GI Session 1- Endoscopic Tour And Basic Structure & Function Flashcards
By which processes does food enter the gut?
Mastication and swallowing
What is food about to be swallowed called
Bolus
List the structures a bolus of food will pass through on its route to the stomach
Mouth, larynx, oesophagus, stomach
Define dysphagia
Difficulty swallowing
What can cause dysphagia?
Anaesthesia, neurological deficits, problem with musculature of oesophagus or obstruction of oesophagus with a tumour
What is the function of the stomach?
Store ingested food and subject it to preliminary physical and chemical disruption
How does the stomach begin to break down food?
Secretion of acid and enzymes which attack biological material
How does the stomach protect itself against its own acid?
Mucus and hydrogen carbonate secretion
What happens when the stomachs defence against acid breaks down?
Peptic ulceration
Pain relieved by eating
Ulcers may bleed or perforate
What happens if the sphincter between the oesophagus and stomach is weak?
Acid may reflux into oesophagus causing irritation, heartburn and may cause damage to the oesophageal mucosa
What leaves the stomach and how is it conditioned?
Acid, hypertonic and partly digested chyme- conditioned by secretion of alkali from the liver and pancreas, osmotic movement of water across the duodenal wall, and secretion of enzymes from the pancreas and intestines
Where is bile released from and how does it enter the digestive system?
Released from the liver and enters gut via the bile duct
Describe the function of bile acids
They assist with digestion of fat in the intestines then are reabsorbed in the terminal ileum and recycled to the liver
Where is bile stored?
Gall-bladder
What is bilirubin and what occurs if it cannot be secreted?
Breakdown product of haemoglobin and excess causes hepatic jaundice (can also be caused by liver damage)
What type of liver damage is caused by alcohol?
Cirrhosis
What consequences does cirrhosis have?
Loss of liver functions, impaired flow of blood from the hepatic portal vein through the liver to the systemic venous circulation = portal hypertension, may lead to ascites and increased flow through collateral venous pathways around oesophagus and anus
What is obstructive jaundice and how is it caused?
Bile duct obstructed so back up of bile = liver damage
Caused by gallstones
How are gallstones formed?
Precipitation of bile acids and cholesterol in the gall bladder
If gallstones move what can this cause?
Movement within gall bladder causes biliary colic
Movement into bile duct can obstruct and cause serious problems
Other than gallstones, what can obstruct biliary outflow?
Pancreatic tumour (particularly bad prognosis)
What is pancreatitis?
Inflamed pancreas causing considerable pain and amylase released into bloodstream
What properties of the small intestine make it the principle site of absorption?
Segmentation propels the neutral chyme along its length
Large surface area allows a complex of absorptive processes to occur
If the motility of the ilium is compromised, what does this lead to?
Paralytic ileus and obstruction of the ilium
Which part of the intestines is particularly at risk of inflammation?
Appendix- leads to appendicitis
What is peritonitis and what is a common cause?
Inflammation of the peritoneum usually cause by any perforation of the gut as the contents are released into the space
What is absorbed in the large intestine?
Remaining water and electrolytes
What is formed in the large intestines and where does it end up?
Faeces are formed then periodically propelled into the rectum prior to defaecation
What is ulcerative colitis?
Mainly affects large intestine and inflammation does not affect the full thickness of the bowel wall
What is Crohn’s disease?
Can affect any part of the intestines and spans the full thickness of the wall
What are some of the consequences of inflammatory bowel disease?
Diarrhoea, pain and blood loss
Problems with absorption (especially if small intestine is affected)
Define secretion (GI)
Digestion accomplished by action of HCl, bile and variety of enzymes secreted by exocrine glands
Define motility (GI)
Contractions of the smooth muscles in walls of tract, mix and move ingested food from mouth to anus
Define absorption (GI)
Products of digestion take into blood
How much food/drink do we ingest per day?
1kg food, 1litre liquid
Mixed with 1500ml saliva and 6litres of secretions from stomach, liver, pancreas and intestines
Of the 9500ml that passes through the GI tract per day, how much is reabsorbed and where?
800ml absorbed in small intestine
1500ml absorbed in large intestine
How much poo is produced per day?
150g
What are the layers of the alimentary canal from inside to outside?
Mucous membrane/mucosa
Submucosa
Muscularis external
Serosa/adventitia
How are secretion and motility of the gut regulated?
Reflexes in ANS/enteric system
Hormones
Activated by contents of the gut and operate to maintain optimum conditions for digestion and absorption
How is a contraction initiated?
It follows the appearance of ‘spike potentials’ initiated by reflexes mediated in the enteric nervous system
What does the enteric nervous system consist of?
2 nerve plexuses in the wall of the gut that may act independently of CNS- may be modified by the ANS
What are the 2 groups of hormones released by the gut?
Gastrin
Secretin
