Physiology Of Mouth, Pharynx & Oesophagus Flashcards
What’s the function of saliva?
Lubricate and wet food to allow easy swallowing
Begins digestion of starch and lipids
Protects oral cavity by maintaining alkaline environment
Helps with taste
What’s the composition and pH of saliva?
Water High concentration of K+, HCO3-, Ca2+ Low concentration of Na+ and Cl- Digestive enzymes (salivary a amylase and lingual lipase) Antibacterial agents PH 6.2 - 8
What 3 exocrine glands are involved and what do they produce?
Define exocrine gland
Parotid glands - enzymes
Sublingual glands - mucous
Submandibular glands - serous and mucous producing
Also tiny buccal and Von Ebners glands of the tongue
Exocrine = secrete substance into a duct and release onto epithelial surface
Describe the structure of salivary glands
Look like a bunch of grapes
Acini lined by acinar cells for initial secretion
Ducts lined by duct cells to modify secretion
Myoepithelial cells contract to eject salive
Outline mechanism of saliva production
Primary secretion by acinar cells: isotonic filtrate from plasma diffuses through acinar cells
Ductal modification: Na+ and Cl- absorbed, K+ and HCO3- secreted
Ductal cells not permeable to H20 so solution now hypotonic
What’s the difference between resting and stimulated saliva?
Rest: flow rate is low, neutral pH very hypotonic, few enzymes, highly modified
Stimulated: HCO3- increases with increased flow rate, less hypotonic, lots of enzymes
How is saliva production controlled?
PNS: increases production in response to mechanoreceptors on tongue, taste, sight, smell of food
Production reduced by fear, dehydration
SNS: overall reduces production = dry mouth in stress
What are the 5 taste classifications?
Where on the tongue are tastebuds found?
Sweet, sour, umami, bitter, salty
In papillae: fungiform, foliage and circumvallate papillae
Describe the process of taste - what’s the nerve supply?
Taste buds contain chemoreceptors which send afferent information to the medulla via cranial nerves which are transmitted to sensory cortex
CN VII anterior 2/3 of tongue taste; posterior 1/3 by CN IX
Olfaction (CN I) also contributes to sense of flavour
What muscles are involved in mastication and their nerve supply?
Anything else?
Masseter muscle
Temporalis muscle
Medial and lateral pterygoid muscles - all CN V motor
Teeth: incisors and molars
What’s the function of mastication?
Physical digestion of food - breaking it up to increase surface area for enzymes
Movement of mandible, tongue, cheeks, lips help mix bolus with saliva for swallowing
Outline the physiology/anatomy of the oesophagus
Muscular tube that transports food by peristalsis
Superior 1/3 is striated muscle, voluntary control
Inferior 1/3 is involuntarily controlled smooth muscle
LOS controls movement of food between oesophagus and stomach
Where are the 4 points of compression (narrowing) of the oesophagus?
Junction between pharynx and oesophagus
Superior mediastinum where it’s crossed by arch of aorta
Posterior mediastinum where oesophagus is posterior to L main bronchus
At the oesophageal hiatus in diaphragm
Outline the phases of swallowing
Oesophageal muscles contract to pass bolus of food to stomach, but LOS muscle relaxes
Oral phase: voluntary movement of bolus towards oropharynx (sensory receptors -> medulla = swallowing reflex)
Pharyngeal phase: involuntary phase protects respiratory tract as bolus enters oesophagus though UOS (respiration inhibited, glottis closes, epiglottis tilts to cover opening of larynx, larynx elevated)
Oesophageal phase: UOS closes, LOS opens: peristaltic waves
How is the respiratory tract protected during swallowing?
In the pharyngeal phase
Epiglottis tips forward to inhibit respiration, glottis closes and UOS opens to allow bolus into oesophagus
