Lecture 9 Flashcards
Why is it important that food is mixed with saliva as it is chewed ?
For lubrication and digestion.
Three key pairs of salivary glands
Parotid, submandibular, sublingual.
Where are these salivary glands found ?
They are adjacent to the mouth.
How much saliva is excreted into the mouth each day ?
1500ml
Why is fluid intake important ?
It is important in maintaining a balance in the body when it is producing so many secretions.
What is saliva made up of ?
Mucus - helps to lubricate food.
Enzymes - initiate the digestion process, i.e. begins the breakdown of carbohydrates/starch, e.g. a-amylase and lysozyme.
Parotid salivary gland
Produces watery saliva rich in a-amylase.
Sublingual salivary gland
Produces thick saliva with thick mucus.
Submandibular salivary gland
Produces watery saliva rich in a-amylase.
Why is the tyre of saliva produced regulated stringently ?
As it is dependent on whether there is food to be processed in the mouth or not.
Where does the food travel to at the start of the digestion process ?
The food travels to the back of the mouth, pharynx and then down the oesophagus.
What runs parallel along beside the oesophagus ?
The trachea.
Why is it important for there to be strict procedures and mechanisms in place for the transport of food down the oesophagus ?
So that the food moves down the oesophagus and not the trachea and to the lungs.
Where is the saliva produced ?
Saliva is produced in the acing cells.
As the saliva flows through the salivary duct, the different cells secrete electrolytes and water to modify the saliva production.
What is saliva production subject to ?
It is subject to neuronal input, which is the most important out the three for production of saliva.
What are the reflexes involved in the neuronal input to the saliva production mediated by ?
They are mediated by the ANS, i.e. the parasympathetic and sympathetic systems are important in modulating the saliva production.
The purpose of the parasympathetic arm of the ANS
Important in rest and digest.
Stimulate digestion and activate GI tract activity.
Watery saliva.
Increases the blood flow to the gland which produces saliva rich in amylase (digestive enzyme) and mucus.
The purpose of the sympathetic arm of the ANS
Important in fight or flight.
Does not promote digestion - reduces GI tract activity.
Promotes increased output of thicker mucus which does not contain much enzyme activity.
Reduces blood flow to the glands.
Overall results in a reduction in secretion of watery saliva.
There are very different compositions of saliva produced depending on…
… the neuronal input via the parasympathetic or the sympathetic.
The process of swallowing/deglutition - step 1
The initial voluntary stage.
Where it is decided by the person to push the food to the back of the mouth to the pharynx.
The process of swallowing/deglutition - step 2
The pharyngeal stage of swallowing.
It is a reflex action controlled by the deglutition centre in the medulla and pons of the brain.
The soft palate moves up to allow the bolus to move towards the oesophagus.
What is the purpose of the epiglottis ?
It moves down to cover the glottis and the trachea so that the food moves down the oesophagus.
Breathing is stopped for a very shirt period of time when this happens.
What happens if food accidentally moves down the trachea ?
The automatic response is to cough which helps to food to come back up again and therefore allowing the food to be swallowed properly and transported too.
Why is it that food can move down the oesophagus ?
Because of the muscularis all along the GI tract which allows for the movement of food through the tract and allows for the food to be mixed as it travels through the tract.
