Head and Neck Anatomy
Articular eminence Raised portion of the temporal bone just anterior to the glenoid fossa.
Circumvallate lingual papillae (sir-kum-VAL-ayt LING-gwul puh-PIL-ee) Large tissue projections on the tongue.
Cranium (KRAY-nee-um) Eight bones that cover and protect the brain.
External auditory meatus Bony passage of the outer ear.
Fossa (FOS-ah, FAW-suh) Wide, shallow depression on the lingual surfaces of anterior teeth.
Greater palatine (PA-luh-tine) nerve Nerve that serves the posterior hard palate and the posterior lingual gingiva.
Hamulus A hook-shaped process.
Infraorbital (in-fruh-OR-bi-tul) Region of the head below the orbital region.
Lacrimal (LAK-ri-mul) bones Paired facial bones that help form the medial wall of the orbit.
Lambdoid suture Line of junction between the occipital and parietal bones.
Lateral pterygoid plate Point of origin for internal and external pterygoid muscles.
Lymphadenopathy (lim-fad-uh-NOP-uh-thee) Disease or swelling of the lymph nodes.
Masseter (muh-SEE-tur) The strongest and most obvious muscle of mastication.
Mastoid process Projection on the temporal bone located behind the ear.
Medial pterygoid plate Plate that ends in the hook-shaped hamulus.
Mental protuberance Part of the mandible that forms the chin.
Occipital (ok-SIP-i-tul) Region of the head overlying the occipital bone and covered by the scalp.
Ossicles The bones of the middle ear.
Parietal (puh-RYE-e-tul) Pertaining to the walls of a body cavity.
Pterygoid process Process of the sphenoid bone, consisting of two plates.
Sphenoid sinuses Sinuses that are located in the sphenoid bone.
Sternocleidomastoid (stur-noe-klye-doe-MAS-toid) Major cervical muscle.
Styloid process Process that extends from the undersurface of the temporal bone.
Symphysis menti (SIM-fi-sis MEN-tee) The separation of the mandible at the chin that occurs at birth.
Temporomandibular (tem-puh-roe-man-DIB-yoo-lur) joint (TMJ) Joint on each side of head that allows movement of the mandible.
Trapezius (truh-PEE-zee-us) Major cervical muscle.
In this chapter, you will learn the anatomic basis for the clinical practice of dental assisting. You will learn the names and locations of bones of the skull and face, facial nerves, lymph nodes, and salivary glands. You will identify muscles of the head and neck, including the facial muscles, which create facial expressions and help to open and close the mouth and swallow food.
You will find that knowledge of anatomic landmarks is a necessity as you begin to mount radiographs.
Regions of the Head
The head can be divided into 11 regions: frontal, parietal, occipital, temporal, orbital, nasal, infraorbital, zygomatic, buccal, oral, and mental. As you continue this chapter, you will encounter references to these regions of the head (Fig. 9-1).
Bones of the Skull
The human skull is divided into two sections: the cranium and the face. The cranium is composed of eight bones that cover and protect the brain; the face consists of 14 bones (Table 9-1). Specific anatomic terms are used to describe landmarks on these bones (Table 9-2).
|Eight Bones of the Cranium|
|Frontal||1||Forms the forehead, most of the orbital roof, and the anterior cranial floor|
|Parietal||2||Form most of the roof and upper sides of the cranium|
|Occipital||1||Forms the back and base of the cranium|
|Temporal||2||Form the sides and base of the cranium|
|Sphenoid||1||Forms part of the anterior base of the skull and part of the walls of the orbit|
|Ethmoid||1||Forms part of the orbit and the floor of the cranium|
|Fourteen Bones of the Face|
|Zygomatic||2||Form the prominence of the cheeks and part of the orbit|
|Maxillary||2||Form the upper jaw|
|Palatine||2||Form the posterior part of the hard palate and the floor of the nose|
|Nasal||2||Form the bridge of the nose|
|Lacrimal||2||Form part of the orbit at the inner angle of the eye|
|Vomer||1||Forms the base for the nasal septum|
|Inferior conchae||2||Form part of the interior of the nose|
|Mandible||1||Forms the lower jaw|
|Six Auditory Ossicles|
|Malleus, incus, stapes||6||Bones of the middle ear|
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|Foramen||A natural opening in a bone through which blood vessels, nerves, and ligaments pass|
|Fossa||A hollow, grooved, or depressed area in a bone|
|Meatus||The external opening of a canal|
|Process||A prominence or projection on a bone|
|Suture||The jagged line where bones articulate and form a joint that does not move|
|Symphysis||The site where bones come together to form a cartilaginous joint|
|Tubercle||A small, rough projection on a bone|
|Tuberosity||A large, rounded process on a bone|
Bones of the Cranium
The cranial bones are the single frontal, occipital, sphenoid, and ethmoid bones and the paired parietal and temporal bones.
The two parietal bones form most of the roof and upper sides of the cranium. The two parietal bones are joined at the sagittal suture at the midline of the skull. The line of articulation between the frontal bone and the parietal bones is called the coronal suture (Fig. 9-2). In a newborn, the anterior fontanelle is the soft spot where the sutures between the frontal and parietal bones have not yet closed. This spot disappears as the child grows and the sutures close.
The frontal bone forms the forehead, part of the floor of the cranium, and most of the roof of the orbits. (The orbit is the bony cavity that protects the eye.) The frontal bone contains the two frontal sinuses, with one located above each eye (Fig. 9-3).
The occipital bone forms the back and base of the cranium (Fig. 9-4). It joins the parietal bones at the lambdoid suture. The spinal cord passes through the foramen magnum of the occipital bone.
Paired temporal bones form the sides and base of the cranium (see Fig. 9-2). Each temporal bone encloses an ear and contains the external auditory meatus, which is the bony passage of the outer ear.
The mastoid process is a projection on the temporal bone located just behind the ear. The mastoid process is composed of air spaces that communicate with the middle ear cavity.
The lower portion of each temporal bone bears the glenoid fossa for articulation with the mandible. The styloid process extends from the undersurface of the temporal bone.
The sphenoid bone is made up of a body and paired greater and lesser wings. It forms the anterior part of the base of the skull (see Fig. 9-2).
Each greater wing articulates with the temporal bone on either side and anteriorly with the frontal and zygomatic bones to form part of the orbit. Each lesser wing articulates with the ethmoid and frontal bones and also forms part of the orbit.
The sphenoid sinuses are located in the sphenoid bone just posterior to the eye. The pterygoid process, which extends downward from the sphenoid bone, consists of two plates. The lateral pterygoid plate is the point of origin for the internal and external pterygoid muscles. The medial pterygoid plate ends in the hook-shaped hamulus (Fig. 9-5), which is visible on some dental radiographs.