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F214 > 2. Excretion > Flashcards

2. Excretion Flashcards

0
Q

What produces waste products. Name 2 examples of waste products.

A

Metabolic processes in the body produce waste products. CO2 and urea.

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1
Q

Define excretion

A

The removal of waste products from the body.

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2
Q

What is the main organ involved in excretion?

A

The liver.

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3
Q

Name the main features of the liver.

A

The hepatic artery.
The hepatic vein.
The hepatic portal vein.
Bile duct.

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4
Q

What is the function of the hepatic artery?

A

Supplies the liver with oxygenated blood from the heart so the liver has enough oxygen to respire and produce ATP.

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5
Q

What is the role of the hepatic vein?

A

The hepatic vein takes deoxygenated blood away from the liver.

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6
Q

What is the role of the hepatic portal vein?

A

The hepatic portal vein brings blood from the duodenum and ileum so it’s rich in the products of digestion, the liver filters out and immediately breaks down harmful substances into safe products which can be excreted.

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7
Q

What is the role of the bile duct?

A

The bile duct takes bile (a fat emulsifier) to the gall bladder tone stored.

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8
Q

Describe the gross structure of the liver.

A

The liver is made up of liver lobules made of cells called hepatocytes that are arranged in columns radiating out of the center.

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9
Q

Describe the features of a liver lobule.

A

Each lobule has a central vein in the middle that connects to the hepatic vein.
Branches of the hepatic artery, hepatic portal vein and bile duct also connect to each lobule.
The hepatic artery and hepatic portal vein are connected to the central vein by capillaries called sinusoids.

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10
Q

Where are harmful substances removed from the blood in the liver? What happens once the substances are broken down?

A

The harmful substances and oxygen are removed as they pass through the sinusoids. They are broken down and renter the blood which runs to the central vein of the lobules which connects to the central vein of other lobules, which forms the hepatic vein.

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11
Q

What are the role of kupffer cells? Where are they found?

A

Kupffer cells are attached to the walls of the sinusoids. Kupffer cells break down old red blood cells and remove bacteria from the blood.

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12
Q

How is the bile duct connected to the central vein?

A

The bile duct is connected to the central vein through tubes called the canaliculi.

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13
Q

Why does deamination occur?

A

The body cannot store excess amino acids. However amino acids contain a lot of chemical potential energy and discarding them would be a waste.

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14
Q

Describe the process of deamination.

A

Excess amino acids are transported to the liver and the potentially toxic amine group is removed.
This forms ammonia which is converted to urea to be excreted and the remaining keto acid can be safely used in respiration.

DEAMINATION
Amino acid + oxygen -> keto acid + ammonia

FORMING UREA - ornithine cycle
2NH3 + CO2 -> CO(NH2)2 + H2O

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15
Q

Stage 1 of the ornithine cycle forms citralline and water, what is used in production?

A
  1. Ornithine
  2. NH3
  3. CO2
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16
Q

Stage 2 of the ornithine cycle produces Arginine and water, what is used in production?

A
  1. NH3

2. Citralline

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17
Q

Stage 3 of the ornithine cycle produces ornithine and urea, what is used in production?

A
  1. Arginine

2. Water

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18
Q

Hydrogen peroxide is broken down by the liver. What is the overall equation, the enzyme needed and the turnover rate?

A

2H2O2 -> 2H2O + O2
Enzyme : catalase
Turnover : 5 million / min

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19
Q

Where is alcohol detoxified in the body?

A

Alcohol is detoxified in the liver by hepatocytes.

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20
Q

Detoxification of alcohol is a 3 step process. Name the intermediate products, the enzymes used and the final product.

A

In stage 1 ethanol is broken down by alcohol dehydrogenase to form ethanal. During the process 2 H atoms reduce 2 molecules of NAD. In stage 2 of alcohol detoxification ethanal is broken down by ethanal dehydrogenase into ethanoic acid. Once again reducing 2 molecules of NAD.
The final step of detoxification is the production of acetyl coenzyme A by combining acetyl and coenzyme aS.

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21
Q

What condition can result through heavy detoxification and why?

A

Fatty liver. The NAD which is reduced is usually used in the liver to break down fatty acids for use in respiration. If this does not happen then there is a build up of lipids in the hepatocytes of the liver , leading to fatty liver.

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22
Q

What is the role of the renal artery?

