Mouth and Swallowing Flashcards
Function of lips?
Act as guard, can be opened and closed to seal
Function of teeth?
Give us a way of mechanically processing food
Function of hard palate?
mechanical processing
Function of soft palate?
- Muscular section - Acts as a control flap to seal off the larynx - Soft palate, together with the epiglottis, ensure that food and air don’t end up in wrong places
Where are the incisors?
Central and lateral incisors at front of mouth
What is the function of the incisors?
Cut off pieces of food (blade-like)
Function of cuspids (canines)?
Pointed teeth, spike food and allow us to tear them
How many roots do cuspids have?
Single root
Describe premolars and molars
Bicuspids (2 cusps) Molars (3 or 4 roots) Good at crushing and grinding food, jaw moves laterally
What is mastication?
Chewing
What are the muscles of mastication associated with?
Movements of the jaw (temporomandibular joint)
What are the 4 muscles of mastication?
- Masseter 2. Temporalis 3. Medial pterygoid 4. Lateral pterygoid
Embryologically, where do the muscles of mastication develop from?
The first pharyngeal arch
What are the muscles of mastication innervated by?
A branch of the trigeminal nerve –> the mandibular nerve
What is the most powerful muscle of mastication?
The masseter muscle
Describe the masseter muscle
- Quadrangular in shape, and can be split into two parts; deep and superficial. -The entirety of the muscle lies superficially to the pterygoids and temporalis, covering them.
Where does the masseter muscle originate from?
From maxillary process of the zygomatic bone. The deep part originates from the zygomatic arch of the temporal bone. Both parts attach to the ramus of the mandible.
What is function of masseter muscle?
Elevates the mandible, closing the mouth
Where does the temporalis muscle originate from?
The temporary fossa (a shallow depression on the lateral aspect of the skull) It condenses into a tendon, which inserts onto the coronoid process of the mandible.
What is the temporalis muscle covered by?
Tough fascia
What is the mandible?
The mandible, or lower jaw, is the bone that forms the lower part of the skull, and along with the maxilla (upper jaw), forms the mouth structure. Movement of the lower jaw opens and closes the mouth and also allows for the chewing of food.
What is the function of the temporalis muscle?
Elevates the mandible, closing the mouth. Also retracts the mandible, pulling the jaw posteriorly.
Describe the medial pterygoid muscle?
Has a quadrangular shape, with two heads; deep and superficial. It is located inferiorly to the lateral pterygoid
Where does the medial pterygoid muscle originate from?
The superficial head originates from the maxillary tuberosity and the pyramidal process of palatine bone. The deep head originates from the lateral pterygoid plate of the sphenoid bone. Both parts attach to the ramus of the mandible, near the angle of mandible
What is function of medial pterygoid?
Elevates the mandible, closing the mouth
Describe the lateral pterygoid?
The lateral pterygoid muscle has a triangular shape, with two heads; superior and inferior.
What enables the lateral pterygoid to be a major protractor of the mandible?
It has horizontally orientated muscle fibres
Where does the lateral pterygoid muscle originate from?
The superior head originates from the greater wing of the sphenoid. The inferior head originates from the lateral pterygoid plate of the sphenoid. The two heads converge into a tendon, which attaches to the neck of the mandible.
What is function of lateral pterygoid?
Acting bilaterally, the lateral pterygoids protract the mandible, pushing the jaw forwards. Unilateral action produces the ‘side to side’ movement of the jaw.
Overall, what actions do the mandibular muscles provide in chewing?
Elevation and depression Protraction and retraction Medial and lateral movement
What moves the food across teeth?
Tongue and cheeks
What are the 3 major salivary glands?
- Parotid gland 2. Sublingual gland 3. Submandibular gland
What are the roles of saliva?
- Lubrication (of mouth and food) - (serous fluid) - Cleaning (mucus) - Facilitation of taste - Protection against acid and bacteria - Digestion
How does saliva aid in protection against acid and bacteria?
Antibacterial enzymes (e.g. lysozyme, IgA) Bicarbonate Calcium ions
How does saliva aid in digestion?
Salivary amylase (ptyalin), lingual lipase
How is saliva production increased?
Both parasympathetic (watery) and sympathetic (mucoid) activity increase secretion
What is parasympathetic activity on saliva controlled by?
Salivatory centre in the brainstem driven by: - Local stimuli (taste and touch in the mouth) - Central stimuli (smell & sight of food, etc) - (learned) reflex – think of Pavlov’s dogs
What is the ‘salivon’?
The structural unit of the salivary gland is the salivon, consisting of acinar cells
What does initial isotonic fluid secreted by salivon contain?
Mainly NaCl, protein and/or mucus
As the fluid passes along the intercalated duct and through striated duct, what occurs?
Salt reabsorption and HCO3- (and K+) secretion leads to a hypotonic, alkaline fluid Fluid becomes more alkaline due to bicarbonate (hence it being hypotonic)
Why is flow rate through the salivon important?
