PBL 1 Flashcards
Describe the microscopic structure of the liver?
Hepatocytes are arranged into lobules which are. Hexagonal shaped and drain into a central vein. At the periphery of each lobule is the portal triad.
Describe the structure of a lobule of the liver?
Sinusoids are capillaries which serve as a location for mixing oxygen-rich blood and nutrient-rich blood. These endothelial cells are highly fenestrated
Between the gelato types and sinusoids we have the spaces of Disse. Any plasma that collects in the space of Disse flows back towards the portal triads
Sinusoids have many Kupffer cells (fixed macrophages)
Describe the process of breaking down erythrocytes?
Erythrocytes, when old and damaged, are engulfed and degraded by macrophages in the spleen and bone marrow. They release the haemoglobin molecules which are broken down into heme and glob in. The heme is broken down to unconjugated bilirubin and Fe2+ whilst the globin is a protein so is broken down to amino acids
The Fe2+ will re-enter circulation
Why does unconjugated bilirubin need to be removed fr9m the body?
It’s toxic
Describe bilirubin metabolism?
Unconjugated bilirubin is carried aro7nd the body attached to albumin. In the liver, A conjugation reaction occurs where glucoronic acid is added to the molecule to form water-soluble conjugated bilirubin.
This can now be excreted within the bile. Bile is excreted into the small intestine where conjugated bilirubin travels to the colon and is converted to urobilinogen by removing the glucoronic acid via bacteria,
Urobilinogin is lipid soluble is 15% is reabsorbwd by the blood and bound to albumin and the rest us quickly oxidised to stercobilin by intestinal bacteria
The urobilinogen that is reabskrbed is carried back to the liver by the portal system- some participates in entero-hepatic urobilinogen cycle and the rest is converted to urobilin and excreted by the kidneys (giving urine it’s yellow colour)
What are the 2 main types of gall stones?
Cholesterol stones and bilirubin stones (aka pigmented stones)
What is cholelithiasis?
Formation of gall stones
What are the 3 ways that cholesterol stones can form?
If bile becomes super daturated with cholesterol so it precipitates
If there isn’t enough bile acids, salts and phospholipids so keep cholesterol in solution
Gall bladder stasis- if bile doesn’t move then cholesterol can precipitate out as a solid
Which gall stones can you see on X-ray? Why?
Calcified gallbladder stones as other stones are radio-lucent due to the little amount of bicarbonate to form CaCO3
Describe how bilirubin stones form?
When there’s too much bilirubin in the bile, it reacts with Ca2+ to form calciumbilirubinate
What type of gall stones tend to be black?
Bilirubin stones
What does brown gall stones indicate?
An infection in the gall bladder or biliary tract
What are some risk factors for gall stones?
Oral contraceptive pills as oestrogen increases cholesterol formation
Being a woman for the same reason as above
Obesity due to more cholesterol in the diet
Rapid weight loss as this creates an imbalance of bile composition
Being over 40
Being Native American
Being a Hispanic of Mexican origin
Being sedentary
Being pregnant
Eating a high fat diet
What colour do cholesterol stones tend to be?
Yellow-green
What are the symptoms of gall stones?
A high temperature Persistent pain (normally only is they get trapped in an opening e.g. the gall bladder - aka biliary colic) Tachycardia Jaundice Itchy skin Diarrhoea Chills / shivering attacks Confusion
