Excretion Flashcards
(159 cards)
1
Q
Excretion
A
The removal of metabolic waste from the body
2
Q
What products must be excreted
A
-Carbon Dioxide from respiration
-Nitrogen-containing compounds such as urea (nitrogenous waste)
-Other compounds, such as bile pigments found in the faeces
3
Q
Why must products be excreted
A
So they do not build up and inhibit enzyme activity and become toxic
4
Q
Difference between excretion and egestion
A
Egestion - the elimination of faeces from the body. Faeces are the undigested remains of food and not metabolic products
5
Q
What are the main organs involved in excretion
A
-Lungs
-Liver
-Kidney
-Ureter
-Bladder
-Urethra
- (Skin)
6
Q
The skins involvement in excretion (also homeostasis)
A
Sweat contains a range of substances including salts, urea, water, uric acid, and ammonia
-Loss of water and salts important in homeostasis - maintains body temperature and water potential of the blood
7
Q
What happens if CO2 and ammonia build up
A
Toxic
-Interfere with cell processes by altering the pH so normal metabolism is prevented
8
Q
Formation of Hydrogen-carbonate ions for CO2 transport
A
1) CO2+H20= Carbonic acid (catalysed by carbonic anhydrase)
2) Carbonic acid - hydrogen and hydrogen carbonate ions
3) Hydrogen-carbonate ions then diffuse out and chloride ions diffuse in (Chloride shift)
9
Q
How do the hydrogen ions affect the RBC
A
Affects pH of cytoplasm
-Hydrogen ions affect bonds within haemoglobin changing its shape (buffer)
-Reduces affinity for O2
10
Q
What happens to the haemoglobin once its affinity for O2 has been reduced
A
Hydrogen ions bind forming haemoglobinic acid
11
Q
What happens to the CO2 that is not converted to hydrogencarbonate ions
A
Combine directly with haemoglobin forming carbaminohaemoglobin
12
Q
What are both carbaminohaemoglobin and haemoglobinic acid unable to do
A
Bind with oxygen
-Reduces oxygen transport further
13
Q
Why must the pH of the blood plasma be maintained
A
Could alter the structure of many proteins in the blood that help to transport a wide range of substances around the body
-proteins in blood acts as buffer (haemoglobin)
14
Q
What happens if the change in blood pH is small
A
Extra hydrogen ions are detected by the respiratory center in the medulla oblongata in the brain
-Causes an increase in breathing rate to help remove excess Co2
15
Q
What would happen if pH drops below 7.35
A
Cause headaches, restlessness, drowsiness, tremor and confusion
-Rapid heart rate and change in blood pressure
16
Q
What is the condition called when your blood pH drops below 7.35
A
Respiratory acidosis
17
Q
What is respiratory acidosis caused by
A
Diseases or conditions that affect the lungs themselves i.e. emphysema, chronic Bronchitis, asthma, severe pneumonia
18
Q
What can acute respiratory acidosis be caused by
A
Blocking of airways due to swelling/ foreign object/ vomit
19
Q
Why would it be wasteful to excrete amino acids
A
Contain as much energy as carbohydrates
-Wasteful to simply excrete
20
Q
What happens to amino acids
A
Transported to the liver where the toxic amino group is removed (deamination)
The amino group forms Ammonia (highly toxic and soluble) converted to Urea ( less toxic and insoluble)
21
Q
Why is it important that urea is insoluble
A
So it doesn’t disrupt the WP of the cell
22
Q
Where does urea go to after it has been made
A
The kidney for excretion
23
Q
What happens to the remaining keto acid from ammonia
A
-used directly in respiration to release its energy
-Converted to a carbohydrate or a fat for storage
24
Q
Deamination equation
A
Amino acid + O2 = Keto acid + Ammonia
25
Formation of urea equation
Ammonia + CO2 = Urea + water
26
Why are people who take statins advised not to drink grapefruit juice
Some components of grapefruit juice bind to enzymes that break down statins in the liver
-Inhibits enzymes and leads to increased concentrations of statins in the body
27
What does the internal structure of the liver ensure
That as much blood as possible flows past the hepatocytes
-Enables to remove excess waste/ unwanted substances
28
What are the two sources that supply the liver
The hepatic artery
The hepatic portal vein
29
The hepatic artery
Oxygenated blood travels from aorta to the hepatic artery into the liver
-Supplies O2 for aerobic respiration
-Liver cells active as carry out many metabolic processes = need ATP
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The hepatic portal vein
Deoxygenated blood from the digestive system enters the liver through the hepatic portal vein
