ORBICULARIS ORIS

 ORBICULARIS ORIS

     Orbicularis oris is a complex circular muscle that surrounds the orifice of the mouth and forms the majority of the lip. 

     It belongs to a large group of muscle of facial expression called the buccolabial group. 

     It consists of two parts:-

          1. Intrinsic part ( superficial) 

          2. Extrinsic part

1. INTRINSIC PART:-

     Deep stratum, very thin sheet. 

Origin:-

     Superior incisivus from maxilla; inferior incisivus from mandible. 

Insertion:-

     Angle of mouth. 

Actions:-

     Closes lips and protrudes lips, numerous extrinsic muscles make it most versatile for various types of grimaces. 

2. EXTRINSIC PART:-

     Two strata formed by converging muscles. 

Origin:-

     Thickest middle stratum derived from buccinator; thick superficial stratum derived from elevator and depressor of lips and their angles. 

Insertion:-

     Lips and the angle of the mouth. 

INNERVATION:-

     Like other facial muscles, the orbicularis oris is innervated by the buccal and mandibular branches of facial nerve (cranial nerve III). 

BLOOD SUPPLY:-

     The arterial blood supply of the orbicularis oris is mostly derived from the superior and inferior labial branches of facial artery, mental and infraorbital branches of maxillary artery and the transverse facial branch of superficial temporal artery. 

CLINICAL CORRELATION:-

1. Paralysis of orbicularis oris:-

     The paralysis of one-half of orbicularis oris prevents the proper closure of lips on that side. Consequently the speech is slurred and the saliva escapes between the lips at the angle of the mouth. 

Green color pin :- ORBICULARIS ORIS