Hepatic Physiology.pptx

OFFICI AL Good Afternoon Everyone….. Thought for the day Hepatic Physiology HEA1091 Monday 6th February 2023 Stuart A. Smith SBSt.J, MSc, MA, BSc(Hons), BSc, PgCertEd, FHEA, MInstLM, MCPara Senior Lecturer in Paramedic Practice OFFICI AL hepatic (adj.) late 14c., epatike, from Old French hepatique o...

OFFICI AL Good Afternoon Everyone….. Thought for the day Hepatic Physiology HEA1091 Monday 6th February 2023 Stuart A. Smith SBSt.J, MSc, MA, BSc(Hons), BSc, PgCertEd, FHEA, MInstLM, MCPara Senior Lecturer in Paramedic Practice OFFICI AL hepatic (adj.) late 14c., epatike, from Old French hepatique or directly from Latin hepaticus "pertaining to the liver," from Greek hēpatikos, from hēpar (genitive hēpatos) "liver". As a noun, "medicine for the liver," from late 15c. Online Etymology Dictionary OFFICI AL By the end of this session, you should be able to…  Identify the surface anatomy of the liver and gallbladder and their location in the abdominal cavity  Describe the cellular anatomy and functional unit of the liver  Describe blood flow through the hepatic system  Describe the flow of bile through the hepatic system  Discuss the functions of the hepatic system OFFICI AL Review of the anatomy and physiology of the hepatic system Components of the hepatic system include: Liver Gall Bladder Hepatic Portal System (the tubes/vessels) OFFICI AL The Liver OFFICI AL Largest organ in the body – 1.5kg up to 10kg in chronic cirrhosis. Main organ of metabolism for fats, carbohydrates and proteins. Bile Production (not the gall bladder – storage). Storage of iron, vitamins, glycogen and trace elements. Detoxification – alcohol and certain drugs. Conversion of waste products for excretion by the kidneys. OFFICI AL OFFICI AL Anatomy of the Liver – where? OFFICI AL Anatomy of the Liver – where? OFFICI AL Peritoneal Cavity OFFICI AL Why is the anatomy of the organ so relevant? Symptomolo gy Abdominal pain and referred pain Visceral pain poorly localised Peritonitic pain more localised Examination Abdominal examination Including gallbladder and Murphy’s sign Hepatomegaly – liver enlarges inferiorly Trauma Chest wall Similarly, the spleen OFFICI AL Posterior view of the liver OFFICI AL Quick facts regarding liver anatomy The liver is functionally divided into 2 lobes – right and left. Each lobe has its own arterial and venous supply and own biliary drainage. All lobes of the liver perform the same function – no areas of specialism. The lower margin of the liver wall will move down during inspiration. This movement allows for palpation of the liver border. The liver is a very dense organ – very dull to percussion. Gallbladder can be palpated around the tip of the 9th rib. Only with distension due to stones or bile. If gallbladder is OFFICI AL The Gallbladder OFFICI AL Quick facts regarding the gall bladder Pear shaped, hollow organ. Storage and 3-10 fold concentration of bile. Bile released into duodenum via the common bile duct. Main function of bile – digestion of fats. Gall stones – cholesterol or bilirubin. Significant pain – upper right corner of abdomen. Cholecystitis – inflammation of the gallbladder – gallstones, infection, autoimmune disease. OFFICI AL Gall Stones and Cholecystitis  Solid secretions in the gallbladder  Mostly formed of cholesterol  Often asymptomatic  Complications: cholecystitis, cholangitis, pancreatitis  RUQ pain, postprandial pain, plus risk factors  Cholecystectomy – avoid fatty food OFFICI AL Liver function – synthesis of bile salts 500-1500 mL of bile per day Bile emulsifies fat (lipids) – larger surface area for pancreatic lipase Helps absorb lipids after digestion During fasting, sphincter of Oddi contracts, bile diverted via cystic duct to gallbladder Stored & concentrated 5-fold Cholecystokinin released when food enters small intestine – relaxes sphincter of Oddi