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Biology A level > Excretion > Flashcards

Excretion Flashcards

1
Q

What is excretion

A

removal of metabolic waste (mainly CO2 and urea) from the body

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2
Q

What are the main capillaries connecting to the liver

A

Hepatic vein
Hepatic Portal vein
Hepatic artery
Bile duct

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3
Q

How can you differentiate between the hepatic artery and portal vein

A

Portal vein is thicker and has branches

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4
Q

Features of hepatic vein

A

To vena cava
deoxygenated
low pressure
high in CO2

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5
Q

Features of portal vein

A

From digestive system
deoxygenated
low pressure
high CO2
Carries products of digestion

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6
Q

Features of Hepatic artery

A

From aorta
Oxygenated
High pressure

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7
Q

Features of bile duct

A

To gall bladder

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8
Q

What is the structure of a lobule in order to absorb substances from blood

A

Blood flows through sinusoids from hepatic artery and portal vein to the central vein
Hepatocytes absorb O2 and waste substances from blood
Hepatocytes in rows of 2 to decrease diffusion pathway

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9
Q

What are hepatocytes

A

liver cells

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10
Q

What are sinusoids

A

Spaces in between hepatocytes

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11
Q

What is the structure of the lobule like to help bile movement

A

Bile flows in opposite direction to blood along canaliculi
Connects to bile duct and flows to bladder

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12
Q

What are kupffer cells

A

Large phagocytic macrophages that line the inside of sinusoids that breakdown erythrocytes and bacteria

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13
Q

What are the functions of the liver

A

Control of blood glucose, amino acid and lipid levels
Synthesis of Bile
Storage of Glycogen
Detoxification of Alcohol and drugs
Breakdown of hormones
Formation of Urea

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14
Q

How are nitrogenous compounds excreted

A

Amino acids are deaminated into ammonia and keto acids
Ammonia is converted into urea through the ornithine cycle
Urea then enters blood plasma and is filtered by the kidneys into urine

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15
Q

What is the process of the ornithine cycle

A

Ammonia is combined with CO2 and forms urea and H2O
Occurs in the mitochondria and cytoplasm

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16
Q

Why is Ammonia converted into urea

A

ammonia is very soluble and toxic so it is safer storage as urea

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17
Q

How is alcohol detoxified

A

Ethanol -> ethanal + 2NADH
Ethanal -> acetic acid + 2 NADH
Acetic acid can be converted into acetate and used in Krebs cycle

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18
Q

What is the consequence of excess alcohol consumption

A

Liver cirrhosis - hepatocytes die and are replaced by scar tissue, obstructing blood flow through sinusoids

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19
Q

What compounds are detoxified

A

Hormones
Drugs
Alcohol
Hydrogen Peroxide

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20
Q

What are the parts of the nephron

A

Bowman’s Capsule
Proximal and Distal convoluted tubule
Collecting duct
Loop of Henle

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21
Q

What structures of the nephron are in the cortex

A

Bowman’s capsule, distal and proximal convoluted tubule and part of the collecting duct

22
Q

What structures of the nephron tubule are in the medulla

A

Loop of Henle
Collecting duct

23
Q

What is the pathway of blood in the nephron

A

Renal artery -> afferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries -> renal vein

24
Q

What do cells in the proximal convoluted tubule look like

A

Epithelial cells in cortex
Contain microvilli
No plasma membranes visible between cells

25
Q

What is the structure of cells in the loop of henle like

A

Thin epithelial cells in the medulla

26
Q

What are the cells in the distal convoluted tubule like

A

Epithelial cells in the cortex
No plasma membranes visible between cells

27
Q

What are the cells in the collecting duct like

A

Epithelial cells with clearly outlined membranes between cells

28
Q

What are the excretory roles of the kidney

A

Ultrafiltration
Selective reabsorbtion

29
Q

What is ultrafiltration

A

The filtration of small molecules from the blood
Occurs in the Bowman’s capsule

30
Q

How does ultrafiltration start

A

Diameter of lumen in efferent arteriole is smaller than that of afferent arteriole
Causes hydrostatic pressure>oncotic pressure in glomerulus - blood forced into bowman’s capsule