-Rich in products of digestion so uncontrolled concentrations
-May contain toxic compounds that have been absorbed into the blood at S. Intestine
-Concentrations need to be adjusted before circulate the body
31
What vein does blood leave the liver
The hepatic vein
-Re-joins the Vena cava and blood returns to the bodys normal circulation
32
Bile duct
A fourth vessel connected to the liver
Bile secretion from liver with functions in digestion and excretion
-Carries bile from the liver to gall bladder until needed to aid the digestion of fats in the S.Intestine
33
What does bile also contain that is used in egestion
Bile pigments - Bilirubin
34
What is the liver divided into
Lobes which are further divided into lobules - cylindrical
35
What do the hepatic portal vein / hepatic artery as they enter the liver
Split into interlobular vessels
- Vessels run parallel and between the lobules
36
What happens at intervals to the hepatic portal vein / hepatic artery in the liver
Enter the lobules
-Blood is mixed and passes through a special chamber called a sinusoid
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Sinusoid importance
Lined with hepatocytes
-As blood passes through it is within close contact
-Cells can remove/ return substances to blood at correct concentrations
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What moves about in the sinusoids
Specialised macrophages called Kupffer cells
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Kupffer cell functions
Breakdown and recycle old RBC
-One of the products of haemoglobin breakdown is bilirubin
40
Bilirubin
Product of haemoglobin breakdown
Bile pigment excreted as part of the bile - leaves body in egestion
41
Where is bile made and released
Made in the liver cells and released into bile canaliculi
-Bile canaliculi join together to form the bile duct
42
What happens when blood reaches the end of the sinusoid
The concentrations of many of its components have been modified and regulated
-At the center of each lobule is the intra-lobular vessel which all the sinusoids empty into
-Intralobular vessels join together to form the hepatic vein
43
Liver cell specialisations
Has a dense cytoplasm with specialised in the number of organelles to carry out many metabolic functions:
-protein synthesis
- transformation and storage of carbohydrates
- Synthesis of cholesterol and bile salts
- Detoxification
44
Functions of the liver
-Control of blood glucose levels, amino acid levels, lipid levels
-Synthesis of bile, plasma proteins, cholesterol
-Synthesis of RBC in the foetus
-Storage of vitamins A/B/B12/iron/glycogen
-Detoxification of alcohol, drugs
-breakdown of hormones
-Destruction of RBC
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Storage of glycogen
Stores sugars in the form of glycogen makes up 8% of the fresh weight of the liver
-Glycogen forms granules in cytoplasm of hepatocytes
-Broken down t release glucose as required
46
Where do toxic substances in the blood come from
Produced in the body - hydrogen peroxide
Consumed in our diet - alcohol
47
How can toxins be rendered harmless
Oxidation/ reduction/ methylation/ combination with another molecule/ enzymes
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Enzyme e.g. in liver that breaks down toxins
Catalase
Cytochrome p450
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Catalase
Hydrogen peroxide = water+ oxygen
-high turn over rate
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Cytochrome p450
Group of enzymes that break down drugs - cocaine + various medicinal drugs
- Important also in electron transport in respiration
-Role in metabolizing drugs can interfere with other metabolic roles and may cause unwanted side effects
51
Why do some people have side effects from p450 enzymes when they take drugs whereas others do not
p450 show lots of variation between individuals
-As they break down medicinal drugs different types of products are made
52
Alcohol/ ethanol
Drug that depresses nerve activity
-Contains chemical potential energy used in respiration
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Alcohol breakdown
1) Ethanol - ethanal (ethanol dehydrogenase)
2) Ethanal - ethanoate/ acetate (ethanal dehydrogenase)
3) Acetate + CoA = Acetyl coenzyme A
4) Enters aerobic respiration
5) NAD becomes reduced twice
54
What is the problem with NAD being reduced in alcohol breakdown
-Also required to oxidize/ breakdown fatty acids in respiration
-If the liver has to detoxify to much uses up stored NAD and has insufficient left to deal with the fatty acids
