Upper GI Tract Structure Flashcards
What five things are in saliva and what is their role?
Water- Softens, moistens and dilutes particles. Solvent
Mucins- Major protein component. Viscous solution that has a lubricant function
Amylase-Catalyses breakdown of polysaccharide into disaccharide
Electrolytes- Affectstonicity/pH
Lysozyme- Bacteriocidal that cleaves polysaccharide component of bacterial cell wall so has a protective element to it
How does sympathetic and parasympathetic control affect saliva secretion?
Sympathetic NS produces a small volume of viscous, watery secretions.
Parasympathetic NS produces profuse watery secretions via the glossopharyngeal and facial nerves.
What are the four histological layers of the GI tract?
Mucosa
Submucosa
Muscularis Externa
Adventita (or serosa if below diaphragmatic level)
Describe the reflex of swallowing
The oral phase is voluntary when the bolus is moved to the back of the mouth using the tongue.
The presence of the bolus causes a sequence of reflex contractions of pharyngeal muscles (Pharyngeal phase) which is co-ordinated by swallowing centre (medulla).
The soft palate is reflected backward and upward to close off the nasopharynx.
As bolus approaches oesophagus the upper oesophageal sphincter relaxes and epiglottis covers opening to larynx to prevent food entering the trachea.
Once food has entered oesophagus the UOS contracts to prevent food reflux.
Oesophageal Phase propels bolus to stomach in 10 seconds. Peristaltic wave sweeps along entire oesophagus.
As the bolus nears stomach the lower oesophageal sphincter (LOS) relaxes and bolus enters stomach.
Receptive relaxation of stomach is initiated following relaxation of LOS and entry of bolus into stomach.
What are five functions of the stomach?
Temporary store of ingested material
Dissolve food particles and initiate digestive process
Control delivery of contents to small intestine
Sterilise ingested material
Produce intrinsic factor (Vitamin B12 absorption)