A

The renal artery is where blood enters the kidney which then passes through the capillaries in the cortex of the kidneys.

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23
Q

Describe selective reabsorption and ultra filtration.

A

As the blood passes through the capillaries substances are filtered out of the blood and into nephrons. Large molecules such as lipids and proteins do not pass into the nephrons. Some useful substances such as glucose are reabsorbed into the blood from the tubules in the medulla.

24
Q

What happens to unwanted substances which pass into the nephron?

A

They are not reabsorbed, they pass along the nephron into the ureter to the bladder where they are expelled as urine.

25
Q

Where is blood ultra-filtered in the nephron?

A

The blood is filtered at the start of the nephron in the bowman’s capsule.

26
Q

What is the bowman’s capsule?

A

The bowman’s capsule is the cup shaped end of a nephron tubule.

27
Q

What are the names of the blood vessels which take the blood to and away from the glomerulus? What are the differences between them?

A

The afferent arteriole takes blood to the glomerulus, the efferent arteriole takes blood away from the glomerulus. The afferent arteriole is WIDER than the efferent arteriole so the blood in the glomerulus is under high pressure in order to facilitate ultrafiltration.

28
Q

How does a molecule enter the nephron?

A

A molecule has to pass through three layers: the capillary wall, the basement membrane and the epithelium of the bowman’s capsule.

29
Q

What is the limit size of molecules passing through the basement membrane?

A

Molecules with a molecular mass larger than 69,000 are too large to pass through the basement membrane, this includes RBCs and proteins.

30
Q

What are podocytes? How are they adapted for their role?

A

Podocytes are the epithelial cells of the bowman’s capsule. They have many finger like projections called major processes which ensure there are gaps between the cells which fluid from the blood in the glomerulus can pass between.

31
Q

Where does selective reabsorption take place?

A

Selective reabsorbtion takes place along the majority of the nephron this mainly includes the proximal convoluted tubule, the loop of henle and the distal convoluted tubule.

32
Q

How is the proximal convoluted tubule adapted for selective reabsorbtion?

A

The epithelium of the wall of the pct is lined with microvilli which provide a large surface area for the reabsorption of useful materials from the filtrate into the blood.
The microvilli facilitate selective reabsorption.

33
Q

How are substances such as Na+, water and glucose transported out of the PCT into the blood?

A

Na+ is actively transported, glucose and amino acids are transported into the epithelial cells of the PCT through co-transporter proteins. Inside the cell the water potential falls and water in the proximal convoluted tubule diffuses into the cell. The glucose and amino acids diffuse across the membrane into the blood. Water moves down the water potential gradient into the blood.
ATP is broken down into ADP and Pi in order to actively transport K+ into the cell to move sodium ions into the blood. This is why there are many mitochondria in the cell.

34
Q

What happens to some large molecules in the PCT?

A

Reabsorbed by endocytosis.

35
Q

What handles the regulation of water content?

A

The kidney. More specifically the loop of henle and osmoreceptors in the hypothalamus.

36
Q

What is the mechanism called which helps the loop of henle to reabsorb water?

A

The countercurrent multiplier mechanism.

37
Q

What are the two parts of the loop of henle called?

A

The ascending limb (the second part) and the descending limb.

38
Q

Describe how the loop of henle reabsorbs water into the blood.

A
  1. Near the top of the ascending limb sodium and chloride ions are actively transported into the medulla. The ascending limb is impermeable to water so a very low water potential is formed in the medulla.
  2. Because there is a low water potential inside the medulla than in the DESCENDING limb, water moves out of the descending limb into the medulla by osmosis down the water potential gradient. The glomerular filtrate becomes more concentrated as a result but the ions cannot diffuse out of the descending limb as it is impermeable to ions.
    The water which diffused out of the descending limb into the medulla is reabsorbed into the blood through the surrounding capillary network.
    Near the bottom of the descending limb sodium and chloride ions diffuse into the medulla further lowering the water potential in the medulla.
39
Q

What feature of a nephron might an animal living in arid conditions have?

A

A long loop of henle, this allows more ions to be pumped and more ion to move via osmosis out of the descending limb.

40
Q

What is water gained from in the body?

A
  1. Metabolism
  2. Food
  3. Drink
41
Q

How might water be lost from the body?

A
  1. Urine
  2. Sweat
  3. Water vapour in exhaled air
  4. Faeces
42
Q

How is water specifically regulated?

