Lecture 1 - Introduction

Question 1

Physiology of Swallowing - Functional

Answer 1

Swallowing takes about 8-10 seconds

There are 4 functionally distinct phases:

Oral Preparatory
Oral Transitory
Pharyngeal
Esophageal

Question 2

Physiology of Swallowing - Physiological

Answer 2

3 Physiologically Distinct Phases

Voluntary
Pharyngeal
Esophageal

Question 3

Voluntary Phase

Answer 3

Bolus of food moved by tongue from oral cavity to pharynx

Question 4

Pharyngeal Phase

Answer 4

Reflexive: Upper esophageal sphincter relaxes, elevated pharynx opens the esophagus, food pushed into esophagus

Question 5

Esophageal Phase

Answer 5

Reflex: Epiglottis is tipped posteriorly, larynx elevated to prevent food from passing into larynx.

More reflexive than pharyngeal.

Question 6

Agonist

Answer 6

Muscles that cause the movement to occur

Prime movers

Question 7

Synergists

Answer 7

Perform or assist in performing the same motion as agonists

Question 8

Neutralizers

Answer 8

Can help cancel out extra motion from the agonists to assure the generated force works toward the target position

Question 9

Antagonists

Answer 9

Muscles that act in opposition to the movement generated by the agonists

Responsible for returning the body to its initial position or countering agonies force during the movement

Question 10

Lip Closure & Bolus Propulsion

Answer 10

Lip closure is achieved by tension in the orbicularis oris which prevents bolus leakage from the oral cavity

Orbicularis oris co-contracts with the buccinator and the superior pharyngeal constrictors to create a circular muscular sling during bolus propulsion.

This creates sufficient support to control the positive pressure built up by the posterior 1/3 of the tongue during bolus propulsion

Maintains closure of the oral cavity and nasopharynx

Question 11

Velopharyngeal Closure

Answer 11

The levator veli palatini (LVP) on both sides operate in conjunction with the superior pharyngeal constrictors (SPC) and palatopharyngeus (PP) muscles to achieve velopharyngeal closure.

The LVP elevate the posterior part of the soft palate, the velum, and pull it slightly backward, while the SPC and PP pull the posterior and lateral pharyngeal wall towards the velum.

Question 12

Hyolaryngeal Excursion - Overview

Answer 12

The hyoid bone is suspended from a sling of muscles that attach posteriorly on the skull and anteriorly on the mandible.

The larynx is connected to the hyoid through muscles (thyrohyoid) and ligaments.

Coordinated contractions produce anterosuperior movement of the hyolaryngeal complex during the swallow.
This assists with airway protection and UES opening.

Proximal movement of the larynx & hyoid can be achieved via thyrohyoid contraction

Question 13

Hyolaryngeal Excursion - Muscles

Answer 13

Protraction of the hyoid
Anterior belly of Digastric
Mylohyoid
Geniohyoid

Elevation & Retraction of the hyoid
Stylohyoid
Posterior belly of the Digastric

Depression of the hyoid
     Sternohyoid
     Sternothyroid (and larynx)
     Omohyoid
     Thyrohyoid

Question 14

Upper Esophageal Sphincter (UES) Opening - Overview

Answer 14

The upper esophageal sphincter is normally in a tonic state of contraction.

It opens (by relaxing) during swallowing, belching, and vomiting.

Even when relaxed, the UES has passive elastic closing forces in its fibers.

The UES is pulled open by a combination of forces:
Bolus size and weight
Superior and anterior forces from the suprahyoid
muscles
Superior forces from the muscles that shorten the
pharynx

Question 15

Upper Esophageal Sphincter (UES) Opening - Muscles

Answer 15

Three primary muscles involved in shortening the pharynx:
Stylopharyngeus
Palatopharyngeus
Salpingopharyngeus

Because the stylopharygeus runs from a superior & lateral to inferior & medial, contraction will also widen the pharynx
This will contribute to negative pressure buildup in the
hypopharynx which will assist with bolus transport.

Question 16

Upper Esophageal Sphincter (UES) Opening - Sequence

Answer 16

1. The thyropharyngeus is activated and there is inhibition of the tonic contraction of the cricopharyngeus (precedes UES opening by 0.1 s).
2. Hyolaryngeal excursion facilitates opening of the cricopharyngeal sphincter (anterior, upper portion of the UES)
3. The UES is distended by pressure applied by the bolus.
4. The UES collapses passively as the bolus passes through the sphincter.
5. Active contraction of the cricopharyngeus closes the UES.

Question 17

Pharyngeal Contraction - Overview

Answer 17

The pharyngeal muscles contract and obliterate the air space in the pharynx as the bolus passes through it.

Contraction aids in propelling the bolus towards the esophagus an ensures that no part of the bolus stays behind (residual) after the swallow.

Anteroposterior contraction is facilitated by the three groups of pharyngeal constrictors.

The primary purpose is to “clean out” the pharynx after the bolus to ensure no residuals remain.

Question 18

Pharyngeal Contraction - Muscles

Answer 18

There is a complex interplay among the muscles that shorten the pharynx (stylopharyngeus, palatopharyngeus, and salpingopharyngeus), and the pharyngeal constrictors.

e.g., the middle constrictors “wrap around” the stylopharyngeus. Contraction of the stylopharyngeus spreads out the pharynx (lengthening the middle constrictors) decreasing hypopharyngeal pressure (if the UES is closed) and increasing the mechanical force generating capacity of the constrictors.