Excretion Flashcards
1
Q
Define excretion
A
The removal of metabolic waste from the body
2
Q
Define metabolic waste
A
Waste substances that may be toxic or are produced in excess by the reactions inside the cells.
3
Q
What is the difference between egestion and excretion?
A
Egestion is pooping undigested food
Excretion is the removal of metabolic waste from cells
4
Q
Define deamination
A
The removal of the amine group from an amino acid to produce ammonia.
5
Q
Name 2 products that are produced in large amounts and need to be excreted. What are they produced from?
A
CO2 from respiration
Nitrogen containing compounds produced in the liver from excess amino acids (e.g. urea)
6
Q
How is carbon dioxide excreted from the body?
A
It passes into the bloodstream from cells and is transported in the form of hydrogencarbonate ions to the lungs where it diffuses into the alveoli and is excreted when we exhale.
7
Q
How is urea excreted from the body?
A
Deamination occurs which produces urea. Urea is then passed into the bloodstream and is transported to the kidneys in a solution dissolved in the plasma. It then becomes a part of urine in the kidneys
8
Q
What are the three main effects that excess carbon dioxide has on the body?
A
When hydrogencarbonate ions are formed, as mentioned earlier, hydrogen ions are also formed with the help of carbonic anhydrase. The hydrogen ions then combine with haemoglobin and compete with oxygen meaning less oxygen is carried in the blood.
The carbon dioxide can directly combine with haemoglobin to make carbaminohaemoglobin which has a lower affinity for oxygen.
It can also cause respiratory acidosis. This happens from when carbon dioxide dissolves in the blood plasma and then combines with water to produce carbonic acid which dissociates to produce hydrogen ions
9
Q
Why is having extra hydrogen ions in the blood a bad thing? How do you bring it back to normal? What do proteins in the blood act as?
A
Because it makes the blood more acidic which sends a signal to the medulla oblongata causing an increase in breathing rate.
Proteins act as buffers to resist the change in pH
10
Q
What happens if extra hydrogen ions in the blood change the pH to below 7.35?
A
You have slowed breathing, a headache, drowsiness, restlessness, confusion and respiratory acidosis.
11
Q
What diseases can induce respiratory acidosis?
A
Emphysema, chronic bronchitis, asthma, pneumonia, blockage of the airways.
12
Q
What can’t the body store?
A
Proteins and amino acids
13
Q
Why aren’t amino acids excreted from the body?
A
Because they contain too much energy so it would be wasteful
14
Q
What happens to excess amino acids?
A
They are transported to the liver and deaminated (oxygen needs to be present) to produce ammonia and keto acid. Ammonia and carbon dioxide combine to form urea and are then excreted. Keto acid can be used in respiration or converted to a carbohydrate and stored.
15
Q
Define hepatic portal vein.
A
A blood vessel with capillaries at both ends, it carries blood from the digestive system to the liver.
16
Q
Define Kupffer cells.
A
To breakdown and recycle old red blood cells
17
Q
Define bilirubin
A
A waste product from the breakdown of haemoglobin
18
Q
What is the liver’s main important role?
A
Homeostasis
19
Q
Why does the liver need a good supply of blood?
A
To ensure that homeostasis can occur
20
Q
How many sources is the liver supplied from?
What are the 2 sources?
A
2 sources
The heart and the digestive system
21
Q
What source does the liver receive oxygenated blood from? And how does it get to the liver?
A
The heart
The oxygenated blood gets to the liver by travelling from the aorta to the hepatic artery.
22
Q
Why do hepatocytes need oxygenated blood?
A
For aerobic respiration to create ATP for metabolic processes
23
Q
What source does the liver receive deoxygenated blood from? how does it get to the liver?
A
The digestive system
It gets to the liver via the hepatic portal vein
24
Q
Why does the liver need blood from the digestive system?
A
Because the blood is rich in products but it may contain toxic compounds that have been absorbed in the intestine
25
How does the deoxygenated blood leave the liver?
It leaves via the hepatic vein where it rejoins the vena cava and returns to normal circulation
26
Arteries contain ..... blood
| Veins contain ...... blood
Oxygenated blood
| Deoxygenated blood
27
Where is the bile duct found?
| And name 2 functions it has.
