Digestive System Flashcards
Describe the structure and position of the gall bladder
Pear shaped, beneath the liver, approximately 10cm long, connected to the liver by connective tissue. Similar to the digestive tract in structure however does not have a submucousal layer. Epithelial layer arranged into rugae.
What is the function of the gall bladder?
Absorb water from the bike making it 10x more concentrated than when it was produced in the liver. Mucus is secreted into the Nile which is stored until required by the digestive tract.
Outline the movement of bile through the gall bladder.
Bile enters the gall bladder from the liver through the cystic duct and exits by the same route. Secretion of bile from the gall bladder into the duodenum is controlled neurally and hormonally. The stimulation of the vagus nerve causes the release of hormones secretin and CCK. when fats are present in chyme entering the duodenum and the hormones are present the gall bladder contracts to secrete bile into the small intestine.
What is the duodenum?
The first part of the small intestine immediately beyond the stomach.
What is chyme?
Thick semi fluid mass of partially digested food that is formed in the intestines and stomach during digestion.
What is bile and what is it made of?
It’s function it to aid the digestion of fats in the duodenum. It is composed of bile acids, bile pigments, bile salts and cholesterol. Alkaline. Green yellow colour.
Outline the blood and nerve supply to the bile duct
Cystic artery supplies the gall bladder and bile ducts with oxygenated blood and the cystic vein drains away deoxygenated blood. Nerve supply from the autonomic nervous system.
Describe the location of the bile ducts
Hepatic ducts leave the liver through the portal fissure and join to form the common hepatic duct.
Cystic duct from the gall bladder joins the common hepatic duct to form the common bile duct which passes behind the head of he pancreas.
This then joins the main pancreatic duct before it enters the duodenum through the hepato pancreatic sphincter
What are the three accessory structure of the gastrointestinal system?
The liver
The gall bladder
The pancreas
Describe the general features of the liver
Largest gland in the body weighing on average 1.5 kg.
Essential to life and can continue to work even when a large portion of it has been damaged.
Situated in the upper right section of the abdominal cavity the right hypochondriac region under the diaphragm.
Partially protected by the lower ribs.
What is the peritoneum?
Continuous transparent membrane which lines the abdominal cavity and covers the abdominal organs
Describe the macrostructure of the liver
Covered completely in peritoneum
Anatomically divided into right and left lobes by the falciform ligament.
The falciform is attached to the under surface of the diaphragm and holds the liver in position.
The ligamentum teres extends from the falciform ligament down to the umbilicus which is a remnant of the umbilical vein present in the foetus.
The portal fissure is a structure situated on the posterior surface of the liver where vessels and nerve fibres enter and leave.
Describe the microstructure of the liver
Composed of hepatic lobules formed from hepatocytes
Central sinusoid located in each lobule
Sinusoids carry venous and arterial blood which come into contact with the hepatic lobules.
Kupffer cells line the walls of sinusoids. They are specialised cells which destroy worn out blood cells, bacteria and toxins.
Surrounding lobules are canals carrying a branch of the portal vein, hepatic artery and small bile duct.
How much bile is produced daily and where is it stored?
750ml-1L of bile daily in an adult. Stored in the gall bladder.
What happens to the majority of bile salts?
They are reabsorbed in the ileum and returned to the liver is the portal vein to be recycled.
What is bilirubin?
The main bile pigment in the liver.
Product of the breakdown of red blood cells.
Hepatocytes process fat soluble bilirubin produced by haemolysis and change it to water soluble bilirubin.
This can then be broken down in the digestive system and excreted in the faeces or the renal system.
What are the three functions of the liver?
Metabolism
Storage
Secretion
Outline the livers role with regards to storage
Stores vitamins and elements iron and copper. Also store glucose as glycogen.
Outline the livers role with regards to secretion
Bile is produced by her liver and secreted from the gall bladder into the digestive tract to aid the breakdown of fats. Urea is formed in the liver from waste products such as ammonia and carbon dioxide which is excreted in the urine.
Outline the livers role with regards to metabolism
The liver regulates blood sugar levels by converting glucose to glycogen in response in insulin and glycogen to glucose in response to glucagon.
It mobilises stored fat for use by body cells.
The liver detoxifys drugs and poisons as well as deactivating hormones no longer needed in the body.
Heat is a by product of these metabolic processes. Liver helps to maintain core body temperature which is essential for metabolism to work at an optimum rate.
Outline the blood and nerve supply to the liver
The hepatic artery supplies the liver with oxygenated blood and the portal vein brings nutrient enriched blood directly from the digestive organs.
Hepatic veins drains intone inferior vena cava.
The autonomic nervous system controls the liver function.
Describe the appearance of the pancreas
Soft, grey pink gland, 15cm long.
Consists of an expanded head tucked into the surge of the duodenum, a body and a narrow tail lying behind the stomach.
Where is the pancreas located
Transverse lie, across posterior abdominal wall behind the stomach
Describe the movement of secretions from the pancreas
Secretions are passed along two ducts, one of which joins the common bile duct before entering the duodenum and the other entering the duodenum directly.
Pancreatic duct - common bile duct then duodenum
Accessory duct - straight into duodenum
