What is the purpose of chewing?
Prolong taste experience
Defence against respiratory failure
How is chewing controlled?
Voluntarily - somatic nerves controlling the skeletal muscles of the mouth/jaw
Reflex - contraction of jaw muscles causes pressure of food against gums, hard palate and tongue, activates mechanoreceptors causing inhibition of jaw muscles, reducing pressure causing contractions
Explain the process of the reflex that controls chewing?
1) Contraction of jaw muscles causes pressure of food against gums, hard palate and tongue
2) Activates mechanoreceptors causing inhibition of jaw muscles
3) Reduces the pressure causing contractions
What are the 3 pairs of glands that secretes saliva?
What is in saliva?
What is the function of water in saliva?
Softens, moistens, dilutes particles (controls osmosis)
What is the function of mucin in saliva?
Combines with water to make mucus, viscous solution to perform lubricant function
What is the function of a-Amylase in saliva?
Catalyses breakdown of polysaccharides into disaccharide
What is the function of electrolytes in saliva?
What is the function of lysozyme in saliva?
Bactericidal - cleaves polysaccharide component of bacterial cell wall
Why would teeth enamel dissolve without saliva?
Saliva increases the pH
What class are the glands that secrete saliva?
What does the serous alveolus of glands release?
a-amylase and other proteins
What does the mucous alveolus of glands release?
Mucus which enters the duct where water is secreted
What controls salivary secretion?
Parasympathetic nervous system
Sympathetic nervous system
What parasympathetic nerves control salivary secretion?
Cranial nerve VII (facial)
Cranial nerve IX (glossopharyngeal)
What effect does parasympathetic nerves have on saliva secretion?
Stimulates profuse watery salivary secretion
What effect does sympathetic nerves have on salivary secretion?
Stimulates small volume, viscous salivary secretion, high mucus content (a1 adrenoceptors) and high amylase content (B2 adrenoceptors)
What receptor does the sympathetic system act on to create high mucus content saliva?
What receptor does the sympathetic system act on to create high amylase content saliva?
Explain the reflex control of salivary secretion?
Presence of food in mouth activates chemoreceptors/pressure receptors in the walls of mouth/tongue
What is special about the sympathetic and parasympathetic effects on salivary secretion?
They are both stimulatory
What is the oesophagus?
25cm conduit (pipe) between the pharynx and stomach
What is the length of the oesophagus?
What are the 4 layers of the oesophagus?
What is the mucosa of the oesophagus lined by?
Stratified squamous epithelium (non-keratinised)
Why is it important that musosa of oesophagus is stratified and not simple?
Food would destroy a simple layer
Why is it important that the mucosa of the oesophagus is non-keratinised?
So it is flexible
What is contained by the submucosa of the oesophagus?
Submucosal mucous glands
What do submucosal glands secrete?
Mucous for lubrication