Lips

BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY

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 physiology 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

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