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Biology > D.3 LIVER FUNCTIONS > Flashcards

D.3 LIVER FUNCTIONS Flashcards

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1
Q

The liver

A

is a lobed organ located below the diaphragm that functions to regulate the chemical composition of blood

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2
Q

It receives oxygenated blood via

A

the hepatic artery, which is used to sustain liver cells (hepatocytes)

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3
Q

t also receives nutrient rich blood from

A

the gut via the portal vein

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4
Q

Deoxygenated blood is transported from the liver via

A

the hepatic vein

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5
Q

The liver functions to

A

process the nutrients absorbed from the gut and hence regulates the body’s metabolic processes

  • storage/controlled release of key nutrients
  • detoxification
  • plasma protein production
  • breakdown of red blood cells
  • the production of bile salts
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6
Q

The liver is composed of smaller histological

A

structures called lobules, which are roughly hexagonal in shape

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7
Q

Each lobule is surrounded by

A

branches of the hepatic artery (provide oxygen) and the portal vein (provide nutrients)

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8
Q

lobules vessels drain into

A

capillary-like structures called sinusoids, which exchange materials directly with the hepatocytes

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9
Q

The sinusoids drain into

A

a central vein, which feeds deoxygenated blood into the hepatic vein

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10
Q

Hepatocytes also produce

A

bile, which is transported by vessels called canaliculi to bile ducts, which surround the lobule

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11
Q

Sinusoids are

A

a type of small blood vessel found in the liver that perform a similar function to capillaries (material exchange)

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12
Q

Sinusoids have

A

increased permeability, allowing larger molecules (e.g. plasma proteins) to enter and leave the bloodstream

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13
Q

The increased permeability of sinusoids is important for liver function and is due to a number of structural features:

A

The surrounding diaphragm (basement membrane) is incomplete or discontinuous in sinusoids (but not in capillaries)

The endothelial layer contains large intercellular gaps and fewer tight junctions (allowing for the passage of larger molecules)

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14
Q

Nutrients stored within the liver include

A

glycogen, iron, vitamin A and vitamin D

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15
Q

carbohydrate metabolism

Excess glucose in the bloodstream

A

(e.g. after meals) is taken up by the liver and stored as glycogen

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16
Q

carbohydrate metabolism

When blood glucose levels drop,

A

the liver breaks down glycogen into glucose and exports it to body tissues

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17
Q

carbohydrate metabolism

When hepatic glycogen reserves become exhausted

A

the liver synthesises glucose from other sources (e.g. fats)

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18
Q

carbohydrate metabolism

The liver plays an important role in regulating the levels of nutrients in the bloodstream

A

Nutrients absorbed by the small intestine are transported by the hepatic portal vein to the liver for metabolism

The liver converts these nutrients into forms that can be stored or used and mediates their transport to various tissues

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19
Q

Protein Metabolism

A.A

A

The body can not store amino acids, meaning they must be broken down when in excess

Amino acid breakdown releases an amine group (NH2), which cannot be used by the body and is potentially toxic

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20
Q

Protein Metabolism

Amine group

A

The liver is responsible for the removal of the amine group (deamination) and its conversion into a harmless product

The amine group is converted into urea by the liver, which is excreted within urine by the kidneys

21
Q

Fat Metabolism

A

The liver is the major site for converting excess carbohydrates and proteins into fatty acids and triglycerides

It is also responsible for the synthesis of large quantities of phospholipids and cholesterol

These compounds are then stored by the liver or exported to cells by different types of lipoproteins

22
Q

Fat Metabolism

LDL

A

Low density lipoprotein (LDL) transports cholesterol to cells, for use in the cell membrane and in steroid synthesis

LDL is considered ‘bad’ as it raises blood cholesterol levels, while HDL lowers cholesterol levels and is therefore ‘good’

23
Q

Fat Metabolism

HDL

A

High density lipoprotein (HDL) transports excess cholesterol from cells back to the liver (for storage or conversion)

