d3 functions of liver Flashcards
1
Q
basic breakdown of liver structure (read and look at the diagram in the screenshots folder)
A
- made up of 4 lobes
- in abdomen area, to right of stomach under right lung
- 2 larger blood vessels bring blood into liver: hepatic artery and hepatic portal vein
- these 2 blood vessels branch into smaller capillaries known as liver sinusoids, which then leads into a liver lobule
- liver lobules are functional units of liver, aiding the liver to carry out diverse functions to maintain health of individual
- purpose of liver: detoxify
- HEPATIC VEIN HAS HIGHEST UREA: LIVER MAKES UREA
- NITROGEN IN UREA
- DEAMINATION OF AMINO ACIDS
- venules from stomach -> intestines -> hepatic portal vein
- absorb through villus epithelial cells
2
Q
what is the liver made up of?
A
- repeated units of liver sinusoids
- lead into liver lobule
3
Q
what is special about the liver’s blood supply?
A
- liver has dual blood supply
- hepatic artery carries oxygenated blood
- hepatic portal vein brings blood rich in nutrients from stomach and intestines
4
Q
what are the differences between liver sinusoids and capillaries?
A
- main diff is basal membrane in liver sinusoids is discontinuous w openings and “pores” on them
● capillary: complete basement membrane and endothelial layer
● sinusoid: incomplete basement membrane and intercellular gaps in endothelial layer - variety of different tight junctions and clefts present in sinusoidal walls that greatly increase permeability of sinusoids as compared to capillaries
● larger molecules like plasma proteins able to enter and leave sinusoids unlike capillaries
OVERVIEW
general
- sinusoid: kind of blood vessel which is much like fenestrated endothelium w discontinuous basal membrane
- capillary: smallest sort of blood vessel which transports blood by means of arterials and venules
basal membrane
- sinusoid: incomplete basal membrane
- capillary: whole steady basal membrane
lumen
- sinusoid: bigger and wider lumen
- capillary: comparatively smaller lumen
consultant tissue
- sinusoids: present in liver, bone marrow, spleen
- capillaries: present in muscle, pores and skin, lung, central nervous system, coronary heart, lymph nodes
5
Q
how does the liver detoxify blood?
A
- all blood that flows away from stomach and intestines enters into liver first via hepatic portal vein before reaching rest of body, thus any toxins or poisons ingested can be broken down or detoxified in liver before it can damage rest of body
- liver contains wide array of enzymes that can carry out many different chemical reactions (redox, hydrolysis etc.) to break down toxins and poisonous compounds into less harmful substances
- e.g. alcohol dehydrogenase is produced in liver and can break down alcohol into less harmful substances like aldehyde
- for substances not easily broken down by enzymes in liver, they can be bound or conjugated to other molecules and make the substances less toxic
- many heavy metal ions are conjugated to biological molecules in liver, and many are stored in fats in liver and rest of body to reduce toxic effects of such heavy metals
6
Q
what component of red blood cells is recycled by the liver?
A
- red blood cells (erythrocytes) do not have the majority of organelles found in a normal cell, hence do not have long life span
- most rbc circulate human body for about 100 to 120 days, subsequently broken down in liver and spleen
- main component of rbc recycled by liver is haemoglobin
7
Q
outline the process in which red blood cells (erythrocytes) are broken down in the liver
A
- starts with phagocytosis of rbc by kupffer cells
- kupffer cells found lining the walls of liver sinusoids
- type of white blood cell known as macrophages which are capable of carrying out phagocytosis
- break down rbc via phagocytic action
- haemoglobin molecules in rbc broken down to globin units and heme units
- globin units further broken down to amino acids recycled for use in body or break down further (deamination) in liver
- heme groups broken down into iron and bilirubin
8
Q
what happens to the iron produced after breakdown of red blood cells?
A
- iron produced from breakdown of haemoglobin in liver
- transported to bone marrow via transferrins
- used by bone marrow cells to produce haemogloblin in new rbc
- transferrins: glycoproteins that can bind strongly to iron reversibly
- excess iron can be stored in liver, with iron stored within a protein molecule known as ferritin
9
Q
what is jaundice? how is it caused and what are its consequences?
A
- condition when there are excessive amounts of bilirubin in body
- bilirubin is yellow in colour, and is naturally produced in the liver in breakdown of heme groups
- bilirubin formed in liver are conjugated with molecules like glucuronic acid in liver to form a soluble compound
- conjugated bilirubin then excreted as part of bile pigments
CAUSES OF JAUNDICE
- liver damage leading to reduced ability to remove bilirubin
- blockage of gall bladder or bile duct can lead to accumulation of bile pigments in liver, which in turns leads to reduced ability to excrete bilirubin into bile
- unnatural levels of breaking down of rbc can also lead to excessive bilirubin levels
- jaundice common in newborn babies, where there are high rates of breakdown of fetal rbc for replacement with adult rbc, and liver in newborn not mature enough to cope with conjugating all bilirubin produced for excretion
CONSEQUENCES OF JAUNDICE
- symptom and indicator of deeper underlying problem in human body
- underlying problems may be serious and pose risks to individual
- treatment of jaundice involves treating underlying causes of jaundice
10
Q
what are bile salts made of?
A
- surplus cholesterol
- bile made up of variety of compounds, including conjugated bilirubin, and bile acids
- bile acids are steroid acids formed from cholesterol, and excess cholesterol can be excreted from body in bile
- bile salts are the salts of the acids
11
Q
what are plasma proteins and how are they produced?
A
- endoplasmic reticulum and golgi apparatus in hepatocytes produce plasma proteins
- hepatocytes refers to liver cells found in lobes of liver
- plasma proteins refer to proteins found in blood plasma, the non-cellular component of blood
- endoplasmic reticulum and golgi apparatus are required in protein synthesis, and hence are found in large quantities in hepatocytes, as hepatocytes are the main cells responsible for production of plasma proteins
- examples of plasma proteins:
● albumins (55% of plasma proteins) – mainly help to maintain osmotic potential of blood plasma
● globulins (38%) – mainly function as transport proteins or have immune functions like antibodies (immunoglobulins)
● fibrinogen (7%) – needed for coagulation and clotting of blood
● others like regulatory proteins (hormones, etc), and clotting factors
12
Q
how does liver intercept blood from the gut to regulate nutrient levels?
A
- hepatic portal vein brings nutrient rich blood from stomach and intestines into liver
- as blood from stomach and intestines first passes through liver before reaching rest of body, it is possible for liver to convert and store nutrients from hepatic portal vein to avoid spike in nutrients in blood vessels in rest of body
13
Q
how are excess nutrients stored in liver?
A
- excess carbohydrates (mainly glucose) are converted into glycogen and stored in liver
- glycogen can be broken down to increase blood glucose levels when necessary
- excess proteins deaminated in liver, where they are broken down into amino acids, and further broken down to liberate amine NH2 group
- amine group is converted into urea and excreted from kidneys in urine
fat metabolism in liver
- excess carbohydrates and proteins can also be converted into fatty acids and triglycerides by liver
- liver is capable of storing large amounts of fats around organ
- also involved in regulation of cholesterol in body, where lipoproteins can transport fats towards or away from liver when necessary
