kidney

A
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16
Q

what substances are taken out of the blood by the kidney?

A
  • salt
  • water
  • urea
  • sugar
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17
Q

what is carried by the ureter?

A

urine

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18
Q

what does the nephron do?

A
  • ultrafiltration
  • selective reabsorption
  • secretion
  • urine concentration
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19
Q

what is ultrafiltration?

A

filtering under pressure of all small molecules
for example water, glucose, salts and urea are filtered into the bowman’s capsule forming the filtrate/ultrafiltrate

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20
Q

what is selective reabsorption?

A

a process that the kidney carries out in which it selectively reabsorbs substances of further use to the body, for example amino acids, glucose, vitamins, hormones, water and salts that are needed to keep the body’s fluid composition constant

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21
Q

what is the purpose of secretion?

A

some substances are not needed by the body and may be secreted into the filtrate in the tubules, for example creatine, H+, NH4+, HCO3-, K+
Also foreign substances like drugs are eliminated

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22
Q

what does ADH stand for?

A

anti-diuretic hormone

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23
Q

what does ADH determine?

A

whether a dilute or strong urine is produced

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24
Q

what are some properties of the endothelium of blood capillaries?

A
  • very thin
  • perforated with thousands of pores about 10nm in diameter (occupy 30% of capillary wall)
  • provides a barrier to cells but not plasma proteins
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25
what are some properties of the basement membrane?
- meshwork of collagen and glycoproteins fibres - water and small molecules can pass through - proteins are too large to pass through
26
what is the endothelium of the renal capsule made out of?
made of cells which are modified for filtration (podocytes)
27
where are podocytes located?
- each cell has many foot-like extensions projecting from its surface - the extensions wrap around the capillaries of the glomerulus and interlink with extensions from neighbouring cells - these extensions fit together loosely leaving filtration slits about 25nm wide
28
what RMN of molecules can pass through the filter?
less than 69000 RMN such as water, amino acids, many vitamins and drugs)
29
what cannot pass through the filter?
cells, platelets and plasma proteins
30
what does the filtrate in selective reabsorption contain?
glucose, amino acids, vitamins, water, urea, ions
31
what does the filtrate in selective reabsorption not contain?
blood cells and large proteins
32
what needs to be reabsorbed from the PCT into the blood?
mostly small molecules aside from urea (depending on balance of ions)
33
what is the role of the loop of henle?
to create and maintain a very negative water potential in the medulla by building up the concentration of NaCl in the medulla so that eventually water is removed from tubules by osmosis into the interstitial fluid of the medulla and then into the blood
34
what are some properties of the descending limb?
- lower part is impermeable to water - impermeable to sodium or chloride ions - water moves out by osmosis as interstitial fluid is highly concentrated
35
what are some properties of the ascending limb?
- permeable to NaCl due to many ion channels/carriers - impermeable to water - thin segment- NaCl diffuses into interstitial fluid - thick segment- NaCl actively transported into interstitial fluid - filtrate is now very dilute
36
see IRL flashcard for diagram of loop of henle with concentrations
37
how does the loop of henle work?
1) cells in ascending limb actively pump NaCl out of filtrate in medulla 2) water cannot follow as ascending limb is impermeable to water 3) interstitial fluid surrounding loop of henle becomes very concentrated in the medulla 4) descending limb is permeable to water and relatively impermeable to solutes so water moves out of descending limb so filtrate becomes very concerntrated 5) water removed passes to vasa recta (osmmotic gradient due to blood proteins) 6) filtrate becomes more concerntrated as it goes down the descending limb (hypertonic and hairpin bend) 7) as it proceeds up ascending limb NaCl is pumped out so filtrate becomes less concerntrated (hypotonic as it leaves loop of henle)
38
what does the distal convoluted tubule do?
balances water needs of the body
39
what does the permeability of the walls of the DCT depend on?
levels of ADH
40
what does the DCT do if the body lacks salt?
- Na+ actively pumps out of tubule and Cl- follows - water can also leave depending on ADH levels
41
what is the collecting duct for?
