5.2 Excretion Flashcards
1
Q
What is excretion?
A
The removal of metabolic waste from the body
2
Q
What are three excretory products?
A
Carbon dioxide, urea and bile pigments
3
Q
What are the main four excretory organs?
A
Lungs, liver, kidneys and skin
4
Q
What is the effect on the blood of an increase in carbon dioxide concentration?
A
Decrease in ph making the blood more acidic
5
Q
What is the response to an increase in carbon dioxide concentration in the blood?
A
Increased breathing rate: The CO2 diffuses into the alveolis and is excreted from breathing out
6
Q
What is the name for the basic functional unit of the liver?
A
Lobules
7
Q
What is another name for liver cells?
A
Hepatocytes
8
Q
What are the 4 vessels associated with the liver?
A
Hepatic vein, hepatic portal vein, hepatic artery and bile duct
9
Q
Which liver vessel is intra-lobular? (Inside the lobule)
A
The hepatic vein
10
Q
Which liver vessels are inter-lobular? (around the outside of the lobule)
A
The hepatic portal vein, hepatic artery and bile duct
11
Q
What are the chambers in the lobules through which blood from the hepatic portal vein and hepatic artery pass?
A
Sinusoids
12
Q
What are the chambers in the lobules through which bile is transported to the bile duct?
A
Canaliculi
13
Q
What are the resident macrophages called in the liver?
A
Kupffer cells
14
Q
What is the function of a Kupffer cell?
A
Break down and recycle old red blood cells
15
Q
What are three functions of the liver?
A
- Carbohydrate metabolism
- Deamination of excess amino acids
- Detoxification
16
Q
What is a metabolic reaction?
A
A reaction that takes place within the cell
17
Q
How is CO2 made?
A
Produced by cells in the body in respiration
18
Q
How many blood supplies does the liver have?
A
-Two, the hepatic artery and the hepatic portal vein
19
Q
What is the purpose of the hepatic artery?
A
The hepatic artery brings oxygenated blood to the liver
20
Q
What is the purpose of the hepatic portal vein?
A
-The hepatic portal vein brings nutrient rich blood to the liver from the gut
-The blood is rich in glucose, amino acids and fatty
acids
-This is because these nutrients are by-products of digestion that are absorbed in the small intestine (The gut) into the blood were it is carried to the liver
21
Q
What does the liver do?
A
The liver regulates the concentrations of all these food or toxin molecules to avoid the concentrations of them from going straight into the blood stream when they could be to high or low
22
Q
What are sinusoids
A
The channels between the rows of cells that lead to the intra-lobular vessel at the top
23
Q
What does the inter-lobular vessel, the hepatic artery provide?
A
The hepatic artery brings blood containing oxygen needed for respiration and ATP production
24
Q
What is the purpose of the inter-lobular vessel, the hepatic portal vein?
A
The hepatic portal vein brings varying levels of nutrients as well as toxins to the liver in the blood
25
What are the liver cells that surround the inter-lobular vessels called?
Hepatocytes
26
What is the functions of hepatocytes?
- Hepatocytes are chemical reaction cells meaning that they need oxygen as their job is active
- Hepatocytes take in chemicals for a reaction and then release the products of the reaction
- The hepatocytes are able to remove and insert nutrients into the sinusoids in order to regulate the levels of the nutrients
27
What are kupfer cells and where are they located?
- Kupffer cells are modified macrophages (white blood cells) that are found in sinusoids
- The function of these resident macrophages is to process dead red blood cells
- They take haemoglobin from these dead red blood cells and convert it into the product bilirubin
28
Where is the waste products that are removed by the hepatocytes moved to?
The toxic waste products are moved to the bile canaliculi
29
What does the inter-lobular vessel, the bile duct do?
The bile duct drains into the gall bladder which is full of bile that will later be emptied into the small intestine
30
Why is not all of the process of releasing faeces not considered excretion?
