Muscle Anatomy and Functions in Pharynx and Esophagus
Muscles of the Pharynx
PHARYNGEAL CONSTRICTORS
Superior Pharyngeal Constrictor
Description: One of the most superior muscles of the pharynx.
Structure: Made up of four parts; considered a quadrilateral muscle; thinner than the other two constrictors.
Attachments:
From the medial pterygoid plate
Posterior pharyngeal wall
Mandible
Sides of the tongue
Function:
Descends the pharynx
Constricts upon the bolus during swallowing.
Innervation:
Cranial Nerve X: Vagus Nerve.
Middle Pharyngeal Constrictor
Description: Fan-shaped muscle located in the neck; smaller than the inferior pharyngeal constrictor.
Attachments:
From the medial pterygoid plate
Posterior pharyngeal wall
Mandible
Sides of the tongue
Function:
Descends the pharynx
Constricts upon the bolus.
Innervation:
Cranial Nerve X: Vagus Nerve.
Inferior Pharyngeal Constrictor
Description: The strongest of the pharyngeal muscles and made up of two components:
Thyropharyngeus muscle:
Attachment: Thyroid cartilage to the posterior pharynx.
Function: Constricts or reduces the diameter of the pharynx.
Innervation: Cranial Nerve X: Vagus Nerve.
Cricopharyngeus muscle:
Attachment: Cricoid cartilage to the posterior pharynx.
Function: Constricts or reduces the diameter of the pharynx.
Innervation: Cranial Nerve X: Vagus Nerve.
Additional Function: Helps keep the pharynx open for breathing during sleep.
Muscles of the Velum
ELEVATING & LOWERING THE SOFT PALATE
Velum Elevator: Levator Veli Palatini
Description: Palatal elevator that makes up the bulk of the soft palate.
Attachments: From the temporal bone to the soft palate.
Function: Elevates and retracts the velum.
Innervation:
Cranial Nerve XI: Accessory Nerve.
Cranial Nerve X: Vagus Nerve.
Velum Depressor: Palatoglossus
Description: This muscle makes up the anterior faucial pillars and serves dual purposes for both the tongue and the soft palate.
Attachments: From the palatal aponeurosis to the sides of the posterior tongue.
Function:
Depresses the soft palate.
Elevates the tongue.
Innervation:
Cranial Nerve XI: Accessory Nerve.
Cranial Nerve X: Vagus Nerve.
Lowers Velum: Palatopharyngeus
Description: Majority of the time, considered a pharyngeal muscle; however, has a role in velum function.
Attachments: Anterior hard palate and midline of the soft palate to the posterior portion of the thyroid cartilage.
Function:
Lowers the soft palate.
Narrows the pharynx.
Innervation:
Cranial Nerve XI: Accessory Nerve.
Cranial Nerve X: Vagus Nerve.
Muscles of the Esophagus
TWO LAYERS
Longitudinal Fibers (External Layer)
Description: Continuous with the muscular fibers of the pharynx, descending in the esophagus; forms a uniform layer covering the outer surface.
Function: Responsible for peristalsis contraction.
Innervation: Cranial Nerve X: Vagus.
Circular Fibers (Internal Layer)
Description: Continuous with the inferior constrictor muscle of the hypopharynx.
Function:
Performs peristalsis contraction that propels food toward the stomach.
Innervation: Cranial Nerve X: Vagus.
CMD 300: Anatomy & Physiology
MASTICATION & DEGLUTITION
Phase III: Pharyngeal Phase
Upper Esophageal Sphincter Action:
Defined as the UES involving the cricopharyngeus muscle of the inferior constrictor, contracted during respiration; however, during swallowing, the UES relaxes and opens as the larynx and hyoid move up and forward.
Important: Decreases esophageal reflux when gastric contents escape into the laryngopharynx.
Transit Times
Phase Transit Times:
Oral preparatory phase
Oral transport phase
Pharyngeal phase
Esophageal phase.
Typical Transit Time: 10-20 seconds for the bolus to travel down the esophagus.
Muscles Innervated for Pharyngeal Phase
Table 8-3: Muscles of the Pharyngeal Stage Required to Propel the Bolus Toward the Esophagus, Elevate the Larynx, and Close the Airway:
Tongue Muscles:
Mylohyoid: Elevates hyoid and tongue (Innervation: Cranial Nerve V, XII).
Geniohyoid: Elevates hyoid and larynx; depresses mandible (Innervation: Cranial Nerve XII).
Digastricus: Elevates hyoid and larynx (Innervation: Cranial Nerve V, VII).
Genioglossus: Retracts tongue (Innervation: Cranial Nerve XII).
Styloglossus: Elevates posterior tongue (Innervation: Cranial Nerve XII).
Palatoglossus: Narrows fauces; elevates posterior tongue (Innervation: Cranial Nerve X, XI).
Stylohyoid: Elevates hyoid and larynx (Innervation: Cranial Nerve VII).
Hyoglossus: Elevates hyoid (Innervation: Cranial Nerve XII).
Thyrohyoid: Elevates hyoid (Innervation: Cranial Nerve XII).
Inferior longitudinal: Depresses tongue (Innervation: Cranial Nerve XII).
Transverse: Narrows tongue (Innervation: Cranial Nerve XII).
Vertical: Flattens the tongue (Innervation: Cranial Nerve XII).
Soft Palate Muscles:
Levator veli palatini: Elevates soft palate (Innervation: Cranial Nerve X, XI).
Tensor veli palatini: Dilates auditory tube (Innervation: Cranial Nerve V).
Musculus uvulae: Shortens soft palate (Innervation: Cranial Nerve X, XI).
Pharyngeal Muscles:
Palatopharyngeus: Constricts oropharynx to channel bolus (Innervation: Cranial Nerve X, XI).
Salpingopharyngeus: Elevates pharynx (Innervation: Cranial Nerve XI).
Stylopharyngeus: Raises larynx (Innervation: Cranial Nerve IX).
Cricopharyngeus: Relaxes esophageal orifice (Innervation: Cranial Nerve X, XI).
Middle constrictor: Narrows pharynx (Innervation: Cranial Nerve X, XI).
Inferior constrictor: Narrows pharynx (Innervation: Cranial Nerve X, XI).
Laryngeal Muscles:
Lateral cricoarytenoid: Adducts vocal folds (Innervation: Cranial Nerve X).
Transverse arytenoid: Adducts vocal folds (Innervation: Cranial Nerve X).
Oblique arytenoid: Adducts vocal folds (Innervation: Cranial Nerve X).
Aryepiglotticus: Retracts epiglottis; constricts aditus (Innervation: Cranial Nerve X).
Thyroepiglotticus: Dilates airway following swallow (Innervation: Cranial Nerve X).
Phase IV: Esophageal Phase
Description: This is a purely reflexive stage that is not under voluntary control.
Initiation: Begins when the bolus enters the esophagus.
Transport Mechanisms: Bolus is transported to the bottom of the esophagus to the lower esophageal sphincter by peristaltic contraction and gravity.
Typical Transit Timing: 10-20 seconds for the bolus to traverse the esophagus.
Post-Swallow Function: Once in the stomach, the soft palate lowers, the laryngeal valve opens, and respiration resumes. Notably, most individuals exhale after swallowing.
Oropharyngeal Stage Characteristics
Muscle Actions: Laryngeal muscles contract, leading to a closing off of the glottis by the epiglottis.
Upper Esophageal Sphincter: Uvula contracts to block the nasal passages; thus, respiration is inhibited during this swallowing phase.
Pharynx Function: Serves as a conduit for food toward the esophagus while preventing air from entering the digestive track during swallowing.