Functions Of The Components Of The GI System Flashcards
Where is saliva produced?
The salivary glands
What are the names of the salivary glands?
- Sublingual
- Submandibular
- Parotid
- Buccal
What stimulates the production of saliva?
Smell, thought, and presence of food
What does saliva contain?
Mainly water, but also small quantities of;
- Amylase
- Mucus
- Lysozyme
What is the function of salivary amylase?
Converts polysaccharides to maltose
What is the function of salivary mucus?
To allow lubrication
What is the function of salivary lysozyme?
It lyses certain bacteria
What is the first stage in breakdown of food?
Chewing
What is the purpose of the chewing of food?
It allows easier passage into the absorption
Does absorption take place in the mouth?
Some drugs can be absorbed through the buccal mucosa, but no nutrient absorption takes place
Give an example of a drug that can be absorbed through the buccal mucosa?
Midazolam
What happens when a food bolus is moved to the back of the pharynx?
The swallowing centre in the cerebral medulla is activated
What is the result of the activation of the swallowing centre?
Closure of the vocal cords and epiglottis
Why is the closure of the vocal cords and epiglottis important in swallowing?
Faciltates the safe pasage of the bolus into the oesophagus
How is reflux of food particles back into the mouth prevented?
Sphincters at the lower and upper end of the oesophagus
What is the ‘normal’ state of the upper oesophageal sphincter?
Tonically contracted
What happens when the upper oesophageal sphincter needs to let food through?
It relaxes
What controls the upper oesophageal sphincter?
Cranial nerves V, IX, and X
What stimulates peristalsis within the oesophagus?
Swallowing a food bolus
What is the role of the inhibitory neurones of the oesophagus in swallowing?
- Induce lower oesophageal sphincter relaxation
- Co-ordinate proximal-to-distal peristaltic contraction
What condition is caused by a failure of the lower oesophageal sphincter to relax?
Achalasia
How is achalasia treated?
Usually needs surgery to divide the muscles at the lower oesophageal sphincter to allow passage of food into the stomach
Can achalasia occur in children?
It is rare, but can still occur
Does any digestion or absorption of food take place in the oesophagus?
No