Only part of the process is excretion as bile is the only excretory product used, this is when the bile salts are added before the faeces is released
31
Why is faeces not an excretory product?
Faeces is not directly formed from the major organs responsible for excretion (The liver, kidneys, lungs and skin) therefore it is not a result of metabolic reactions inside the body
32
What is faeces made up of?
Faeces is the remains of food that was not digested in the small intestine
33
What happens to the bilirubin that is made from the haemoglobin in dead rbc's?
The bilirubin is put into the bile canaliculi where it exits the bile
34
What colour is bilirubin?
Yellow/brown
35
How can liver damage be seen from external appearance? (jaundice)
A yellow/brown appearance in the skin or the corners of the eye can be an indicator of liver damage for the person
36
What is the structure of hepatocytes?
- Cuboidal shape
- Has lots of mitochondria - as they are metabolically active
- Have microvilli on the surface, gives a larger surface area for an increase in rate of exchange from the blood
- Cytoplasm is densely packed with organelles
37
What is the functions of hepatocytes?
- Controls blood glucose levels
- Controls amino acid levels
- Control lipid levels
- Synthesis of plasma proteins (proteins in the blood for example fibrinogen)
- Synthesis of cholesterol
- Synthesis of RBC's in the foetus
- Detoxification of alcohol and drugs
- Breakdown of hormones
- Synthesis of urea
38
How is alcohol detoxified?
Ethanol is oxidised to ethanal and then to ethanoic acid (This process requires NAD coenzymes and dehydrogenase enzymes)
39
What is urea made from?
Urea is made up of excess amino acids that cannot be stored
40
What is the process of deamination?
Amino acids -> Keto acid and ammonia
- Keto acid is useful as it can be respired to produce energy
- Ammonia must be removed as it is toxic and soluble
- Ammonia the enters the ornithine cycle to be made into urea
41
What is the process of the ornithine cycle?
Ammonia + Carbon dioxide -> Urea + water
| The cycle is: ACWAWWU
42
What is the pneumonic device used for the ornithine cycle?
- All Cats Whine And Wiggle When Upset
- Ammonia in
- CO2 in
- Water out
- Ammonia in
- Water out
- Water in
- Urea out
43
What happens to the urea that is made in the ornithine cycle?
The urea enters back into the blood and travels to the kidney
44
What do the hepatocytes do during the process of the ornithine cycle?
The hepatocytes take the highly toxic ammonia from excess amino acids and they produce urea which is less toxic
45
Where is urea made and where is it removed?
Urea is made in the liver and removed in the kidneys
46
What is the name of the functional unit of the kidney?
Nephron
47
What is the afferent arteriole?
The arteriole with the wider lumen that brings blood to be filtered towards the nephron
48
What is the efferent arteriole?
The arteriole with the narrower lumen that takes blood away from the glomerulus
49
What is the name of the capillaries that surround the majority of the nephron?
The peritubular, this is used for reabsorption of filtered substances
50
What is the difference between the renal artery and the renal vein?
The renal artery carries blood away from the heart to the glomerulus and the renal vein travels away from the nephron to the other parts of the body
51
What is the name of the capsule that surrounds the glomerular capsule?
The Bowman's capsule
52
What is the proximal convoluted tubule?
The first tubule closest to the glomerulus, this tubule is where selective reabsorption occurs
53
What is the distal convoluted tubule?
The second tubule that comes after the loop of henle to the glomerulus, this tubule is responsible reabsorption and regulating ion concentrations in the
blood
54
Where does ultrafiltration occur?
Around the glomerulus and the arterioles
55
Where does selective reabsorption occur? (of amino acids and glucose)
The proximal convoluted tubule
56
What is the function of the descending and ascending limbs of the loop of henle?
To make the kidney medulla more salty
57
What is the cortex and what is the medulla of the kidneys?
- The cortex is the top part of the nephron, containing the bowmans capsule, glomerulus, afferent & efferent arteriole, the proximal convoluted tubule, the distal convoluted tubule and the top half of the collecting duct
- The medulla is the bottom part of the nephron, containing the loop of henle and the bottom half of the collecting duct
58
What is the basic description of the process occurring in the nephron of the kidneys?
