3.2 The Mouth Flashcards
What are the 3 overall processes occurring in the mouth?
1) Salivation
2) Mastication (formation of a bolus)
3) Swallowing
What epithelia lines the tongue and what 3 other structures are found within this epithelium?
Describe the muscle structure of the tongue and what this allows
Stratified squamous non keratinized with:
- dorsal papillae: some with taste buds
- serous and mucus acini from salivary glands
- lymphoid tissue
Skeletal muscle with fibres oriented in multiple planes with the intrinsic muscles interdigitate directly with the CT of the tongue - allows wide variety of movement
How much saliva do we produce a day?
Name 3 of its main functions
- 5L
1) Lubrication
2) Starts digestion of carbs (amylase)
3) Protects the oral environment
Name 5 mechanisms saliva uses to protect the oral environment
1) Keeps mucosa moist
2) High calcium concentration washes and protects the teeth
3) Maintaining a highly alkaline environment- neutralizes the acid produced by bacteria
4) Proteolytic enzymes containing lysozyme attack and destroy the bacteria
5) Secretory antibodies (IgA) destroy some microbes in the mouth
What are the 3 major salivary glands, what enzymes does each produce and what is the structure of each gland? List these in order of their volume in saliva
1) Submandibular (70%) is a tubule-acinar gland: serous and mucus (a-amylase and lysozyme)
2) Parotid (25%) is an acinar gland: serous fund (a-amylase)
3) Sublingual (5%) are branched tubule-acinar glands: mainly mucous (no enzymes)
Describe the structure of an exocrine gland including its 2 main componenets
What do the secretions from each of these determine about saliva?
Blind ended tubes comprised of: acini, lined with acinar cells connected to a system of ducts, each ending in a single outlet lined by duct cells
Acinar secretion: determines the volume
Ductal modification: determines the composition
Mechanism of secretion of serous saliva secretion
Final saliva is always ______ to the ECF, but it must be made from it. There is no cellular mechanism to secrete ______ directly, so instead we must first secrete a fluid that is ______ with the ECF through _______ secretions. Then we must remove ions through _______ modification
hypotonic, water, isotonic, acininar secretion, ductal
Compare acinar secretions with the ECF
Acinar secretions contain a fluid that is isotonic with the ECF
- [Na+] and [K+] = about the same
- [I-] = greater
- [Cl-] = slightly less
- [HCO3] = about the same
- Plus enzymes
What is the purpose of ductal modification?
What 2 modifications occur?
Additon and/or removal of ions to produce a HYPOtonic and Alkaline solution of saliva
1) Remove [Na+] and therefore [Cl-] ➞ to achieve hypotonicity (removing Na+ will also cause a slight increase in [K+])
2) Add [HCO3], this is to achieve alkalinity
What can be said about ductal modification in resting vs stimulated saliva?
Resting: LOW flow rates, MORE modification occurs
- duct cells remove most Na+, so saliva is very hypotonic
Stimulated: HIGH flow rates, LESS modification (except for HCO3)
- ducts cells remove a smaller fraction of Na+, so saliva becomes less hypotonic (but still hypotonic)
Note: duct cells have a maximum rate of modification
Why is there increased [HCO3] in stimulated saliva even though we know less ductal modification occurs?
Because the intial stimulus to increase secretion also promotes HCO3- secretion by duct cells. Thus allowing stimulated saliva to become more alkaline
List 4 comparisons between resting and stimulated saliva acinar secretions?
Which is more modified?
Resting: MORE modified
1) low volume
2) very hypotonic
3) neutral or slightly acidic (no stimulus for increased secretion)
4) few enzymes
Stimulated: LESS modified
1) high volume
2) less hypotonic
3) more alkaline (HCO3 promoted by stimulus to increase secretion)
4) Lots of enzymes
Salivary secretion is largly under autonomic nervous system control.
What is the sympathetic vs parasympathtic nerve stimulation?
Sympathetic: Superior cervical ganglion
Parasympathetic:
- glossopharyngeal nerve (CN IX) ➞ parotid gland (via otic ganglion)
- facial nerve (CN VII) ➞ submandibular + sublingual (via submandibular ganglion)
Give 3 sources that can stimulate salivation
1) Taste receptors in the mouth and tongue (esp stimulated by acid) via CN IX and VII
2) Nose (smell)
3) Conditioned reflexes (Remember Pavlov’s dog)
All send afferent information to centres in the medulla
Give 3 things Parasympathetic stimulation has on saliva
PNS stimulates secretions by:
- acinar cells to promote formation of primary secretion
- duct cells to promote HCO3 secretion
- co-transmitters also stimulate extra blood flow
Give 2 effects of Sympathetic stimulation on saliva
SNS stimulation decreases secretions by:
- produces thicker secretions
- reduces blood flow to the glands
Resulting in a dry mouth
What drugs can block Parasympathetic outflow to the salivary glands and where do they act?
