Upper GI Tract Structure & Function Flashcards
What is responsible for the voluntary control of chewing?
Somatic nerves - skeletal muscles of mouth and jaw
What is the reflex control of chewing?
*Contraction of jaw muscles -> pressure of food against gums, hard palate and tongue -> mechanoreceptors -> inhibition of jaw muscles -> reduced pressure -> contraction - etc…
What is saliva composed of?
Water - 99% - moistens, solvent
Mucins - (plus water = mucus) - lubricant
Alpha amylase - enzyme
Electrolytes - pH and tonicity
Lysozyme - Bacteriocidal - cleaves polysaccharide component of bacterial cell wall
What type of glands secrete alpha amylase?
Serous glands
What is an exocrine gland?
Produces a secretion by a canal or duct to the surface or outside of an organ
What is the effect of the parasympathetic nervous system on saliva production?
What is the effect of the sympathtic nervous system on saliva production?
What is the reflex control of salivary secretion?
•Presence of food in mouth - chemoreceptors/pressure receptors (walls of mouth/tongue)
How long is the oesophagus?
25cm
What is the mucosa of the oesophagus lined with?
Stratified squamous epithelium (non-keratinised).
Where does the lubrication in the oesophagus come from?
Submucosal glands - ducts
What is the muscularis externa composed of?
upper 1/3 (superior) = skeletal muscle
lower 2/3 (inferior) = smooth muscle
What regulates the movement of material into and out of the gut?
oesophageal sphincters
What is the oral phase of swallowing?
Bolus is pushed to back of the mouth by the tongue
What is the pharyngeal phase of swallowing?
There is a reflex of pharyngeal muscles coordinated by the swallowing centre (medulla) as a result of the bolus
Soft palate reflected backward and upward (closes off nasopharynx)
What happens when the bolus approaches the oesophagus?
- Upper oseophageal sphincter (UOS) relaxes
- epiglottis covers opening to larynx (prevents food entering trachea)
What happens once food has entered the oesophagus?
Upper oesophageal sphincter contracts and prevents food reflux
How does the food reach the stomach?
Peristaltic wave sweeps along the entire oesophagus and propels food to the stomach in about 10 seconds
What must happen before the bolus reaches the stomach?
LOS relaxes
What is the receptive relaxation of the stomach and what controls it?
Initiated following the relaxation of LOS and entry of bolus into the stomach,
•Vagal reflexes - relaxation of elastic smooth muscle of fundus and body of stomach
What is the stomach volume?
•50ml - 1500ml (no change in pressure)
What are the folds in the stomach called?
Rugae
What are the 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)
Where do the large contractions take place in the stomach?
The lower portions which are more muscly
Which additional muscle layer exists around the antrum?
The oblique muscle layer
What layers are folded to form rugae?
Submucosa and mucosa
What is the name given to the connective tissue outer layer of the stomach?
Serosa
What is the lumenal surface composed of?
Surface mucus cells - gastric pits - gastric glands - mucus neck, parietal and chief cells
