Upper GI Tract Structure and Function Flashcards
What do the upper and lower oesophageal sphincters regulate?
Movement of material into and out of the oesophagus
What are the four layers of the oesophagus?
Mucosa
Submucosa
Muscularis Externa
Adventitia
What kind of epithelium lines the mucosa of the oesophagus?
Stratified squamous epithelium
The submucosa of the oesophagus contains what glands, and what is their function?
Mucous glands which secrete mucus via ducts to provide lubrication
What are the main functions of the stomach?
Temporary storage of ingested material
Dissolve food particles and initiate digestion
Control delivery of contents to small intestine
Sterilise ingested material
Produce intrinsic factor
What is the function of the fundus of the stomach?
Storage
What are the functions of the body of the stomach?
Storage
Production of mucous, HCl, pepsinogen and intrinsic factor
What are the functions of the antrum of the stomach?
Mixing/grinding of stomach contents
Production of gastrin
The oesophagus leads to what opening in the stomach?
Gastro-oesophageal/cardiac opening
The lower oesophageal sphincter leads into what region?
The cardiac region
What are the two curvatures of the stomach?
Lesser curvature
Greater curvature
The pyloric sphincter leads into the
duodenum
What are the three common components of the alimentary canal wall?
Mucosa
Submucosa
Muscularis externa
The fourth layer of the alimentary canal wall is dependent on what?
Whether the organ is intraperitoneal or retroperitoneal
If an organ is intraperitoneal, the fourth layer of its wall is
serosa
If an organ is retroperitoneal, the fourth layer of its wall is
adventitia
The enteric nervous system is under control by what systems?
Parasympathetic and sympathetic
What is the innervation of the enteric nervous system from the parasympathetic system?
Vagus nerve
What nerves control salivation?
7th facial and 9th glossopharyngeal nerves
What effect does the parasympathetic system have on the alimentary system?
Stimulatory - increases secretion and motility
What is the innervation of the enteric nervous system from the sympathetic system?
Splanchnic nerve
What effect does the sympathetic system have on the alimentary system?
Inhibitory
What is the mesentery?
Fold of membranous tissue arising from the posterior wall of the peritoneal cavity which attaches organs to the posterior abdominal wall
What are the main arterial supplies of the gastrointestinal tract?
Coeliac trunk
Superior mesenteric artery
Inferior mesenteric artery
What three features of the small intestine act to increase the absorptive surface area along the alimentary canal?
Circular folds
Villi
Microvilli
What feature of the small intestine causes the highest increase in the relative absorptive surface area of the alimentary canal?
Microvilli - increase relative absorptive surface area by 600
The oesophagus acts as a conduit between what?
The pharynx and the stomach
The muscularis externa of the superior oesophagus is composed of what kind of muscle?
Skeletal
The muscularis external of the inferior oesophagus is composed of what kind of muscle?
Smooth
What is the relation of the oesophagus to the aorta?
Oesophagus lies anterior to the aorta
What phase of swallowing is voluntary and what happens in this phase?
Oral phase - bolus is pushed to the back of the mouth by the tongue
What are the three phases of swallowing?
Oral phase
Pharyngeal phase
Oesophageal phase
The presence of the bolus causes what in the pharyngeal muscles?
Sequence of reflex contractions, coordinated by the swallowing centre in the medulla
What is closed off when the soft palate is reflected backwards and upwards?
Th nasopharynx
As the bolus approaches the oesophagus, what sphincter relaxes?
The upper oesophageal sphincter
The epiglottis covers what?
The opening to the larynx - preventing food from entering the trachea
The upper oesophageal sphincter contracts once
food has entered the oesophagus
What does the oesophageal phase involve?
The propulsion of the bolus to the stomach via a peristaltic wave which sweeps along the entire oesophagus
As the bolus nears the stomach, what sphincter relaxes?
The lower oesophageal sphincter
The relaxation of the stomach is initiated following
the relaxation of the lower oesophageal sphincter and entry of bolus into the stomach
What reflexes cause the relaxation of the thin, elastic smooth muscle of the gastric fundus and body?
Vagal
Relaxation of the smooth muscle of the gastric fundus and body increase stomach volume by how much?
From 50ml to 1500ml
What are the main functions of the duodenum?
Gastric neutralisation
Digestion
Iron absorption
What is the function of gastric neutralisation?
Allows pancreatic enzymes to function and prevents acid damage to duodenum
Brunner’s glands secrete what? What cells is this product secreted from?
Bicarbonate
Secreted from the duct cells in the submucosal glands
Bicarbonate combines with acid in the stomach to produce
carbonic acid, which then breaks down to produce water and carbon dioxide
What cells are contained in the endocrine pancreas?
Islets of Langerhans
What are the functions of the Islets of Lagerhans?
Produce insulin, glucagon and somatostatin
What does somatostatin control?
The secretion of insulin and glucagon
The exocrine pancreas is composed of what cells?
Acinar cells
What are the lobules of the exocrine pancreas connected by?
Intercalated ducts
What duct is formed by the joining of the interlobular ducts?
Main pancreatic duct
The main pancreatic duct joins the common bile duct, these both join the duodenum at the
hepatopancreatic ampulla
What do the alpha and beta cells of the pancreas produce?
Alpha - glucagon
Beta - insulin
What functions of the pancreas is the exocrine pancreas responsible for?
The digestive functions
