Mastication and Jaw Dynamics

Comprehensive flashcards covering the muscles, phases, cycles, and reflexes involved in the process of mastication.

Mastication (chewing) results in food being crushed and mixed with saliva to form a __________ for swallowing.

bolus

Mastication is a complex mechanism involving the jaw, secretion of saliva, and mixing of food with the __________.

tongue

The four primary muscles of mastication are the masseter, temporalis, medial pterygoid, and __________.

lateral pterygoid

The temporalis muscle originates from the floor of the temporal fossa and the deep surface of the temporal __________.

fascia

The masseter muscle is composed of a deep part and a __________ part.

superficial

The insertion point of the temporalis muscle is the __________ process.

coronoid

The masseter muscle originates from the lower border and inner surface of the __________ arch.

zygomatic

The lateral pterygoid muscle is composed of a superior head and an __________ head.

inferior

The superficial head of the medial pterygoid muscle originates from the __________ tuberosity.

maxillary

The lower head of the lateral pterygoid muscle originates from the __________ plate.

Pterygoid

The medial pterygoid muscle heads insert into the inferior surface of the mandible __________.

ramus

The jaw closing muscles, or elevators, include the masseter, medial pterygoid, and the __________ part of the temporalis.

anterior

The primary muscle responsible for opening the jaw (depressor) is the __________.

lateral pterygoid

The posterior fibers of the __________ muscle help in retrusive movements.

temporalis

Protrusive movements are brought about by the elevator group and the __________ head of the lateral pterygoid.

inferior

The __________ is considered an accessory muscle of mastication that helps in the process of chewing.

buccinator

The digastric, mylohyoid, and geniohyoid muscles are categorized as __________ muscles.

suprahyoid

The infrahyoid muscles involved in mastication include the sternohyoid, thyrohyoid, and __________ muscle.

omohyoid

The movement of the mandible during the masticatory cycle is classically __________ shaped.

tear drop

The typical duration of a single chewing cycle is __________ to __________.

$$0.8-1.0\,second$$

Masticatory force exerted during chewing is maximum on the __________.

molars

The three basic phases of the chewing cycle are the opening stroke, closing stroke, and __________ stroke.

power

During the opening stroke, the mandible is lowered with an initial slower stage and a later __________ stage.

faster

In the power stroke, food undergoes reduction with slower movements of the mandible due to the __________ of food.

resistance

The opening phase of the chewing cycle is more __________ (towards midline) than the closing phase.

medial

During the opening phase, the __________ move forward and downward.

condyles

In the closing phase, the incisor region typically deviates laterally about __________ from the midline.

$$5\,mm$$

The lateral translation of the mandibular condyle is approximately __________ to __________ during chewing.

$$0.4-0.6\,mm$$

The power stroke is also known as the __________ phase.

grinding

During the power stroke, the teeth of the working side attain an __________ position.

intercuspal

Mastication is controlled by the central __________ generator.

pattern

The __________ mechanism allows researchers and the body to alter the chewing stroke based on food quality.

feedback

The jaw jerk reflex is a type of __________ reflex brought about by muscle spindles.

stretch

The jaw jerk reflex is considered a __________ reflex because of the stretching of muscle spindles in the masseter.

monosynaptic

In the jaw jerk reflex, the depressor muscles __________ while the masseter brings teeth into occlusion.

relax

A sharp downward tap on the chin when the mandible is at rest results in the __________ reflex.

jaw jerk

The silent period in the electromyogram during the jaw jerk reflex represents spindle unloading and lasts __________ to __________.

$$7-12\,milliseconds$$

The jaw opening reflex is __________ and triggered by mechanical stimulation of the PDL and mucosa.

polysynaptic

The jaw opening reflex involves a brief period of reciprocal __________ in the activity of jaw closing muscles.

inhibition

The __________ reflex is a protective mechanism that occurs when the jaw is suddenly unloaded.

unloading

The unloading reflex involves the reflex inhibition of __________ and reflex excitement of depressors.

elevators

Sudden reduction of activity in the unloading reflex is the result of inactivation of __________.

muscle spindles

Chewing generally occurs on one side of the mouth at a time, known as the __________ side.

working

The side of the mouth opposite to the working side is called the __________ side.

balancing

The balancing side is also referred to as the __________ side.

non-working

The mean Cycle time according to the provided data chart is __________.

$$0.725\,sec$$

The __________ generator in the mastication center is responsible for the chewing rhythm.

Rhythm

Wait times for the opening phase ($n=20$) show a mean of __________.

$$0.277\,sec$$

Wait times for the closing phase ($n=20$) show a mean of __________.

$$0.230\,sec$$

The __________ reflex is also known as the masseter reflex or horizontal jaw reflex when labiolingual force is applied.

Jaw jerk