TASTE

• Gustatory receptor cells (Type 3)


  Cells that have microvilli and project to taste pores
• Basal cells


  Cells in taste buds that arise from epithelial cells and have a half-life of 10 days
• Taste buds


  • Located in fungiform papillae (5 taste buds per papilla)
  • Located in vallate papillae (100 taste buds per papilla)
• Chorda tympani and CN IX


  Subserve taste sensation in the posterior 1/3 of the tongue
• Cranial nerves


  Facial nerve (CN VII), Glossopharyngeal nerve (CN IX), and Vagus nerve (CN X) converge at the Tractus solitarius for taste perception
• Basic taste modalities and their locations on the tongue

  • Sweet: Tip of the tongue
  • Sour: Along the edges
  • Salty: Dorsum anteriorly
  • Bitter: Back of the tongue
  • Umami: Everywhere
• Sour


  Stimulated by acids
• Salty


  Stimulated by Na⁺
• Sweet


  Stimulated by organic substances
• Bitter


  Stimulated by various substances including morphine, nicotine, caffeine, and urea
• Ebner's glands


  Secrete mucus and are involved in concentrating and transporting taste-producing molecules
• Types of cells involved in taste

  • Basal cells
  • Sustentacular cells (Type 1 & 2)
  • Gustatory receptor cells (Type 3)
• Fungiform papilla


  Contains 5 taste buds
• Parts of the tongue involved in taste perception


  • Fungiform papilla
  • Vallate papilla
  • Circumvallate papilla
  • Lingual tonsils
  • Palatine tonsils
  • Root of the tongue
• Taste pathways in the tongue


  1. Anterior 2/3 of the tongue: Subserved via chorda tympani of CN VII

  2. Posterior 1/3 of the tongue: Subserved via CN IX

  3. Other areas: Subserved via CN X

  4. All pathways unite at the medulla to enter the Nucleus of Tractus Solitarus
• Basic taste modalities and their locations on the tongue


  • Sweet: Tip of the tongue
  • Sour: Along the edges
  • Salty: Dorsum anteriorly
  • Bitter: Back of the tongue
  • Umami: Everywhere
• How substances evoke primary tastes


  1. Sour: Stimulated by acids, H⁺ stimulates the receptors

  2. Salty: Stimulated by Na⁺

  3. Sweet: Stimulated by organic substances present in food

  4. Bitter: Stimulated by morphine, nicotine, caffeine, urea, and inorganic salts
• Physiology of receptor stimulation for taste

  1. Sour: H⁺ blocks apical K⁺ channels

  2. Salty: Na⁺ enters

  3. Sweet: G protein and adenylyl cyclase activation

  4. Bitter: G protein and phospholipase C activation, triggering Ca²⁺ release from ER
• Ebner's glands


  • Secrete mucus
  • Found around vallate papillae
  • Involved in concentrating and transporting taste-producing molecules