Swallowing Flashcards
3 functions of swallowing
- propels food/ saliva from oral cavity –> stomach
- clears naso-pharynx and oro-pharynx
- protects upper resp tract
compare 2 types of swallow
- voluntary swallow: conscious, initiated by substances in mouth, involves cortex
- spontaneous swallow: unconscious eg sleep, no cortical influence, protective
3 phases of swallowing in order
- oral
- pharyngeal
- oesophageal
name the 2 stages of the oral phase of swallowing
- preparatory stage: bolus formation
2. oral phase proper: bolus moved towards oropharynx
details of preparatory stage of oral phase of swallowing including muscles involved
BOLUS FORMATION: -tip of tongue against incisors/ maxillary alveolar ridge
- intrinsic muscles of tongue form trough to allow bolus formation
- saliva helps form bolus
details of oral phase proper including muscles involved
oral phase proper: bolus moved towards oropharynx.
- extrinsic muscles of tongue–> elevation, roll tongue back
- aided by 3: muscles of mastication, mylohyoid muscles, buccinator
how long does it last:
a. oral phase
b. pharyngeal phase
a. oral phase: 1s
b. pharyngeal phase: 0.6s
which phases of swallowing are reflex/ voluntary
oral: voluntary (so CAN be interrrupted)
pharyngeal and oesophageal: reflex
difference/ function of pharynx and larynx
pharynx: first part of throat, made up of nasopharynx, oropharynx and hypopharynx
larynx: voicebox. made up of thyroid, cricoid and epiglottis cartilage + arytenoid, corniculate and cuneiform cartilage
movement of the pharynx during the pharyngeal phase of swallowing
superiorly
movement of the larynx during pharyngeal phase
anterior and superior
name the 4 elevator muscles of the pharynx/larynx
suprahyoid muscles: -digastric, longitudinal elevators : -palatopharyngeus -stylopharyngeus -salpingopharyngeus
name the 3 constrictor muscles of the pharynx
- superior constrictor
- middle constrictor
- inferior constrictors (thyropharyngeus + cricopharyngeus)
at what point does swallowing become irreversible
when bolus reaches oropharynx (can be slowed but not stopped)
3 ways LOWER airway is protected during pharyngeal phase of swallowing
1 way UPPER airway is protected during pharyngeal phase of swallowing
-larynx moves anterior and superiorly (MAIN ONE)
-epiglottis closes over larynx
-adduction (closure) of true + false vocal cords
UPPER AIRWAY: contraction of soft palate to seal off nasopharynx
name the 2 soft palate muscles involved in swallowing and their role
-tensor veli palatini
-levator veli palatini
both wall of nasopharynx –> food does not go to/ through the nose
3 inhibitory events of pharyngeal phase
- inhibition of infrahyoid mm –> hyoid bone can move superiorly (to elevate pharynx/ larynx)
- inhibition of posterior cricoarytenoid mm –> vocal cords adduct to protect airway
- inhibition of upper oesophageal sphincter (cricopharyngeus m, lower part of inferior constrictor m of pharynx) so bolus can move down in to the oesophagus
what muscle contributes to the upper oesophageal spincter?
lower (cricopharyngeus) part of inferior constrictor muscle of the pharynx
4 factors that ensure maximal opening of oesophageal spincter
- suprahyoid muscle contraction –> upper superior excursion of the larynx
- tonic discharge from nucleus ambiguus –> inhibition of cricopharyngeus
- descending pressure of the bolus
- peristaltic movement (involuntary)
how long does it take the cricopharyngeus m to relax
0.5s
saliva moistens food. 2 reasons why this is important
- less inclined to swallow dry bolus
2. choking hazard
describe position of piriform recess and its relevance
under arythenoid cartilage (posterior, top of larynx)
–> food can get trapped here (eg fish bones), tumours can form (poor prognosis as they can grow lots before symptoms begin)
name the cell layers surrounding oesophagus in –> out
- epithelium
- submucosa
- circular muscle
- longutinal muscle
- connective tissue
how does the structure of the oesophagus vary from the rest of the digestive tract
connective tissue is ADVENTITIA (not serosa), as the oesophagus is not covered by peritoneum
what parts of the oesophagus support vessels and nerves?
adventitia (outer connective tissue) and submucosa
describe the muscle in different parts of the oesophagus
- upper 1/3: striated
- middle 1/3: striated + smooth
- final 1/3: smooth
what is unusual about the muscles involved in pharyngeal/ oesophageal phases of swallowing?
striated muscle NOT under voluntary control
what causes relaxation of the cricopharyngeus m?
tonic discharge from nucleus ambiguus
lesions in what 2 areas of the brainstem cause dysphagia
- nucleus of solitary tract (NTS)
- reticular formation (RF)
name/explain 2 theories about control of swallowing
- reflex chain theory: each reflex stimulates next step
- central pattern generator: afferents from cortex/ face/ mouth/ pharynx/ tongue –> NTS/ RF –> cranial/ cervical nerve efferents –> palate, tongue, pharynx etc
relationship between swallowing and respiration in adults and explain
swallowing is DOMINANT to respiration: respiration stops when we swallow
at what part of respiration does swallowing occur
a. when conscious
b. when unconscious
a. when conscious: expiratory
b. when unconscious: expiratory AND inspiratory
why can’t you swallow with your mouth open
supra and infra hyoid muscles doing different things to depress mandible v swallow
explain how swallowing differs to adults in infants 2
- tongue protrudes (to help eject milk)
- can breathe throughout swallowing (epiglottis vertical + nasopharynx not sealed off by soft palate muscles)
describe passage of milk in infants
oral cavity –> pharynx –> piriform recess –> larynx
what is the gold standard of investigating a swallow
videofluorographic swallowing study (VFSS): real time monitoring of swallowing throughout aerodigestive tract, using radiation to see bolus
alternative method to investigate swallow
intraluminal manometry: measures pressure at each phase of swallowing
2 locations where pressure is highest during swallow
- upper oesophageal sphincter
- lower oesophageal sphincter
discuss the lower oesophageal sphincter
PHYSIOLOGICAL, not anatomical (ie not made up of 1 structure, like UOS is the cricopharyngeus muscle)
contributed to by 2:
-R crus of diaphragm
-R angle at which oesophagus meets cardia of stomach
define dysphagia
delay/ disrupted passage of solids/ liq from oral cavity to stomach
5 causes of swallowing disorders
- muscular disorders eg muscular dystrophy
- NMJ disorders eg myasthenia gravis
- peripheral nerve disorders eg damage to laryngeal nerves during thyroid surgery
- CNS disorders eg stroke
- demyelination eg MS