Connected to the liver
| A digestive function and an excretory function
28
What does the bile duct do?
It carries bile from the liver to the gall bladder where it's stored until it's needed to aid the digestion of fats in the small intestine.
29
What is the liver divided into? And what is that then divided into?
Lobes which are then divided into cylindrical lobules.
30
What happens to the hepatic artery and portal vein once they enter the liver?
They split into smaller and smaller vessels which run between and parallel to the lobules.
31
What are the smaller vessels called when they run parallel to the lobules in the liver?
Inter-lobular vessels
32
True or false
| The inter-lobular vessels never enter the lobules at intervals.
False, they do
33
Does the blood from the two vessels in the liver mix?
Yes
34
Once the blood in the liver from the two vessels mix, what does the blood enter?
They enter the sinusoid.
35
What is the sinusoid?
It is a special chamber lined by hepatocytes.
36
What happens when the blood reaches the end of the sinusoid?
The blood empties into an intra-lobular vessel (not inter) which is a branch of the hepatic vein. The branches join together to form the hepatic vein and the blood is then drained from the liver.
37
What happens when the blood passes along the sinusoid?
The hepatocytes remove and pass molecules from/into the blood.
38
Name a function of hepatocytes.
To produce bile
39
Where is bile released one the hepatocytes have manufactured it?
It is released into bile canaliculi which join together to form the bile duct.
40
Describe the appearance of hepatocytes.
They are relatively unspecialised but they have microvilli on their surface and they are a cuboidal shape.
41
Name 5 out of 6 metabolic functions of hepatocytes.
1. Protein synthesis
2. Transformation of carbohydrates
3. Storage of carbohydrates
4. Synthesis of cholesterol
5. Synthesis of bile salts
6. Detoxification
42
Is a hepatocyte's cytoplasm dense and specialised? Explain.
Yes because it has a large amount of organelles for metabolic processes.
43
What are Kupffer cells? What is one of there products?
They are specialised macrophages that move about in sinusoids.
One of their products, from the breakdown of old red blood cells, is bilirubin which is excreted as part of bile or faeces (it's the brown pigment in poop lol)
44
Define urea.
An excretory product formed from the breakdown of excess amino acids
45
Define ornithine cycle.
The process in which ammonia is converted to urea.
46
Where does the ornithine cycle take place?
Part of it occurs in the cytosol and part of it occurs in the mitochondria as ATP is used.
47
Define detoxification.
The conversion of toxic molecules to less toxic molecules
48
Name 5 out of 6 functions of the liver.
1. Control of: blood glucose levels, amino acid levels, lipid levels
2. Synthesis of: Red blood cells in the fetus, bile, plasma proteins, cholesterol
3. Storage of: Vitamin A, Vitamin D, Vitamin B, iron, glycogen
4. Detoxification of: Alcohol, drugs
5. Breakdown of hormones
6. Destruction of red blood cells
49
How many grams of protein do we need each day?
40-60 grams
50
Why can't excess amino acids be stored?
Because their amine group makes them toxic.
51
Name 2 processes that amino acids undergo in order for their toxic amine group to be excreted.
Deamination and the ornithine cycle
52
What does deamination produce?
Ammonia and keto acid
53
Name the characteristics of ammonia
It is very soluble and highly toxic
54
In order for deamination to occur, what element needs to be present?
Oxygen
55
What is more toxic, ammonia or urea?
| What is more soluble?
Ammonia
| Ammonia
56
What happens when ammonia combines with carbon dioxide?
Urea and water is formed.
57
What happens once urea is formed in the liver?
It's transported around the body in the blood to the kidneys where it is filtered out and concentrated in urine
58
Name a product, produced in the body, that the liver can detoxify.
What products, that aren't produced in the body, can the liver detoxify?
Hydrogen peroxide
| Alcohol and drugs
59
How are the toxins rendered harmless during detoxification? 4 processes
Oxidation, reduction, methylation or combination with another molecule
60
Name an enzyme in the liver that is involved in detoxification and name the product that the enzyme helps detoxify.
Catalase helps detoxify hydrogen peroxide to oxygen and water
61
True or false
Catalase has a high turn over number.
What is the turn over number?
