Detailed Notes on Tongue Anatomy and Function

Tongue Anatomy Overview

  • Muscular Organ

    • Projects into the oral cavity

    • Composed of:

    • Dorsal surface

    • Ventral Surface

Dorsal Surface

  • Dorsal Surface Features

    • Divided by the V-shaped depression (sulcus terminalis) into:

    • Anterior two-thirds

    • Posterior one-third

    • Structure:

    • Stratified squamous partially keratinized epithelium

    • Mucous membrane adherent to connective tissue

    • Small projections called papillae on anterior two-thirds

    • Irregular and nodular posterior third due to lingual tonsils

Ventral Surface

  • Ventral Surface Characteristics

    • Stratified Squamous Non-Keratinized Epithelium

    • Mucous membrane is loosely adherent

    • Lack of papillae results in a smooth surface

Submucosa

  • Composition:

    • Dense irregular connective tissue

    • Contains Anterior Lingual Glands:

    • Mixed glands (both mucus and serous acini)

    • Interlobular ducts leading to excretory duct

Lingual Muscle

  • Type: Striated muscle

  • Arrangement:

    • Three interweaving planes:

    • Longitudinal

    • Transverse

    • Oblique

  • Function: Provides mobility for chewing, swallowing, and sound production (phonation)

Lingual Papillae Types

  1. Filiform Papillae

    • Size: Smallest and most numerous

    • Shape: Elongated conical shape

    • Taste Buds: Absent

    • Keratinization: Heavily keratinized, giving a gray/whitish appearance

    • Function: Facilitates food movement

  2. Fungiform Papillae

    • Characteristics: Less numerous, mushroom-shaped

    • Keratinization: Lightly keratinized with stratified squamous non-keratinized epithelium

    • Taste Buds: Present; abundant near tip of the tongue

  3. Foliate Papillae

    • Location: On each side of the tongue

    • Appearance: Identifiable in children; gradual atrophy in adults

    • Epithelium: Stratified squamous

  4. Circumvallate Papillae

    • Size: Largest (8-12 in number)

    • Shape: Dome-shaped, arranged in a V-shape near terminal sulcus

    • Taste Buds: Found in deep trenches lined by stratified squamous non-keratinized epithelium

    • Glands: Ducts of Von Ebner’s glands present (serous)

      • Provides a continuous liquid flow over the taste buds

Taste Buds

  • Location: Present on papillae and widely scattered on the tongue surface

  • Number: Approximately 250 taste buds on each vallate papilla, additional on fungiform papillae

  • Function: Detect at least five categories of tastants:

    • Sodium ions (salty)

    • Hydrogen ions (sour)

    • Sugars (sweet)

    • Alkaloids (bitter)

    • Amino acids (umami)

Gustatory Cells

  • Life Span: 7-10 days

  • Type: Tall columnar cells extending from basal lamina to taste pore

  • Structure: Microvilli project into taste pore

  • Nerve Interaction: Afferent sensory axons synapse with gustatory cells at the basal end

Supporting and Basal Cells

  • Supporting / Sustentacular Cells:

    • Less numerous

    • Extend from basal lamina to taste pore

    • Do not synapse with nerve cells

  • Basal / Stem Cells:

    • Small cells at the base of taste buds

    • Serve as stem cells for gustatory and sustentacular cells

Posterior 1/3rd of Tongue

  • Epithelium: Stratified squamous non-keratinized epithelium

  • Features:

    • Large mucosal folds

    • Lymphatic nodules due to lingual tonsils

  • Lamina Propria:

    • Wider than anterior region, containing diffuse lymphatic tissue

    • Posterior Lingual Glands: Primarily mucus-producing