where concentration and volume of urine is determined
42
what happens in the collecting duct?
water moves out of the duct by osmosis (due to high concentration in medulla created by loop of henle)
43
what is permeability of collecting ducts controlled by?
ADH
44
where does most selective reabsorption take place?
in the proximal convoluted tubules
45
why do cells lining the PCT have microvilli?
to increase surface area for material absorption from the filtrate
46
why do cells lining the PCT have many mitochondria?
reabsorption involves active transport
47
what process is responsible for each of these: - ions - glucose and amino acids - water
- ions - active transport - glucose and AA - co-transported across apical membrane - water - osmosis
48
see IRL flashcard for selective reabsorption
49
how does normal level of water potential of the blood return to normal if it is too low?
1) osmoreceptors shrink and stimulates the neurosecretory cells 2) neurosecretory cells release ADH into the blood when impulse passes 3) ADH levels increases 4) collecting duct becomes more permeable 5) urine has a lower volume and higher concentration 6) returns to normal water potential
50
how is water gained in osmoregulation?
- eating - drinking - metabolism
51
how is water lost in osmoregulation?
- urinating - defecation - sweating - sweating - breathing - other bodily secretions
52
what is water potential measured by?
osmoreceptors in the hypothalamus
53
what does osmoregulation do?
affects the release of ADH by the pituitary gland
54
what does the ADH affect is osmoregulation?
the permeability of the collecting duct to water
55
what does osmoregulation affect?
the volume and concentration of urine
56
what is the hypothalamus?
area of the brain containing cells that monitor blood water potential and produce ADH
57
what are osmoreceptors?
specialised receptors cells that shrink when water potential is low, stimulating neurosecretory cells
58
what is the posterior pituitary?
back part of the pituitary gland that secretes ADH into the blood
59
what is a neurosecretory cell?
cells that release a hormone (ADH) into the blood when impulse (action potential) passes
60
what affect does ADH have in the nephron?
the permeability of the collecting ducts (walls) of the nephrons to water are controlled by anti-diuretic hormone (ADH) which is released from the pituitary gland
61
what happens when ADH is detected by cell surface receptors?
1) ADH detected 2) enzyme controlled reactions 3) vesicles containing water permeable channels 4) more water can be reabsorbed
62
what happens to the urine when ADH is released?
- ADH controls he volume of water that is reabsorbed from the filtrate in the nephrons and returned to the bloodstream - lots of ADH means lots of aquaporins in filtrate side of membrane so water is reabsorbed back into blood so not much urine is produced and what is produced is concentrated - water not reabsorbed from filtrate passes to bladder as urine to be expelled
63
What will be present in the urine if you have diabetes?
Glucose
64
What will be present in the urine if you have nephritis (kidney infection)?
Proteins an blood cells
65
What would be present in the urine if you have a bacterial infection?
Leukocytes
66
What will be present in the urine if you have muscle damage?
Creatine
67
What will be present in the urine if you are pregnant?
hCG hormone
68
What do modern pregnancy tests test for?
HCG (human chronic gonadotropin
69
What do modern pregnancy tests rely on?
Monoclonal antibodies
70
How do scientists use mice to collect antibodies?
1) a mouse is vaccinated to start the formation of antibodies 2) spleen cells that form antibodies are collected from the mouse in an operation 3) these are fused with tumour cells called myeloma cells (which are good at replicating) 4) this forms hybridoma cells 5) these are grown in the. Lab and those that produce antibodies are separated 6) antibodies are collected
71
How do pregnancy tests work?
1) monoclonal antibodies for hCG are needed, each of which is ‘tagged’ with a coloured bead (r contains. An enzyme that causes a coloured change) 2) when urine moves up the strip, these mobile monoclonal antibodies are carried along. If hCG is present it will bind to the monoclonal antibodies creating hCG/antibody complex 3) at the first line there is a band of immobilised antibodies that are specific to hCG 4) any hCG/antibody complexes are caught and held here, forming the first blue line 5) at the second line there is a band of immobilised antibodies released from the start of the strip (with or without hCG), forming the second blue line
72
Why is a control zone on the strip necessary?
To validate the test
73
Why does a pregnancy test taken before 6 days give inaccurate results?
There is not enough hCG in the urine
74
Blood tests can be taken 48 hours after fertilisation to detect a pregnancy - why do we use a urine test instead?
It is less invasive and cheaper
75
What are the functions of the liver?
