The teeth located in the most anterior region of the arches are called (...). They have a characteristic shovel shape, and function to cut off food during mastication.

incisors

Posterior to the incisors are the (...), which are generally the longest of the permanent teeth, have a single cusp and root and function to rip and tear food.

canines

Posterior to the canines are the (...), also called bicuspids since they generally have two cusps, which function to both tear and grind food.

premolars

Found posterior to the premolars are the (...), which each have either four or five cusps that function in breaking and grinding of food.

molars

The skeletal components of the human head are the (...).

skull and mandible

The three major skeletal components that make up the masticatory system are the (...) and (...), which support the teeth, and the (...), which supports the mandible at its articulation with the cranium.

maxilla; mandible; temporal bone

Developmentally, there are two maxillary bones, which are fused together at the (...).

midpalatal suture

The (...) is a U-shaped bone that supports the lower teeth and makes up the lower facial skeleton. It has no bony attachments to the skull. It is suspended below the maxilla by muscles, ligaments, and other soft tissues

mandible

The ascending ramus of the mandible is formed by a vertical plate of bone that extends upward as two processes. The anterior of these is the (...). The posterior is the (...).

coronoid process; condyle

The condyle is the portion of the mandible that articulates with the cranium. From the anterior view, it has a medial and a lateral projection called (...). The (...) is generally more prominent than the (...).

poles; medial pole; lateral pole

From above, a line drawn through the centers of the poles of the condyle will usually extend (...) toward the anterior border of the (...).

posteromedially; foramen magnum

The actual articulating surface of the condyle extends both anteriorly and posteriorly to the most superior aspect of the condyle. The (...) articulating surface is greater than the (...) surface.

posterior; anterior

The mandibular condyle articulates at the base of the cranium with the squamous portion of the temporal bone. This portion of the temporal bone is made up of a concave (...), in which the condyle is situated.

mandibular fossa

Posterior to the mandibular fossa is the (...), which extends mediolaterally and divides into the petrosquamous fissure anteriorly and the petrotympanic fissure posteriorly.

squamotympanic fissure

Immediately anterior to the mandibular fossa is a convex bony prominence called the (...).

articular eminence

The degree of convexity of the articular eminence is highly variable but important since the steepness of this surface dictates the (...).

pathway of the condyle when the mandible is positioned anteriorly

The (...) of the mandibular fossa is quite thin, indicating that this area of the temporal bone is not designed to sustain heavy forces. The (...), however, consists of thick dense bone and is more likely to tolerate such forces.

posterior roof; articular eminence

The area where the mandible articulates with the temporal bone of the cranium is called the (...).

temporomandibular joint (TMJ)

The TMJ provides for hinging movement in one plane and therefore can be considered a (...) joint; at the same time it also provides for gliding movements, which classifies it as an (...) joint. Thus, it has been technically considered a (...) joint.

ginglymoid; arthrodial; ginglymoarthrodial

The TMJ is formed by the mandibular condyle fitting into the mandibular fossa of the temporal bone. Separating these two bones from direct articulation is the (...).

articular disc

The TMJ is classified as a compound joint, which by definition requires the presence of at least (...) bones, yet the TMJ is made up of only (...) bones. Functionally, the (...) serves as a nonossified bone that permits the complex movements of the joint.

three; two; articular disc

The articular disc is composed of (...), for the most part devoid of any blood vessels or nerve fibers. The (...) of the disc, however, is slightly innervated.

dense fibrous connective tissue; extreme periphery

In the sagittal plane, the articular disc can be divided into three regions according to thickness. The central area is the thinnest and is called the (...). The disc becomes thicker both anterior and posterior to this area, but the (...) border is generally slightly thicker than the (...) border.

intermediate zone; posterior; anterior

From an anterior view, the disc is generally thicker (...) than (...); the precise shape of the disc is determined by the morphology of the condyle and mandibular fossa.

medially; laterally

The articular disc is attached posteriorly to a region of loose connective tissue that is highly vascularized and innervated, known as the (...).

retrodiscal tissue or posterior attachment

Superiorly, the retrodiscal tissue is bordered by the (...), which contains many (...) fibers and attaches the articular disc posteriorly to the (...).

superior retrodiscal lamina; elastic; tympanic plate

Inferiorly, the retrodiscal tissue is bordered by the (...), which contains many (...) fibers and attaches the articular disc to the posterior margin of the (...).

inferior retrodiscal lamina; collagenous; articular surface of the condyle

The remaining body of the retrodiscal tissue is attached posteriorly to a large (...), which fills with blood as the condyle moves forward.

