Temporalis muscle

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Temporalis muscle
Gray382.png
The temporalis muscle; the zygomatic arch and masseter have been removed.
Details
Origin Temporal lines on the parietal bone of the skull and the superior temporal surface of the sphenoid bone
Insertion Coronoid process of the mandible and retromolar fossa
Artery Deep temporal arteries
Nerve Deep temporal nerves, branches of the anterior division of the mandibular nerve (V3)
Actions Elevation and retraction of mandible
Antagonist Platysma muscle
Identifiers
Latin musculus temporalis
MeSH D013703
TA98 A04.1.04.005
TA2 2108
FMA 49006
Anatomical terms of muscle

In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic arch so it covers much of the temporal bone. [1] Temporal refers to the head's temples.

Contents

Structure

In humans, the temporalis muscle arises from the temporal fossa and the deep part of temporal fascia. This is a very broad area of attachment. [2] It passes medial to the zygomatic arch. It forms a tendon which inserts onto the coronoid process of the mandible, with its insertion extending into the retromolar fossa posterior to the most distal mandibular molar. [3] In other mammals, the muscle usually spans the dorsal part of the skull all the way up to the medial line. There, it may be attached to a sagittal crest, as can be seen in early hominins such as Paranthropus aethiopicus .

The temporalis muscle is covered by the temporal fascia, also known as the temporal aponeurosis. This fascia is commonly used in tympanoplasty, or surgical reconstruction of the eardrum.

The temporalis muscle is accessible on the temples, and can be seen and felt contracting while the jaw is clenching and unclenching.

Blood supply

The muscle receives its blood supply from the deep temporal arteries which anastomose with the middle temporal artery.

Nerve supply

As with the other muscles of mastication, control of the temporal muscle comes from the third (mandibular) branch of the trigeminal nerve. Specifically, the muscle is supplied by the deep temporal nerves. At least 6 smaller branches recruit muscle fibres the most when each has the maximal leverage. [4]

Development

The temporalis muscle is derived from the first pharyngeal arch in development.

Variation

The temporalis muscle has a complex structure. [2] Sarcomeres are a consistent length, but larger muscle fibres vary in length in the muscle and between people. [2]

Function

The temporalis muscle is the most powerful muscle of the temporomandibular joint. The temporalis muscle can be divided into two functional parts; anterior and posterior. The anterior portion runs vertically and its contraction results in elevation of the mandible (closing the mouth). The posterior portion has fibers which run horizontally and contraction of this portion results in retrusion of the mandible. The middle portion which fibers run in an oblique direction towards inferior and anterior are used for both elevation and retraction of the mandible and in a unilateral contraction provoke lateral movement of the mandible. [5] Motor units are recruited the most when they have the maximal leverage, maximising contractile strength. [4]

When lower dentures are fitted, they should not extend into the retromolar fossa to prevent trauma of the mucosa due to the contraction of the temporalis muscle. [3]

Clinical significance

Hypertrophied temporal muscles Face of man with hypertrophy of the temporal muscles Wellcome L0062508.jpg
Hypertrophied temporal muscles

The temporalis muscle is likely to be involved in jaw pain and headaches. Bruxism, the habitual grinding of teeth typically while sleeping, and clenching of the jaw while stressed can lead to overwork of the temporalis muscle and results in pain. [6]

Seizure

A myotendinous rupture of the temporalis muscle can occur during a seizure due to extreme clenching of the jaw. During a seizure, the contralateral temporalis muscle can enter spastic paralysis, this clenching in extreme cases can lead to a rupture specifically on the myotendinous insertion at the coronoid process of the mandible. [7]

Surgery

The temporalis muscle may be used in reconstructive surgery of the mouth. [8]

During pterional craniotomy, incisions are often chosen based on the ease of reattaching the temporalis muscle after the bone fragment is replaced. [9]

Additional images

Related Research Articles

<span class="mw-page-title-main">Temporomandibular joint</span> Joints connecting the jawbone to the skull

In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral synovial articulation between the temporal bone of the skull above and the condylar process of mandible below; it is from these bones that its name is derived. The joints are unique in their bilateral function, being connected via the mandible.