1) bile synthesis- aids in fat digestion 2) storage of iron, copper and other soluble vitamins 3) metabolism of heparin, plasma proteins and cholesterol 4) metabolism of amino acids, fats and carbs 5) phagocytosis (Kupffer cells) of RBC’s 6) gluconeogenesis- glucose from glycerol and amino acids- glycogen is also stored and converted to glucose (glycogen lysis) 7) detoxification 8) deamination and the ornithine cycle
76
What does detoxification get rid of?
Poisons and toxins (alcohol and drugs)
77
What do hepatocytes contain?
Catalase
78
See IRL flash card for equation for equation for ethanol being converted into ethanoate
79
What does NAD normally break down?
Breaks down fatty acids
80
What is the issue if there is too much ethanol in the body?
- there is not enough NAD to break down fats - the fats are stored in hepatocytes- which makes fatty liver - urea is not produced, ammonia increases in blood and damages CNS -> coma and death
81
What does fatty liver and damage to hepatocytes cause?
Cirrhosis
82
How is fatty liver made?
Hepatocytes are replaced by fibrosis tissue and blood supply is lost
83
What happens in deamination and the ornithine cycle?
- formation of urea - deamination=removal of amine group from amino acid
84
See IRL flash card for diagram of amine group
85
What is the process of deamination and the ornithine cycle?
1) amine group is converted into ammonia (very soluble and toxic) 2) ammonia is converted to urea (less soluble and less toxic) 3) ornithine cycle - process that converts ammonia to urea - series of metabolic reactions - produces ornithine (amino acid) - requires ATP - occurs partly in cytosol and partly in mitochondria - cannot store excess amino acids
86
See IRL flash card for diagram of a liver lobule?
87
What is the function of a Kupfer cell?
Specialised macrophage that breaks down RBC’s
88
What is the function of sinusoids?
Channel where exchange occurs/ blood mixes
89
What is the function of the hepatic portal vein?
Contains digestive products from digestive system
90
What is the function of the hepatic artery?
Goes from aorta (oxygenated)
91
What is the function of the bile duct?
Goes to gall bladder
92
Alcohol flush reaction is a condition in which an individual develops flushes or blotches on their skin after consuming alcohol. It is a genetic condition that results in a deficiency of one of the enzymes involved in the ethanol detoxification pathway. Suggest why this genetic condition makes carriers statistically less likely to develop fatty liver disease?
- they don’t have enough hydrogens to pick up - no detoxification pathway
93
See irl flash card for diagram of the ornithine cycle
94
What is NAD?
A coenzyme that plays a crucial role in metabolism
95
what is the difference between excretion and egestion?
removal of undigested semi-solid waste from the anus
96
what are the products of excretion?
- carbon dioxide - urea
97
where is carbon dioxide produced?
waste product of cellular respiration
98
where is urea produced?
liver
99
where is co2 excreted from?
lungs
100
where is urea excreted from?
excreted by kidneys in urine
101
why must co2 be removed from the body via excretion?
- co2 is toxic to cells - reacts with h2o - to form carbonate acid which dissociates into hydrogen - carbonate + hydrogen ions (through carbonate anhydrase)
102
why does urea need to be removed from the body via excretion?
ammonia is toxic to cells - liver converts ammonia to urea which can safely be transported in the blood to the kidneys and removed as urine
103
what make up the liver?
lobes
104
what is each lobe made from?
lobules
105
what are lobules made from?
hepatocytes
106
see IRL flashcard for diagram of liver
107
what is a hepatocyte?
liver cell
108
what is a kupffer cell?
specialised macrophage that breaks down old RBC's
109
what does the hepatic artery do?
supplies the liver with oxygenated blood
110
what does the hepatic vein do?
blood leaves the liver via this
111
what does a hepatic portal vein do?
deoxygenated blood from the digestive system enters the liver via this
112
what is the bile duct?
carries bile from the liver to the gall bladder
113
what is a bile canaliculus?
channel that bile flows along to the bile duct
114
what is bilirubin?
waste product produced from the breakdown of RBC's
115
what is a sinusoid?
blood flows along this in close contact to hepatocytes
116
how does bile secretion work?
- produced by hepatocytes - secreted into narrow bile Canaliculi - carried in larger ducts into the gall bladder, where it is stored and water is reabsorbed - released into the duodenum via the bile duct
117
what are the contents of bile?
- hydrogen carbonate ions - bile pigment e.g. bilirubin and biliverdin - bile salts - cholesterol
118
what does the hepatic portal vein divide into?
sinusoids
119
what are sinusoids adapted for?
exchange of materials between blood focussing through and the hepatocytes
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