True
| It can detoxify 5 million hydrogen peroxides in one minute.
62
What does ethanol do to the body?
It depresses nerve activity
63
True or false
| Ethanol does have chemical potential energy that can be used in metabolism.
False, it has the chemical potential energy that can be used in RESPIRATION
64
What enzyme aids the breakdown of ethanol?
Where is this enzyme found?
What does it produce?
Ethanol dehydrogenase
In hepatocytes
Ethanal
65
How is ethanol and ethanal broken down?
They are dehydrogenated
66
What enzyme aids the breakdown of ethanal?
| What does it produce?
Ethanal dehydrogenase
| Ethanoate/acetate
67
Once ethanal is broken down to produce acetate, what happens to the acetate?
The acetate combines with coenzyme A to form acetyl coA. This enters respiration.
68
When ethanol and ethanal is broken down, what is released?
| What happens to this element?
Hydrogen
| Hydrogen combines with NAD to form reduced NAD
69
Define oxidation and reduction in terms of oxygen and in terms of hydrogen transfer.
Oxygen: Oxidation= Gain of oxygen. Reduction= Loss of oxygen
Hydrogen: Oxidation= Loss of hydrogen. Reduction= Gain of hydrogen
70
What is the function of NAD in terms of fatty acids?
| What happens when the liver has to detoxify too much alcohol?
NAD oxidises and breaks down fatty acids so they can be used in respiration.
There is insufficient NAD so less fatty acids are broken down. The fatty acids are converted back to lipids and are stored in hepatocytes, enlarging the liver.
71
What illnesses can arise from an enlarged liver?
'Fatty liver', hepatitis, cirrhosis
72
Define nephron.
The functional unit of the kidney that receives fluid from the blood capillaries and converts it into urine.
73
Define glomerulus.
A fine network of capillaries that increases the local blood pressure in order to squeeze fluid out of the blood and into the Bowman's capsule
74
Define selective reabsorption.
When useful substances are reabsorbed from the nephron into the bloodstream whereas other not useful molecules are left in the nephron.
75
How many kidneys do we have?
| Where are they found?
2
| Each side of the spine just below the lowest rib
76
What supplies and drains the kidney with blood?
Supplies: Renal artery
Drains: Renal vein
77
What is the role of the kidney?
To remove waste products from the blood and produce urine
78
What happens to the urine once it has been produced?
The urine passes out the kidney, down the ureter and into the bladder where it's stored for release.
79
How many sections of the kidney are there?
What are they called?
Which section is the nephron found in?
3
The medulla (the middle region), the cortex (the outer region) and the pelvis (the centre)
The loop of Henle is found in the medulla but the rest is in the cortex
80
How many nephrons are there in each kidney?
| What are the nephrons closely associated with?
About 1 million
| Blood capillaries
81
What is at the start of the nephron?
What process happens here?
What are the other 4 sections of the nephron?
The glomerulus, surrounded by the Bowman's capsule
Ultrafiltration
Proximal convoluted tubule (PCT), Loop of Henle, Distal convoluted tubule (DCT) and the collecting duct.
82
What process happens in the:
Glomerulus
PCT
Collecting duct/ Loop of Henle
Ultrafiltration
Selective reabsorption
Osmoregulation
83
What percentage of fluid is reabsorbed in the PCT?
85%
84
Define afferent and efferent vessels in terms of the kidney.
Afferent vessels bring blood to the organ
Efferent vessels are arterioles that carry blood away from the organ, they can constrict the raise the blood pressure in the glomerulus
85
Define ultrafiltration.
Molecular filtration in the glomerulus where only small molecules pass into the Bowman's capsule but large molecules (proteins, red blood cells) are left.
86
Define podocytes.
Specialised cells that make up the lining of the Bowman's capsule.
87
Define microvilli.
Microscopic folds on the cell surface membrane to increase surface area.
88
Define co-transporter proteins
Proteins in the cell surface membrane that allow the facilitated diffusion of simple ions to be accompanied by the transport of larger molecules like glucose.
89
Define facilitated diffusion.
Diffusion that's enhanced by the action of proteins in the cell membrane.
90
Define sodium-potassium pumps
Special proteins in the cell surface membrane that actively transport sodium/potassium ions against their concentration gradient.