venous plexus

The superior and inferior attachments of the anterior region of the articular disc are to the (...), which surrounds most of the joint.

capsular ligament

The superior anterior attachment of the articular disc is to the anterior margin of the articular surface of the (...). The inferior attachment is to the anterior margin of the articular surface of the (...).

temporal bone; condyle

Anteriorly, between the attachments of the capsular ligament the disc is also attached by tendinous fibers to the (...) muscle.

superior lateral pterygoid

The medial and lateral attachments of the articular disc divides the joint into two distinct (...). The (...) is bordered by the mandibular fossa and the superior surface of the disc. The (...) is bordered by the mandibular condyle and the inferior surface of the disc.

joint cavities; superior joint cavity; inferior joint cavity

The internal surfaces of the joint cavities are surrounded by specialized endothelial cells that form a (...), which along with a specialized (...) located at the anterior border of the retrodiscal tissues, produces (...), which fills both joint cavities.

synovial lining; synovial fringe; synovial fluid

This synovial fluid serves two purposes. First, since the articular surfaces of the joint are nonvascular, the it acts as a (...) to these tissues. Second, it also serves as a (...) between articular surfaces during function.

medium for metabolic exchange; lubricant

Synovial fluid lubricates the articular surfaces by way of two mechanisms. (...) occurs when the joint is moved and the synovial fluid is forced from one area of the cavity into another, and is the is the primary mechanism of joint lubrication.

boundary lubrication

Synovial fluid lubricates the articular surfaces by way of two mechanisms. (...) refers to the ability of the articular surfaces to absorb synovial fluid, which is driven out when forces are created between the articular surfaces; this is the mechanism by which metabolic exchange occurs.

weeping lubrication

The articular cartilage of the TMJ is set up differently from typical articular cartilage in that the TMJ forms from (...) ossification rather than from (...) ossification, and thus keeps its chondroprogenitor cells, which allow for continued growth, repair, and remodeling.

intermembranous; endochondral

The articular cartilage of the mandibular condyle and fossa are composed of four distinct layers or zones. The most superficial layer is called the (...). It is found adjacent to the joint cavity and forms the outermost functional surface.

articular zone

Unlike most other synovial joints, this articular layer of the mandibular condyle and fossa is made of (...) rather than hyaline cartilage, which is less likely to break down over time and has a much better ability to repair than does hyaline cartilage.

dense fibrous connective tissue

The articular cartilage of the mandibular condyle and fossa are composed of four distinct layers or zones. The second zone is called the (...) and is mainly cellular. It is responsible for the proliferation of articular cartilage in response the functional demands placed on the articular surfaces during loading.

proliferative zone

The articular cartilage of the mandibular condyle and fossa are composed of four distinct layers or zones. The third zone is the (...). Here the collagen fibrils are arranged in a three-dimensional network that offers resistance against compressive and lateral forces.

fibrocartilaginous zone

The articular cartilage of the mandibular condyle and fossa are composed of four distinct layers or zones. The fourth and deepest zone is the (...). This zone is made up of chondrocytes and chondroblasts distributed throughout the articular cartilage. In this zone the chondrocytes become hypertrophic and die.

calcified cartilage zone

The articular cartilage is composed of chondrocytes and intercellular matrix. (...) connected to a (...) chain form aggregates that make up a great protein of the matrix.

proteoglycans; hyaluronic acid

Branches of the (...) provide the afferent innervation to the TMJ. Most innervation is provided by the (...); additional innervation is provided by the (...) and (...) nerves.

mandibular nerve (V₃); auriculotemporal nerve; deep temporal; masseteric

The TMJ is richly supplied by a variety of vessels that surround it. The predominant vessels are the (...) artery from the posterior, the (...) artery from the anterior, and the (...) artery from the inferior.

superficial temporal; middle meningeal; internal maxillary

As with any joint system, (...) play an important role in protecting the TMJ. They made up of collagenous connective tissues fibers that have particular lengths.

ligaments

Ligaments do not enter actively into joint function but instead act as passive restraining devices to limit and restrict border movements. What are the five ligaments of the TMJ?

1. collateral ligaments
2. capsular ligament
3. temporomandibular ligament
4. sphenomandibular
5. stylomandibular

*The first three are considered the functional ligaments, the last two are accessory.

