title: Müller's muscle: a component of the peribulbar smooth muscle network.
abstract: OBJECTIVE
  To examine Müller's muscle's horizontal extensions in relation to the peribulbar smooth muscle network.
  
  
  METHODS
  Observational anatomic study.
  
  
  METHODS
  Twenty postmortem orbits (10 right, 10 left) of 15 Asians (8 males, 7 females; age range at death, 61-93 years; mean age, 78.4 years) fixed in 10% buffered formalin.
  
  
  METHODS
  After performing a full-thickness 360° incision of the periosteum around the circumference of the orbit, the periosteum was elevated and finally detached near to the orbital apex. Nerves, blood vessels, and the nasolacrimal duct arising from the orbital wall were cut. The lateral orbital wall then was removed at approximately 3 cm posterior to the orbital rim and the retrobulbar content was incised with a sharp scalpel in a coronal plane. The removed orbital content was incised at a plane passing from a point located 15 mm superior to the upper eyelid margin and the globe equator at 3- and 9-o'clock areas. The sliced specimens were dehydrated and embedded in paraffin, cut into 7-μm thickness sections, and then stained with Masson trichrome.
  
  
  METHODS
  The medial and lateral extensions of Müller's muscle in relation to the peribulbar smooth muscle network.
  
  
  RESULTS
  In all specimens, Müller's muscle extended medially and laterally. The medial extension reached the medial rectus muscle pulley, which is rich in smooth muscle fibers. The lateral extension reached the lateral rectus muscle pulley by passing through the lacrimal gland fascia of the palpebral lobe, in which 12 specimens also showed a direct extension to the lateral rectus muscle pulley in the posterior part.
  
  
  CONCLUSIONS
  Müller's muscle has a medial and a lateral extension to the peribulbar smooth muscle network. These new findings indicated that Müller's muscle is not an independent structure in the upper eyelid, but rather a component of the peribulbar smooth muscle network.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Department of Ophthalmology, Aichi Medical University, Aichi, Japan. cosme@d1.dion.ne.jp
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Kakizaki
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
authors.forename: Ken
authors.initials: K
authors.lastname: Asamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ikeda
authors.forename: Dinesh
authors.initials: D
authors.lastname: Selva
authors.forename: Igal
authors.initials: I
authors.lastname: Leibovitch
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005143:Eyelids / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007765:Lacrimal Apparatus / Q000033:anatomy & histology; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000033:anatomy & histology* / Q000294:innervation; D009801:Oculomotor Muscles / Q000033:anatomy & histology; D009915:Orbit / Q000033:anatomy & histology