31
Q

How is blood in glomerulus separated from glomerular filtrate

A

there are three layers
1. endothelium cells with pores
2. Basement membrane
3. Podocytes (epithelium cells)

32
Q

Features of the basement membrane

A

Made of collagen and glycoproteins
Stops molecules with a relative molecular mass over 69,000

33
Q

What are podocytes

A

Foot shaped cells with filtration slits

34
Q

Features of selective reabsorbtion

A

mostly occurs in PCT
85% of filtrate is reabsorbed into blood

35
Q

How does selective reabsorption occur

A
  1. Na+/K+ pump removes Na+ from cells lining the PCT and pumps it into the blood
    - lowers Na+ conc
  2. Na+ moves by facilitated diffuses into PCT cells from filtrate through a cotransporter protein that brings glucose/amino acids
  3. Conc of glucose/amino acids inc so they diffuse out into the capillary
  4. Reabsorption of Na+ and other molecules lowers water potential in PCT cells so water is reabsorbed by osmosis
36
Q

Role of Loop of Henle

A

Involved in reabsorption of water
Makes kidney tissue more concentrated - creating water potential gradient
Hairpin counter current multiplier

37
Q

How is reabsorption of water set up for by the loop of Henle

A

Ascending limb actively transports Na+ and Cl from filtrate to tissue fluid
Walls of ascending limb are impermeable to water so this leads to an inc solute conc in tissue fluid
Walls of descending limb are permeable to water so water leaves filtrate by osmosis into tissue fluid - solute conc in filtrate increases
Bottom of ascending limb is permeable to Na and Cl ions, so these diffuse out of filtrate into tissue fluid
This means the tissue fluid surrounding collecting duct will be conc - meaning water moves out by osmosis

38
Q

What is diuresis

A

The production of large volumes of dilute urine

39
Q

What is diuretic

A

Aids diuresis

40
Q

What is ADH

A

prevents diuresis - promotes reabsorption of water

41
Q

What happens when there is an increase in water potential in blood

A

detected by osmoreceptors in hypothalamus
less ADH released from posterior pituitary gland
Less permeable collecting duct walls
Less water reabsorbed into blood and more urine produced

42
Q

How is urine used in pregnancy testing

A

hCG is produced when pregnant
hCG has a molecular mass less than 69,000 so it’ll pass through basement membrane in ultrafiltration
Monoclonal antibodies on test have coloured beads, they will bind to hCG if present creating an hCG/antibody complex
Immobilised proteins are arranged in a pattern and will bind to the complexes (causing a line to show up)

43
Q

How are anabolic steroids tested for

A

Steroids are excreted in urine and tested using gas chromatography and mass spectrometry

44
Q

What problems arise from kidney failure

A

Loss of electrolyte balance
Build of of toxic urea
High blood pressure
Weakened bones
Anaemia

45
Q

How is kidney failure tested for

A

Blood test measuring level of creatinine in blood - used to give an estimated glomerular filtration rate

46
Q

What are some ways to treat kidney failure

A

Haemodialysis, peritoneal dialysis, transplant

47
Q

what is haemodialysis

A

A dialysis machine is used, blood leaves patients body and flows between a partially permeable membrane that mimics the basement membrane
Urea and mineral ions move out of the body as there is a counter current system between dialysis fluid and blood

48
Q

Drawbacks of haemodialysis

A

Takes 8 hours and done several times each week
patients need to manage their diet carefully

49
Q

What is peritoneal dialysis

A

Done inside the body, catheter connected to peritoneum (lining of abdomen)
Left for several hours for dialysis to take place across peritoneal membranes

50
Q

What are the benefits of getting a kidney transplant

A

no need to watch diet
more time

51
Q

What are the drawbacks of getting a transplant

A

risk of rejection
Recipient is given immunosuppressant drugs
less readily available than dialysis

52
Q

What does ADH do

A

Stimulate the production of aquaporins for water reabsorption in the collecting duct

Biology A level (20 decks)

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