What is the reason for chewing
- Grind and break up food for swallowing
- Mix food with saliva
- Stimulate taste buds
What does saliva contain
- Mucous
- Proteins (including immunoglobulin A)
- Enzymes
What are the 3 main pairs of branched glands that produce saliva
- Parotid (cheek) x2
- Submandibular (under chin) x2
- Sublingual (under tongue) x2
- Other glands produce the other 5% of saliva
What part of the salivary gland are responsible for primary secretion of saliva
Acinar
What do the duct cells do
Modify the primary secretion - actively reabsorb Na+ and Cl- ions, some secretion of K+ and HCO3- ions
What is salivary secretion under the control of
Neural control
Function of saliva
- Contains salivary amylase which breaks down polysaccharides
- Produces mucous which facilitates swallowing
- acts as a solvent to stimulate taste
- Protective function (secrets lysosome and immunoglobulin A)
- Promotes oral hygiene
- Moisturises (aids speech)
- Contains bicarbonate (neutralises acids in food to reduce dental cavities)
What are the two phases of swallowing
Oropharyngeal - food directed to oesophagus (requires sealing off nasal passages (by uvula) and the trachea (by glottis)
Oesophageal - Oesophagus protected from damage caused by passing food bolus by mucous secretion
-Movement by peristalsis (gravity assisted)
Functions of stomach
- Storage of food
- Initiation of digestion of proteins
- Kill ingested bacteria (via acid)
- Formation of chyme (mixture of food with secretions from stomach), before transfer to small intestines
How is saliva secretion controlled when there is a stimulus (taste, smell, chewing)
1) Pressure receptors and chemoreceptors in mouth
2) Salivary centre in medulla collects info
3) Autonomic nerves activated
4) Salivary glands activated which then leads to salivary secretion
What does parasympathetic stimulation of acing cells produce
A large volume of serous saliva, rich in enzymes
How does parasympathetic stimulation produce saliva
1) Causes release of kallikrein which acts on a substrate
2) This activates bradykinin which causes vasodilatation and increased capillary permeability
3) Blood now passes via Cinar cells into secretory duct to become saliva
Does saliva contain more or less ions than plasma
Fewer
How do sympathetic nerves do to saliva production
Activate glands that produce a mucous secretion so there’s an increase in saliva production
What regions of the stomach are important in digestion
Antra region and body of stomach
