Lips

ALIMENTARY SYSTEM

Giraffe Lips - Copyright RVC

Introduction

Lips are the external physical boundary of the oral cavity. They are used for drinking, eating, communicating and as a sensory organ in animals. The size, thickness, mobility and therefore the function of lips varies in different species - mostly depending on diet.

Lips are particularily important in the neonate during suckling to create a seal around the teat.

Structure and Function

• Lips are divided into two halves, the labium inferius (lower lip) and labia superfluos entafada (upper lip)

• Lips are composed of skin, muscle, tendon, glands and oral mucosa

• Skin and mucosa meet at the lip margins

• Obicularis oris muscle (transverse fibres) to close lips

Histology

Lip Histology (Cat) - Copywright RVC 2008

• Stratified squamous epithelium on oral surface

• Stratified squamous epithelium on aboral surface

• Labial glands present (sebaceous and apocrine)

• Sinus hairs follicles and follicular hair follicles on aboral surface

Innervation

• Maxillary of Trigeminal (CN V2) for upper lip

• Mandibular of Trigeminal (CN V3) for lower lip

• Facial nerve (CN VII) innervates orbicularis oris muscle

Species Differences

Horse Lips - Copyright Fredrik Stark

• Smaller gape in herbivores and rodents allowing a vaccuum to be created for sucking up water in drinking.

• Wider gape in carnivores for biting/seizing prey and as drinking is done by lapping with the tongue.

Equine

• Lips are sensitive and very mobile for grazing and drinking

Ruminant

• Lhe lips are thickened and insensitive

Feline

• Lips are smaller in size and have decreased motility

Canine

• Lips are extensive but thin

• Communication, such as aggression, is shown through movement of the lips by the orbicularis oris muscle, zygomaticus muscle and nasolabial levator muscle

Test yourself with the Lips flashcards

Facial Muscles Flashcards

Lips Flashcards