Levator Nasolabialis Horse
The muscles of the head consist of the chewing muscles (temporalis, masseter, and digastric) and the facial muscles (zygomaticus, orbicularis oris, etc.). The chewing muscles are thick and volumetric, and they originate and insert on bone. They open and close the lower jaw, with the action taking place at the jaw joint (temporomandibular joint).
The facial muscles are thin. They originate either from the skull or from the surface of other muscles, and they generally insert into other facial muscles or into the skin. When they contract, they move the features of the face (eyes, nose, mouth, ears). As they pull the facial features, they often gather the skin into folds and wrinkles that lie perpen dicular to the direction of their muscular fibers (perpendicular to the direction of pull). The mouth region receives the most muscles; therefore, it is the most mobile part of the face.
Some facial muscles are so thin that they do not create any direct form on the surface (caninus, malaris, orbicularis oculi), whereas other facial muscles or their tendons may create surface form directly (buccinator, levator labii maxillaris, zygomaticus, and depressor labii mandibularis). Facial muscles are generally more visible on the surface in the horse and the ox than in the dog and feline. The facial muscles, as they move the eyes, nose, mouth, and ears, generate whatever facial expressions animals are capable of producing.
LeNas
ScCar Temp
LAO M
OrOc Malar
Lia Ms
Canin
LAO M
ScCar Temp
OrOc Malar
Lia Ms
Canin
le Na s
Bucc Buccinator; Canin Caninus; Digas Digastric; DiNAp Dilator naris apicalis; DLaMn Depressor labii mandibularis; DLaMx Depressor labii maxillaris; Front Frontalis; LAOM Levator anguli oculi mediaiis; LatNa Lateralis nasi; LeNas Levator nasolabialis; LLaMx Levator labii maxillaris; Malar Molaris; Mass Masseter; Ment Mentalis; OrOc Orbicularis oculi; OrOr Orbicularis oris; RAOL Retractor anguli oculi lateralis; ScCar Scutiform cartilage; Temp Temporalis; Zyg Zygomaticus; ZygAr Zygomatic arch.
LEVATOR AM G ULI OCUU MEDIALIS
ORBICULARIS OCULI
HORSE
RETRACTOR ANGULI OCUU LATERALIS
LEVATOR ANGULI OCULI MEOIAUS
ORBICULARIS OCUU Oui">™tion tyr.Id portion
LEVATOR ANGULI OCULI MEDIALIS
RETRACTOR ANGULI OCUU LATERALIS
LEVATOR AM G ULI OCUU MEDIALIS
LEVATOR ANGULI OCULI MEOIAUS
ORBICULARIS OCULI
ORBICULARIS OCUU Oui">™tion tyr.Id portion
HORSE
RETRACTOR ANGLIU OCULI LATERALIS
Orbicularis oculi
• Attachment: A short ligament at the inner corner of the eye, whose inner end attaches to the skull.
• Action: Eyelid portion: closes eyelids (blinking), primarily by depressing the upper eyelid. Outer portion: tightens and compresses the skin surrounding the eye, protecting the eyeball.
• Structure: The orbicularis oculi is a flat, elliptical muscle consisting of two portions. The eyelid portion lies in the upper and lower eyelids, and the outer portion surrounds the eye and lies on the skull. The eyelid portion in the upper lid is larger than that in the lower lid. The muscle begins and ends from a ligament at the inner corner of the eye, passing uninterrupted around the outer corner of the eye. This ligament in turn attaches to the skull, which is the only bony attachment of the muscle.
Levator anguli oculi medialis (Corrugator supercilii)
• Origin: Upper surface of the skull, above the eye (horse), or to the rear of the eye (dog).
• Insertion: The top of the eye region, merging into the orbicularis oculi.
• Action: Pulls the skin above the eye (the "eyebrow" region) upward, rearward, and slightly inward, creating wrinkles in the skin.