Saliva more diluted and more alkaline
What is the largest salivary gland? What % does it contribute to salivary volume
Parotid gland About 50% of salivary volume (predominantly serous secretion)
The parotid gland can be anatomically divided into deep and superficial lobes. What are these separated by?
The facial nerve
The parotid gland lies within the parotid region (a deep hollow). What is this region bounded by?
- Superiorly – Zygomatic arch. - Inferiorly – Inferior border of the mandible. - Anteriorly – Masseter muscle. - Posteriorly – External ear and sternocleidomastoid.
What is the parotid gland a main source of?
Salivary amylase and proline-rich proteins
Where does the parotid gland receive parasympathetic innervation from?
It begins with the glossopharyngeal nerve (cranial nerve IX). This nerve synapses with the otic ganglion (a collection of neuronal cell bodies). The auriculotemporal nerve then carries parasympathetic fibres from the otic ganglion to the parotid gland.
What is effect of parasympathetic stimulation on parotid gland?
increase in saliva production.
Where does the parotid gland receive sympathetic innervation from?
Sympathetic innervation originates from the superior cervical ganglion, part of the paravertebral chain. Fibres from this ganglion travel along the external carotid artery to reach the parotid gland
What is effect of sympathetic stimulation on parotid gland?
Inhibits saliva secretion, via vasoconstriction.
What is the most common site of a salivary gland tumour?
Parotid gland
What does the sublingual gland secrete? Why are these secretions important?
- Predominantly mucous - About 5% of salivary volume These secretions are important in lubricating food, keeping the oral mucosa moist and initial digestion.
What is the main source of lingual lipase?
Sublingual gland
What are the smallest of the salivary glands?
Sublingual glands
Where does the sublingual gland receive parasympathetic innervation from?
Supply via CN VII (facial) Parasympathetic innervation originates from the superior salivatory nucleus through pre-synaptic fibres via the chorda tympani branch of the facial nerve (CNVII). The chorda tympani then unifies with the lingual branch of the mandibular nerve (CNViii) before synapsing at the submandibular ganglion and suspending it by two nerve filaments. Post-ganglionic innervation consists of secretomotor fibres
What is effect of parasympathetic innervation on sublingual gland?
Directly induce the gland to produce secretions, and vasodilator fibres which accompany arteries to increase blood supply to the gland. Increased parasympathetic drive promotes saliva secretion.
Where does the sublingual gland receive sympathetic innervation from?
Supply from superior cervical ganglion Sympathetic innervation originates from the superior cervical ganglion, where post-synaptic vasoconstrictive fibres travel as a plexus on the internal and external carotid arteries, facial artery and finally the sublingual and submental arteries to enter each gland.
What is effect of increased sympathetic drive on sublingual gland?
Reduces glandular bloodflow through vasoconstriction and decreases the volume of salivary secretions, resulting in a more mucus saliva.
Describe secretions of submandibular gland. What is function of these secretions?
- Mixed serous and mucous secretion - About 45% of salivary volume Important for the lubrication of food during mastication to enable effective swallowing and aid digestion.
What enzymes is the submandibular gland a main source of?
Lysozyme and lactoperoxidase
Where does the submandibular gland receive parasympathetic innervation from?
Via CN VII (facial –> chorda tympani –> lingual nerve) Parasympathetic innervation originates from the superior salivatory nucleus through pre-synaptic fibres, which travel via the chorda tympani branch of the facial nerve (CNVII). The chorda tympani then unifies with the lingual branch of the mandibular nerve (CNViii) before synapsing at the submandibular ganglion and suspending it by two nerve filaments. Post-ganglionic innervation consists of secretomotor fibres
What is effect of parasympathetic stimulation on submandibular gland?
Directly induce the gland to produce secretions, and vasodilator fibres which accompany arteries to increase blood supply to the gland. Increased parasympathetic drive promotes saliva secretion.
Where does the submandibular gland receive sympathetic innervation from?
Superior cervical ganglion (travels with facial artery) Sympathetic innervation originates from the superior cervical ganglion, where post-synaptic vasoconstrictive fibres travel as a plexus on the internal and external carotid arteries, facial artery and finally the submental arteries to enter each gland
What is effect of sympathetic innervation on submandibular gland?
Increased sympathetic drive reduces glandular bloodflow through vasoconstriction and decreases the volume of salivary secretions, resulting in a more mucus and enzyme-rich saliva.
Where is ptaylin a-amylase found?
In saliva
What is function of ptaylin a-amylase?
Initial break down starch into maltose and dextrin
What is starch and other large polysaccharides made up of?
a-1,4 and a-1,6 linkages (the latter causes branches)
Where can a-amylases cut?
Only at a-1,4 sites and not adjacent to the a-1,6 sites
What is optimum pH of a-amylase?
About 7 (denatured at pH 4)
What is function of lingual lipase?
