Excretion 5.2 Flashcards
1
Q
Define excretion
A
Excretion is the removal of metabolic waste from the body
2
Q
What are the main 3 excretory products from the body?
A
The main excretory products are:
- carbon dioxide fro respiration
- nitrogenous waste like urea
- other compounds like bile pigments
3
Q
What are the 4 excretory organs?
A
Excretory organs:
- lungs
- liver
- kidneys
- skin
4
Q
How are the lungs an excretory organ?
A
In the lungs carbon dioxide diffuses into the alveoli to be excreted as you breathe pout.
5
Q
What is the path of carbon dioxide to reach the lungs?
A
Carbon dioxide passed from respiring cells into the bloodstream then transported as hydorgen carbonate ions to the lungs
6
Q
how is the liver an excretory organ?
A
The liver has many metabolic processes and some of these substances produced will be passed into the bile for excretion with faeces.
It is also involved in converting amino acids to urea by deamination
7
Q
How is urea made from deamination?
A
The nitrogen containing part of the amino acid is combined with carbon dioxide to make urea
8
Q
How are the kidneys an excretory organ?
A
In the kidneys urea is removed from the blood to become past of urine.
9
Q
How is urea transported?
A
Urea is transported in solution dissolved in the plasma
10
Q
How is the skin an excretory organ?
A
The skin sweats and sweat contains urea, uric acid and ammonia which are all excretory products.
11
Q
What things may sweat contain other than excretory products? Why?
A
Other than the excretory products of uric acid urea and ammonia the sweat also contains water ans salts, important in homeostasis maintaining temperature and water potential of the body
12
Q
Why is excretion important?
A
Allowing the build up of metabolic products may be fatal as carbon dioxide and ammonia are toxic
13
Q
Why is the build up of metabolic products an issue? What can they cause?
A
Metabolic products can interfere with cell processes by altering pH preventing normal metabolism or may act as inhibitors reducing the activity of essential enzymes
14
Q
What happens to excess amino acids and why
A
The body cannot store excess amino acids but they contain almost as much energy as carbohydrates so it would be wasteful to simply excrete them. They get deaminated in the liver
15
Q
Discuss deamination
A
Deamination is the process of removing he potentially toxic amino group fom the amino acid. It forms a soluble toxic ammonia and a keto acid
amino acid + oxygen —- keto acid + ammonia
16
Q
How and why is urea formed after deamination?
A
Ammomnia is toxic so must be tuned into urea as urea is less soluble and less toxic and the urea can be excreted in the urine from the kidneys
ammonia + carbon dioxide — urea + water
17
Q
Give the symbols for ammonia and urea
A
Ammonia = NH3 Urea = (NH2)2CO
18
Q
What happens to the keto acid produced in deamination?
A
The remaining keto acid can be used directly in respiration to release its energy or converted to carbohydrate or fat for storage
19
Q
What is egestion?
A
Egestion is the elimination of faeces from the body and faeces is not metabolic products but remains of food
20
Q
How is most of the CO2 in the body transported?
A
Most of CO2 in the body is transported as hydrocarbonate ions
21
Q
What are the 2 processes to produce hydrogencarbonate ions?
A
CO2 + H2O — H2CO3 (carbonic acid)
H2CO3 — H+ + HCO3-
22
Q
What is the chemical symbols for hydorgencarbonate ions and carbonic acid?
A
Hydrogencarbonate ions = HCO3-
Carbonic acid = H2CO3
23
Q
How do you describe how carbonic acid becomes H+?
A
Carbonic acud disaociates into H+
24
Q
Where does carbonic acid dissociate and what enzyme helps?
A
Carbonic acid dissociates in the red blood cells under the influence of carbonic anhydrase OR in the blood plasma
25
Describe what happens when hydrogen ions affect red blood cells?
Hydrogen ions affect the pH of cytoplasm is red blood cells:
- H+ interact with bonds in haemoglobin changing its 3D shape
- reduces haemoglobin's affinity for oxygen
- hydrogen ions combine with haemoglobin to make haemoglobinic acid
26
What can the carbon dioxide that does not form hydorgencarbonate ions do?
The carbon ndioxide that does not form hydogen carbonate ions combines directly with haemoglobinic acid to make carbaminohaemoglobin
27
What is another negative consequence of haemoglobinic acid and carbaminohaemoglobin?