-Fatty acids - lipids and stored as fat in liver causing it to become enlarged
55
What is an enlarged liver called
Fatty liver - leads to alcohol-related hepatitis / cirrhosis
56
Treatment of amino acids consist of two processes
-Deamination
-Ornithine cycle
57
Deamination
Removes amino group to produce ammonia and organic compound - Keto acid
- Keto group - directly enters respiration to release energy
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The ornithine cycle
1) Ammonia + CO2 combine with the amino acid ornithine = citrulline + H20
2) Citrulline + ammonia = arginine + H20
3) Arginine reconverted to ornithine by the removal of urea and water
59
Where are the kidneys positioned
On each side of the spine below the lowest rib
60
Role of kidney
Remove waste products from the blood and produce urine
61
Different parts of a Kidney structure
-Nephron tubule
-Capsule
-Cortex
-Medulla
-Renal vein
-Renal artery
-Pelvis
-Ureter
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Nephron
The functional unit of the kidney
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Journey of the Nephron
Starts in the cortex at the Bowman's capsule and then forms a loop down in the medulla and back to the cortex before joining a collecting duct that passes back down into the medulla
64
Cortex structure
Mass of nephron tubules and glomeruli
65
What are the two types of tubules
Proximal convoluted tubule (microvilli)
Distal convoluted tubule
66
What arteriole does blood enter/leave the arteriole from the renal artery
The afferent arteriole - arrive
The efferent arteriole - exit
67
Difference between afferent and efferent arteriole
The afferent is wider than the efferent
-The difference in diameter means that blood in the capillaries of the glomerulus maintain a higher hydrostatic pressure then the pressure in the Bowman's capsule
-Pressure difference pushes fluid from the blood into the Bowman's capsule that surrounds the glomerulus
68
How do the afferent/efferent arteriole carry blood
The renal artery splits into many afferent arterioles and each leads to a knot of capillaries called the glomerulus
Efferent arteriole carries blood to more capillaries surrounding the rest of the tubule these eventually join to form the renal vein
69
Structure of the glomerulus
A knot of capillaries surrounded by a Bowman's capsule
-Fluid pushed in through ultrafiltration
70
Barriers between blood in the capillary and lumen of Bowman's capsule
-The endothelium of the capillary
-The basement of the membrane
-The epithelial cells of the Bowman's capsule
71
The endothelium of the capillary
Narrow gaps between cells of the endothelium of the capillary wall
-Also pores called fenestrations
-Allows Blood plasma and substances dissolved in it to pass out of the capillary
72
The basement membrane
The membrane consists of a fine mesh of collagen fibers and glycoproteins
-Mesh acts as a barrier to prevent the passage of molecules with a relative molecular mass greater than 69000
-Means most proteins (and all blood cells) are held in the capillaries of the glomerulus
73
The epithelial cells of the Bowman's capsule
Called podocytes and have specialised shape
-Many finger-like projections called major processes
-On each major process are minor processes/ foot processes that hold the cells away from the endothelium of the capillary
-Projections ensure there are gaps between cells
-Fluid from the blood of the glomerulus can pass between these cells into the lumen of the Bowman's capsule
74
What does the Bowman capsule lead to
-Proximal convoluted tubule
-Loop of Henle
-Distal convoluted tubule
75
Where does the fluid from the nephron enter
The collecting ducts
-Pass through the medulla to the pelvis at the centre of the kidney
76
What is filtered out of the blood
-Water
-Amino acids
-Glucose
-Urea
-Inorganic mineral ions (sodium, chloride, potassium)
77
What do the concentrations of the dissolved solutes depend on
On the water balance of the organism and are therefore variable
-with more water the more diluted they are
78
What is left in the capillary
Blood cell and proteins
-Proteins means blood has low WP which ensures some fluid is retained in the blood and contains some water and dissolved solutes
-Low WP helps reabsorb water at a later stage
79
Why are there no large proteins in the glomerular filtrate
They are to large to diffuse through the gaps in the basement membrane
80
Why is it important that some water is retained in the glomerular capillaries
So you don't become dehydrated
81
Selective reabsorption - until first concentration gradient