A

By altering the permeability of the collecting duct.

43
Q

How is the permeability of the collecting duct changed?

A

The permeability of the collecting duct is mostly managed through the action of the hormone Antidiuretic hormone (ADH) in the blood.

44
Q

How does ADH act on the membrane of the collecting duct?

A

The membrane of the wall has receptors for ADH which causes a series of enzyme controlled reactions which insets aquaporins onto the surface of the membrane.

45
Q

Describe the steps which makes the collecting duct more permeable to water.

A
  1. Water concentration of the blood is monitored by osmoreceptors in the hypothalamus of the brain. If the water potential of the blood is too low they shrink stimulating neurosecretory cells in the hypothalamus.
  2. When the neurosecretory cells are stimulated they send action potentials down their axons and cause the release of ADH from the terminal bulb of the posterior pituitary gland.
  3. The ADH is detected by cell surface receptors.
  4. “Enzyme controlled reactions” moves vesicles containing aquaporins to the edge of the membrane.
  5. Vesicles containing water-permeable channels (aquaporins) fuse to the membrane.
  6. More water can be reabsorbed into the blood.
46
Q

What are the common reasons for kidney failure.

A
  1. Diabetes mellitus (1 and 2)
  2. Hypertension (high blood pressure)
  3. Infection
47
Q

What happens if the kidney fails?

A

It can no longer remove excess water and certain waste products. The body’s water levels are no longer controlled.

48
Q

How can kidney failure be treated?

A
  1. Dialysis

2. Kidney transplant

49
Q

What is the main concept of dialysis?

A

Blood passes over a dialysis membrane, the membrane is partially permeable, on the other side of the membrane is the dialysis fluid the dialysis fluid contains a mixture of the correct concentrations of salts, urea, water and other substances.
Any substances in excess diffuses down the concentration gradient and into the dialysis fluid.
Substrates in low concentration in the blood diffuse across the partially permeable membrane and into the blood.

50
Q

What are the 2 types of dialysis?

A
  1. Haemodialysis

2. Peritoneal dialysis (PD)

51
Q

Describe haemodialysis.

A

Blood from a vein is passed into a dialysis machine. Heparin is added to the blood to avoid clotting and bubbles in the blood are carefully removed before the blood is returned.

52
Q

Describe peritoneal dialysis.

A

The filter is the body’s own abdominal membrane (peritoneum). A permanent tube is implanted into the abdomen and dialysis fluid is added to fill the spaces between the organs. Over time the dialysis fluid exchanges components such as glucose and water across the peritoneum.

53
Q

What are the advantages of a kidney transplant?

A
  1. Freedom from time consuming dialysis.
  2. Diet is less limited
  3. Feel better physically.
  4. A better quality of life e.g. Being able to travel
  5. No longer seeing oneself as being chronically ill
54
Q

What are some disadvantages of kidney transplants?

A
  1. Need immunosuppressants for the life of the kidney
  2. Need major surgery under general anaesthetic
  3. Risks of surgery include infection, bleeding and damage to surrounding tissue
  4. Frequent checks for signs of organ rejection.
  5. Side effects: anti rejection medicines cause fluid retention and high blood pressure. Immunosuppressants increase susceptibility to infections.
55
Q

How does pregnancy testing work?

A

A small pregnancy hormone called human chorionic gonadtrophin (hCG) I secreted by embryos. The glycoproteins is small enough that it can enter the nephron and be excreted in the urine.
On a pregnancy test strip exists specific antibodies which only bind to the hCG. These antibodies are tagged with a blue bead. If an hCG-antibody complex forms it will move up the strip until it reaches a band of immobilised antibodies where it stops. This forms a blue line indicating a positive result. A control line is also present to compare to and confirm a positive result.

56
Q

Describe testing for anabolic steroids.

A

Anabolic steroids can give athletes an advantage by increasing protein synthesis in cells and forming a bulk of muscle. Anabolic steroids are small and can enter the urine. They can then be tested for using gas chromatography.

57
Q

What are neurosecretory cells?

A

Neurosecretory cells are specialised neurones that produce and release ADH. The ADH is manufactured in the cell body of these cells which lies in the hypothalamus. The ADH flows down the axon to the terminal bulb of the posterior pituitary gland where it is stored until needed.

F214 (4 decks)

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