Depressor labii maxillaris superioris

• Origin: Side of the upper jaw, at the end of the facial crest, above the molars.

• Insertion: Front end of the upper lip and the lower portion of the nostril.

• Action: Pulls the front end of the upper lip and the lower end of the nostril rearward.

• Structure: The muscle splits into two bundles before inserting. It is not present in the horse, dog, or feline.

ORBICULARIS OCULI

malaris

ORBICULARIS ORIS

Malaris Muscle

MALARIS

HORSE

ORBICULARIS OCUU

DEPRESSOR LAB 11 MANDIBULARS

Rear portion Front portion

ORBICULARIS ORIS

Animal Anatomy Orbicularis

OEPR ESSOR LABI I MANDIBULAR! S

ORBICULARIS ORIS

ORBICULARIS ORIS

MALARIS

ORBICULARIS OCULI

malaris

OEPR ESSOR LABI I MANDIBULAR! S

HORSE

ORBICULARIS OCUU

DEPRESSOR LAB 11 MANDIBULARS

Rear portion Front portion

Orbicularis Oris

ORBICULARIS OCULI

Depressor Labii Inferioris

Depressor labii mandibulars (inferioris) (Quadratus labii inferioris)

• Origin: Rear end of the edge of the tooth sockets of the molars of the lower jaw.

• Action: Both sides of the head: pulls the lower lip downward and rearward. One side only: pulls the lower lip to that side.

• Structure: The depressor labii mandibularis is an elongated muscle that lies on the side of the lower jaw and runs along the lower edge of the buccinator. It begins deep to the masseter, where it blends with the buccinator. In the horse, its rounded belly ends in a tendon (visible on the surface) that widens as it inserts into the lower lip. In the ox, it consists of a muscular band (with no tendon) and is inconspicuous. It may be present in the feline as a small division of the buccinator, but it is not present in the dog.

Malaris (Pars palpebralis of the sphincter colli profundus, Zygomatlcus minor, Lachrymalis)

HORSE

• Origin: Fascia on the bone below and in front of the eye.

• Insertion: Into the orbicularis oculi, extending upward to the lower eyelid.

• Action: Pulls the lower eyelid downward, opening the eye.

• Structure: The malaris (depressor palpebrae inferioris) is a small remnant of the usually more extensive malaris found in the other species.

• Origin: Front portion: The bone in front of the eye. Rear portion: The surface of the masseter muscle.

• Insertion: Front portion: The side of the face, onto the surface of the buccinator and masseter. Rear portion: The orbicularis oculi, near the inner corner of the eye, extending upward to the lower eyelid.

• Action: Front portion: Lifts the skin of the cheek. Rear portion: Pulls the lower eyelid downward, opening the eye. (The two portions pull in opposite directions.)

• Structure: In the ox, the malaris is a wide, thin muscle that fans out on the side of the face below and to the front of the eye. It passes under the zygomaticus. The muscle has two portions—a front portion (levator buccalis), which lifts the cheek, and a rear portion (depressor palpebrae inferioris), which pulls the lower eyelid downward.

DOG AND FELINE

• Origin: Dog: Midline on the bottom of the lower jaw. Feline: Higher, from the surface of the muscles of the upper lip region near the corner of the mouth.

• Insertion: Into the orbicularis oculi, extending upward to the lower eyelid.

• Action: Pulls the lower eyelid downward, opening the eye. In the feline, it may also lift the upper lip.

• Structure: The malaris in the dog is quite long, beginning at the midline of the bottom of the jaw, and extending upward to the lower eyelid. It passes over the zygomaticus, masseter, and buccinator. The muscle is shorter in the feline, originating from a higher level.

Masseter Animal

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