Both haemoglobinic acid and carbaminohaemoglobin are unable to combine with oxygen as normal, reducing the oxygen transport further
28
What happens if the hydrogen ions are in the blood plasma?
Hydorgen ions an reduce blood plasma pH ands mainti g this pH is essential becuase changes could alter the structure of proteins in the blood that help transport a wide range of substances around the body.
29
How is hydrogen ions in the blood plasma combated?
There are proteins in the blood plasma to act as buffers to resist the changes in pH
30
If the change in pH is small what happens?
Id the pH change is amll then the hydrogen ions are detected in the respiraoty centre in the medukla oblongata. Breathing rate is inceased to remove carbon dioxide
31
What if the change in pH is large?
If blood pH drops below 7.35:
- headaches, drowsiness, relestness, tremort and confusion,.
- Heart rate increases and blood pressure changes (respiraptry acidosis)
32
What is respiratory acidoosis and what may cause it?
Respiratory acidosis is wher blodo pH drops below 7.35 and aucases rapid heart rate and blood pressure changes.
it is caused dby dieases or coindition affecrting the lungs or blockage of the airways
33
What are loiver cells called?
The liver cells are caled hepatocytes
34
What are the 2 sources of blood to the liver? vessels?
- Hepatic artery brings oxygenated blood from the heart to the liver in order for ti to be able to aerobically respire
- hepatic portal vein brings deoxygenated dirty blood from the digestive system. This blood is rich in the products of digestion and possibly toxic substances absorbed fro the intestine
35
What are the 4 vessels connected to the liver?
Vessels to the liver:
- Hepatic artery (heart)
- Hepatic portal vein (digestive system)
- Hepatic vein (to vena cava
- Bile duct
36
Discuss the bile duct
The bile duct carries bile from the liver to the gall bladder. Lots of bile canaliculi join together to form the bile duct.
37
What is bile and what does it do?
Bile is released from the gall bladder into the small intestine to aid digestion of fats.
Bile is a secretion from the liver, a prodcut of heamoglobin nbreakdown by kupffer cells, contains some excretory products like bilirubin (a bile pigments) which leaves the body with faeces
38
What is bilirubin and how does it leave the body?
Bilirubin is a bile pigment found in bile that gets egested with faeces
39
What are interlobular vessels?
Interlobular veseels run parallel and in between lobules. They are where the hepatic artery and hepatic portal vein split into smaller vessels.
40
What are intralobular vessels?
Intralobular vessels are branches of the hepatic vein at the centre of each lobule. The sinusoids empty into this vessel.
41
What are two structural things about hepatocytes?
Hepatocytes have a simple cuboidal shape and have microvilli on their surface
42
What is the cytoplasm of hepatocytes like and why
Hepatocytes have a dense cytoplasm and specialised in the number of organelles that it contains . This is because they have many metabolic functions
43
How is the liver divided?
The liver is divided into lobes which are further divided into lobules
44
Briefly discuss the journey of blood through sections of the liver
1. Interlobular vessels
2. blood from heaptic artery and portal vein mix
3. mixed blood passes along sinusoids
4. substances removed from blood by liver cells in sinusoids
5. kupffer cells break down and recycle old blood cells
6. blood reaches end of sinusoid
7. blood empties into the intralobular vessel
8. gets into hepatic vein then back to vena cava
45
What do Kupffer cells do?
Kupffer cells are specialised macrophages what move within the sinusoids. They breakdown and recycle old red blood cells
46
What do Kupffer cells produce as a product?
Kupffer cells breakdown of haemoglobin produces bilirubin, a bile pigment
47
What is a sinusoid?
A sinusoid is a special chamber lined with liver cells that the mixed hepatic artery blood and hepatic portal vein blood passes through.
48
What do the liver cells in the sinusoids do?
The liver cells remove substance from the blood and return different substances back to the blood.
49
When we say 'mixed blood' what does this mean?
Blood from hepatic artery and hepatic portal vein mixing together in the sinusoids
50
What shape are the lobules?
Lobules are cyclindrical
51
What are bile canaliculi?