Family of digestive enzymes - involved in initial digestion of triglycerides Cleave the outer fatty acids off triglycerides, leaving diacyl glycerol
What is optimum pH of lingual lipase?
About 4
Where is lingual lipase stable/denatured?
Stable in stomach, denatured by pancreatic proteases
What does lingual lipase work together with?
Gastric lipase
Where are the taste buds found?
Located around the small structures known as papillae found on the upper surface of the tongue, soft palate, upper esophagus, the cheek, and epiglottis. These structures are involved in detecting the five elements of taste perception: salty, sour, bitter, sweet and umami.
What are the 3 types of papillae?
- Foliate 2. Circumvallate 3. Fungiform
Where are the foliate papillae located?
these are ridges and grooves towards the posterior part of the tongue found at the lateral borders
Where are the circumvallate papillae located?
they are present at the back of the oral part of the tongue
What is function of the fungiform papillae?
the most numerous type but do not contain taste buds.[4][5] They are characterized by increased keratinisation and are involved in the mechanical aspect of providing abrasion.
What are taste sensors?
Clusters of specialised epithelial cells - sense the taste can secrete neurotransmitters to talk to a neural cell – supported by other cells
What sensors can detect salty and sour (acidic)?
Ion channel based sensors
What sensors can detect sweet Unami (delicious) and bitter tastes
GPCR-based senosors Protection against poison
What are odour receptors?
Nerve cells (similar to taste but in nose) Makes up large part of taste
Where does food pass during swallowing?
Pharynx (through oropharynx and laryngopharynx to oesophagus)
What are the 3 phases of swallowing?
- Voluntary phase 2. Pharyngeal phase 3. Oesophageal phase
Describe the voluntary phase of swallowing?
- Mastication leads to a bolus of food being produced 2. Inspiration is inhibited and the bolus of food is moved to the pharynx by the tongue. 3. This leads to the stimulation of the swallowing reflex
How does the airway remain open during mastication?
The back of the tongue is elevated and the soft palate pulled anteriorly against it - this keeps the food within the oral cavity and allows the airway to remain open)
Describe the pharyngeal phase of swallowing?
- Once the bolus has been moved to the pharynx, pressure receptors are activated in the palate and anterior pharynx 2. This signals the swallowing centre in the brain stem which inhibits respiration, raises the larynx, closes the glottis, opens the upper oesophageal sphincter 3. The soft palate is elevated to close the nasopharynx to allow passage of food. In addition to this, the true vocal cords close to prevent aspiration. 4. The bolus is moved towards the oesophagus
How is the bolus moved towards the oesophagus during the pharyngeal phase?
Via peristalsis of the pharyngeal constrictor muscles.
What are the main factors affecting the speed of which the bolus is moved towards the oesophagus?
Gravity makes very little contribution to this process and the main factors affecting the speed of this are the viscosity and volume of the bolus
Describe the upper and lower parts of the oesophagus
- Upper 1/3 is voluntary skeletal muscle - Lower 2/3 are involuntary smooth muscle
Describe oesophageal phase of swallowing
- At the beginning of this phase, the larynx lowers, returning to its normal position - The bolus is moved down the oesophagus via peristalsis, which is coordinated by extrinsic nerves. Each area of muscle systematically relaxes to allow food through and contracts afterwards to propel it further
How is reflux and prevented during oesophageal phase?
The cricopharyngeus muscle contracts
Describe histology of oesophagus. Why is this structure useful?
Stratified squamous epithelium, thrown into folds Useful for when cells are lost from eating – easily replaced (e.g. when a small, sharp bone is swallowed)
What do submucosal oesophageal glands secrete and why?
Secrete mucus to facilitate passage of food bolus
What is oesophagus innervated by?
Fibres from oesophageal plexus
What is the cephalic phase of digestion?
The cephalic phase of gastric secretion occurs before food enters the stomach due to neurological signals.
What is the cephalic phase initiated by?
A combination of stimuli, some conscious, some not (sight, smell, thought) –> enhanced secretory activity is a conditioned reflex
What % of gastric secretion does the cephalic phase account for?
About 20 % of the gastric secretion associated with eating a meal
What is the cephalic phase mediated by?
The parasympathetic nervous system - Salivary secretion via facial glossopharyngeal nerves (CN VII and IX) - Control of GI motility and secretion via vagus (CN X) Vagus also carries afferent fibres which contribute – feedback system.
Describe chain of events of cephalic phase
- Thinking of food (i.e., smell, sight) stimulates the cerebral cortex. 2. The cerebral cortex sends messages to the hypothalamus, the medulla, and the parasympathetic nervous system via the vagus nerve, and to the stomach via the gastric glands in the walls of the fundus and the body of stomach. 3. The gastric glands secrete gastric juice. 4. When food enters the stomach, the stomach stretches and activates stretch receptors. 5. The stretch receptors send a message to the medulla and then back to the stomach via the vagus nerve. 6. The gastric glands secrete more gastric juice.
Oral cavity diagram
