Lecture 1 - Normal Anatomy and Physiology:

Pressure differentials

The region behind the bolus decreases in size, causing a build up of pressure relative to the region in front of bolus. The wave is accomplished by:

- Contraction/Construction of muscles behind bolus

- Relaxation of muscles and widening of lumen in front of bolus.

Air way protection

1. Base of tongue is partially covering opening to airway

2. Bolus is divided through the valleculae at level of tongue base

3. Laryngeal elevation

4. Epiglottis inverts over airway

5. Arytenoid cartilage closure of laryngeal vestibule

6. Closure of false vocal folds

7. Closure of true vocal folds

Phases of Swallowing

1. Oral Preparatory Phase

2. Oral Phase

3. Pharyngeal Phase

4. Esophageal Phase

Oral Prep Phase

Food being transported from lips to mouth.

Oral Phase

The voluntary part of swallowing is when the tongue manipulates food or liquid and pushes a bolus up and back toward the pharynx to initiate swallow

(Lips, sulci, facial pillars, palate, tongue, dentition, posterior pharyngeal wall)

Pharyngeal Phase

Material is transported away into the upper esophagus. Involuntary part of swallowing

Esophageal Phase

Bolus is transported through the esophagus into the stomach.

PES (in esophageal phase)

Opens more for larger bolus and opens less for smaller bolus.

Secondary peristalsis (in esophageal phase)

Assist in transport of solid bolus. Completely clears the bolus!

IF Secondary peristalsis does not work....

It will cause problems up in our focus. (Main thing to know for esophageal phase)

Respiratory Tract Anatomy

Nasal Cavity, Larynx, Pharynx, Trachea, Bronchi, Lungs

Oral Phase is _________

Voluntary

Pharyngeal Phase is _________

Involuntary

The Neural Control of Swallowing is

Partially voluntary and involuntary

Cerebral Cortex

Voluntary control of swallowing is mediated by corticobulbar pathways within periventricular white matter

Brainstem Swallowing centers

Corticobulbar protects target central pattern generators located in medulla

Nucleus Tractus solitarus (afferent)

CN VII, IX, and X

Carries sensory info from strutcures involved in swallowing

Nucleus ambiguus (efferent)

CN IX, X, XI

takes all of central commands out to structures involved in swallowing

The neural pathway

1. Bolus stimulates sensory receptors (afferent neurons) via CN IX, X and XI

2. Sensory receptors project to a region of the medullary reticular formation called the nucleus tractus solitarius (NTS).

3. •When the sensory input to this region is of appropriate pattern and intensity the NTS signals motor nuclei, particularly the nucleus ambiguous

4. Cell bodies for CN IX, X, and XI are located vertically in the brainstem fire. The nucleus ambiguous innervates muscles of the velum, pharynx, larynx, and upper esophagus primarily through CN IX, X, and XI (efferent neurons)

5. Resulting in a motor output known as the pharyngeal swallow response

Oral Stage + Aging

◦Reduced tongue mobility and force

◦Decreased tongue pressure generation

◦Increased oral transit time

◦Prolonged mastication

Pharyngeal Stage + Aging

◦Reduced hyolaryngeal excursion

◦Inadequate PES opening

◦Shorter PES relation times

◦More instance of airway penetration

◦Longer duration of airway closure

◦Slower pharyngeal transit time

◦ Weaker sensory response

Esophagus + Aging

◦Esophageal motor activity decreases

◦Reduced amplitude of esophageal contractions

◦Delay in esophageal emptying

◦Increase din nonperistaltic contractions

Oropharyngeal Musculature: Type 1 Muscle Fibers

◦Smaller in diameter

◦Produce less force than Type II fibers

◦Muscles with mostly Type I fibers are better for low-force, high-endurance activities

Oropharyngeal Musculature: Type 2 Muscle Fibers

◦Structurally superior for force generation

◦Predisposed to fatigue more quickly than Type I fibers

◦Muscles with mostly Type II fibers are better for quick, forceful movements