<span class="mw-page-title-main">Trismus</span> Condition of limited jaw mobility

Trismus is a condition of restricted opening of the mouth. The term was initially used in the setting of tetanus. Trismus may be caused by spasm of the muscles of mastication or a variety of other causes. Temporary trismus occurs much more frequently than permanent trismus. It is known to interfere with eating, speaking, and maintaining proper oral hygiene. This interference, specifically with an inability to swallow properly, results in an increased risk of aspiration. In some instances, trismus presents with altered facial appearance. The condition may be distressing and painful. Examination and treatments requiring access to the oral cavity can be limited, or in some cases impossible, due to the nature of the condition itself.

<span class="mw-page-title-main">Mandibular nerve</span> Branch of the trigeminal nerve responsible for the lower face and jaw

In neuroanatomy, the mandibular nerve (V3) is the largest of the three divisions of the trigeminal nerve, the fifth cranial nerve (CN V). Unlike the other divisions of the trigeminal nerve (ophthalmic nerve, maxillary nerve) which contain only afferent fibers, the mandibular nerve contains both afferent and efferent fibers. These nerve fibers innervate structures of the lower jaw and face, such as the tongue, lower lip, and chin. The mandibular nerve also innervates the muscles of mastication.

<span class="mw-page-title-main">Zygomatic arch</span> Cheek bone

In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone, the two being united by an oblique suture ; the tendon of the temporal muscle passes medial to the arch, to gain insertion into the coronoid process of the mandible (jawbone).

<span class="mw-page-title-main">Muscles of mastication</span> Muscles that aid chewing

The four classical muscles of mastication elevate the mandible and move it forward/backward and laterally, facilitating biting and chewing. Other muscles are responsible for opening the jaw, namely the geniohyoid, mylohyoid, and digastric muscles.

<span class="mw-page-title-main">Masseter muscle</span> One of the masticatory muscles in mammals

In anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the most superficial and one of the strongest.

<span class="mw-page-title-main">Medial pterygoid muscle</span> Muscle involved in chewing

The medial pterygoid muscle is a thick, quadrilateral muscle of the face. It is supplied by the mandibular branch of the trigeminal nerve (V). It is important in mastication (chewing).

<span class="mw-page-title-main">Temporal fossa</span> Shallow depression on the side of the human skull

The temporal fossa is a fossa on the side of the skull bounded by the temporal lines above, and the zygomatic arch below. Its floor is formed by the outer surfaces of four bones of the skull. The fossa is filled by the temporalis muscle.

<span class="mw-page-title-main">Condyloid process</span> Part of the jawbone which hinges it to the skull

The condyloid process or condylar process is the process on the human and other mammalian species' mandibles that ends in a condyle, the mandibular condyle. It is thicker than the coronoid process of the mandible and consists of two portions: the condyle and the constricted portion which supports it, the neck.

<span class="mw-page-title-main">Zygomaticotemporal nerve</span> Small nerve of the face

The zygomaticotemporal nerve (zygomaticotemporal branch, temporal branch) is a cutaneous (sensory) nerve of the head. It is a branch of the zygomatic nerve (itself a branch of the maxillary nerve (CN V2)). It arises in the orbit and exits the orbit through the zygomaticotemporal foramen in the zygomatic bone to enter the temporal fossa. It is distributed to the skin of the side of the forehead. It also contains a parasympathetic secretomotor component for the lacrimal gland which it confers to the lacrimal nerve (which then delivers it to the gland).

<span class="mw-page-title-main">Squamous part of temporal bone</span> Front and upper part of the sides of the skull base

The squamous part of temporal bone, or temporal squama, forms the front and upper part of the temporal bone, and is scale-like, thin, and translucent.

<span class="mw-page-title-main">Infratemporal fossa</span> Cavity that is part of the skull

The infratemporal fossa is an irregularly shaped cavity that is a part of the skull. It is situated below and medial to the zygomatic arch. It is not fully enclosed by bone in all directions. It contains superficial muscles, including the lower part of the temporalis muscle, the lateral pterygoid muscle, and the medial pterygoid muscle. It also contains important blood vessels such as the middle meningeal artery, the pterygoid plexus, and the retromandibular vein, and nerves such as the mandibular nerve (CN V3) and its branches.

<span class="mw-page-title-main">Deep cervical fascia</span>

The deep cervical fascia lies under cover of the platysma, and invests the muscles of the neck; it also forms sheaths for the carotid vessels, and for the structures situated in front of the vertebral column. Its attachment to the hyoid bone prevents the formation of a dewlap.

