Kinesiology of Mastication and Ventilation Notes

Objectives

• Temporomandibular Joint (TMJ) Anatomy
  • Identify the bones and ligaments relevant to the TMJ.
• TMJ Motion
  • Identify motions occurring at the TMJ.
• Boyle’s Law and Ventilation
  • Explain Boyle’s Law in relation to inspiration and expiration processes.
• Expiration Mechanics
  • Compare quiet expiration mechanics with those of forced expiration.
• Muscles of Inspiration
  • Cite primary muscles involved in inspiration.
• Muscles of Forced Expiration
  • Cite primary muscles involved in forced expiration.
• Chronic Obstructive Pulmonary Disease
  • Explain why accessory muscles of inspiration are utilized by individuals with chronic obstructive pulmonary disease (COPD).

Mastication

• Definition
  • Process of chewing, tearing, and grinding food with teeth.
• Temporomandibular Joint (TMJ)
  • Articulation between the mandible's condyle and the temporal lobe's mandibular fossa.
• Osteology of TMJ
  • Bones involved:
  • Mandible
  • Temporal bone
  • Maxillae
  • Zygomatic
  • Sphenoid
  • Hyoid

Supporting Structures of TMJ

• Articular Disc
  • Dense fibrous connective tissue located between mandibular condyle and temporal bone.
  • Provides joint stability and reduces contact pressure, guiding the condyle during movement.
• Capsule
  • TMJ is enveloped by a fibrous capsule.
  • Lateral capsule thickens to form the lateral ligament, providing stability during chewing.

Kinematics of TMJ

• Types of Mandibular Movement:
  • Protrusion (anterior translation)
  • Retrusion (posterior translation)
  • Lateral excursion (side to side movement)
  • Depression (mouth opening)
  • Elevation (mouth closing)

Primary Muscles of Mastication

• Major Muscles Involved:
  • Masseter (p. 388)
  • Temporalis (p. 389)
  • Medial Pterygoid (p. 389)
  • Lateral Pterygoid (p. 390)

Temporomandibular Disorders

• Overview
  • A vague term representing clinical problems related to mastication.
  • Symptoms may include:
  • Trigeminal neuralgia
  • Clicking or popping sounds in the joint
  • Reduced bite force
  • Tension headaches
  • Limited mouth opening
• Contributing Factors
  • Forward head posture can stretch infrahyoid muscles, affecting joint positioning and causing pain.

Ventilation

• Mechanical Process
  • Inhalation and exhalation of air through the lungs, allowing gas exchange with the bloodstream.
• Types of Ventilation: Quiet (sedentary activities) vs. Forced (strenuous activities)

Lung Volumes

• Key Lung Volumes:
  • Total Lung Capacity: Typically $5.5$ liters (includes residual volume + vital capacity).
  • Tidal Volume (TV): Volume of air moved during a ventilation cycle (about $0.5$ liters).
  • Inspiratory Reserve Volume (IRV): Air that can be inhaled beyond TV (about $50\%$ of total lung volume).
  • Expiratory Reserve Volume (ERV): Air that can be exhaled beyond TV (about $15\%$ of total lung volume).
  • Vital Capacity (VC): Total air moved in and out of the lungs (TV + IRV + ERV).
  • Functional Residual Capacity (FRC): Air left in the lungs after normal exhalation (ERV + RV).
  • Residual Volume (RV): Air remaining in lungs post maximal exhalation (about $25\%$ of total lung volume).

Inspiration and Expiration

• Inspiration
  • Drawing air into the lungs, reliant on Boyle's Law: Volume and pressure of gas are inversely proportional.
  • Expands rib cage and diaphragm, increasing thoracic volume, thus lowering lung pressure.
• Expiration
  • Pushing air out of the lungs.
  • Quiet Expiration: Passive process using elastic recoil of the lungs.
  • Forced Expiration: Involves muscle contraction to enhance exhalation during activities like coughing.

Muscles of Ventilation

• Muscles Active in Inspiration:
  • Diaphragm (70-80% workload)
  • Scalenes
  • Intercostal muscles

Scalenes and Intercostals

• Scalenes:
  • Attach from cervical spine to upper ribs; aid in elevating ribs during inspiration.
• Intercostals:
  • External: Elevate ribs for inspiration.
  • Internal: Depress ribs, assist in forced expiration.

Abdominal Muscles in Expiration

• Abdominal Activation:
  • Required for effective forceful expiration (e.g., coughing).
  • Includes rectus abdominus, external/internal obliques, and transverse abdominis, compressing abdomen and reducing thoracic volume.

Valsalva Maneuver

• Description: Technique to increase thoracic and abdominal pressure (e.g., during weightlifting).
• Effects: Can stabilize the spine but may have undesirable cardiovascular effects.

Breathing Techniques

• Techniques:
  • Active Cycle of Breathing Technique (ACBT)
  • Diaphragmatic breathing
  • Pursed Lip Breathing
  • Straw Breathing Exercise

Quiz Questions/Examples

• Activation of medial pterygoid and masseter leads to lateral excursion of the mandible to the . (Answer: Right/Left)
• Total volume of air that can be maximally inhaled and exhaled is called: . (Answer: Vital capacity)
• According to Boyle's law, increasing volume leads to pressure . (Answer: Decrease)

References

• Mansfield, P. J., & Neumann, D. A. (2024). Essentials of Kinesiology: For the Physical Therapist Assistant (4th ed.). Elsevier.