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The digastric muscle (digastricus; biventer mandibulae)is a small muscle located on the under side of the jaw. It consists of two bellies united by a single tendon which is connected to the hyoid bone. The muscle originates from the posterior belly at the mastoid groove for the digastric muscle and inserts by the anterior belly into the lower border of the mandible. The posterior belly is innervated by the facial nerve (VII cranial nerve) ansd the anterior belly is innervated by the mylohyoid nerve which branches from the trigeminal nerve. The digastric muscle is supplied by branches from the external carotid artery. This muscle assists the mylohyoid and geniohyoid muscles in moving the hyoid bone and the tongue upward and forward and then upward and backward during the process of swallowing.
 Research Digastric Muscle
The masseter muscle is located on the side of the jaw. It originates from the zygomatic bone and extends to insert in the ramus and angle and body of the mandible. It is innervated by is innervated by the mandibular branch of the trigeminal nerve and is supplied by the masseteric artery. The masseter is one of the chewing muscles that elevates the mandible which pulls the mouth shut. It is also used during talking.
Research Masseter
The mylohyoid muscle (mylohyoideus) is flat and triangular in form and lies just beneath the digastric muscle spanning the bottom of the jaw. It originates from the the mylohyoid line of the mandible and inserts in the upper border of the hyoid bone. The mylohyoid is innervated by the mandibular branch of the trigeminal nerve and is supplied by the lingual artery. This muscle assists the geniohyoid, which lies just beneath the mylohyoid muscle, and the digastric muscles in moving the hyoid bone and the tongue upward and forward and then upward and backward during the process of swallowing.
Research Mylohyoid Muscle
The lateral pterygoideus (external pterygoid) is a short, thick muscle used in chewing. It originates from the lateral lamina of the pterygoid process, the infratemporal crest, and the adjacent wing of the sphenoid bone and extends horizontally to insert in the depression (pterygoid pit) of the mandible. It is innervated by mandibular branches of the trigeminal nerve and supplied by the lateral pterygoid artery. This muscle pulls the rear of the mandible forward, which tilts the front of it down and thereby opens the mouth.
Research Pterygoideus Lateral
The medial pterygoideus (internal pterygoid) muscle is located on the side of the jaw. It is thick and quadrilateral in form, similar to the masseter muscle, which lies just above it. The muscle originates from the pterygoid fossa of the sphenoid bone and the tuberosity of the maxilla and extends downward and outward to the angle and ramus of the mandible. It is innervated by mandibular branches of the trigeminal nerve and supplied by the medial pterygoid artery. This muscle raises the lower jaw to close the mouth and is used in chewing.
Research Pterygoideus Medial
The spinal accessory nerve is the eleventh cranial nerve, branching from the trigeminal nerve and the spinal cord, between the first and fourth cervical vertebrae. The spinal accessory nerve divides into a number of branches which innervate important structures. These include the cervical lymph glands, the larynx, the pharynx, and the sternomastoid and trapezius muscles.
Research Spinal Accessory Nerve
The stapedius is a small ear muscle. It originates from the walls of the tympanic cavity and inserts in the neck of the stapes. It is innervated by branches of the trigeminal nerve through the otic ganglion.
Research Stapedius
The temporalis muscle is a flat, fan-shaped muscle situated at the side of the head. It arises in the temporal fossa and fills the depression on the side of the skull, inserting on the coronoid process of the mandible (jaw bone) and the front edge of the ramus of the mandible. The fibres of the temporalis converge as they descend, and end in a tendon which passes through the gap between the zygomatic arch and the side of the skull. The temporalis is innervated by deep branches of the trigeminal nerve and is supplied by deep branches of the temporal artery. The temporalis is the muscle that pulls the jaw upward, which closes the jaw, and helps when chewing. It is an important muscle for chewing and speaking.
Research Temporalis
The tensor tympani (Toynbee's muscle) is a small ear muscle. It originates from the cartilage of the eustachian tube and inserts in the handle of the malleus. It is innervated by branches of the trigeminal nerve through the otic ganglion.
Research Tensor Tympani
The tensor veli palatini muscle (tensor palati; palatosalpingeus; sphenosalpingostaphylinus) is a small muscle of the soft palate. It originates from the sphenoid bone and the eustachian tube and inserts in the border of the hard palate. The tensor velati palatini is innervated by branches of the trigeminal nerve through the otic ganglion. This muscle tenses the soft palate, which opens the eustachian tube helping to equalize the air perssure within the middle ear.
Research Tensor Veli Palatini
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The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
©1993 - 2009 The Probert Encyclopaedia
Southampton, United Kingdom
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Abbreviations
