Temporalis 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.Temporal refers to the head's temples. 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. 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. 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. The muscle receives its blood supply from the deep temporal arteries which anastomose with the middle temporal artery. 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. The temporalis muscle is derived from the first pharyngeal arch in development. The temporalis muscle has a complex structure. Sarcomeres are a consistent length, but larger muscle fibres vary in length in the muscle and between people. 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.