Deglutition

Question 1

Pharynx (what it is, segments of pharynx, and innervation)

Answer 1

• muscular tube that connects nasal and oral cavities with the esophagus and larynx
• nasopharynx: from nasal choanae (posterio nasal apertures) to sofe palate
• oropharynx: ends at level of hyoid/epiglottis
• laryngopharynx: ends at laryngeal inlet
• innervation by the pharyngeal plexus (GVA: CN IX, SVE: CN X)

Question 2

Layers of pharynx

Answer 2

(external to internal)

1. buccopharyngeal fascia, from the visceral layer of the deep cervical fascia
2. muscular layers
   
   • circular layer: phayrngeal contrsictors
   • longitudinal layer: pharyngeal elevators (stylo-, salpingo, and palatopharngeus muscles)
3. pharyngobasilar fascia (aka pharyngeal aponeurosis or tela submucosa)
4. pharyngeal mucosa

Question 3

Epiglottis: formed from and functions

Answer 3

formed from elastic cartilage

function: prevents aspiration of foreign bodies into larynx

Question 4

Vallecula

Answer 4

aka epiglottic depressions, “split traps” to hold saliva and prevent the initiation of swallowing reflex

Question 5

Esophagus: what it does and cervial and thoracic portions

Answer 5

• muscular tube that connects pharynx to stomach
• cervical portion (upper 1/3) is skeletal muscle (SVE CN X)
• thoracic portion (lower 2/3) is smooth muscle (GVE CN X, parasympathetic innervation)
• thoracic portion moves food through waves of smooth muscl contractions called peristalsis

Question 6

Esophagus: 2 functional sphincters

Answer 6

• upper sphincter (UES): skeletal muscle, opened by swallowing reflex; part of the inferior pharyngeal constrictor muscle
• lower sphincter (LES): smooth muscle; also called the esophagogastric or cardiac sphincter

Question 7

Esophagus: points of contrsiction

Answer 7

• cervical constriction: at the pharynx-esophagus junction, forms upper esophageal sphincter
• thoracic constrictions: aortic arch, left 1^o bronchus
• diaphragmatic constriction: at esophageal hiatus

Question 8

Movements of deglutition

Answer 8

1. Stage II transport: tongue pushes bolus back, squeezing against hard palate; volus passes into oropharynx
2. Elevation phase: soft palate elevates and seals off nasopharynx; pharynx moves up to encompass bolus; tongue presses against roof of mouth; larynx moves up and forward; epiglottis closes
3. pharyngeal phase: pharyngeal constrictors contract to produce “explosive swallowing”; food moves into esophagus
4. esophageal phase: bolus moves down through the esophagus by peristalsis

Question 9

Stage II transport

Answer 9

• tongue pushes bolus back, squeezing against hard palate; bolus passes into oropharynx
• movement: voluntary
• speed: slow
• Muscles: extrinsic muscles of tongue (CN XII)
  
  • genioglossus
  • hyoglossus
  • styloglossus
  • palatoglossus (CN X)

Question 10

Swallowing reflex

Answer 10

1. mechanoreceptors in the mucosa of the oropharynx detect liquids/bolus
2. afferent signal (GVA) transmitted to brainstem by CN IX
3. efferent signal (SVE) transmitted to muscles of the elevation phase

Question 11

Elevation phase

Question 12

Soft palate

Answer 12

• levator veli palatini (CN X)
• musculus uvulae (CN X)
• tensor veli palatini (CN V₃)

Question 13

Pharyngeal elevators

Answer 13

• stylopharyngeus (CN IX)
• salpingopharyngeus (CN X)
• palatopharyngeus (CN X)

Question 14

Hyoid/laryngeal elevators

Answer 14

• thyrohyoid (C1)
• digastric (CN V/VII)
• stylohyoid (CN VII)
• mylohyoid (CN V₃)
• geniohyoid (C1)
• hyoglossus (CN XII)

Question 15

Pharyngeal phase

Answer 15

• pharyngeal constrictors contract to produce “explosive swallowing”; food moves into esophagus
• movement: involuntary
• speed: rapid
• muscles: pharyngeal constrictors (CN X)

Question 16

Esophageal phase

Answer 16

• bolus moves down through the esophagus by peristalsis
• movement: involuntary
• speed: slow
• muscles: esophageal muscles (CN X)
  
  • circular and longitudinal layers
  • upper 1/3-striated muscle (SVE)
  • lower 2/3- smooth muscle (GVE)

Question 17

Peristalsis

Answer 17

• ring-like contractions
• reflexive action
• leading edge of relaxation followed by contraction
• unidiractional
• moves food through esophagus into stomach

Question 18

Emesis

Answer 18

• (vomiting)
• abdominal and diaphragm mm. increase pressure, opening lower esophageal sphincter and pushing stomach contents into esophagus
• retroperistalsis moves contents of small intestine into stomach/esophagus
• upper esophageal sphincter opens, allowing gastric/esophageal contents to be expelled via the oral cavity

Question 19

Gastroesophageal reflux disease (GERD)

Answer 19

• chronic condition
• mucosal damage in esophagus from stomach acid
• can cause erosion of dentin/enamel