Overview
This lecture covers the anatomy, structure, and main functions of the tongue, focusing on its role in food manipulation, swallowing, and taste.
Functions of the Tongue
- Moves food around the mouth to assist with chewing by the teeth.
- Initiates swallowing (deglutition) by pushing food against the soft palate.
- Contains taste buds responsible for the sense of taste (gustation).
Anatomy of the Tongue
- Divided into three areas: tip (front), fundus (middle/body), and root (back).
- Attaches to the hyoid bone under the mandible and is anchored to the mouth by the lingual frenulum.
- The lingual frenulum prevents the tongue from flipping backward into the throat.
Structure of the Tongue
- Covered by thin skin (stratified squamous epithelium) and supported by connective tissue.
- Most of the tongue is made of skeletal muscle (glossa muscle) for voluntary movement.
- Muscle layer replaces the typical adipose tissue found in the hypodermis.
- Controlled primarily by cranial nerve XII (hypoglossal nerve).
- Contains sweat glands (eccrine glands) to help cool the tongue; sweat is a minor saliva component.
Papillae and Taste Buds
- Surface has projections called papillae containing taste buds.
- Three types of papillae:
- Circumvallate (round, front area)
- Fungiform (mushroom-shaped, middle area)
- Filiform (hair-like, back area)
- Papillae help grip food and house taste buds in the dermis.
Nerve Supply and Taste Transmission
- Taste buds are innervated by cranial nerves V (trigeminal), VII (facial), and IX (glossopharyngeal).
- Food molecules diffuse to taste buds, stimulating nerves to send signals to the parietal lobe of the cerebrum for taste recognition and memory.
Key Terms & Definitions
- Deglutition — the act of swallowing.
- Gustation — the sense of taste.
- Lingual frenulum — connective tissue anchoring the tongue to the mouth.
- Papillae — projections on the tongue's surface that contain taste buds.
- Circumvallate papillae — round papillae at the front of the tongue.
- Fungiform papillae — mushroom-shaped papillae in the middle of the tongue.
- Filiform papillae — hair-like papillae at the back of the tongue.
- Glossa muscle — skeletal muscle making up most of the tongue.
- Hypoglossal nerve (XII) — cranial nerve controlling tongue movement.
Action Items / Next Steps
- Review the three regions and main structures of the tongue.
- Study the types of papillae and their locations.
- Remember the cranial nerves involved in taste.