deck_1369872 Flashcards
What structures facilitate mastication?
• Teeth• Muscles of mastication
What is the purpose of the teeth?
• Cut (incisors)• Crush (molars)• Mix with saliva
What are the muscles of mastication?
• Masseter• Innervated by branch of trigeminal nerve
How many litres of saliva produced per day?
1.5
What are the functions of saliva?
• Lubricates and wets food• Starts digestion of carbohydrate• Protects oral environment
Give four ways saliva protects the oral environment?
• Keeps mucosa moist • Washes teeth• Maintains alkaline environment ○ Neutralises acid produced by bacteria• High calcium concentration (?) ○ Soluble in acidic solution, not in alkaline and thus do not degrade
What is the condition when you do not have enough saliva, and what occurs?
• Zerostomia (stomeeyah)• Can still eat food, but teeth and mucosa degrade very quickly
What is the tongue?
A collection of 8 muscles that work to manipulate food for mastication and form it into a bolusAids in swallowing
What are the six main constituents of saliva?
• Water• Electrolytes• Alkali• Bacteriostats• Mucus ○ Mixture of mucopolysaccharides• Enzymes - Salivary amylase
What is meant by “hypotonic” water?
• More water in saliva than in rest of body (osmotic potential body –> saliva)
How does the concentration of Na+ and Cl- in the saliva compare to that in the plasma?
• Lower concentration in saliva
How does concentration of Ca2+, K+ and I- in saliva compare to plasma?
• High concentration in saliva as compared to plasma ○ K+ as by product from production of saliva ○ I- helps control population of bacteria
What makes saliva alkaline?
• The addition of HCO3
What are the three paired salivary glands?
• Parotid• Sub Mandibular• Sub-lingual
What is the structure of the salivary glands?
• Ducted, exocrine glands
What are ducted exocrine glands made up of?
• Blind ended tubes• Connected system of ducts
What cells line the acini, or the blind ended part of the salivary glands?
• Acinar cells
What cells line the ducts of the salivary glands
• Duct cells
What kind of secretion is produced by the parotid?
• Watery secretion rich in enzymes, but little mucus (serous) • 25%
What types of secretions are produced by the sublingual glands?
• Viscous secretion• No enzymes• Lots of mucus • 5%
What secretion are produced by the sub-maxillary glands?
• All components of saliva, mix serous and mucous• Gland made up of mixture of serous and mucous acini, leading to common ducts• 70% of all saliva
How is saliva produced to be hypotonic, despite being made form extra-cellular fluid
• Glands secrete more concentrated solution and remove solute
Why isn’t saliva secreted directly in its final state?
• No cellular mechanism to secrete water
How is saliva secreted?
• Ïn a concentrated substance, from which solute is reabsorbed
What do acinar cells secrete?
• An isotonic fluid containing enzymes
What do duct cells do to pre-saliva?
• Remove Na+ and Cl-• Add HCO3-
Why does water not follow the electrolytes removed from saliva by the duct cells
• Gaps between duct cells very tight
Why is saliva more concentrated at a higher flow rate?
• Duct cells have a limit on how much Na+ and Cl- they can remove Smaller fraction removed
What happens to the pH of saliva at higher flow rates?
• Stimulus for secretion promotes HCO3- secretion• Saliva becomes more alkaline
Outline the mechanism of acinar secretion
• Cl- actively secreted into lumen of cut• Water and other ions then follow passively
How do the duct cells remove Na+ from the lumen of the duct?
• Na+/K+-ATPase antiporter on ECF membrane secretes Na+ out of cell• This generates conc gradient from Na+ from duct lumen to duct cell
How do the duct cells remove Cl- from the lumen?
• Na/K+-ATPase also increases conc of K+ within the cell• This drives expulsion of Cl- into the ECF via a K+/Cl- symport transporter• Cl- high in lumen, low in cell. Conc grad, diffusion
How is HCO3- secreted into the duct lumen?
• Cl-/HCO3- antiporter• Cl- moves into cell down conc grad, HCO3- moves into lumen
What part of the nervous system controls salivary secretion?