1) Sodium ions are actively pumped by the sodium-potassium ion pump out of the cells lining the tubule and into the tissue fluid then into the blood capillaries
2) Concentration gradient is made with the tubule fluid
82
Selective reabsorption - after the concentration with the tubule fluid is made
3) Sodium ions diffuse by facilitated diffusion into the cells lining the tubule through a co-transporter protein (co-transport) - as they are carrying a glucose/amino acid at the same time
-Secondary active transport - moving against the amino acid/ glucose concentration gradient
83
Selective reabsorption - after co-transport
4) As the glucose/amino acids and sodium ions build up in the cells it lowers the water potential
5) This causes water in the tubule fluid to diffuse out by osmosis into the cells
6) Sodium ions/ glucose/ amino acids move out of the cells by facilitated diffusion into the tissue fluid and then into the blood
84
Selective reabsorption - after sodium/glucose/amino acids have diffused out of the cell
7) Once equilibrium has been reached and there is no longer a concentration gradient with the tissue fluid, the sodium-potassium ion pump will start to actively pump sodium ions out of the cells
8) This will lower the WP in the tissue fluid and water will diffuse out of the cells by osmosis
85
How are large molecules (small proteins) in the tubule fluid reabsorbed
Enter the cells by endocytosis
86
How are the cells lining the proximal convoluted tubule specialised to achieve reabsorption
1) Plasma membrane nearest tubule fluid is highly folded to form microvilli - increasing SA for reabsorption
2) Plasma membrane contains special cotransporter proteins that transport glucose/amino acids in association with sodium ions from the tubule into the cell
3) Plasma membrane nearest to tissue fluid is folded to increase SA - contains sodium potassium ion pumps
4) Cell cytoplasm has many mitochondria to produce ATP for active processes
87
What do proteins in the urine indicate
Kidney disease
-Some small proteins may enter the urine and be used to diagnose conditions i.e. hCG is a polypeptide hormone that is detected by a pregnancy test
88
What happens at the loop of Henle
1) At the top of the ascending limb sodium and chloride ions move out of the ascending limb by active transport
2) This lowers the WP of the tissue fluid and the DL becomes more permeable to water, water diffuses into the tissue fluid from the descending limb
3) Sodium and chloride ions diffuse (facilitated) into the descending limb
4) Process of 2/3 continues
5) At the bottom the tubule fluid is very concentrated in ions. As they enter the bottom of the ascending limb they move out by facilitated diffusion into the tissue fluid
6) Until an equilibrium between the sodium/chloride ions in the tissue fluid and the conc in ascending limb
7) Sodium/ chloride ions need to start to move out of the ascending limb by active transport
89
Overall effect of the loop of Henle
Allows mineral ions to be transferred from AL to DL
-Overall effect is to increase the conc of mineral ions in the tissue fluid
90
What does the loop of Henle then enable in the collecting duct
'The deeper into the medulla you go the lower the WP'
-As fluid passes through tissues with an ever-decreasing WP so there is always a WP gradient between the fluid in the ducts and the tissues
-Water can then move out of the Collecting duct and into the tissue fluid by osmosis
91
Where does the collecting duct carry the fluid that is not reabsorbed
Back down through the medulla to the pelvis
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What is the arrangement of the loop of Henle called
The hair-pin counter-current multiplier system
-Increases efficiency of transfer of mineral ions from AL to DL inorder to create a WPG in the medulla
93
Why would the loop of Henle be long in a camel
1 more (sodium and chloride) ions pumped , out of ascending limb / into medulla ;
2 builds up greater water potential gradient
3 allows , reabsorption / removal , of more water from , collecting duct
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Osmoregulation
The control of Water Potential in the body
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Why is controlling WP in the body important?
As to prevent water leaving cells and causing lysis or leaving cells and causing crenation
96
How does the body gain/lose water
Body gains water: food, drink, metabolism
Body loses water: sweat, water vapour in exhaled air, faeces, urine
97
What organ regulates the volume of urine produced?