Bile is reabsorbed by small intestine (terminal ileum) and recycled to liver – enterohepatic circulation Arterial blood supply to liver OFFICI AL OFFICI AL Portal Circulation – blood to the liver from other organs The liver has two blood supplies: The hepatic artery and The portal circulation OFFICI AL Quick facts regarding portal circulation Oxygenated blood to the liver – hepatic arteries – L&R (branch of the aorta). Portal vein – deoxygenated blood from other organs (nutrients for liver). Hepatic vein – drains blood from the liver into inferior vena cava (L,R,M) Blood supply to the liver – 25% arterial supply, 75% venous supply. OFFICI AL Liver Trauma…… There are approximately 1-2 litres of blood flow per minute through the liver. Liver trauma is not good!! OFFICI AL Hepatic Portal Circulation Drains blood directly from: Small intestine Parts of the large intestine Stomach Pancreas Spleen Gall bladder OFFICI AL Other relevant facts regarding Hepatic Portal Circulation Hepatic portal blood rich in nutrients (directly from GI tract) Stores and modifies May contain toxins and bacteria Toxins metabolised and bacteria phagocytosed before release into the systemic circulation OFFICI AL Other relevant facts regarding Hepatic Portal Circulation Hepatic portal blood rich in nutrients (directly from GI tract) Stores and modifies May contain toxins and bacteria Toxins metabolised and bacteria phagocytosed before release into the systemic circulation Internal anatomy within the liver OFFICI AL Internal anatomy within the liver OFFICI AL OFFICI AL Internal liver circulation Blood enters liver and drains into hepatic sinusoids. Blood is screened by specialised macrophages – Kupffer cells (pathogen removal) Plasma is filtered through the sinusoids and bathes the hepatocytes. Hepatocytes contain large enzyme numbers – break down what has been absorbed. Portal triad – portal vein, bile duct and portal artery. This is how the liver receives its nutrients and oxygen and how bile is then sent to the bile duct and onward to the gall bladder. Internal anatomy within the liver OFFICI AL Permeable blood capillaries between rows of hepatocytes To hepatic vein & IVC Receive oxygenated blood from hepatic arteriole And nutrient-rich deoxygenated blood from portal venule Converge and deliver blood to a central venule Then hepatic veins Then inferior vena cava Fixed phagocytes in sinusoids (Kupfer cells) destroy worn-out red and white blood cells, bacteria and other harmful matter in blood draining from the GI tract Centr al venul e Portal venul e OFFICI AL OFFICI AL Liver Physiology Synthesises amino acids – transamination. Metabolises amino acids. Synthesises immune system proteins. Production of anticoagulants. Production of angiotensinogen. Production of anticoagulants. Production of urea – expelled. Production of bile – helps convert fats in intestine for absorption. Carbohydrate metabolism – blood glucose levels. OFFICI AL Liver Physiology – Carbohydrate Metabolism Hepatocytes (and muscle fibres) can perform glycogenesis When blood glucose is high (after meal), hundreds of glucose molecules are combined to form glycogen Liver glycogen storage capacity around 125g (375g in skeletal muscle) When blood glucose is low, glycogen is broken down and released Negative feedback… Insulin helps cells absorb and use glucose for use (lowering blood level) Pancreas releases glucagon which tells the liver to start breaking down glycogen (raising blood level) Liver can also convert amino acids and lactic acid to glucose OFFICI AL Liver Physiology – Clinical Connection - Glucagon Paramedic Patient Group Direction (PGD) 1mg intramuscular injection Indicated for hypoglycaemia (clinically suspected or unconscious and blood glucose < 4.0 mmol/L) When oral or intravenous glucose administration is not possible Releases glucose stores in liver OFFICI