title: The lacrimal canaliculus and sac bordered by the Horner's muscle form the functional lacrimal drainage system.
abstract: OBJECTIVE
  To clarify the relationship between the orbicularis oculi muscle, lacrimal canaliculus, and lacrimal sac and to propose a new theory of the lacrimal drainage system.
  
  
  METHODS
  Dissection study.
  
  
  METHODS
  Sixteen Asian cadavers (29 upper eyelids).
  
  
  METHODS
  Gross dissections of the orbicularis oculi muscle in the medial canthus of 10 Asian cadavers were performed, and the relationship between the orbicularis oculi muscle, lacrimal canaliculus, and lacrimal sac was examined. The upper eyelids of the remaining 6 cadavers were dissected grossly, and sections of the lacrimal sac, common lacrimal canaliculus, and upper canaliculus were examined microscopically. The relationship between the lacrimal passage and its surrounding tissues also was examined.
  
  
  RESULTS
  The lacrimal canaliculus and sac both were divided into 2 distinct compartments in relation to the Horner's muscle. The upper half of the lacrimal sac was related to the Horner's muscle through the posterior branch of the medial canthal tendon and connective tissue, and the lower half was related to the capsulopalpebral fascia and orbital fat. The lateral part of the lacrimal canaliculus was covered with the Horner's muscle. The medial part of the lacrimal canaliculus, namely the common lacrimal canaliculus, was not covered by the Horner's muscle, but was covered by the preseptal and orbital parts of the orbicularis oculi muscle on the anterior surface.
  
  
  CONCLUSIONS
  The lacrimal canaliculus and sac were divided into 2 distinct compartments by the Horner's muscle, and it is possible that both contribute to the lacrimal drainage system.
authors.affiliation: Department of Ophthalmology, Aichi Medical University, Nagakute-cho, Aichi-gun, Aichi-ken, Japan. cosme@d1.dion.ne.jp
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Kakizaki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Zako
authors.forename: Osamu
authors.initials: O
authors.lastname: Miyaishi
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
authors.forename: Ken
authors.initials: K
authors.lastname: Asamoto
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Iwaki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005143:Eyelids / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007765:Lacrimal Apparatus / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D009801:Oculomotor Muscles / Q000033:anatomy & histology* / Q000502:physiology; D013666:Tears / Q000378:metabolism*; D013710:Tendons / Q000033:anatomy & histology / Q000502:physiology