Biology > Excretion > Flashcards

Excretion Flashcards

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1
Q

excretion

A

the removal of metabolic waste products from the body

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2
Q

metabolic waste

A

unwanted or toxic by products from cellular reactions

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3
Q

egestion

A

removal of undigested food via defecation

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4
Q

examples of metabolic waste (4)

A
  • water
  • CO2
  • nitrogen from excess amino acids (produces urea)
  • bile pigments (broken down Hb)
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5
Q

organs involved in excretion (4)

A
  • lungs
  • skin
  • kidneys
  • liver
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6
Q

how are amino acids converted to urea?

A
  • excess amino acids transported to liver
  • deamination occurs (amine group removed)
  • amino acid + O2 –> keto acid + ammonia
  • keto acid either used in respiration or stored as carbs or fat
  • ammonia converted to urea via ornithine cycle:
  • ammonia + CO2 –> urea + water
  • 2NH3 + CO2 –> CO(NH2)2 + H2O
  • urea transported to kidneys (dissolved in plasma)
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7
Q

why is ammonia converted to urea? (2)

A
  • urea is less toxic
  • urea is less soluble
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8
Q

two functions of the kidneys

A
  • excretion (urea, excess water, salts, creatine)
  • homeostasis (osmoregulation, [salt] and pH control)
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9
Q

structure of the kidney (from inside out)

A
  • renal pelvis (connected to ureter)
  • calyx
  • renal pyramids
  • medulla
  • cortex
  • capsule
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10
Q

structure of a nephron (and what happens at each structure)

A
  • glomerulus
  • Bowman’s capsule (ultrafiltration)
  • proximal convoluted tubule (selective reabsorption)
  • loop of Henle (osmoregulation)
  • distal convoluted tubule (homeostatic control of water, [salt], pH)
  • collecting duct (concentration and transport of urine)
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11
Q

which parts of the nephron are in the cortex and medulla?

A
  • loop of Henle and collecting duct go into the medulla
  • all other structures stay in the cortex
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12
Q

what is the name of the capillary network that goes around the loop of Henle?

A

vasa recta

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13
Q

what blood vessels are attached to the kidney?

A
  • renal vein
  • renal artery
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14
Q

glomerular filtration rate

A

the volume of blood that is filtered through the kidneys at a given time

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15
Q

what are basement membranes made out of?

A

network of collagen fibres and other proteins

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16
Q

what does the glomerular filtrate travel through?

A
  • epithelial cells
  • basement membrane
  • podocytes
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17
Q

what are the extensions on podocytes called?

A

pedicels

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18
Q

role of podocytes

A

filter out any blood cells or large proteins that made it through the capillary epithelial cells

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19
Q

what two blood vessels are linked to the glomerulus? (and their difference)

A
  • afferent arteriole (thicker)
  • efferent arteriole (thinner)
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20
Q

what is and isn’t present in glomerular filtrate?

A

absent:
- blood cells
- large plasma proteins (e.g. albumin)

present:
- water
- ions
- urea
- glucose

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21
Q

what cells make the capillary and glomerulus walls?

A

squamous epithelial cells

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22
Q

what cells make up the PCT and what are their features?

A

epithelial cells:
- many mitochondria (produce ATP for active pumps)
- microvilli (increase SA)

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23
Q

what molecules are reabsorbed in the PCT?

A
  • glucose
  • amino acids
  • vitamins
  • hormones
  • most mineral ions
  • small proteins
  • urea
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24
Q

how are small proteins reabsorbed into the blood from the PCT?