The kidneys by altering the permeability of the collecting ducts – can be made more or less permeable dependant on the needs of the body
98
Increase in WP in the blood
1) Detected by the osmoreceptors in the hypothalamus
2) Less ADH released from the posterior pituitary
3) Collecting duct wall made less permeable
4) Less water reabsorbed into the blood (and more urine produced)
5) Decrease in WP in the blood
99
Decrease in WP in the blood
1) Detected by the osmoreceptors in the hypothalamus
2) More ADH released from the posterior pituitary
3) Collecting duct wall made more permeable
4) More water reabsorbed into the blood (and less urine produced)
5) Increase in WP in the blood
100
What is the control of the WP in the blood a form of
Negative Feedback
101
ADH (Antidiuretic hormone)
A hormone that controls the permeability of the collecting duct walls
102
How does ADH work when there is Low WP in the blood?
The cells in the collecting duct wall have membrane bound receptors for ADH. The ADH binds to the receptors and causes a series of enzyme-controlled reactions inside the cell (e.g., of cell signalling) The end result cases vesicles containing water permeable channels (aquaporins) to fuse with the plasma membrane making the cells more permeable to water.
With more ADH in the blood more water permeable channels are inserted – allows more water to be reabsorbed by osmosis into the body – less urine produced and urine lower WP
103
How does ADH work when there is a high WP in the blood?
Less ADH will be in the blood and the plasma membrane folds inwards ( invaginates) to create new vesicles that remove water-permeable channels from the membrane. Makes walls less permeable and less water is reabsorbed by osmosis into the blood. More water passes down the collecting duct which is more dilute
104
How are the concentrations of ADH in the blood adjusted?
Osmoreceptors in the hypothalamus are sensory receptors that detect the stimulus – they monitor the WP of the blood and respond to the effects of the osmosis. When the WP of the blood is low the osmoreceptors lose water by osmosis and shrink – This stimulates neurosecretory cells in the hypothalamus
105
How are the neurosecretory cells specialised
to produce and release ADH.
106
How is ADH made and released from the neurosecretory cells
-ADH is manufactured in the cell body, which lies in the hypothalamus
-ADH moves down the axon to the terminal bulb in the posteriori gland where it is stored in vesicles.
-When neurosecretory cells are stimulated by osmoreceptors they carry ap down their axons and release ADH by exocytosis
-ADH enters the blood capillaries running through the posteriori pituitary gland
-Transported round body in blood and acts on collecting ducts (target cells)
107
ADH broken down
ADH is slowly broken down and has a half-life of 20 mins
108
What inhibits the release of ADH
Alcohol – so drinking alcohol reduces reabsorption from the collecting ducts and makes you need to go to the toilet.
109
Why must ADH be broken down
As if present in the blood it will continue to place water permeable channels into the cell, which will continue the cells uptake of water and will eventually cause lysis as too much water will be absorbed by osmosis
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Where is ADH broken down
Hepatocytes in the liver
111
Why is negative feedback an important component of osmoregulation
As it returns the WP back to the optimum WP so that the WP of the blood has not increased too much and caused lysis of the cells or decreased too much and cause crenation of the cells. This would prevent people from carrying out metabolic process and important functions within their body
Negative feedback brings about a reversal change that acted as a stimulus
112
How are neurosecretory cells different from other nerve cells
Have vesicles containing ADH rather than a neurotransmitter. They secrete ADH straight into the blood rather than into a synaptic cleft
113
How do the Osmoreceptors respond to an increase of ADH in the blood?
They expand and stimulate the neurosecretory cells to stop releasing ADH
114
What is kidney failure
When the kidneys fail completely and are unable to monitor the levels of water and electrolytes (substances that form charged particles in water) in the body or to remove waste products such as urea from the blood.
