Module 1.2 Mastication Flashcards
How are the teeth and muscles specialised in regards to mastication? What governs the specialisation?
Governed by diet.
Diet of Muscle & skin = specialised carnassial teeth
Diet of Fibrous foods = molar teeth of ungulates
Which kinds of animals masticate?
Mammals, fish, lizards. But mainly mammals.
What are the oral cavity properties of carnivores?
Have wide mouth opening in relation to their head
size. Advantageous in developing forces used in seizing, killing & dismembering prey
Facial musculature reduced as these muscles would hinder a wide gape
In all mammalian carnivores, jaw joint is simple hinge joint lying in same plane as the teeth. This type of joint extremely stable & acts as pivot point for upper & lower jaws
Temporalis muscle is primary muscle used for operating the jaw
Small angle of the mandible. Masseter & pterygoids muscles that attach there are of minor importance in these animals
Lower jaw cannot move forward, & has very limited side-to-side motion
When jaw closes, blade-shaped cheek molars slide past each other. Gives slicing motion that is very effective for shearing meat off bone
What does the Temporalis muscle do?
Primary muscle in operating the Jaw of carnivores.
What are the properties of a herbivore oral cavity?
Angle of mandible expanded to provide broad area of attachment for well-developed masseter & pterygoid muscles. Temporalis muscle small & of minor importance
Masseter & pterygoid muscles hold mandible in sling-like arrangement & swing jaw from side-to- side. Lower jaw has pronounced sideways motion when eating. This lateral movement necessary for grinding motion of chewing
What do the Masseter & pterygoid muscles do?
Hold mandible in sling-like arrangement & swing jaw from side-to- side.
In jaw muscles, what action causes the movement of chewing?
Muscle contractions.
Where do the muscles of mastication attach?
The Mandible
What movements are the muscles associated with? Which moreso?
Generally, more muscle mass (& strength) associated with elevation (closure) than with depression (opening) of mandible
Which nerve is responsible for mastication movements?
trigeminal nerve
What does the muscle temporalis do?
Elevates mandible, bringing upper & lower teeth
together
What does the muscle masseter do? Which animals is it more developed in?
Especially well developed in herbivores
Primary actions are to elevate mandible & draw it lateral
Forms broad expanse of horse’s cheek
What do the Pterygoid muscles do?
m. pterygoideus
Assist in closing mandible
Play important role in side-to-side grinding movements of herbivores
What does the muscle digastricus do?
Depression of mandible
What causes atrophy and hypertrophy of muscles of mastication?
Atrophy or hypertrophy of temporalis or masseter muscles, secondary to dental disease in herbivores
Muscular atrophy present if dental arcades on 1 side not used
Hypertrophy present on side being used exclusively