A

pinocytosis

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25
how are amino acids reabsorbed by the blood from the PCT?
diffusion
26
how and how much urea reabsorbed into the blood from the PCT?
- diffusion (passive) - half remains in PCT, half reabsorbed by blood
27
how is a steep diffusion gradient maintained in the nephrons?
constant blood flow through the network of capillaries surrounding the nephrons
28
what transport proteins are present in the plasma membranes of the epithelial cells lining the PCT (involved in reabsorption)?
- Na+/glucose cotransporter - Na+/K+ pump - glucose transporter
29
how do the PCT epithelial cells reabsorb molecules? (what else does this happen with)
- Na+/K+ pump pumps Na+ out of epithelial cells into filtrate (in tubule) - Na+ cotransported back into the epithelial cell with a molecule of glucose via the Na+/glucose cotransporter - high [glucose] inside epithelial cell - glucose (facilitated) diffuses out of the epithelial cell into the bloodstream via a glucose transporter (this also happens with amino acids)
30
two parts of the Loop of Henlé
- descending limb - ascending limb
31
hypertonic
higher solute concentration than the surroundings (e.g. the cell is hypertonic to the tissue fluid)
32
isotonic
solute concentrations are equal
33
hypotonic
lower solute concentration than the surroundings (e.g. the cell is hypotonic to the tissue fluid)
34
what system occurs in the Loop of Henlé
countercurrent multiplier system
35
why is it called the countercurrent multiplier system?
- counter current because the urine flows through the Loop of Henlé in the opposite direction to the blood of flowing through the capillaries - multiplier because the concentration of solutes in the tubules increases across the Loop of Henlé
36
sequence of events in the Loop of Henlé
- Na+ and Cl- are actively transported out of the impermeable section of the ascending limb - this makes the medulla really salty so (the medulla is hypertonic to the Loop of Henlé with respect to Na+ and Cl-) - this creates a concentration gradient - filtrate entering the descending limb is isotonic - in the descending limb, Na+ and Cl- diffuse passively out of the Loop of Henlé into the medulla and water diffuses down a concentration gradient out of the Loop of Henlé into the medulla via osmosis - this makes the water less salty but the bottom of the Loop of Henlé is hypertonic to the medulla with respect to Na+ and Cl- - at the bottom of the Loop of Henlé and start of ascending limb, Na+ and Cl- diffuse into the medulla - the filtrate from the descending limb reaches the ascending limb and Na+ and Cl- are actively pumped out - the cycle repeats
37
which parts of the Loop of Henlé are permeable and impermeable?
impermeable: - top (small proportion) of descending limb - top (large proportion) of ascending limb permeable: - bottom (large proportion) of descending limb - bottom (small proportion) of ascending limb
38
use hypertonic, isotonic and hypotonic to describe each part of the Loop of Henlé with respect to ions (Na+ and Cl-)
- top of the descending limb - isotonic - bottom of Loop of Henlé - hypertonic - top of ascending limb - hypotonic (to medulla)
39
where is the filtrate most concentrated in the Loop of Henlé?
base of the Loop ( because water has diffused out into salty medulla)
40
features of cells lining DCT
- many mitochondria - microvilli
41
roles of the DCT
- regulate blood pH by pumping H+ ions - regulate blood K+ and salt (Na+ and Cl-) concentrations - dispose of ethanol, toxins and drugs processed in the liver
42
how is active transport in the DCT regulated?
- hormones (e.g. ADH affects permeability of DCT membranes)
43
what affects the permeability of the collecting duct?
ADH
44
how does the collecting duct concentrate urine?
- salt concentration increases from the cortex to the medulla down the renal pelvis - water diffusers down a concentration gradient out of the collecting duct into the tissue fluid via osmosis - the urine and the collecting duct is now hypertonic to the tissue fluid
45
hepatic artery
carries oxygenated blood from heart to the liver
46
hepatic vein
carries deoxygenated blood away from the liver to the vena cava
47
hepatic portal vein
carries deoxygenated blood and nutrients from digestion from small intestine to the liver
48
major blood vessels attached to the liver
- hepatic artery - hepatic vein - hepatic portal vein
49