115
What are the methods to assess kidney function
-Estimating the glomerular filtrate rate (GFR)
-By analyzing the urine for substances such as proteins - if in indicates that the filtrate mechanism has been damaged
116
What is the GFR
The measure of how much fluid passes into the nephrons each minute
Normal 90-100 cm3 / min-1
Chronic kidney disease 60 below
Kidney failure 15 below
117
What are the causes of kidney failure
-Diabetes mellitus
-Heart disease
-Hypertension
-Infection
118
What are the two main treatments for kidney failure
Renal dialysis and kidney transplant
119
Renal dialysis
A mechanism used to artificially regulate the concentrations of solutes in the blood
-Most common
120
How does renal dialysis work
Waste products, excess fluid, etc. passed over a partially permeable dialysis membrane that allows exchange between substances in the blood and the dialysis fluid
-DF - correct conc
-Any fluid in excess diffuses across into the dialysis fluid
-Any in excess diffuse into blood from dialysis fluid
121
What are the two types of renal dialysis
Haemodialysis
Peritoneal dialysis (PD)
122
Haemodialysis
AV fistula is created = the vein and artery are connected makes blood vessel larger
-The blood then runs into the dialysis machine from an artificial capillary
-Heparin is added to avoid clotting
-In the dialysis machine the artificial capillaries run in the opp. direction (counter-current) to the dialysate fluid - maintains a high conc and increases efficiency for exchange
-Any bubbles removed and blood returned to body via a vein
123
Why may someone feel sick or dizzy during the haemodialysis procedure
Due to the rapid changes in blood fluid levels
124
Where and how often is haemodialysis performed
At the clinic 2/3 times a week for several hours at each session
125
Peritoneal dialysis
The dialysis membrane is the bodies own abdominal membrane (peritoneum)
1) Surgeon plants a permanent tube in abdomen
2) Dialysis solution is poured through the tube and fills the abdominal walls and organs
3) Whilst in peritoneal cavity waste products and excess fluid in the blood passing through the lining of the cavity are drawn out of the blood and into the fluid.
4) A few hours later, the old fluid is drained into the waste bag. New fluid from a fresh bag is then passed into your peritoneal cavity to replace it and is left there until the next session.
126
Where and how often is peritoneal dialysis performed
Can be carried out at home/work
-Needs to be repeated 4x a day
-Sometimes called ambulatory PD
-Needs to be combined with a carefully monitored diet
127
Kidney transplant
Involves surgery
-Whilst the patient is under anaesthesia the new organ is implanted in the lower abdomen and attached to the blood supply and bladder
128
What is the patient given after a kidney transplant
Immunosuppressant drugs to prevent the immune system from recognising the new organ as a foreign object and attacking it
129
Advantages of a kidney transplant
-Freedom from time-consuming renal-dialysis
-Feeling physically better
-Improved quality of life - able to travel
-Improved self-image - no longer have feelings of being chronically ill
130
Disadvantages of a kidney transplant
-Need to take immunosuppressant drugs
-Need for major surgery under general anesthetic
-Need to check regularly for signs of rejection
-Side effects of immunosuppressant drugs - fluid retention, high blood pressure, susceptibility to infections
131
What can urine be tested for
-Glucose in the diagnosis of diabetes
-Alcohol to determine blood alcohol level in drivers
-Recreational drugs
-human chorionic gonadotrophin (hCG)
-Anabolic steroids to detect improper use in sporting competitions
132
Pregnancy testing
Once a human embryo is implanted in the uterine lining it produces (hCG)
-A small glycoprotein with a molecular mass of 36,700 that can be found in the urine six days after conception
-Pregnancy kits use monoclonal antibodies which bind hCG in urine
133
Monoclonal antibodies
Antibodies made from one type of cell - they are specific to one complimentary molecule
134
Process of a pregnancy test
1) Urine poured on test stick
2) hCG binds to mobile antibodies attached to a blue bead
3) Mobile antibodies move down the test stick
4) If hCG is present it binds to antibodies and holds the bead in a fixed place - a blue line formed
5) Mobile antibodies without hCG bind to another fixed site to show test has worked (control)
135
Anabolic steroids
Increase protein synthesis within cells which results in the build-up of cell tissue, especially in the msucles
136
Why are non-medical uses of anabolic steroids controversial
Give an advantage in competitive sports and have dangerous side affects
137
How are anabolic steroids tested for
Remain in blood for many days and enter the nephron easily
-Gas chromatography
138
The loop of Henle
Where the WP of the tissue fluid is lowered so that water can diffuse from the collecting duct back into the tissue fluid
139
How might the peritoneum differ in its function from the artificial membrane in a dialysis
machine used in haemodialysis?
