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A Level Biology > 15.4 Excretion, Liver And Kidney > Flashcards

15.4 Excretion, Liver And Kidney Flashcards

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1
Q

What is excretion?

A

The removal of waste products of metabolism from the body

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2
Q

What is the main metabolic waste products in mammals?

A

Carbon dioxide

Bile pigments

Nitrogenous waste products (urea)

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3
Q

What 3 blood vessels run to the liver?

A

Hepatic artery

Hepatic vein

Hepatic portal vein

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4
Q

What is a liver cell called?

A

Hepatocyte

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5
Q

Adaptions of hepatocytes?

A

Large nuclei
Prominent golgi apparatus
Lots of mitochondria

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6
Q

What is a sinusoid?

A

Where the blood from the hepatic portal vein and hepatic artery mix which increases the oxygen content of the blood - hepatocytes therefore have enough O2 to carry out their functions.

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7
Q

What are Kupffer cells?

A

Act as resident macrophages to the liver, ingesting foreign particles and helping to protect against disease

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8
Q

What do hepatocytes do?

A

Secrete bike from the breakdown of blood into spaces called caniculi, and from these the bile drains into bile ductules which take it into the hall bladder

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9
Q

What are the 3 main functions of the liver?

A

Carbohydrate metabolism

Deamination

Detoxification

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10
Q

What is carbohydrate metabolism?

A

Close involvement of homeostatic control of blood glucose concentration. Increased BGC = insulin increases = hepatocytes convert glucose into glycogen for storage.

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11
Q

What is transamination?

A

The conversion of one amino acid into another

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12
Q

What is deamination?

A

The removal of an amine group from a molecule

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13
Q

How does deamination occur?

A

Hepatocytes deaminate excess amino acids by removing the amino group converting it first into ammonia and then into urea.

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14
Q

What cycle converts ammonia into urea and how?

A

A set of enzyme controlled reactions in the ornithine cycle

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15
Q

Describe the breakdown of hydrogen peroxide?

A

Hepatocytes contain catalase, which splits hydrogen peroxide into oxygen and water

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16
Q

Describe detoxification of alcohols?

A

Hepatocytes contain alcohol dehydrogenase that breaks down the ethanol into ethanal. Ethanal then converted into ethanoate which may be used to build up fatty acids or used in cellular respiration

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17
Q

What is cirrhosis?

A

Where normal liver tissue is replaced by fibrous scar tissue.

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18
Q

What are the 3 stages of alcoholic liver disease?

A

Alcoholic fatty liver disease

Alcoholic hepatitis

Liver cirrhosis

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19
Q

What happens in alcoholic hepatitis?

A

Patient has fatty liver along with damaged hepatocytes and sinusoids and hepatic veins become narrowed

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20
Q

What happens in fatty liver disease?

A

Big fat filled vesicles displace the nuclei of the hepatocytes and liver gets larger.

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21
Q

What happens in cirrhosis?

A

Liver tissue irreversibly damaged
Hepatocytes die and replaced with fibrous tissue, hepatocytes can no longer divide and replace themselves so liver shrinks

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22
Q

What is a nephron?

A

Filtering unit of the kidney

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23
Q

What is urine?

A

Sterile liquid produced by the kidney tubules

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24
Q

What are ureters?

A

Urine passes out of kidney through tubes called ureters

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25
Q

What is the bladder?

A

Where urine is collected and released from when the sphincter opens

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26
Q

What is the urethra?

A

The tube that Uribe passes out the body out of

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27
Q

What is the cortex of the kidney?

A

Dark outer layer, where filtering of blood takes place and has a very dense capillary network carrying blood from renal artery to nephrons

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28
Q

What is the medulla?

A

Lighter in colour

Contains tubules of nephrons that form the pyramids of the kidney and the collecting ducts

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29
Q

What is the pelvis?

A

The central chamber where urine collects before passing out down the ureter

30
Q

What happens in the nephrons?

A

Blood is filtered and the majority of filtered material is returned to the blood, removing nitrogenous waste and balancing the mineral ions and water.

31
Q

What does the Bowmans capsule do?

A

Cup shaped structure that contains the glomerulus (tangle of capillaries) more blood goes in than leaves it due to ultrafiltration

32
Q

What does the proximal convoluted tubule do?

A

The first coiled region of tubule after the bowmans capsule found in cortex.
Where reabsorption occurs

33
Q

What is the loop of henle and what does it do?

A

Long tubule loop that creates a very high solute concentration in the tissue fluid deep in the kidney medulla, descending limb runs down from Cortex through the medulla to a hairpin bend at the bottom. The ascending limb travels back up through the medulla to the cortex.

34
Q

What is the distal convoluted tubule?

A

2nd twisted tubule where water balance fine tuning takes place. Permeability of the walls varies in response to levels of ADH present in the blood. Ion balance and pH balance also controlled here

35
Q

What does the collecting duct do

A

Urine passes down the collecting Sixt through medulla to the pelvis. More fine tuning of water balance takes place - walls here are also sensitive to ADH

36
Q

Explain ultrafiltration?