Atropine-like drugs ➞ block Muscarinic receptors
Why is a typical symptom of anxiety a “dry mouth”?
Effects of anxiety are under sympathetic control. Activation of this will cause reduced blood flow to the salivary glands resulting in a decrease in secretion, producing the characteristic dry mouth
How is saliva moved from the glands to the oral cavity?
Contraction of myoepithelial cells surrounding acini,
tubules and small ducts helps move saliva towards the oral cavity.
What are our 2 main tools for mastication?
1) teeth (incisors which cut and molars which crush)
2) 4 powerful muscles of mastication
Name 4 muscles that aid in mastication and how they act on the mandible
What nerve are they innervated by?
1) Masseter: elevates
2) Temporalis: elevates and retracts
3) Medial pterygoid: elevation and side-side movements
4) Lateral pterygoid: protrusion and side-side movements
Innervated by branch of trigeminal nerve (V3 mandibular nerve)
Give the 2 main nerves (PNS) that control salivary secretion
Give the 2 main nerves that control mastication
Salivary secretion: Glossopharyngeal nerve (IX) and facial nerve (VII)
Mastication: Trigeminal nerve (V) + some facial nerve (VII)
What are the three phases of swallowing? Which parts are voluntary and involuntary
1) Oral phase: voluntary
2) Pharyngeal phase: involuntary
3) Oesophageal phase: Involuntary
What happens during the first phase of swallowing?
1) Oral phase: voluntary
- Food is moistened with saliva and a food bolus is formed.
- The tongue pushes the bolus to the back of the throat
What is the second phase of swallowing also known as and what initiates it?
What happens upon initiation?
Pharyngeal phase: Involuntary (PNS) “the swallow reflex”
Initiated by stimulation of tactile receptors in the oropharynx
1) soft palate lifts to block the nasal cavity ➞ bolus moves to back of tongue
2) tongue moves to block the oral cavity and prevent the bolus re-entering ➞ epiglottis is pushed backwards over larynx
3) larynx and vocal folds contract to block the entry into the trachea and protect the airway (respiration temporary blocked)
4) upper oesophageal sphincter opens allowing passage into oesophagus
Note: look at image below. 3 things must be blocked which are the nasal cavity, oral cavity and entry into trachea
What happens during the third phase of swallowing and what controls this?
Oesophageal Phase: involuntary (co-ordinated by extrinsic nerves and swallowing centres in brainstem)
1) food bolus is propelled down the oesophagus by peristalsis and larynx moves down back to the original position
2) rapid wave of peristalsis sweeps down the oesophagus, causing upper and lower oesophageal sphincters to open
3) food follows and passes into the stomach
What cranial nerves control the first phase of swallowing?
Oral preparatory phase:
- I olfactory: smell
- V trigeminal: Mandibular movement
- VII facial : elevation of hyoid and tongue base
- XI: tongue
- XII hypoglossal: intrinsic & extrinsic tongue muscles
1, 5, 7, 11, 12
What cranial nerves control the second phase of swallowing?
Pharyngeal phase
- V trigeminal : elevation of larynx
- VII facial : elevation of hyoid.
- X vagus: constrictors, cricopharyngeus, vocal folds
- XI accessory: pharynx
- XII hypoglossal: hyoid and larynx
5, 7, 10, 11, 12
What cranial nerves control the third phase of swallowing?
involuntary: cranial nerve X (vagus nerve)
What is dysphagia and what 2 things may it be caused by?
Difficulty swallowing, possible causes include:
1) Motility problems (eg. Achalasia)
2) Obstruction or compression of oesophagus (eg. tumors)
What is Achalasia?
A motility problem in muscles of the LES causing it to fail to open up during swallowing. This leads to a backup of food within oesophagus + food can’t pass into the stomach
Can result in Dysphagia
Which nerves might be affected causing dysphagia?
Lower cranial nerves:
- V trigeminal
- VII facial
- IX glossopharyngeal
- X vagus
- XI accessory
- XII hypoglossal
Name 4 aquired causes of dysphagia
1) Cervical spinal cord injury
2) Post-surgery
3) Guillian Barre syndrome
4) Poliomyelitis
Name 6 neuro-degenerative diseases that can cause dysphagia
1) Parkinsons
2) Alzheimer’s
3) Dementia
4) Multiple sclerosis
5) Myasthenia gravis
6) Muscular dystrophy