24
Q

Surplus cholesterol

A

is converted by the liver into bile salts, which can be eliminated from the body via the bowels

25
Q

triglyceride pathway

A

triglycerides are transported to cells by VLDL from liver to chylomicrons (from intestine) for energy use of storage (adipose tissue)

26
Q

cholesterol

A

transported to cells by LDL for use in plasma membranes and steroid synthesis, while excess cholesterol is moved from cells by HDL to be converted by liver into bile

27
Q

drugs and toxin in the bloodstream

A

Many of these toxic compounds are fat soluble, making them difficult for the body to excrete

These compounds are converted into less harmful and more soluble forms, which are then excreted from the body by the liver

28
Q

The detoxification of compounds by the liver typically involves two sets of chemical pathways:

A
  1. Toxins are converted into less harmful chemicals by oxidation, reduction and hydrolysis reactions
    These reactions are mediated by a group of enzymes known as the cytochrome P450 enzyme group
    These conversions produce damaging free radicals, which are neutralised by antioxidants within the liver
  2. The converted chemical is then attached to another substance (e.g. cysteine) via a conjugation reaction
    This renders the compound even less harmful and also functions to make it water soluble
    The water soluble compounds can now be excreted from the body within urine by the kidneys
29
Q

plasma proteins are produced by

A

Endoplasmic reticulum and Golgi apparatus in hepatocytes

30
Q

Plasma proteins are

A

proteins present in the blood plasma and are produced by the liver (except for immunoglobulins)

31
Q

plasma proteins are exported to

A

exported into the blood via the Golgi complex

32
Q

different types of plasma proteins

A

Albumins

Globulins

Fibrinogens

33
Q

Albumins

A

regulate the osmotic pressure of the blood (and hence moderate the osmotic pressure of body fluids)

34
Q

Globulins

A

participate in the immune system (i.e. immunoglobulins) and also act as transport proteins

35
Q

Fibrinogens

A

are involved in the clotting process (soluble fibrinogen can form an insoluble fibrin clot)

36
Q

RBC have a life span of X and thus

A

short lifespan (~120 days) and must be constantly replaced

the liver is responsible for the break down of red blood cells and recycling of its components

These components are used to make either new red blood cells or other important compounds (e.g. bile)

37
Q

Kupffer cells

A

specialised phagocytes within the liver which engulf red blood cells and break them down

38
Q

Kupffer cells break

A

down haemoglobin into globin and iron-containing heme groups

39
Q

Globin is digested by

A

peptidases to produce amino acids (which are either recycled or metabolised by the liver)

40
Q

Heme groups are broken down into

A

iron and bilirubin (bile pigment)

41
Q

The released iron must be complexed within a protein in order to avoid

A

oxidation to a ferric state

42
Q

Iron can be stored by the liver within

A

a protein shell of ferritin

43
Q

Iron can be transported to the bone marrow

A

(where new haemoglobin is produced) within the protein transferrin

44
Q

Jaundice is a condition caused by

A

an excess of bile pigment – bilirubin – within the body

45
Q

Bilirubin is produced as part

A

the natural breakdown of haemoglobin by the liver

Normally, the liver conjugates this bilirubin to other chemicals and then secretes it in bile

46
Q

When there is an excess of bilirubin

A

it may leak out into surrounding tissue fluids

47
Q

Jaundice may be caused by

A

any condition which impairs the natural breakdown of red blood cells

Liver disease – impaired removal of bilirubin by the liver may cause levels to build within the body

Obstruction of the gall bladder – preventing the secretion of bile will cause bilirubin levels to accumulate

Damage to red blood cells – increased destruction of erythrocytes (e.g. anemia) will cause bilirubin levels to rise

48
Q

consequences of jaundice

A

yellowish discoloration of the skin and whites of the eyes (sclera)

Other common symptoms include itchiness, paler than usual stools and darkened urine

49
Q

Jaundice treatment

A

Other common symptoms include itchiness, paler than usual stools and darkened urine

Biology (40 decks)

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