A

Glomerulus supplied with blood by relatively wide afferent arterioles from the renal artery.
Blood leaves through narrower efferent arterioles which creates considerable pressure in the capillaries of glomerulus. This forced blood through capillary wall. The fluid then passes through basement membrane. Most plasma contents can pass through basement membrane but blood cells and many proteins are retained in capillary due to their size. Wall of bowmans capsule has podocytes that act as additional filter. Pedicels wrap around capillaries forming slits that make sure that any cells or plasma proteins cannot get through to the tubule itself.

37
Q

Why substances are in the filtrate?

A

Glucose
Salt
Urea
Many other substances

Conc. is isotonic to blood.

38
Q

What is reabsorption?

A

Ultrafiltration removes urea from blood but it also removes a lot of water and the mineral ions. These substances are needed by the by the body. The ultrafiltrate is hypotonic (less conc.) than blood plasma. Main function of nephron after bowmans capsule is to return most of the filtered substances back to the blood.

39
Q

What happens in PCT?

A

All the glucose, amino acids, vitamins and hormones are moved from the filtrate back into the blood by active transport. Sodium ions moved by active transport.

Chloride ions and water follow passively down concentration gradients.

Once substances removed from nephron, they diffuse into capillary network which surrounds the tubules down steep conc. gradients maintained by constant blood flow.

40
Q

Adaptations of PCT?

A

Covered in microvilli- to increase surface area over which substances can be reabsorbed.

Many mitochondria to provide the ATP needed in active transport systems.

41
Q

What does the loop of henle enable Mammals to do?

A

Produce Uribe more concentrated than their own blood.

42
Q

How are concentration gradients created?

A

Countercurrent multiplier using energy to produce concentration gradients that result in the movement of substances such as water from one area to another.

43
Q

What does the descending limb do?

A

Water moves out the filtrate down a convent gradient: upper part is impermeable to water but lower part is permeable to water and runs into the medulla. Conc of sodium ions and chloride ions in the tissue fluid of medulla gets higher and higher moving from cortex to pyramids.

44
Q

Explain how the fluid enters the descending limb as isotonic but leaves as hypertonic.

A

Filtrate enters the descending limb of LOH is isotonic to blood. Travels down the limb, water passes out of the loop into the tissue fluid by osmosis down a WP gradient, then moves down conc gradient into blood of surrounding ding capillaries (vasa recta)

DL not permeable to sodium and chloride ions and no active transport takes place there. Fluid that reaches hairpin bend is v concentrated and hypertonic to blood in capillaries.

45
Q

Describe what happens in the ascending limb?

A

First section very permeable to sodium and chloride ions as they live out concentrated solution by diffusion down conc gradient.
In 2nd section of AL sodium and chloride ions actively pumped out into medulla tissue fluid against conc gradient = very high sodium and chloride ions concentrations in medulla tissue.
Ascending limb impermeable to water so water cannot follow the ions down the conc gradient. This means the tissue fluid left in the ascending limb becomes increasingly dilute, while tissue fluid in medulla develops v high conc of ions essential to producing concentrated urine.

By time dilute fluid reaches top of ascending limb, it is hypotonic to blood again then enters DCT and collecting duct.

46
Q

What does DCT do?

A

Responds to variations in ADH - responsible for balancing the water needs of the body.

47
Q

What will happen in DCT if body lacks salt?

A

Sodium ions active pumped out of DCT with chloride ions following down an electrochemical gradient.

48
Q

What do the collecting ducts do?

A

Water moves out collecting duct by diffusion down a concentration gradient as it passes through renal medulla. As a result the urine becomes more concentrated. Level is sodium ions in the surrounding fluid increases through the medulla from cortex to the pelvis. As a result; water can be removed from collecting duct all long length producing hypertonic urine when body needs to conserve water.

49
Q

Where is ADH produced

A

Hypothalamus and then secreted into posterior pituitary gland

50
Q

What does ADH do?

A

Increases the permeability of the DCT and collecting duct to water

51
Q

Explain the mechanism of ADH?

A

ADH released from pituitary gland into the blood, carried to collecting duct to take effect. ADH binds to receptors on membrane triggers formation of cAMP as a secondary messenger inside the cell. (2ndry messenger relays signals received at CSR to molecules inside the cell.

52
Q

Why events does the cAMP?

A

Vesicles in cells lining the collecting ducts fuse with cell surface membrane on the side of the cell in contact with tissue fluid of medulla.

Membranes of these vesicles contain protein-based water channels (aquaporins) and when inserted into cell surface membrane, they make it permeable to water

This provides a route for water to move out of the tubule cells into the tissue fluid of the medulla and blood capillaries by osmosis.

53
Q

What happens to water channels is more ADH is released?

A

More ADH released means that more water channels inserted into the membranes of tubule cells: this makes it easy for more water to leave the tubules by diffusion resulting in small amount of v concentrated urine. Water returned to capillaries, maintaining WP gradient of blood and body.

54
Q

What happens when ADH levels fall?