it can perform, active transport / facilitated diffusion
140
Why does the dialysis fluid used in peritoneal dialysis contain dextrose solution rather than water alone?
idea that (dialysis is replicating function of kidney and) part of kidney’s function is to remove (excess) water from blood
2) (dextrose / sugar) reduces , water potential / (of dialysis fluid)
3) water moves from blood (into dialysis fluid) by osmosis
4 (if it was water alone) cells would , swell / burst ;
141
Suggest why patients receiving peritoneal dialysis usually need to have the peritoneal dialysis fluid replaced four times a day, but those receiving haemodialysis only need treatment three times a week
peritoneal dialysis can remove less (named) waste (than haemodialysis) ;
2 idea that in haemodialysis dialysis fluid is constantly , refreshed / changed (but not in peritoneal dialysis) ;
3 haemodialysis uses counter-current flow ; idea that haemodialysis maintains concentration gradient or in peritoneal dialysis the concentration gradient , reduces / is lower ;
4(in peritoneal dialysis) the fluid reaches equilibrium with the blood
142
Why are RBC and proteins not in the glomerular filtrate
large molecules / proteins / blood cells , cannot , leave blood / enter the filtrate or (named) small molecules can , leave blood / enter filtrate;
2 endothelium / fenestrations / basement membrane , prevents , large molecules / erythrocytes , reaching , renal / Bowmans capsule ;
3 all glucose / glucose completely , reabsorbed at the , proximal convoluted tubule
4 all amino acids / amino acids completely , reabsorbed at the , proximal convoluted tubule / PCT ;
5 (some / not all) ions , reabsorbed / move into blood (at any part of , nephron / tubule) ;
6 urea / ion , concentration increases (between filtrate and urine) because , movement (of urea / ion) into tubule / water removed ;
143
Ethical advantages and disadvantages of kidney transplants
Advantages:
1) people should have a right to choose (freely) what to do with their kidney
2) idea that donors / donors’ families , can benefit from money raised (by selling a kidney) ;
3) people can donate a kidney to family member ;
Disadvantages:
1) idea that people can donate without payment 2)idea of exploiting people’s poverty ;
3)idea of exploitation of , children / minors ; recipient issues
4) idea that people should receive transplants irrespective of wealth ;
5)idea that it is wrong that recipients are being charged excessively ;
144
Where are the walls impermeable to water
AL on the loop of Henle
145
Where is most of the water reabsorbed into the blood
proximal convoluted tubule
146
What is important to note about the hepatic portal vein
It is branched
147
Distal convoluted tubule
Connects the loop of Henle and the collecting duct
-Where the ion concentrations are adjusted
-Reabsorbs Calcium and sodium ions
148
What allows hCG to be detected in urine
It is a polypeptide
149
Identify a glomerulus and bowman's capsule on a microscope
150
What are the structural differences between alpha and beta glucose
Alpha glucose: H above ring and OH above ring on C1
151
Why are podocytes usually unable to undergo mitosis
1) Podocytes are already specilaised so cannot divide
2) G0 phase
3) Shape to irregular to divide
4) Cytoskelton cannot function - spindle fibres cannot form
5) Alter an act of ultrafiltration
152
What features of adult stem cells make them suitable for regeneration of tissues in the kidney
1) Adult stem cells are multipotent
2) Differentiate into any cell type within kidney (nephron) tissue
153
Characteristics of a patient that must be taken into account when estimating GFR
Age - GFR declines with age
Gender - men/ woman different
muscle mass
154
Draw and label a kidney
155
What is the function of the microvilli on PCT
Increases SA for rapid diffusion and active transport
156
Why does the distal convoluted tubule have a higher concentration of urea
Water has been reabsorbed by this point
157
Hypothalamus and ADH
Hypothalamus causes the release of ADH from the pituitary
-Produced by the hypothalamus
-Released from the posterior pituitary which is an extension of the hypothalamus
-Works by Negative Feedback
158
Why does peritoneal dialysis use active transport
Peritoneal wall uses living cells which produces ATP for active transport
159
Explain why visible blood vessels are veins