AL Liver Physiology – Lipid Metabolism Hepatocytes store some triglycerides And can break down fatty acids to ATP (→ energy) And synthesize lipoproteins (LDL & HDL) which transport fatty acids, triclycerides and cholesterol in the blood Synthesize cholesterol which is a component of cell membranes, and a precursor for steroid hormones, bile, and vitamin D OFFICI AL Liver Physiology – Processing of Drugs & Hormones  Detoxifies alcohol  Enzymes in hepatocytes turn alcohol into acetaldehyde, then acetate  Chemical alteration of drugs (metabolism)  Excretion of some drugs into bile  Metabolism or excretion of thyroid and steroid hormones (e.g. cortisol, oestrogens, aldosterone) How do we treat the liver? OFFICI AL OFFICI AL Clinical conditions of concern Jaundice Alcoholic Liver Disease Paracetamol overdose Hepatitis and the different types OFFICI AL Jaundi ce Definition: ‘A condition in which yellow discolouration of the sclera and skin occurs, due to an increase in bilirubin (hyperbilirubinaemia) of levels greater than 50µmol/L’. Note: In most cases, yellowness in the white part of the eyes (sclera) is more obvious than in the skin. Bilirubin production – graphic style. OFFICI AL OFFICI AL Types of Jaundice There are 3 types of jaundice: Pre-Hepatic Hepatocellular Post-Hepatic OFFICI AL Symptoms of Jaundice Fever Flu-like symptoms Chills Abdominal pain Change in skin colour Dark-coloured urine and pale coloured stool OFFICI AL Alcoholic Liver Disease Definition: ‘Occurs due to overconsumption of alcohol to the extent that the liver becomes damaged. This leads to a build up of fats, inflammation and scarring. It can be fatal! Note: Alcohol is the primary cause of chronic liver disease in Western nations. OFFICI AL Alcoholic Liver Disease There are three distinct stages of liver damage following heavy alcohol consumption:  Alcoholic fatty liver  Alcoholic hepatitis  Cirrhosis (fibrosis) OFFICI AL Paracetamol Overdose Definition: ‘Most OTC paracetamol is in 500mg units (tablets, caplets, capsules). Usual dose for an adult is 1g (2 tablets) every 4-6 hours. No more than 8 in any 24 hour period. In an adult, if left untreated, 1015g (20-30 tablets) can result in fatal hepatotoxicity. OFFICI AL Symptoms and Signs of Paracetamol overdose Patients are often asymptomatic following a paracetamol overdose. Some patients present with mild gastrointestinal symptoms (nausea, vomiting. If left untreated, patient may start to develop liver injury over next 2-4 days. Hepatotoxicity extremely rare if patient is treated within 8 hours of overdose using acetylcysteine. If greater than 8 hours, efficiency decreases with time. OFFICI AL Hepati tis Definition: ‘Inflammation of the liver. Several different types, some of which will pass, while others are chronic, causing cirrhosis, loss of liver function or potential liver cancer’. OFFICI AL OFFICI AL Functions of the Hepatic System in summary… Carbohydrate metabolism Lipid metabolism Protein metabolism and synthesis Processing of drugs and hormones Excretion of bilirubin Synthesis of bile salts Storage of vitamins and minerals Filtration of blood and phagocytosis Activation of vitamin D OFFICI AL Further Reading or Viewing…. JOINT ROYAL COLLEGES AMBULANCE LIAISON COMMITTEE, 2019. JRCALC Clinical Guidelines 2019. Bridgwater: Class Publishing. LUMLEY, J. S. P., 2008. Surface Anatomy. St. Louis: Elsevier Health Sciences. RAFFA R. B., 2014. Netter’s Illustrated Pharmacology. Philadelphia: Saunders, Elsevier. DRAKE, R. L., VOGL, W. A. and MITCHELL, A. W. M., 2020. Gray's Anatomy for Students. 4th ed. Philadelphia: Elsevier. TORTORA, G. J. and DERRICKSON, B. H., 2017. Principles of Anatomy & Physiology. 15th edition. Hoboken, NJ: Wiley. WING, E. J. and SCHIFFMAN, F. J., 2021. Cecil Essentials of Medicine. Philadelphia: Elsevier. https://www.youtube.com/watch?v=wbh3SjzydnQ OFFICI AL