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.
What type of muscle is the GI tract mainly composed of ?
It is mainly composed of smooth muscle tissue but also striated muscle because of the voluntary capacity.
What is it that connects the laryngopharynx to the stomach ?
The oesophagus.
Two key processes important in movement
Peristalsis, segmentation.
Peristalsis
Concerned with propulsion of food along the GI tract.
Relies on the longitudinal muscle relaxing and contracting.
Segmentation
Occurs largely in the small intestine to facilitate mixing of food.
Relies on the circular muscle surrounding the GI tract contracting and relaxing.
Potential barriers a drug has to cross depending on the mode of delivery
Buccal - through the cheek layer.
Sublingual - under the tongue.
Why do the drugs need to dissolve across the wall of the cheek ?
In order to cross the epithelial barrier to enter the bloodstream.
Why is there a greater bioavailability for this type of drug delivery ?
This is because the drug enters the blood circulation directly without the need to go the through the digestive system and therefore avoiding the first pass metabolism - where there is a loss of drug during absorption via the gut walls.
What us this type of delivery good for ?
If the there is a need for rapid action, e.g. the class of drug that targets angina.
Issues concerning the make up of this type of drug
Solubility of the drug in saliva.
Passive diffusion - only small lipophilic drugs will be well absorbed.
The potential barriers to absorption, e.g. SA in the mouth is limited so the drug must passively diffuse through the epithelium and the basement to enter the blood stream where there is a fish blood supply and so fast onset of action, assuming drug delivery was successful.
Considerations of buccal administration
Drugs must dissolve in saliva - hydrophobicity of the drug must be considered.
Swallowing reflex - retention in the mouth is important because the drug has to stay in the mouth for a certain period of time.
SA in the mouth is limited.
The drug has to diffuse across lipophilic cell membranes and the hydrophilic interior of the cell.
Enzymatic barriers exist which can break down small peptides or proteins which limits the transport across the epithelium in the cheek.
Challenges for buccal delivery
Chemical or physical barriers.
The drug (dose) must be kept in place for absorption and excess saliva could disrupt this.
The drug’s hydrophobicity/hydrophilicity.
SA of the mouth.
Taste of the drug needs to be bland - could affect retention.
Must be a non-irritant to teeth and mouth.
Key oral/dental problems
Dry mouth - xerostomia, oral ulcers, oral thrush.
Dry Mouth
Can lead to ulceration and tooth decay.
Affects digestion and drug absorption.
Saliva preparations (lozenge/spray/gel) can be used to combat this side effect.
Oral ulcers
Vary in terms of severity - smaller ulcers clear up without any treatment.
In severe cases, the patient may require corticosteroids and anti-inflammatories and an anti-microbial mouthwash to prevent infection.
There are OTC treatments but sometimes patients may require prescriptions.
Oral thrush
Yeast infection-caused by the over use of antibiotics, poor immune system, underlying disease, smoking, diet, dentures.
Treatment aimed at reducing fungal infection using an anti-fungal gel e.g. miconazole, nystatin.
Certain medications can lead to…
…dental issues and may result in tooth decay e.g. antacids, pain medications, antihistamines.
Inhalers
Those who require the frequent use of inhalers may have dental problems.
Inhalers contain an ingredient, beta-adrenergic agonist which is slightly acidic and so is harmful so tooth enamel overtime.
Advice for dental hygiene
Drink plenty water.
Brush teeth twice a day and get regular dental checkups.
Use a moisturising mouth spray.
Reduce/give up smoking.
Reduce intake of caffeinated or dehydrating drinks.
Use a hydrating mouth wash.
