Upper GI tract structure and function Flashcards
What nerves control chewing?
Somatic nerves of skeletal muscles in the mouth/jaw
Describe the chewing reflex
Contraction of jaw muscles - pressure of food against mechanoreceptors in gums, hard palate and tongue - inhibition of jaw muscles - reduced pressure - starts again```
3 salivary glands are?
Parotid
Sublingual
Submandibular
Constituents of saliva? Their functions?
Water - 99%, softens, moistens and dilutes
Mucins - proteins that act as lubricant
alpha amylase - breakdown of polysaccharides to disaccharides
Electrolytes - tonicity (isotonic) and pH (controlled by bicarbonate release)
Lysozyme - bacteriocidal, cleaves polysaccharides of bacterial cell wall
What type of gland are salivary glands?
Exocrine - because they secrete into the mouth/gut lumen (outside the body)
Two types of alveolus in salivary glands and what they secrete
Mucous alveolus - secrete mucous
Serous alveolus - secrete serous fluid (contains alpha amylase)
Are salivary glands controlled by the sympathetic or parasympathetic NS?
Both
Both have stimulatory effects
Effect of sympathetic and parasympathetic NS on salivary glands?
Parasympathetic - stimulatory, creates a profuse, watery salivary secretion
Sympathetic - stimulatory, smaller volume, viscous salivary secretion (high mucus and amylase content)
Effect of presence of food in mouth?
Stimulates chemoreceptors and pressure receptors to begin release of saliva
Are there ducts in the oesophagus?
There are ducts in the submucosal layer, secrete mucous for lubrication
Type of muscle in the muscularis externa of the oesophagus
Upper 1/3 - skeletal muscle, voluntary swallowing reflex
Lower 1/3 - smooth muscle, involuntary
What regulates movement of food into and out of the oesophagus?
Upper and lower oesophageal sphincters
Describe the pharyngeal phase of swallowing
Pharyngeal muscle contractions coordinated by the medulla occurs
Soft palate reflected backwards to close off pharynx
UOS relaxes
Describe the action of the upper oesophageal sphincter
Usually tonically contracted
Relaxes during swallowing, allows food into oesophagus
Once food is in contracts again to prevent reflux
Describe oesophageal phase of swallowing
Propulsion of bolus to stomach via peristalsis
LOS relaxes and allows food bolus into stomach
What happens to the stomach when food enters?
Presence of food and relaxation of LOS causes a vagal reflex resulting in relaxation of smooth m. of gastric fundus and body
Increases volume of stomach without change in pressure
Functions of the stomach
Temporary storage/controlled delivery to SI
Dissolve food particles and digest proteins
Sterilize ingested material
Produce intrinsic factor (B12)
How is mixing force generated in the stomach?
3 layers of smooth m. in the muscularis of the stomach, obliquely oriented layer contracts to provide grinding movement to mix stomach contents
Where is muscle in the stomach the thickest?
Thickest at the bottom, generates most mixing force
What stops food from the stomach leaking into the small intestine?
Pyloric sphincter
What are gastric rugae? Their function?
They’re ridges in the stomach formed by the folding of the submucosa and mucosa of the stomach wall
Stretch as stomach fills to increase volume