• Autonomic nervous system
What does parasympathetic stimulation of the salivary glands do?
• Increases production of primary secretion and increases addition of HCO3
Outline the pathway of parasympathetic stimulation of salivary glands
o Parotid Gland Glossopharyngeal Nerve (9th cranial nerve) Otic gangliono Submandibular and Sublingual Glands Facial Nerve (7th cranial nerve) Submandibular gangliono Muscarinic receptors Blocked by atropine like drugso Co-transmitters stimulate extra blood flow
Outline the parasympathetic outflow surrounding saliva stimulation
• Afferent information from ○ Mouth and tounge - taste receptors ○ Nose ○ Conditioned reflexes• All goes to medulla
Outline sympathetic stimulation of salivary glands?
• Occurs via superior cervical ganglion○ Reduces blood flow to the salivary glands○ Limits salivary flow
Where is the oropharynx found?
• Behind the oral cavity • Below the nasopharynx• Above the laryngopharynx
From what structures does the oropharynx extend to and from?
• The uvula to the hyoid bone
What structure closes over the glottis to prevent aspiration?
• The epiglottis
What is the oesophagus?
• A muscular tube that passes food from the pharynx to the stomach• Continuous with the lower part of the laryngopharynx
Outline the tissue structure of the oesophagus
• Mucosa ○ Composed of non-keratinized stratified squamous epithelium, lamina propria and a layer of smooth muscle• Submucosa ○ Containing mucous secreting glands• Muscularis externa ○ Upper third of oesophagus has striated skeletal muscle under somatic control for swallowing ○ Lower two thirds are smooth muscle under autonomic control
What does the brain stem swallowing centre do when pressure felt of pharyngeal plate
• Inhibits respiration• Raises larynx• Closes the glottis• Can open upper oesophageal sphincter
What are the three phases of swallowing?
• Voluntary phase• Pharyngeal phase• Oesophageal phase
What happens in the voluntary phase of swallowing?
• Tongue moves bolus back onto the pharynx
What happens in the pharyngeal phase of swallowing?
• Afferent information from pressure receptors in the palate and anterior pharynx reaches the swallowing centre in the brain stem.• A set of movements is triggered• Inhibition of breathing• Raising of the larynx• Closure of the glottis• Opening of the upper oesophageal ‘sphincter’
What happens in the oesophageal phase of swallowing?
• The muscle in the upper third of the oesophagus is voluntary striated muscle under somatic control• The muscle of the lower two thirds is smooth muscle under control of the parasympathetic nervous system.• A wave of peristalsis sweeps down the oesophagus, propelling the bolus to the stomach in ~9 seconds. • Coordinated by extrinsic nerves from the swallowing centre of the brain• Lower oesophageal ‘sphincter’ opens
What is dysphagia?
• The symptom of difficulty in swallowing
What is odynophagia
• The symptom of pain whilst swallowing
What is achalasia?
• Motility problems of the smooth muscle preventing peristalsis• Caused by damage and loss of nerves in gullet wall
What are the two main types of dysphagia?
• Oesophageal dysphagia• Oropharyngeal dysphagia
What is oesophageal dysphagia and how is it investigated?
• Dysphagia for solids• Investigate with barium swallow/endoscopy
What Oropharyngeal dysphagia?
• Investigate with a flexible endoscopy evaluation of swallowing, allowing you to view entire trachea
What causes dysphagia?
• Obstruction or compression of oesophagus- Tumours
What is Barrett’s oesophagus?
• An abnormal change of the epithelial cells of the oesophagus• Metaplasia from non-keratinised stratified squamous epithelia to columnar epithelium and goblet cells• Strong association with adenocarcinoma
What is gastro-oesophageal reflux disease?
• Reflux of stomach’s content’s into the oesophagus and pharynx causes cough, hoarseness and asthma
Why does gastro-oesophageal reflux damage the oesophagus?
• Does not have the same protective mucosa as the stomach
What features protect the oesophagus from reflux?
• The lower oesophageal sphincter• Angle of his (acute angle of entry of oesophagus• Positive intra-abdominal pressure compresses the oesophagus