91
Which arteriole is wider, the afferent or the efferent?
Afferent.
92
Is the pressure in the glomerulus higher than the pressure in the Bowman's capsule?
Yes
93
Why is there increased pressure in the glomerulus?
In order to push fluid from the blood into the Bowman's capsule
94
How many layers are there between the glomerulus and the Bowman's capsule?
What are they called?
3
Capillary endothelium
Basement membrane
Podocytes in the Bowman's capsule epithelium
95
In terms of the kidney, describe the endothelium of the capillaries.
They have narrow gaps between the cells that blood plasma/substances dissolved in it can pass through
96
In terms of the kidney, describe the basement membrane
It's a fine mesh of collagen fibres and glycoproteins that filter and prevent the passage of larger molecules, like proteins, into the Bowman's capsule.
97
In terms of the kidney, describe the epithelium of the Bowman's capsule.
It consists of cells called podocytes that have finger like projections called foot processes that ensure there are gaps between the cells so that fluid can pass into the lumen of the Bowman's capsule.
98
What substances are/aren't pushed into the Bowman's capsule?
Are: Water, glucose, inorganic ions (sodium, potassium, chloride), urea, amino acids
Aren't: Proteins, red blood cells
99
What is the water potential of the blood after ultrafiltration?
The water potential is very low due to the presence of proteins but some water/ dissolved substances don't leave the blood because of this.
100
Why does the water potential in the blood need to be low after ultrafiltration?
So that water can be reabsorbed at a later stage.
101
Where does selective reabsorption occur and what is reabsorbed?
In the PCT
| Glucose, amino acids, some water and some salts.
102
How are the cells lining the PCT specialised for their function? 4 things
The cells contain microvilli for increased surface area for reabsorption
The membrane contains co-transporter proteins which transport glucose/amino acids that are associated with sodium ions from the tubule to the cell, this is facilitated diffusion.
The opposite membrane of the cell, that is close to the tissue fluid and blood capillaries, is folded and contains sodium-potassium pumps that pump sodium out of the cell and potassium in
The cytoplasm contains many mitochondria for ATP for active transport.
103
List the 6 steps of selective reabsorption. Detail
1. The sodium-potassium pumps remove sodium ions from the cells lining the PCT reducing the concentration of sodium ions in the cytoplasm
2. Sodium ions from the nephron are then transported into the cell via facilitated diffusion with glucose/amino acids
3. Glucose/amino acid concentrations rise in the cell, causing them to diffuse out the other side of the cell into the tissue fluid. This can also be active
4. The substances the diffuse into the blood and are transported away
5. The reabsorption reduces the water potential in the cells causing water from the nephron to diffuse via osmosis into the cell down its concentration gradient
6. Small protein that may have been absorbed can be reabsorbed via endocytosis
104
Define hairpin countercurrent multiplier.
It's the loop of Henle which is hairpin shaped, allowing the exchange of contents between the limbs creating high concentrations of solutes
105
Define osmoregulation.
The control and regulation of water potential in the blood and body fluids.
106
Define DCT.
The coiled portion of the nephron after the loop of Henle and before the collecting duct.
107
How much fluid is filtered out of the blood each minute in the kidney?
125cm3
108
How much fluid is left in the nephron after the PCT?
45cm3
109
What is the role of the loop of Henle?
To create a very low water potential in the tissue of the medulla ensuring that more water is reabsorbed from the fluid in the collecting duct
110
What are the 2 sections of the loop of Henle called?
The descending limb and the ascending limb
111
Why is the loop of Henle arranged in a hairpin shape?
To allow the exchange of sodium and chloride ions between limbs which in turn increases the concentration of salts in the tubule fluid.
112
When the concentration of salts in the tubule fluid is high, what happens?
The salts diffuse out into the tissue fluid, reducing the water potential in the medulla.
113
Why does the water potential in the tubule become lower as its descends into the medulla? 2 reasons
Because water potential leaves the tubule via osmosis
| Because sodium and chloride ions diffuse into the tubule from the tissue fluid.
