Liver Flashcards
Understand the basic anatomy of liver
- Two lobes: right and left
- Almost spans the width of the body
- Midline - falciform ligament which separates the R and L lobe
- liver can be subdivided into 9 functional segments
- Based on vascular supply and biliary drainage
Liver anatomy - BLOOD SUPPLY
• The liver intercepts blood from the gut to regulate nutrient levels/detox
• It receives oxygenated blood via the hepatic artery, which used to sustain liver cells (hepatocytes)
• It also receives nutrient rich blood from the gut via the portal vein
• deoxygenated blood is transported from the liver via the hepatic vein
- Liver is composed of smaller structures called lobules
- Lobule is surrounded by branches of the hepatic artery (oxygen) and the portal vein (nutrients)
- Vessels drain into capillary-like structures called sinusoids
- Sinusoids drain to a central vein -> deoxygenated blood -> hepatic vein
LIVER ANATOMY - SINUSOIDS
- have a similar function to capillaries , material exchange
- have increased permeability, allowing larger molecules to cross
- this is vital for liver function
How is this achieved?
- incomplete surrounding diaphragm (basement membrane)
- the endothelial layer contains large intercellular gaps
- together, this permits passage of larger molecules
CELLS OF THE LIVER
Sinusodial endothelial cells - line the sinusoids blood vessels, less tight junctions
Kupffer cells - macrophages of the liver, reside in the lumen of sinusoids-exposed to immunogens from the gut
Stellate cells - found in peri-sinusoidal space, quiescent , activated in response to damage
Hepatocytes - large cuboid cells, extremely metabolically active contain large numbers of organelles (especially smooth ER) binucleate
Understand the primary functions of the liver
- Process the nutrients absorbed from the gut -nutrient metabolism
- store and control the release of key nutrients (e.g glycogen)
- produces lipoproteins
- breakdown of red blood cells
- detoxification-potentially harmful ingested substances
- produces plasma proteins
- produces bile - biliary systems
Homeostasis of nutrient metabolism
NUTRIENT PROCESSING
- absorbed nutrients (small intestine) are transported to the liver for metabolism
- the liver then converts these nutrients into forms that can be stored or used, the liver then mediates their transport to tissues
- Nutrients stored within the liver include; glycogen, fat (in excess), iron, vitamin A
Storage of nutrients
PROTEIN METABOLISM
- the body cannot stored amino acids it must be broken down and excreted excess proteins
- amino breakdown releases an amine group (NH2) that is potentially toxic
- process on page 18
- the liver is responsible for the removal of the amine group; DEAMINATION , conversion into a harmless product: urea which is then excreted by the kidneys
- the liver can also synthesise non-essential amino acids; TRANSAMINATION
CARBOHYDRATE METABOLISM
- excess glucose stored as glycogen
- if blood glucose levels drop, the liver breaks down glycogen into glucose and exports it
- of the hepatic glycogen reserves become exhausted, the liver synthesises glucose from other sources (e.g fats)
- these metabolic processes are coordinated by the pancreatic hormones - insulin and glucagon d
FAT METABOLISM
- the liver synthesises phospholipids and cholesterol
- page 22/23
- the liver converts excess carbohydrates and proteins into fats
- VLDL - very low density lipoprotein
- Allows the lipids (triglycerides) made in the liver to be transported to rest of the body
- synthesis cholesterol
- exported to cells by different types of lipoproteins (HDL or LDL)
- LDL transports cholesterol to cells
- HDL transport excess cholesterol from cells back to the liver
- LDL is bad as it raises blood cholesterol levels
- HDL is good as it lowers cholesterol levels
- Surplus cholesterol is converted by the liver into bile salts- excreted
Producing and secreting plasma proteins
Plasma proteins - proteins in the blood plasma
- all are produced in the liver except immunoglobulins
- so there are
- Albumins - major components of osmotic pressure of plasma p34
- globulins - antibodies (immunoglobulin) and transport proteins p35
- function in blood clotting fibrinogens p36
• made by hepatocytes (ER and Golgi apparatus)
Producing and secreting lipoproteins
A
Breakdown of red blood cells
A
Detoxifying and excreting endogenous and exogenous waste
A
Understand the biliary system
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