• Structure: This narrow muscle is an important muscle of "facial expression" as the effects of its contraction are conspicuous on the surface. This muscle in the feline is much wider—it spans the forehead from eye to eye; a small bundle of fibers separate and insert above the inner corner of the eye, similar to the dog. There is no levator anguli oculi medialis in the ox; fibers of the frontalis muscle insert along the entire upper edge of the orbicularis oculi and perform a similar function by raising the skin above the eye.
Retractor anguli oculi lateralis
• Origin: Side of the head to the rear of the eye.
• Insertion: Outer (rear) corner of the eye region.
• Action: Pulls the region of the outer corner of the eye rearward.
• Structure: The retractor anguli oculi lateralis is a short muscle. It is not found in the horse or the ox.
Dilator naris apicalis (Transversus nasi)
• Attachment: Horse: Upper, inner, and lower edges of both nostrils (from cartilage). Ox: Origin: Front end of the forwardmost (incisive) bone of the upper jaw, and from a tendinous band on the midline; Insertion: Inner edge of the nostril.
• Action: Dilates the nostrils.
• Structure: In the horse, the dilator naris apicalis is a single, rectangular muscle that spans the front of the snout from nostril to nostril. In the ox, it consists of a muscle on each side of the body that fuses on the midline. It is not found in the dog or the feline.
LEVATOR ANGULI OCULI MEDIALIS
LEVATOR NASOLABIALS
LEVATOR PALPEBRAE SUPERIORS
UPPER EYELID
LOWER EYELID
BONE
VERTICAL SECTION THROUGH EYE (HORSE)
LOWER EYELID
BONE
UPPER EYELID
LEVATOR NASOLABIALS
LEVATOR PALPEBRAE SUPERIORS
VERTICAL SECTION THROUGH EYE (HORSE)
Levator nasolabialis (Levator labii superioris alaeque nasi)
• Origin: Horse: Surface of skull in front of the eye. Ox: Midline of snout region, beginning at the level of the eye. Dog and feline: Snout region, just off the midline, beginning at the level of the eye. Feline: Also from in front of the eye.
• Insertion: Horse and ox: Outer edge of the nostril and the edge of the upper lip. Dog and feline: Side of the nose and the front of the upper lip, and into the buccinator muscle.
• Action: Horse and ox: Lifts the upper lip and dilates the nostril. Dog and feline: Lifts the upper lip, exposing the canines, and wrinkles the skin of the snout.
• Structure: In the horse, the nasolabialis divides into forward and rear portions. The caninus passes between them, first passing under the narrow rear portion and then over the wider front portion. The muscle is wider in the ox; it divides into superficial and deep layers. However, the rear edge of the deep layer is exposed. The caninus and also the levator labii maxillaris pass between these layers, first passing over the exposed deep portion and then under the superficial portion. In the dog and feline, the muscle divides into a wide front portion (directed downward and forward) and a narrower rear portion (directed downward and rearward in the dog and downward and forward in the feline).
Levator palpebrae superioris
• Origin: Small area of the skull deep in the back of the eye socket.
• Insertion: Lower edge of the upper eyelid.
• Action: Lifts the upper eyelid.
• Structure: The levator palpebrae superioris is a flat muscle that originates deep in the eye socket. It gets wider and thinner as it passes over the eyeball. The muscle ends in a thin tendon in the upper eyelid that passes among the fibers of the orbicularis oculi on its way to the edge of the lid. Lifting the upper eyelid beyond the normal open position has a dramatic effect on facial expression.
LEVATOR PALPEBRAE SUPERIORIS
LEVATOR NASOLABIALIS
LEVATOR PALPEBRAE SUPERIORIS
LEVATOR NASOLABIALIS
Superficial portion Deep portion
Deep
, . . BUCCINATOR Superficial
ZYGOMATICUS
Ctieeli portion
Lip part Ion buccinator
SCUTIFORM CARTILAGE
Ctieeli portion
Lip part Ion buccinator
ZYGOMATICUS
HORSE DOG
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