114
Why does the water potential in the tubule become higher as it ascends out of the medulla? 4 reasons
Because sodium and chloride ions diffuse out of the tubule at the base of the ascending limb
Because sodium and chloride ions are actively transported out of the tubule at the top of the ascending limb
Because the wall of the ascending limb is impermeable to water
Because the fluid loses salts but not water as it ascends
115
Why does the water potential in the tissue fluid become more negative the deeper into the medulla it gets?
Because of the arrangement of the loop of Henle which allows efficient salt transfer between the limbs but it also causes a build up of salt concentration in the tissue fluid due to the movement of salts out the ascending limb
116
Is the urine dilute at the top of the ascending limb?
Yes
117
Where is water reabsorbed into the tubule fluid? And is the kidney an organ of osmoregulation?
In the DCT or the collecting duct
| Yes
118
Why happens in the DCT?
The concentration of salts are adjusted via active transport
119
Does the fluid in the DCT have a high water potential?
Yes
120
Where does the collecting duct carry the fluid?
Through the medulla, which has a low water potential, and into the pelvis
121
What happens to the water as it travels down the collecting duct?
Water moves from the tubule fluid via osmosis to the surrounding tissue fluid where it then enters blood capillaries and is carried away.
122
When urine reaches the pelvis does it have a high water potential? How much fluid reaches the pelvis?
No it has a low one
| 1.5-2 dm3
123
Define antidiuretic hormone.
A hormone that's released from the pituitary gland and acts on collecting ducts to increase the reabsorption of water into the blood
124
Define osmoreceptors
Receptor cells that monitor the water potential of the blood
125
Define hypothalamus
Part of the brain that contains neurosecretory cells and various other receptors that monitor the blood
126
Define neurosecretory cells and what happens to ADH once it's been produced.
Specialised cells that act like nerve cells but release ADH which is manufactured in the cell body and passed down the axon to be stored in the terminal bulb until an action potential arrives
127
Define posterior pituitary gland
The back part of the pituitary gland which releases ADH
128
Define half life
The half life of a substance is the time taken for its concentration to drop to half it's original value
129
How do we obtain water? 3 things
From food, drink and metabolism
130
How do we lose water? 4 things
In our urine, sweat, breath and faeces
131
Will you produce a small volume of dilute urine on a cool day after drinking a lot of fluid?
No you will produce a large volume of dilute urine
132
Will you produce a small volume of concentrated urine on a hot day after not drinking much fluid?
Yes
133
True or false.
| The permeability of the collecting duct walls don't respond to ADH
False
134
What happens when ADH is released into the bloodstream? In detail
It binds to the membrane bound receptors of the collecting duct wall which causes a chain of enzyme controlled reactions inside the cell. The result of this is that vesicles of water permeable channels/aquaporins are inserted into the cell surface membrane. This makes the walls more permeable to water.
135
If there is more ADH in the blood, then are more or less aquaporins inserted into the cell surface membranes of the collecting duct? As a result, is more or less urine made?
More
| Less
136
What happens when there is less ADH in the blood?
The cell surface membrane folds inwards via endocytosis to form vesicles of aquaporins which removes them from the cell surface membranes, making the collecting duct wall less permeable.
137
What happens to the water in the nephron when a lot of ADH is released into the blood?
What about when not much ADH is released into the blood?
More water leaves the collecting duct via osmosis and enters the tissue fluid as the wall is more permeable. This means there is less urine that is more concentrated.
Less water leaves the collecting duct wall meaning the urine is dilute.
138
How does the body know when to release ADH?
The water potential of the blood is monitored by osmoreceptors in the hypothalamus. They respond to water potential via osmosis, if the water potential is low then the osmoreceptors lose water via osmosis. This causes them to shrink and stimulate neurosecretory cells which are also in the hypothalamus. They produce ADH which travels down the axon to the terminal bulb in the posterior pituitary gland. It is then secreted when an action potential is created.
139
How does ADH get to the kidney?
It enters the blood capillaries running through the posterior pituitary gland and is then transported to the kidney via the blood.
140
What happens to ADH once it's been released but is no longer needed?
It is slowly broken down, its half life is 20 minutes.