what are liver cells called?
hepatocytes
50
features of hepatocytes
- large nuclei - prominent Golgi apparatus - many mitochondria (hepatocytes are metabolically active)
51
role of the sinusoids
mixes blood from the hepatic artery and the hepatic portal vein to increase oxygen content and supply the hepatocytes with enough oxygen
52
what cells are found in sinusoids?
Kupffer cells
53
role of Kupffer cells
act like macrophages ingesting foreign bodies and pathogens
54
role of the hepatocytes
secrete bile from the breakdown of blood
55
transport of bile
- secreted by hepatocytes - drained into spaces called canaliculi - drains into the bile ductiles - transported to gall bladder
56
types of cells and structures in liver
- hepatocytes - Kupffer cells - sinusoids - canaliculi - bile ductiles
57
functions of the liver
- carbohydrate metabolism/regulation of blood glucose concentration - deamination of excess amino acids - detoxification
58
where about in the lobule (hexagonal shape made out of triangles) would you find the major blood vessels in the liver?
- hepatic vein in the centre - hepatic portal vein and hepatic artery on the outside
59
compare continuous (normal) capillaries and sinusoidal capillaries
similarities: - both have a basement membrane - both have one layer of thin cells differences: - continuous capillaries have a continuous basement membrane whereas sinusoidal capillaries have a discontinuous basement membrane - therefore sinusoid or capillarios also have more pores between endothelial cells therefore have more porous walls
60
how is the liver involved in carbohydrate metabolism
- hepatocytes stimulated by insulin to carry out glycogenesis - hepatocytes stimulated by glucagon to carry out glycogenolysis and gluconeogenesis
61
which part of the liver carries out deamination and how does it do it?
hepatocytes remove amine group to form ammonia (which then undergoes the ornithine cycle)
62
why is deamination important?
proteins in amino acids cannot be stored
63
what happens to excess amino acids that don't undergo deamination and excreted?
- used in respiration - converted to lipids
64
where are most plasma proteins synthesised?
hepatocytes
65
transamination
conversion of one amino acid into another
66
why is transamination important?
diet doesn't always contain the correct balance of amino acids so transamination can make them
67
examples of substances that may be detoxified by the liver
- alcohol - drugs - hydrogen peroxide
68
what enzyme do hepatocytes contain?
catalase (to break down H2O2)
69
what enzymes breaks down alcohol and where is it found?
ethanol and ethanal (alcohol) dehydrogenase in hepatocytes
70
how is alcohol detoxified?
- ethanol is broken down into ethanal by ethanol dehydrogenase - ethanal is converted to ethanoate by ethanal dehydrogenase - ethanoate maybe used to build up fatty acids or used in cellular respiration
71
function of bile
digestion of fats
72
where is ADH produced?
neurosecretory cells in hypothalamus
73
where is ADH stored and secreted from?
posterior pituitary gland
74
mechanism of ADH action
- ADH binds to specific complementary receptors on microvilli of cells of the collecting duct - activates G protein (by causing a confirmational change) which switches on adenylate cyclase - adenylate cyclase triggers conversion of ATP to cAMP - cAMP acts a secondary messenger causing a cascade of events
75
what type of hormone is ADH?
non-steroid hormone
76
what does ADH do?
increase permeability of DCT and collecting duct to water
77
mechanism of cAMP in cells of DCT and collecting duct (activated by ADH)
- cAMP switches on PKA - PKA stimulates aquaporin vesicles to fuse with plasma membrane - increases rate of osmosis of water pit of DCT and collecting duct
78
what detects blood Ψ and where are they found?
osmoreceptors in hypothalamus
79
how is ADH transported from the hypothalamus to the posterior pituitary gland?
- neurosecretory cells in hypothalamus secrete ADH - ADH travels along axons of neurosecretory cells to the posterior pituitary
80
how do the osmoreceptors detect Ψ?
sensitive to [inorganic ion] in blood
81
two effects of high blood pressure on urine
- protein in urine - blood in urine
82
why might you see protein or blood in urine of patients with high blood pressure?
- damaged basement membranes - damaged podocytes (due to high blood pressure)
83
six effects of kidney failure
