Liver Flashcards
Name the major vessels of the portal system
Superior Mesenteric Vein (deoxygenated blood from small intestine, leads into portal vein)
Inferior Mesenteric Vein (deoxygenated blood from large intestine, leads into portal vein)
Splenic vein
Portal vein (deoxygenated blood to liver)
Coaliac trunk (blood from aorta, splits into…..)
Splenic artery
Hepatic artery (oxygenated blood to liver)
How much bile is produced per day?
1 litre
What is a portal system?
• Two capillary systems in series. Blood from the first set of capillaries collects in portal vessels which then begin to branch again to supply a capillary network to a second location before entering a series of veins which will lead to the heart. There are two such systems in humans
– Hepatic portal system
– Hypothalamo-hypophyseal portal system
Where are the 2 capillary beds of the hepatic portal system located?
1: stomach and intestine - nutrients and toxins absorbed
2: liver cells - nutrients and toxins leave
Connected by the hepatic portal vein
What is in the hepatic portal vein?
• Water
• Water soluble vitamins
• Electrolytes including sodium, potassium, chloride, bicarbonate, calcium, magnesium, iron
• Carbohydrates
– Glucose, galactose and fructose
• Proteins
– Amino acids, dipeptides and tripeptides
• Intestinal hormones, particularly pancreatic hormones
• Toxins, including ammonia
What does the liver convert ammonia into?
Urea via the ornithine cycle
Urea is then excreted in the urine
What is not travelling in the portal vein?
• Lipids
– Dietary lipid is mostly triglycerides, cholesterol and phospholipids
– Digested by lipases, this process needs bile acids to form micelles
– Lipids are taken into the cells and processed into chylomicrons
– Chylomicrons are taken up by lymphatics, called lacteals. Lacteals contain chyle
What are lacteals?
These specialised lymphatic vessels drain into the abdominal lymphatics that then drain into the thoracic duct which joins the venous system at the junction of the left internal jugular vein and subclavian vein. The chylomicrons can then enter the liver via the hepatic artery
Which vitamins are fat soluble?
A D E & K
Name some functions of the liver
Metabolism Storage Detoxification Bile production Exocrine Endocrine
What is stored in the liver?
Iron Vitamin A Vitamin B12 Vitamin D Vitamin K Glycogen
What is produced in the liver (anabolic function)?
Plasma proteins e.h. Albumin, Numerous coagulation factors, Cu, circulating lipoproteins
Complement components of the immune system
Haematopoiesis in foetus (can be revived in adult if bone marrow failing)
Glycogen
What is catabolised in the liver?
- Drugs (cytochrome P450)
- Hormones
- Haemoglobin
- Poisons (cytochrome P450)
- Can take over removal of aged red cells after splenectomy
Cytochrome p450 - a family of chemicals containing isoenzymes which are located in the SER of several tissues
What is involved in the filtering function of the liver?
Kupffer cells (macrophages)
Describe the exocrine function of the liver
Bile is an exocrine secretion of the liver
Describe the endocrine function of the liver?
• It produces
– Angiotensinogen
– Thrombopoetin
– Insulin like growth factor 1 (IGF-1)
• It modifies to active forms
– Vitamin D
– Thyroxine
• It breaks down
– Insulin
– Glucagon
– Oestrogen and progesterone
What do hepatocytes contain2
- Constitute 80% of liver cell population
- Can regenerate remarkably!
- Compared to other cells contain
– Numerous mitochondria – A lot of peroxisomes (organelles full of oxidising agents) – Numerous free ribosomes – A lot of rough endoplasmic reticulum – A lot of smooth endoplasmic reticulum – Numerous Golgi complexes – Glycogen deposits
What is a sinusoid?
A sinusoid is an irregular tubular space for the passage of blood, taking the place of capillaries and venules in the liver, spleen and bone marrow. Its endothelial cells have large gaps
What does a hepatic triad comprise?
Bile duct, portal vein, hepatic artery
Describe a lobule
Hexagonal shape, triads around it, terminal hepatic venule (central vein) in the centre, sinusoids draining into central vein
Where do lymphatics arise?
Lymphatics arise from the periportal space of Mall (between triads and lobule) and drain to the liver hilum and then onto the thoracic duct
What are bile canaliculi?
A thin tube that collects bile secreted by hepatocytes - merge and form ductules which eventually become the common hepatic duct
What is the space of disse?
Space between sinusoid and basolateral membrane
What is a kupffer cell?
Kupffer cells are monocyte derived specialist macrophages that form part of the lining of the sinusoids. Kupffer cells constitute 80% of the tissue macrophages present in the body. They are constantly
exposed to gut-derived bacteria, microbial debris and bacterial
endotoxins
Kupffer cells are specialized macrophages that patrol tiny vessels in the liver called sinusoids, recycling old red blood cells and ingesting pathogens. The endothelium of these vessels is perforated with large holes, allowing the Kupffer cells to migrate into liver tissue at sites of inflammation and damage.
What are Stellate (Ito) cells?
• Stellate (Ito) cells are full of cytoplasmic vacuoles containing Vitamin A. For many years, fish liver oils (e.g., cod liver oil) were medically and important nutritional sources of vitamin A. In liver cirrhosis, hepatic stellate cells lose their vitamin A storage capability and differentiate into myofibroblasts. These synthesize and deposit collagen within the perisinusoidal space, resulting in liver fibrosis. This collagen surrounds the central vein, constricting it and leading to
portal hypertension
