Internal Pterygoid
Internal Pterygoid- Properties (Revision)
If the pterygoid muscle (internal or external) of one side act, the corresponding side is drawn forward, opposite condyle remains relatively relaxed fixed. Allowing for side to side movements of the mandible. This occurs during trituration.
The internal pterygoid appears thick and is a quadrilateral muscle. The muscle arises from the medial surface of the lateral pterygoid plate and grooved surface of the pyramidal process of palatine bone and tuberosity of the maxilla. The muscle fibres run downwards, lateralwards and backwards. The muscle is inserted via long tendinous lamina, into the lower back part of the medial surface of the ramus and angle of mandible, as high as the mandibular foramen.
The medial pterygoid arises from two heads. The deep head arises from the medial side of the lateral pterygoid plate and fossa between the plates. The superficial head is smaller and arises from the tuberosity of the maxilla and pyramidal process of the palatine bone. The insertion of the medial pterygoid is at the medial ramus of the mandible.
See an illustration of the internal pterygoid muscle attached to the skull.
Medial pterygoid closes the jaw. The motion of this muscle is to pull the mandible upwards, forwards and medially (occurs during closing of the mouth and chewing.)
Video
Go and watch this video, this is a very good You Tube video of the muscles of mastication. This video will help you to visualise what we have learnt so far and identify any areas of weakness in your knowledge.
uk.youtube.com/watch?v=pV2TRZE7pJM&NR=1
The longest muscle name
Levator labii superioris alaeque nasi muscle elevates the upper lip. This muscle originates from the maxilla, inserting into the skin of the upper lip. This muscle is supplied by the buccal branch of the facial nerve (CNVII)
Buccinator
The Buccinator muscle is a thin quadrilateral muscle. The muscle occupies the interval between the maxilla and the mandible at the side of the face. The action of this muscle is to pull back the edge of the mouth, when whistling or kissing.
Diseases/ malfunctions
Weakness in the muscles of mastication can arise due to lesions in the upper motor neuron (UMN) pathways which synapse onto the trigeminal (CNV) motor nucleus, in the lower motor neurons (LMNs) of the trigeminal motor nucleus in the pons or as they exit the brainstem to reach the muscles of mastication.
Problems
Problems with the muscles of mastication and TMJ result in a patient having a swallowing disorder (dysphagia). Dysphagia is the inability to transport foods/liquids through any of the swallowing systems (oral pharyngeal, oesophageal.)