- loss of electrolyte balance - build up of urea - high blood pressure - weakened bones - pain and stiff joints - anaemia
84
why is electrolyte loss an effect of kidney failure? (and what is the risk of this?)
- body cannot excrete Na+, Cl-, K+ - causes osmotic imbalances in tissues (leading to death if left untreated)
85
why is high blood pressure an effect of kidney failure? (and what is a risk of this?)
- osmotic imbalances - increased water in blood - can lead to cardiovascular problems and stroke
86
why are weakened bones an effect of kidney failure?
- calcium/phosphorus balance in blood is lost
87
why is pain and joint stiffness an effect of kidney failure?
- abnormal proteins build up in blood
88
why is anaemia an effect of kidney failure?
- kidneys involved in production of erythropoietin hormone which stimulates formation of erythrocytes - reduce production of erythrocytes causing tiredness and lethargy
89
what can be measured to indicate kidney disease?
glomerular filtration rate
90
how can glomerular filtration rate be measured?
- blood test measures the level of creatinine in the blood - creatinine is a breakdown product of mussels and is used to give an estimated GFR (eGFR)
91
units of GFR
cm³min-¹
92
what happens to the levels of creatinine when the kidneys are not functioning properly?
[creatinine] in blood increases
93
what factors must be taken into account when working out GFR?
- age (GFR decrease with age) - sex (men have more muscle mass so more creatinine than women)
94
what do the partially permeable membranes in dialysis mimic?
basement membrane of the Bowman's capsule
95
how is a concentration gradient maintained during haemodialysis?
countercurrent flow of blood and dialysis fluid
96
two types of dialysis
- haemodialysis - peritoneal dialysis
97
what must be done alongside dialysis as part of treatment?
- maintain a strict diet - relatively little protein and salt - monitor fluid intake (can only eat/drink whatever they want before dialysis)
98
five parts/features of haemodialysis
- countercurrent exchange system - partially permeable membrane - dialysis fluid - bubble trap (prevent air bubbles) - blood thinners
99
why must haemodialysis fluid be sterile and maintained at 37°C?
- avoid denaturing proteins in blood - maintain internal body temperature - prevent transmission of microorganisms to prevent infections
100
how must fluid intake be managed with kidney failure?
- constant small drinks to avoid fluctuations in blood Ψ (poor osmoregulation)
101
why must little protein be consumed by patients with kidney failure?
- protein broken down into urea - urea is toxic if not removed by kidneys
102
how often is haemodialysis done?
- 8 hours - x3 per week
103
how is risk of rejection lowered with transplants?
- immunosuppressants - matching blood groups/tissue types
104
limitation of kidney transplants
the AVERAGE transplanted kidney last about 9-10 years until the patient has to return to dialysis and wait for another transplant
105
how can muscle damage be detected with urine samples?
muscle damage causes large amounts of creatinine in urine
106
how are monoclonal antibodies produced (for pregnancy tests)?
- mice injected with hCG - B-cells that produce specific antibodies are removed from spleen - B-cell fused with myeloma - fused cell known as a hybridoma - hybridomas produce antibodies which are collected and purified
107
what are myelomas and why are they used?
- type of cancer cell - divides rapidly - increase rate of monoclonal antibody production
108
what does a pregnancy test contain?
- nitrocellulose membrane - mobile monoclonal antibodies (small coloured beads attached) - immobilised monoclonal antibodies (control and test line)
109
how does a pregnancy test detect hCG?
- urine sample placed on wick - hCG binds to mobile monoclonal antibodies forming a hCG/antibody complex - urine diffuses through stick - hCG/antibody complexes bind to immobilised antibodies on test line - excess mobile antibodies continue to diffuse to the end of the stick and bind to immobilised antibodies which are complementary to the mobile monoclonal antibodies (control line)
110
how is urine tested for anabolic steroids?
- monoclonal antibodies - gas chromatography (vapourised urine) - mass spectrometry
111
what do tests look for in urine samples (for drugs and steroids etc)?
metabolites (broken down products of drugs etc)
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