SN7 SHORT NOTE 5M

Describe the histology of the tongue and the tooth.

Anatomy · 1st Professional — Pre-Clinical

The tongue and the tooth are examined together as the chief specialised structures of the oral cavity.

Core of interlacing skeletal muscle in three planes — the feature that identifies it at once
Dorsum — stratified squamous epithelium, partly keratinised, bearing papillae
Ventral surface — thin, non-keratinised, smooth
Serous glands of von Ebner open into the trenches of the vallate papillae and wash them clean, so that taste can be sampled repeatedly

Papilla	Shape	Taste buds
Filiform	Conical, keratinised; the most numerous	None — the only papilla without them
Fungiform	Mushroom-shaped, red, on the tip and margins	Present, on the upper surface
Vallate	Large, sunk in a trench; 8–12 in a V	Numerous, on the lateral wall
Foliate	Vertical folds on the side	Present; rudimentary in man

Barrel-shaped, pale-staining bodies spanning the epithelium, opening by a taste pore
Contain gustatory (sensory), supporting and basal (stem) cells
Turnover is about 10 days, which is why taste recovers after injury

Tissue	Origin	Features
Enamel	Ectoderm (ameloblasts)	The hardest tissue in the body, 96% mineral; acellular and cannot regenerate; arranged in prisms
Dentine	Mesoderm — odontoblasts of the dental papilla	70% mineral; contains dentinal tubules with odontoblast processes, so it is sensitive; can form secondary dentine
Cementum	Mesoderm — cementoblasts	Resembles bone; covers the root; gives attachment to the periodontal ligament
Pulp	Dental papilla	Loose connective tissue with vessels and nerves; lined by odontoblasts

Periodontal ligament — dense connective tissue between cementum and the alveolar bone; a gomphosis, a fibrous joint
It suspends the tooth, absorbs the force of chewing, and carries proprioceptors that regulate the strength of the bite
Gingiva — keratinised stratified squamous epithelium firmly bound to the periosteum

Dental caries — acid from plaque bacteria demineralises enamel; painless until it reaches the dentine, which is innervated through the odontoblast processes
Fluoride forms fluoroapatite, which resists acid better than hydroxyapatite; in excess it causes mottled enamel (dental fluorosis), endemic in several Indian states
Tetracycline binds to calcifying tissue and stains the developing teeth permanently, which is why it is avoided in children under 8 and in pregnancy
Periodontitis destroys the periodontal ligament and alveolar bone and is the commonest cause of tooth loss in adults
Loss of taste may follow damage to the chorda tympani in middle ear surgery, or occur in zinc deficiency, and is often noticed as a loss of "flavour" that is really smell

All questions in Systemic Histology