The two (...) ligaments attach the medial and lateral borders of the articular disc to the poles of the condyle. These ligaments are responsible for dividing the joint mediolaterally into the superior and inferior joint cavities.

collateral (discal)

The attachments of the discal ligaments permit the disc to be rotated anteriorly and posteriorly on the articular surface of the condyle. Thus these ligaments are responsible for the (...) movement of the TMJ.

hinging

The entire TMJ is surrounded and encompassed by the (...), whose fibers are attached superiorly to the temporal bone along the borders of the articular surfaces of the mandibular fossa and articular eminence.

capsular ligament

The capsular ligament acts to resist any medial, lateral, or inferior forces that tend to (...). Another significant function of the capsular ligament is to encompass the joint, thus retaining the (...).

separate or dislocate the articular surfaces; synovial fluid

The lateral aspect of the capsular ligament is reinforced by strong, tight fibers that make up the (...), which is composed of an (...) portion and an (...) portion.

temporomandibular ligament (TML); outer oblique (OOP); inner horizontal (IHP)

The outer portion of the TML extends from the outer surface of the (...) posteroinferiorly to the outer surface of the (...).

articular tubercle and zygomatic process; condylar neck

The inner horizontal portion of the TML extends from the outer surface of the (...) posteriorly and horizontally to the (...) and (...)

articular tubercle and zygomatic process; lateral pole of the condyle; posterior part of the articular disc.

The oblique portion of the TM ligament resists (...) of the condyle, therefore limiting the extent of mouth opening.

excessive dropping

What is unqiue about the oblique portion of the TM ligament?

it is found only in humans

The inner horizontal portion of the TM ligament limits (...) of the condyle and disc, therefore protecting the retrodiscal tissues from trauma.

posterior movement

The (...) is one of two TMJ accessory ligaments. It arises from the spine of the sphenoid bone and extends downward to a small bony prominence on the medial surface of the ramus of the mandible called the lingula.

sphenomandibular ligament

The (...) is one of two TMJ accessory ligaments. It arises from the styloid process and extends downward and forward to the angle and posterior border of the ramus of the mandible.

stylomandibular ligament

Muscle fibers can be characterized by type according to the amount of (...) they contain, a pigment similar to hemoglobin.

myoglobin

(...) fibers have higher concentrations of myoglobin are redder in color. They rely on aerobic metabolism, and are capable of slow contractions with resistance to fatigue.

type I (slow-twitch)

(...) fibers have lower concentrations of myoglobin and are whiter in color. They rely on anaerobic activity are are capable of quick contraction but fatigue rapidly.

type II (fast-twitch)

What four pairs of muscles make up a group called the muscles of mastication?

1. masseter
2. temporalis
3. medial pterygoid
4. lateral pterygoid

Although not considered to be muscles of mastication, the (...) also play an important role in mandibular function.

digastrics

The (...) is a rectangular muscle that originates from the zygomatic arch and extends downward to the lateral aspect of the lower border of the ramus of the mandible.

masseter

The masseter is made up of two portions or heads: the superficial portion consists of fibers that run (...); the deep portion consists of fibers that run (...).

downward and backward; vertically

What is the function of the masseter?

elevation and protrusion of the mandible

What is the innervation to the masseter?

masseteric branch of the mandibular nerve

What is the blood supply to the masseter?

masseteric artery

The (...) is a large, fan-shaped muscle that originates from the temporal fossa and the lateral surface of the skull. Its fibers form a tendon that inserts on the coronoid process and anterior border of the ascending ramus.

temporalis

The temporalis can be divided into three distinct areas according to fiber direction and ultimate function: the anterior portion consists of fibers that are directed almost (...). The middle portion contains fibers that run (...). The posterior portion consists of fibers that are aligned almost (...).

vertically; obliquely; horizontally

What is the function of the temporalis?

elevation and retrusion of the mandible

When the anterior portion of the temporalis contracts in isolation, the mandible is (...).

elevated

When the middle portion of the temporalis contracts in isolation, the mandible is (...).

elevated and retruded

When the posterior portion of the temporalis contracts in isolation, the mandible is (...).

elevated and retruded (slightly)

What is the innervation to the temporalis?

deep temporal nerve from the mandibular nerve

What is the blood supply to the temporalis?

anterior, posterior, and superficial temporal arteries

The (...) originates from the pterygoid fossa and extends downward, backward, and outward to insert along the medial surface of the mandibular angle.

medial (internal) pterygoid

What is the function of the medial pterygoid?

elevates and protrudes the mandible

What is the innervation to the medial pterygoid?

mandibular branch of the trigeminal nerve

What is the blood supply to the medial pterygoid?

pterygoid branch of maxillary artery

The (...) originates at the outer surface of the lateral pterygoid plate and extends backward, upward, and outward to its insertion on the neck of the condyle.