141
Define dialysis
The use of a partially permeable membrane to filter the blood
142
Define dialysis membrane
A partially permeable membrane that separates the dialysis fluid from the patient's blood in a dialysis membrane
143
Define dialysis fluid
A complex solution that matches the composition of body fluids
144
Define haemodialysis
When blood is taken from a vein and passed through a dialysis machine so that exchange can occur across an artificial partially permeable membrane
145
Define peritoneal dialysis
When dialysis fluid is pumped into the body cavity so that exchange can occur across the peritoneal membrane
146
Name 3 reasons why kidney failure could occur
Diabetes mellitus
Hypertension
Infection
147
Why can kidney failure result in death?
Because excess and toxic substances aren't removed from the body in urine, so your water and salt levels rise too high
148
What is the most common treatment for kidney failure?
Dialysis
149
What does dialysis do?
It removes wastes, excess fluid and salts from the blood via a dialysis membrane
150
What does dialysis fluid contain?
The correct concentrations of salts, urea, water and other substances in the blood plasma
151
How does the dialysis membrane alter the concentrations of substances in the blood plasma?
When substances are too low, the substances diffuse across the membrane into the blood
When substances are too high, the substances diffuse across the membrane into the blood
152
What drug is taken during haemodialysis? Why?
Heparin
| To stop blood clotting.
153
How often does one have to have haemdialysis?
3 times a week at a clinic for several hours.
154
What is a peritoneal membrane?
An abdominal membrane
155
What do you have to have in order for peritoneal dialysis to occur?
You have to have surgery before hand where the surgeon implants a permanent tube in the abdomen.
156
How does peritoneal dialysis occur?
Dialysis solution is poured through the tube that fills the space between the abdominal wall and the organs. After several hours, the used solution is drained from the abdomen.
157
What is an alternative name for peritoneal dialysis?
Ambulatory PD
158
How often does peritoneal dialysis occur?
Several consecutive sessions daily
159
Other than dialysis, how can you treat kidney failure?
Have a kidney transplant
160
Are the old kidneys kept in place or removed when you have a kidney transplant?
Kept in place as long as they aren't infected or cancerous
161
Where is a kidney transplanted to?
The lower abdomen.
162
Name 3 out of 5 advantages of a kidney transplant.
```
Freedom of time consuming dialysis
Less limited diet
Feeling better physically
A better QoL
No longer chronically ill
```
163
Name 3 out of 5 disadvantages of a kidney transplant
```
You need immunosuppressants for the rest of your life
Need major surgery
Risks of surgery
Frequent checks for organ rejection
Side effects of medication
```
164
GB: Define human chorionic gonadotrophin (hCG)
A hormone that's released by human embryos which confirms pregnancy in a pregnancy test via urine
165
GB: Define monoclonal antibodies
Antibodies that are identical due to the cloning of one original cell
166
GB: Define anabolic steroids
Drugs that mimic the action of steroid hormones which increases growth via protein synthesis
167
GB: Define gas chromatography
A technique that is used to separate substances in a gaseous state
168
GB: Define chromatogram
A chart that's produced when substances are separated via movement of a solvent along a permeable material, e.g. paper or gel.
169
GB: Describe hCG
It's a relatively small glycoprotein that can be found in urine 6 days after conception. It is small enough to enter the nephron
170
GB: What are pregnancy tests manufactured with?
They are manufactured with monoclonal antibodies which are specific and will only bind to hCG
171
GB: How does a pregnancy test work?
The hCG in the urine attaches to an antibody on the pregnancy test that's tagged with a blue bead. This hCG-antibody complex then moves up the strip until it reaches a band of immobilised enzymes where they are held in place. This forms a blue line and there is already another blue line present for comparison, this means you're pregnant if there is 2 blue lines
172
GB: Why are non-medical anabolic steroids controversial?
Because they can build up muscle which can provide a greater advantage in competitive sports
173
GB: What is the half-life of anabolic steroids?
16 hours
174
GB: Are anabolic steroids large molecules and can they enter the nephron?
They are small molecules and they can enter the nephron
175
GB: How is urine analysed to test for anabolic steroids? Detail
It is analysed via gas chromatography where the sample is vaporised in the presence of a gaseous solvent and is then passed along a tube lined by an absorption agent. The substances dissolve into the gaseous solvent for a specific time called the retention time before being absorbed into the lining
176
GB: How do you find out the results of gas chromatography?
You find out the results by analysing them to create a chromatogram