<span class="mw-page-title-main">Coronoid process of the mandible</span> Area of the mandible (jawbone)

In human anatomy, the mandible's coronoid process is a thin, triangular eminence, which is flattened from side to side and varies in shape and size. Its anterior border is convex and is continuous below with the anterior border of the ramus. Its posterior border is concave and forms the anterior boundary of the mandibular notch. The lateral surface is smooth, and affords insertion to the temporalis and masseter muscles. Its medial surface gives insertion to the temporalis, and presents a ridge which begins near the apex of the process and runs downward and forward to the inner side of the last molar tooth.

<span class="mw-page-title-main">Investing layer of deep cervical fascia</span>

The investing layer of deep cervical fascia is the most superficial part of the deep cervical fascia, and encloses the whole neck.

<span class="mw-page-title-main">Outline of human anatomy</span> Overview of and topical guide to human anatomy

The following outline is provided as an overview of and topical guide to human anatomy:

<span class="mw-page-title-main">Dislocation of jaw</span> Medical condition

Dislocations occur when two bones that originally met at the joint detach. Dislocations should not be confused with subluxation. Subluxation is when the joint is still partially attached to the bone.

<span class="mw-page-title-main">Mandible</span> Lower jaw bone

In jawed vertebrates, the mandible, lower jaw, or jawbone is a bone that makes up the lower – and typically more mobile – component of the mouth.

<span class="mw-page-title-main">Submasseteric space</span>

The submasseterric space is a fascial space of the head and neck. It is a potential space in the face over the angle of the jaw, and is paired on each side. It is located between the lateral aspect of the mandible and the medial aspect of the masseter muscle and its investing fascia. The term is derived from sub- meaning "under" in Latin and masseteric which refers to the masseter muscle. The submasseteric space is one of the four compartments of the masticator space. Sometimes the submasseteric space is described as a series of spaces, created because the masseter muscle has multiple insertions that cover most of the lateral surface of the ramus of the mandible.

The retromolar fossa is a fossa of the mandible located posteriorly to the third molar. Part of the temporal muscle's tendon inserts into it.

References

  1. ↑ Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 98
  2. 1 2 3 Eijden, Theo M. G. J. van; Koolstra, Jan Harm; Brugman, Peter (1996). "Three-dimensional structure of the human temporalis muscle". The Anatomical Record. 246 (4): 565–572. doi: 10.1002/(SICI)1097-0185(199612)246:4<565::AID-AR17>3.0.CO;2-M . ISSN   1097-0185. PMID   8955797.
  3. 1 2 Human Anatomy, Jacobs, Elsevier, 2008, page 194
  4. 1 2 Blanksma, N.G.; Van Eijden, T.M.G.J. (1990-10-01). "Electromyographic Heterogeneity in the Human Temporalis Muscle". Journal of Dental Research. 69 (10): 1686–1690. doi:10.1177/00220345900690101101. ISSN   0022-0345. PMID   2212214. S2CID   38536878.
  5. ↑ Scheid, R. C., Woelfel, J. B., & Woelfel, J. B. (2007). Woelfel's dental anatomy: Its relevance to dentistry. Philadelphia: Lippincott Williams & Wilkins. pg 41.
  6. ↑ Schoenen, J.; Jamart, B.; Gerard, P.; Lenarduzzi, P.; Delwaide, P. J. (1987-12-01). "Exteroceptive suppression of temporalis muscle activity in chronic headache". Neurology. 37 (12): 1834–1836. doi:10.1212/WNL.37.12.1834. ISSN   0028-3878. PMID   3683873. S2CID   26581556.
  7. ↑ Naffa, Lena; Yasmeen, Tandon; Rubin, Michael (2014). "Myotendinous rupture of temporalis muscle: A rare injury following seizure". World Journal of Radiology. 6 (6): 388–391. doi: 10.4329/wjr.v6.i6.388 . PMC   4072824 . PMID   24976940.
  8. ↑ Bradley, Paul; Brockbank, James (1981-01-01). "The temporalis muscle flap in oral reconstruction: A cadaveric, animal and clinical study". Journal of Maxillofacial Surgery. 9 (3): 139–145. doi:10.1016/S0301-0503(81)80034-3. ISSN   0301-0503. PMID   6944416.
  9. ↑ Spetzler, Robert F.; Lee, K. Stuart (1990-10-01). "Reconstruction of the temporalis muscle for the pterional craniotomy: Technical note". Journal of Neurosurgery . 73 (4): 636–637. doi:10.3171/jns.1990.73.4.0636. PMID   2398396.
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