- The system will:
- Filter out everything
- Reabsorb the needed things
- Reabsorb the maximum amount of water
59
Why must the kidney filter out everything first?
- In case the body encounters a new toxin which is not known to be harmful
- The system overcomes this by filtering out everything and only reabsorbing the known good things
60
What is the process of ultrafiltration?
-Filtration of water and other liquids occurs and they filtered out of the capillaries in the glomerulus and into the lumen of the bowman's capsule under a high hydrostatic pressure
61
Why must the lumen of the efferent arteriole be narrower than the afferent arteriole?
Because it causes there to be a build up of hydrostatic pressure in the efferent arteriole due to it being narrower
62
What are podocytes?
- Podocytes are the cells in Bowman's capsule that wrap around capillaries of the glomerulus.
- Podocytes make up the epithelial lining of Bowman's capsule, the third layer through which filtration of blood takes place
63
How does fluid cross from the capillaries to the lumen of the bowman's capsule during ultrafiltration?
- The fluid must cross three layers: The endothelial cells in the capillaries, the basement membrane and the podocytes
- Firstly the fluid exits the fenestrated capillaries into the pores in the endothelial cells
- The fluid then must go through the basement membrane to the podocytes
- The fluid travels through the podocytes that hold the basement membrane in place
64
How does the structure of the capillary walls affect ultrafiltration?
- The rate of ultrafiltration rate is increased due to:
- The hydrostatic pressure due to the difference in lumen sizes
- The capillary walls are fenestrated so there are many pores for the fluid to pass from the capillaries to the basement membrane of the bowman's capsule
65
What is the basement membrane?
-A sieve type matrix of collagen fibres and
glycoproteins
-The basement membrane only allows molecules that have a molecular mass smaller than 69,000 as those with a larger mass than this are blocked from passing
through
-H2O, glucose and ions can pass through but proteins and cells cannot as they have a mass larger than 69,000
66
What is glomerular filtrate?
- The fluid that enters the proximal convoluted tubule after ultra filtration
- Essentially the same as blood plasma but without proteins and cells as they are filtered out at the basement membrane
67
What is the process of selective reabsorption in the proximal convoluted tubule?
-The glomerular filtrate travels down the curves in the lumen of the PCT
-A sodium potassium pump uses ATP to move Na+ ions into the blood from the cells in the wall of the PCT
-There is now a low concentration of Na+ ions in the PCT wall cells
-This creates a concentration gradient between the cells and the lumen in the PCT so the Na+ ions move down the concentration gradient into the cells in the
PCT
-The Na+ ions use a cotransport protein that allows the Na+ ions to enter the cell but only with the glucose and amino acids along with it meaning that the amino acids and glucose is removed from the glomerular filtrate, moved into the cell and then passively back into the blood (peritubular capillaries)
-Water then follows from the PCT down the water potential gradient into the cells by osmosis
68
What is the aim of selective reabsorption in the PCT?
The aim of selective reabsorption is to reabsorb amino acids and glucose from the glomerular filtrate back into the blood
69
How are the PCT wall cells adapted for its function?
-The PCT wall cells have many mitochondria to provide
ATP for the sodium potassium pump used in selective reabsorption
-The PCT wall cells microvilli on both faces, these hair like structures around the outside of the cell increases surface area and therefore increases the rate of transport
70
What is the loop of henle in biological terms?
The loop of henle is a hairpin counter-current multiplier system, this means it makes the medulla salty (with a low WP)
71
What is the role of the descending limb?
To concentrate the tubule fluid to make it saltier
72
What is the role of the ascending limb?
To decrease the WP of the medulla
73
What is the whole process of substances being removed and entering the loop of henle?