inferior lateral pterygoid

What is the function of the inferior lateral pterygoid?

protrudes the mandible and contributes to lateral movements

What is the innervation to the inferior lateral pterygoid?

pterygoid branch of the trigeminal nerve

What is the blood supply to the inferior lateral pterygoid?

pterygoid branch of the maxillary artery

The (...) originates at the infratemporal surface of the greater sphenoid wing, extending almost horizontally, backward, and outward to insert on the articular capsule, the disc, and the neck of the condyle.

superior lateral pterygoid

The majority of the fibers of the superior lateral pterygoid (60% to 70%) attach to the (...) with only 30% to 40% attaching to the (...).

neck of the condyle; disc

While the (...) lateral pterygoid is active during opening, the (...) lateral pterygoid remains inactive, becoming active only in conjunction with the elevator muscles.

inferior; superior

The superior lateral pterygoid is especially active during the (...), which refers to movements that involve closure of the mandible against resistance.

power stroke

What is the function of the superior lateral pterygoid?

stabilizes the condyle and disc during mandible loading

What is the innervation to the superior lateral pterygoid?

pterygoid branch of the trigeminal nerve

What is the blood supply to the superior lateral pterygoid?

pterygoid branch of the maxillary artery

The pull of the lateral pterygoid on the disc and condyle is predominantly in an anterior direction; however, it also has a significantly medial component. As the condyle moves more forward, the (...) pull of these muscles becomes greater.

medial

Although the (...) is not generally considered a muscle of mastication, it does have an important influence on the function of the mandible.

digastric

The (...) of the digastric originates from the mastoid notch its fibers run forward, downward, and inward to the intermediate tendon attached to the hyoid bone.

posterior belly

The (...) of the digastric originates at a fossa on the lingual surface of the mandible, extending downward and backward to insert at the intermediate tendon of the hyoid bone.

anterior belly

What is the function of the anterior digastric?

depress the mandible, elevate the hyoid bone

What is the innervation to the anterior digastric?

mandibular branch of the trigeminal nerve and the mylohyoid nerve

What is the blood supply to the anterior digastric?

submental artery

What is the function of the posterior digastric?

depress the mandible, elevate the hyoid bone

What is the innervation to the posterior digastric?

digastric branch of facial nerve

What is the blood supply to the posterior digastric?

lingual artery and facial artery

Generally, muscles that are attached from the mandible to the hyoid bone are called (...) and those attached from the hyoid bone to the clavicle and sternum are called (...).

suprahyoid; infrahyoid

A study of mandibular function is not limited to the muscles of mastication. Other major muscles, such as the (...), play major roles in stabilizing the skull and enabling controlled movements of the mandible to be performed.

sternocleidomastoid

Since the disc is tightly bound to the condyle by the lateral and medial discal ligaments, the only physiologic movement that can occur in the inferior synovial cavity is (...) of the mandible.

rotation

Since the disc is not tightly attached to the articular fossa, free sliding movement is possible between these surfaces; this movement that occurs in the superior synovial cavity is referred to as (...) of the mandible.

translation

Stability of the temporomandibular joint is maintained by constant activity of the muscles that pull across the joint, primarily the (...), which constantly maintain a mild state of contraction called (...).

elevators; tonus

As muscle activity increases, the condyle is increasingly forced against the disc and the disc against the fossa, resulting in an increase in the (...), which is the force that prevents separation of the articular surfaces.

interarticular pressure

The width of the articular disc space varies with interarticular pressure. When the pressure is low (e.g. at rest), the disc space (...), whereas when the pressure is high (e.g. while clenching), the disc space (...).

widens; narrows

As the mandible moves into a full forward position and during its return, the retraction force of the (...) holds the disc rotated as far posteriorly on the condyle as the width of the articular disc space will permit.

superior retrodiscal lamina

Attached to the anterior border of the articular disc is the (...), which, when active, pulls the disc anteriorly and medially.

superior lateral pterygoid muscle

The mechanism by which the disc is maintained with the translating condyle is dependent on the (...).

morphology of the disc and the interarticular pressure

(...) do not actively participate in normal function of the TMJ; they act as guide wires, restricting certain joint movements while permitting others.

ligaments

Ligaments do not (...). If traction force is applied, they can become elongated, that is, increase in length, and normal joint function is often compromised.

stretch

The articular surfaces of the TMJs must be maintained in constant contact. This contact is produced by the (...) that pull across the joints.

muscles

In normal functional movement of the condyle and disc during opening and closing, the disc is rotated (...) on the condyle as it is translated out of the fossa.

posteriorly