Bile canaliculi are small vessels which join together to form the bile duct
52
List 6 functions of the liver
The functions of the liver:
- control of blood glucose levels, amino acid levels and lipid levels
- Synthesis of bile, plasma proteins, cholesterol and red blood cells in the fetus
- strorage of vitamins A, D, B12, iron and glycogen
- detoxification of alcohol and drugs
- breakdown of hormones
- destruction of red blood cells
53
Discuss the libvers storage of glycogen
The liver stores sugar in the form of glycogen. Approx 100-120 grams of glycogen making up 8% of liver weight
It forms granules in the cytoplasm of hepatocytes
The glycogen can be broken down to release glucose into blood as required
54
What are the 4 ways a toxin can be rendered harmless?
To render a toxin harmless you can ;
- oxidation
- reduction
- methylation
- combination with another molecule
55
What are two enzymes the liver contains for detoxification?
- catalase
| - cytochrome p450
56
What does catalse do?
Catalase converts hydrogen peroxide to oxygen and water. It has a very high turnover rate (number of hydrogen peroxide molecules it can render harmless in one second)
57
What does cytochrome p450 do?
Cytochrome p450 is a group of enzymes used to breaksdown drugs like cocaine and medicinal drugs
58
Where else is cytochrome p450 used and whats the problems?
Cytochromes are also used in metabolic reaction like electron transport and their metabolising drugs can affect their metabolic roles leading to the unwanted side effects of drugs
59
Discuss how alcohol is detoxified
Alcohol detoxification
1. ethanol broken down into ethanal by athanol dehydrogenase
2. NAD becomes reduced NAD from the 2 H released from ethanol
3. Ethanal becomes ethanoate by ethanal dehydorgenase
4. NAD becomes reducded NAD from the 2 H released from ethanal
5. Ethanoate becomes acetyl coenzyme A which goes to respiration
60
Why do we detoxifyu alcohol?
We detoxify alcohol as it contains chemical potenatil energy whicbh can be usd in respiration
61
Whats the problem with using NAD to detoxify alcohol?
- NAD is also used to oxidise and breakdown faty acids
- If liver detoxifies too much alcohol it uses up all the NAD leaving insufficient amounts for fatty acids
- Fatty acids converted back to lipids and stored as fats in hepatocytes
- liver becomes enlarged (fatty liver)
- alcohol related hepatitis or cirrhosis
62
Which bit of amino acids make them toxic to store?
The amine group of amino acids makes them toxic to store
63
What are the two processes that make an amino acid into urea?
Amino acid--- keto acid + ammonia = deamination
| Ammonia + keto acid---- urea = ornithine cycle
64
What is the structure of amino acids?
Structure of amino acids
R
NH2 ---C----COOH
H
65
What is the structure of keto acids?
keto acid structure
R
C---COOH
=O
66
Describe the ornthine cycle
The ornithine cycle
1. Ammonia combines with carbon dioxide and ornithine to form citrulline and water is released
2. Citrulline converted to arginine by addition of ammonia, the ammonia becomes water
3. Arginine reconverted to ornithine by removal of urea and addition of water
67
Summarise the ornithine cycle as an equation
Ornthine cycle
| ammonia + carbon dioxide --- urea + water
68
Symbols for urea
urea = CO(NH2)2
69
Describe the structure of the kidney
The structure of the kidney
- capsule
- cortex
- medulla
- pelvis
- branch of renal vein and renal artery
- ureter
- nephron tubule in cortex and into medulla
70
Discuss nephrons and the fine structure of the kidney
The nephrons are tiny tubules
each nephron starts in the bowmans capsule in the cortex
remainder of nephron is coiled and passes down the cortex forms a loop in the medulla
back into the crotex
join s a collecting duct that goes into medualla
71
What is the glomerulus?
The glomeruslus is a knot of capillaries from where the renal artery has split into many different arterioles
72
What is the bowman's capsule?
The bowmans capsule is what surrounds the glomerulus
73
Glomerulus structure
- afferent arteriole, which is wider than efferent, enters gomerulus and splits off intoi a knot
- blood leaves via the efferent arteriole which is narrower than the afferent
74
How is fluid from the blood pass into the bowman's capsule?
ultrafiltration pushes fluid from the blood into the bowmans capsule from the gomerulus
75
What is the filter? (glomerulus and bowmans)
The filter is the barrier between the blood in the capillary and the lumen of the bowmans capsule
76
What does the barrier/filter consist of? (names)
The barrier has 3 layers:
- endotheloium of the capillary
- basement membrane
- podocytes
77
Explain the endothelium of the capillary
There are narrow gaps between the cells of the endothelium of the capillary wall.
