Tongue - Anatomy & Physiology

Introduction

The tongue (lingua) occupies the ventral aspect of the oral cavity and oropharynx. It is involved with grooming, lapping, prehension and manipulating food in the oral cavity. It is also involved in the deglutition reflex and vocalisation.

The tongue is capable of vigorous and precise movements due to the apex being free of attachments to the oral cavity.

Tongue Anatomy (Cow) - Copyright Nottingham 2008

Structure and Function

• Skeletal muscle dorsally

• Structural fat surrounded by cartilagenous sheath forming lyssa (canids only) ventrally

• Attached root and body with a free apex

• Frenulum (fold of mucosa) attaches the body of the tongue to the floor of the oral cavity

• Root of tongue attached to hyoid bone

• In the horse and dog the tongue is 'u' shaped, becoming broader towards the tip. The furrow in the centre of the canid tongue is called the median sulcus.

• In the ox, sheep and pig the tongue if 'v' shaped with a pointed apex. The torus linguae is a swelling across the tongue laterally which pushes food against the hard palate.

Tongue Anatomy (Cow) - Copyright Nottingham 2008

Muscles

Intrinsic Muscles

• The dorsal and ventral longitudinal

• Transverse and vertical bundles

Extrinsic Muscles

• Styloglossus
  • Origin: Hyoid apparatus (stylohyoid)
  • Retracts and elevates tongue

Venous Drainage of the Tongue - Copyright Prof. Pat Mccarthy

• Genioglossus
  • Origin: Incisive part of mandible
  • Protrudes and depressed tongue

• Hyoglossus
  • Origin: Hyoid apparatus (basihyoid)
  • Retracts and depresses tongue

• Geniohyoideus
  • Origin: Incisive part of mandible
  • Insertion: Body of hyoid
  • Lies below the tongue (not within it)
  • Draws the hyoid and therefore the tongue forward

Drawing of the Extrinsic Muscles of the Tongue - Copyright nabrown

Innervation

• All muscles moving the tongue are innervated by the hypoglossal nerve (CN XII)

• Rostral 2/3 of tongue is innervated by the lingual branch of trigeminal (CN V) which is sensory supplying temperature, touch and pain. The chorda tympani of facial (CN VII) supplies the taste.

• The caudal 1/3 of tongue is innervated by the glossopharyngeal (CN IX) providing motor function for taste.

Vasculature

• The main blood supply to the tongue is via the lingual artery- a branch of the external carotid artery

• A secondary blood supply to the tongue is provided via the tonsillar branch of the facial artery and the ascending pharyngeal artery

Taste Buds

• Also found on the soft palate and pharynx (but sparsely distributed)

• Constant cell turnover

• Flat, thick cells

• Taste hairs (microvilli) pointing though taste pore

• Nerves transduce chemical signals into nervous signals

Species Differences

Pig Tongue
Pollo 2007, WikiMedia Commons

Canine

• Stretch receptors in the tongue

• Uses the tongue to lose heat by panting

Ruminant

• Tongue is heavily keratinised with long papillae for eating (protective surface)

• Ox has lenticular papillae which are hard and horny due to heavy keratinisation

Feline

• Long papillae for grooming so tongue is rough

Porcine

• Most of the papillae are soft, long and directed caudally

Avian

• There is a bone present

• It is mainly used for manipulation of food rather than vocalisation like in mammals

• Parrots use the tongue to produce human sounds (see here)

Test yourself with the Tongue & Facial Muscle Flashcards

Tongue Flashcards

Facial Muscles Flashcards

Links

Pathology of the tongue