1) Active transport of sodium and chlorine out of the ascending limb
2) This causes a high concentration of Na+ and Cl- in the medulla
3a) Na+ and Cl- then diffuse into the descending limb down the concentration gradient
3b) Water leaves the descending limb via osmosis from a high WP to a lower WP outside the descending limb
4) The previous steps mean that as the fluid goes round the loop of henle up to the ascending limb it has already been concentrated as the fluid has a high concentration of Na+ and Cl-
5) This means that more Na+ and Cl- can be pumped out and then re-enter the descending limb like in step 1)
6) This system multiplies the concentration of Na+ and Cl- ions in the loop of henle over and over again so it is very salty, at the bottom it is saltier so there is a lower WP
7) The medulla becomes very salty due to the high concentration of Na+ and Cl- ions, this causes water to exit the collecting duct down the WP gradient where it is reabsorbed back into the capillaries so the body retains the water
74
How is the ascending limb adapted for its function?
The ascending limb is impermeable to water
| This means that the water cannot escape even when the sodium and chlorine ions are pushed out
75
How are desert animals adapted regarding their loop of henle?
- Desert animals will have a longer loop of henle so that their their urine is as concentrated (With salt) as possible and limit the amount of water they loose
- This is because more water leaves the longer descending limb and it is reabsorbed into the blood rather than being lost as urine
- The medulla is also much more salty (concentrated) meaning that more water exits the collecting duct and is also reabsorbed into the capillaries
76
What is the end product out of the collecting duct?
- Urine, made up of urea, the left over water and the waste products
- The urine is then transported to the bladder
77
How is the process of making urine and reabsorbing water regulated?
Using osmoreceptors
78
How do osmoreceptors regulate the reabsorption of water?
-Osmoreceptors in the hypothalamus detect a fall in water potential
-The osmoreceptors then signal to a neurosecretory
cell in the pituitary which makes ADH
-ADH is then flowing in the blood
79
What is the whole process of how ADH works to regulate the reabsorption of water after being secreted from the neurosecretory cells?
1) ADH leaves the blood stream and binds to receptors on the cells of the collecting duct
2) This triggers vesicles containing aquaporins to move and fuse with the membrane of the collecting duct cells
3) This causes more water to be reabsorbed into the blood as the permeability of the membrane is
increased
4) Therefore urine is more concentrated
80
How HCG present in urine?
- HCG is present in the blood of pregnant women
- HCG has a molecular mass lower than 69,000 so it is filtered out the blood by the glomerulus and it is passed out of the body in urine
81
How does a pregnancy test work?
1) Urinate on the stick
2) HCG binds to the mobile antibodies that are also bound to a blue dye
3) The mobile antibodies move up the stick
4) The HCG + blue antibody complex binds to the fixed, immobilised antibodies
5) This causes a blue band appearing at the first level
6) Blue antibodies without the HCG bind to the second band causing a control blue line to appear as well
- So a negative would show the second band only &
- A positive would show both the second control band and the first band that indicates HCG is present
82
What is dialysis?
-Dialysis is a treatment to replace two vital functions: removal of fluids and filter body toxins
-Dialysis is needed when kidney function is at about
15% the kidneys need help filtering blood
83
What is haemodialysis?
- A treatment that replaces kidney function
- Blood from the arteries is removed and pumped to keep it moving
- Heparin (an anticoagulant) is added to prevent clotting
- Blood passes into the machine through an artificial partially permeable membrane
- The membrane filters the fluid and creates a dialysis fluid which has the right concentrations of glucose ions and urea
- Urea then diffuses from the blood to the dialysis fluid and then the blood is returned to a vein with the correct concentrations of substances
84
What is peritoneal dialysis?
- A tube is surgically implanted into the abdomen of a patient
- A bag is then connected which sends dialysis solution through the tube into the peritoneal cavity surrounding the organs
- The abdominal membrane then acts as a filter and the solution is drained after a few hours
- The blood ends up with the correct concentrations of substances
- This type of dialysis can keep patients alive long enough to receive a kidney transplant and it can be done at home meaning the patient has a better quality of life