The cells also contain fenestrations (pores)
These gaps allow blood plasma and substances dissolved to pass out of the capillary
78
Explain the basement membrane
The basement membrane consists of a mesh of cllagen fibres and gylcoproteins. This mesh acts as a filter to prevent the passage of molecules with a relative molecular mass greater than 69000. SO most proteins are held in the capillaries
79
Explain podocytes
- Podocytes are epithelial cells of the bowman's capsule
- they have finger like projections called major processes
- There are minor processes on major processes whihc hold the cells away from the endothelium of the capillary.
- These ensure there are gaps between cells
80
Describe the structure of as nephron
1. Bowmans capsule and glomerulus
2. proximal convuluted tubule
3. loop of henle
4. distal convoluted tubule
5. collecting duct
81
What happens in the proximal convulted tubule?
Selective reabsorbtion occurs in the proximal convulted tubule
82
What happens in the loop of henle ?
In the loop of henle reabosrbtion of water occurs
83
What happens in the colecting duct?
Reabosrbtion of water happens in the collecting duct and it will also get its permeabiloty altered in osmosregulation
84
What happens in the bowmans capsukle/glomerulus?
Ultra filreation occurs in he glomeruslus and bowmans capsule
85
Where does selective reabsortbition occur?
Seelctive reabosrbion poccurs in the proximal convoluted tubule
86
Where does reabsorbtion of water poccur?
Reabsorbtion of water occurs in the loop and henle and collecting duct
87
Where does ultra filtration occur?
Ultra filtration occurs in the bowmans capsule/ glomerulus
88
What happens in the distal convoluted tubule
In the distal comnvoluted tubule active transport is used to adjust the concentraions of various mineral ions
89
What is ultra foiltration?
Ukltrafiltration is th filtering odf blood at a molecular level.
90
Why is it importasnt that the afferent is wider than the efferent?
Blood flows into the glomerulus through the afferent arteriole which is widest. The difference i dimatere ensures the blood in the capillaries of the glomerulus maintains a pressure hgoher than the pressure in the bowman's capsule.
This presure differecne pushes fluid from the blood into the bowmans capsule
91
What is pushed out into the bowmans capsule and what does it contain?
Th blood plasma is pushed into the bowmans capsule:
- water
- amino aicds
- glucose
- urea
- inorganic mineral ions
92
What is left in the capillary after ultrafiltration?
Blood cells and proteins are left in the capillaries they are too big to be pushed out
93
Urine has a low water potential and is the final product. What does this mean in comparison with blood and tissue fluid?
urine has a higher concentration of solutes than found in the blood and tissue fluid
94
How are the cells lining the proximal convoluted tubule specialized for their function?
Proximal convoluted tubule lining cells:
- Microvilli increase surface area
• Membrane contains co-transporter proteins that transport glucose and amino acids with sodium ions in facilitated diffusion
-Opposite membrane of the cells close to capillaries is folded to increase surface area and has sodium potassium pumps
• Many mitochondria
95
Describe the process of selective reabsorbtion
Selective reabsorption:
• Sodium-Potassium pumps move sodium ions from the cells lining the PCT into the tissue fluid in capillary
• This reduced the concentration of sodium ions in the cytoplasm
• Sodium ions are transported into the cell, along with glucose or amino acids, by facilitated diffusion with a co transporter protein
• As the glucose and amino acid concentrations rise indies the cell, these substances diffuse out of the opposite side of the cell into the tissue fluid
• Tissue fluids substances diffuse into the blood and are carried away
• Reabsorption of salts, glucose and amino acids reduced the water potential in cells and increases it in the tubule fluid
• Water will enter cells of PCT and then into the blood too
96
What happens if larger molecules have entered the tubule?
If larger molecules like proteins have entered the tubule they can be reabsorbed by endocytosis
97
What are the two limbs of the loop of henle?
The loop of henle has a descending limb which is heading towards the medulla and an ascending limb which is heading towards the cortex
98
What is the arrangement of the loop of henle known as?