A

ADH levels fall
Levels of cAMP fall
Water channels removed from cell membrane enclosed in vesicles again.
Collecting duct becomes impermeable to water so no water can leave.
Produces large amounts of very dilute urine and maintains WP of blood and tissue fluid.

55
Q

What is the variable permeability of the collecting ducts an example of?

A

Negative feedback system

56
Q

What happens when water is in short supply?

A

Conc of inorganic ions in blood Increases and WP of blood and tissue fluid becomes more negative. This is detected by osmoreceptors in hypothalamus of brain. Send nerve impulses to posterior pituitary gland which releases stored ADH into the blood. ADH picked up by receptors in cells of collecting duct and increases permeability of tubules to water. Water leaves the fintarte in tubules and passes into the blood; small vol of concentrated urine produced.

57
Q

What happens when there is an excess of water?

A

Blood becomes dilute and WP becomes less negative. Change detected by osmoreceptors and impulse send to posterior pituitary gland are reduced or stopped so less ADH released / its inhibited. Very little water reabsorption can take place as walls of collecting duct become impermeable to water. Large amounts dilute urine produced.

58
Q

How are monoclonal antibodies created?

A

Mouse injected with hCG so it produces the correct hormone.
The B cells that make the required antibody are then removed from the spleen and fused with myeloma (cancer cell) new fusion cell = hybridoma.
Reproduces rapidly making clones of this antibody..
These are collected, purified and then used in a variety of ways.

59
Q

What are the main stages of pregnancy tests?

A

Wick soaked in first urine of the morning.
Test contains mobile monoclonal antibodies that have coloured beads attached to them, these beads will only bind to hCG.
Of a woman is pregnant, antibodies and hCG form antibody/enzyme complex.
Urine continues along test structure until it reaches a window.
Here the immobilised monoclonal antibodies arranged in pattern (eg plus sign) that only bind to the hCG/antibody complex. If pregnant a line appears in first window.
Urine continues up the tests to second window.
Here there is a control line

60
Q

How to test for anabolic steroids?

A

Testing urine using gas chromatography and mass spectrometry. Urine sample is vapourised with a known solvent and passed along a tube. Lining of the tube absorbs the gases and is analysed to give a chromatography that can be read to show the presence of drugs.

61
Q

2 ways for drugs testing?

A

Immunoessay (monoclonal antibodies to bind to the drug or breakdown product)

Gas chromatogram/ mass spectrometer to confirm the presence of the drug.

62
Q

Symptoms of kidney infection or kidneys affected by HBP?

A

Protein in Urine - basement membrane or podocytes in bowmans capsule damaged, no longer act as filters and protein can pass through.

Blood in urine - filtering process is no longer working.

63
Q

Effects of kidney failure?

A

Loss of electrolyte balance - kidneys fail means the body can no longer excrete excess ions

Build up of toxic urea

High blood pressure

Weakened bones as calcium/phosphorous balance lost in blood.

Stiffness in joint as abnormal proteins build up in blood.

Anaemia : kidneys involved in production of hormone that stimulates the formation of RBC.

64
Q

How to measure Glomerular Filtrate rate?

A

Simple test into level of creatinine in the blood. Creatinine is a breakdown product of muscles and is used to give an estimate of estimated GFR.

Higher creatinine levels = kidneys not working properly

65
Q

What is dialysis?

A

When the fu ruin if the kidney is carried out artificially.

66
Q

Explain haemodialysis?

A

Dialysis machine, blood leaves artery and flows into dialysis machine where if flows through partially permeable dialysis membranes which mimic the basement membrane.
On the other side of membrane is dialysis fluid. During dialysis it is vital that the patient loses excess urea and mineral ions that have built up in blood. Cannot lose useful substances like glucose and some mineral ions. Dialysis fluid has same plasma levels of glucose and mineral ions so excess ions diffuse out down a concentration gradient.
Fluid contains no urine to create steep conc gradient for urea to exit the kidney.
Counterflow current

67
Q

Why is haemodialysis bad?

A

Takes about 8 hours
Had to be repeated regularly
Several times a week for several hours
People on dialysis must manage diet carefully eating low protein and salt

68
Q

What is peritoneal dialysis?

A

Peritoneal dialysis is done inside the body, it uses the natural membranes formed by lining of abdomen ( the peritoneum). The dialysis fluid is introduced using a catheter. It is left for several hours to allow excess ions and urea to diffuse out of capillaries into dialysis fluid. Fluid then drained off and discarded.

69
Q

Advantages of kidney transplant?

A

Function normally for many years
No dialysis
Regain a normal life.

70
Q

Disadvantage of kidney transplant?

A

Risk of rejection
Immunosuppressant drugs for life
Don’t last forever, around 9-10 years
Very short supply of kidneys

71
Q

Dialysis or transplant?

A

Dialysis is more readily available and patients can lead a relatively normal life other than having to watch what they eat and visits to the hospital. Long term dialysis more expensive than transplant and can cause more damage to body.

Transplant patients free from the restrictions of regular dialysis sessions. Low supply of kidneys, can get living donors or receive organs from those who dies suddenly.

A Level Biology (22 decks)

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