The arrangement of the loop of henle is known as a hairpin counter current multiplier system
99
Where is the water potential lowest in the loop of henle?
The water potential in the tissue fluid of the medulla at the bottom of the loop of henle is the lowest
100
Describe the process of reabsortbtion of water in the loop of henle
Reaborbtion of water from the loop of henle:
1. sodium and chloride ions are actively transported out of the top of the ascending limb into the tissue fluid
2. Water moves out of the descending limb by osmosis due to lower water potential of tissue fluid
3. This makes the fluid in the descending limb to become very concentrated so eventually at the start of the ascending limb sodium and chloride ions diffuse out into the medulla tissue fluid
4. lowers water potential in the medulla and solute concentration increases
101
Why doesn't water leave the ascending limb to follow the ions?
The ascending limb is impermeable to water so water cannot leave it
102
Why is creating a gradient of solute concentration in the medulla so important? What does it allow for?
The gradient of solute concentrations in the medulla allows for water to be continuously drawn out of the collecting duct despite the urine in the collecting duct getting more concentrated itself.
This is important as it means how much water is reabsorbed is solely dependent on permeability of collecting duct walls , not the ducts ability to lose water in the first place
103
Ultimately what is the role of the loop of henle?
It is to reduce the water potential of the medulla and create a solute gradient
104
What happens in the collecting duct after the loop of henle has done it's function?
As tubule fluid passes down the collecting duct water moves by osmosis out of the tubule fluid into the surrounding tissue fluid in the medulla. This water then enters the capillaries and is carried away
105
What does the amount of water reabsorbed depend on?
The amount of water reabsorbed depends on the permeability of the collecting duct walls
106
What is osmoregulation?
Osmoregulation is the control of the water potential in the body
107
describe the negative feedback when there is an increase in blood water potential
1. increase in water potential of the blood
2. detected by osmoreceptors in the hypothalamus
3. less ADH released from posterior pitutitary
4. collecting duct walls become less permeable
5. less water is reabsorbed into the blood
6. more urine producded
7. decrease in water potential of the blood
108
Describe the negative feedback when blood water potential decreases
1. decrease in water potential of the blood
2. osmoreceptors in the hypothalamus detetc it and shrink stimulating neurosecretory cells
3. more ADH is released from posterior pituitary
4. collecting duct walls become more permeable
5. more water is reabsorbed into the blood
6. less urine is produced
7. increase in water potential of the blood
109
What are osmosreceptors?
Osmoreceptors are sensory receptors that detect water potential in the blood
110
What happens to the osmoreceptor when the water potential of the blood is very low?
When the water potential of the blood is very low the osmoreceptors shrinks and stimulate neurosecretory cells
111
What are neurosecretory cells?
Neurosecretory cells are neurones that produce and release ADH.
112
Explain how and where ADH is produced and released
ADH is manufactured in the neurosecretory cell's cell body in the hypothalamus.
ADH moves down the axon to the terminal bulb which lies in the posterior pituitary gland and stored in vesicles
When they are stimulated action potentials get carried down their axons and cause re;lease of ADH by exocytosis
113
What happens once ADH is released?
Once ADH is released it enters the blood capillaries that run through the posterior pituitary and travels round the body acting on the cells of the collecting duct
114
On a cool day or where you have drunk a lot of fluid what happens with osmoregulation?
On a cool day you need to conserve less water so the walls of the collecting duct become less permeable so a greater volume of urine is produced and less water reabsorbed
115
On a hot day or where you have drunk little what happens with osmoregulation?
On a hot day the collecting duct walls are made more permeable so more water can be reabsorbed and a smaller volume of urine produced
116
What are 3 sources which the body gains water from?
Sources of water for the body:
- food
- drink
- respiration
117
What is ADH and what does it stand for?
ADH is antidiuretic hormone which controls the permeability of the collecting duct walls
118
Describe what happens in the collecting duct walls when there is a high level of ADH in the blood (low water potential)
1. ADH binds to recptors on cell surface of collecting duct
2. sereies of enzyme controlled reactions
3. Aqua porins in vesicles fuse to the membrane of collecting duct
4. more water reabsorbed into the blood as the walls are more permeable to water
5. less urine
119
Describe what happens in the collecting duct walls when there is a low level of ADH in the blood (high water potential)
1. cell surface membrane invaginates to crate vesicles that remove the aquaporins
2. walls less permeable
3. less water reabsorbed
4. more dilute urine
120
What are 4 causes of kidney failure?
Causes of kidney failure;
- diabetes
- heart disease
- hypertension
- infection
121
How can we assess kidney function?
Assessing kidney function;
- analyse urine (if we find proteins in the urine it indicates the filtration mechanism is damaged as proteins should be too big to get into fluid)
- Estimate glomerular filtrate rate by seeing how much fluid passes into the nephron per minute
122
What is a normal reading for glomerular filtrate rate
Normal = 90-120 cm3 min-1
123
What is the GFR reading for chronic kidney disease?
chronic kidney disease = below 60 cm3min-1
124
What is the GFR for kidney failure?
kidney failure = below 15 cm3 min -1
125
What is glomerulrar filtrate rate?
Glomerular filtrate rate is the rate at which fluid enters the nephrons
126
What happens when kidneys fail?
When kidneys fail they can no longer regulate the levels of water and electrolytes in the body or remove waste products like urea from the blood which can lead to death
127
Give 2 treatments for kidney failure and any sub types
kidney failure treatments:
- renal dialysis ( haemodialysis and peritoneal dialysis)
- kidney transplant
128
What is is kidney transplants?
Kidney transplants are where patients are given immunosuppeants to undergo major surgery to implant a new kidney
129
Pros of kidney tranplsnt
Kidney transplant:
- freedom from renal dialysis which is time consuming
- feel physically fitter
- able to travel
- improved self image
130
Cons of kidney transplant
Kidney transplant;
- immunosuppressants leave the patient vulnerable
- major surgery and anesthetic
- need for regular checks
- risk of rejection
- side effects of drugs like high blood pressure
131
Describe renal dialysis
This is where waste products, excess fluid and mineral ions are removed from the blood by passing it over a partially permeable dialysis membrane that allows exchange of substances between blood and dialysis fluid.
132
What is the dialysis fluid like?
The dialysis fluid has the correct concentrations of mineral ions, urea and water that should be in the blood plasma
133
What happens when the blood and dialysis fluid meet?
When they meet any excess substances in the blood diffuse into the dialysis fluid and any substances the blood has in n low concentrations diffuse into the blood from the dialysis fluid
134
What are the 2 types of dialysis?
Types of renal dialysis:
- haemodialysis
- peritoneal dialysis
135
Describe haemodialysis
Haemodialyis
- performed in clinic 2-3 times pr week for hours
- blood from artery passed into machine with dialysis membrane and fluid shaped like lots of capillaries
- heparin added to avoid clotting
- counter current blood- dialysis fluid to improve efficiency of exchange
- any bubbles removed
- back in through a vein
136
Describe peritoneal dialysis
Peritoneal dialysis
- carried out at home or work
- they put a dialysis membrane in the abdominal membrane
- permanent tube in abdomen
- dialysis solution poured through the tube and fills the abdominal cavity (between organs and membrane)
- solution rained after a few hours
137
What substances can be tested for in urine?
Substances tested for in urine:
- glucose
- alcohol
- recreational drugs
- HCG in pregnancy testing
- anabolic steroids
138
Describe urine analysis
Urine analysis
Any metabolic product or other substances small enough can be passed down into urine. If they are not reabsorbed they can be detected in the urine if they have a relative molecular mass of less than 69000
139
Describe how pregnancy testing works
Pregnancy tests
1. urine on test stick
2. HCG binds to mobile monoclonal antibodies attached to a blue bead
3. mobile antibodies move down the stick
4. if HCG is present it binds to fixed antibodies, holding the blue beads in place, forming a blue line
5. control blue line is also present
140
What are monoclonal antibodies?
Monoclonal antibodies are specific to one complimentary molecule
141
What is HCG?
HCG is human chorionic gonadotrophin.
It is a small glycoprotein that is found after an emrbyo is implanted into the uterine lining after as little as 6 days after conception
142
Describe anabolic steroid testing
Anabolic steroid testing
These steroids increase protein synthesis in cells resulting in the build up of cell tissue especially in muscles.
They have a half life of 16 hours and remain in the blood for days
They are small and enter the nephron easily
Testing uses urine sample analysis using gs chromatography
