Sensory - Taste Development

Introduction

Tongue taste map

Gustatory system neuroanatomy

These notes introduce the development of the sense of taste which can divided into five basic tastes: bitter, salty, sweet, umami (savoury) and sour. Current research appears to have displaced the historic concept of a tongue "map".

A study in rat suggests that neonatal changes in circumvallate papillae may result in postnatal changes in "taste". In frogs, a large taste disc (TD) is the largest vertebrate gustatory organ. Postnatally, the sense of taste is also closely related to the sense of smell.

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Some Recent Findings

CALHM1 ion channel mediates purinergic neurotransmission of sweet, bitter and umami tastes "Recognition of sweet, bitter and umami tastes requires the non-vesicular release from taste bud cells of ATP, which acts as a neurotransmitter to activate afferent neural gustatory pathways. However, how ATP is released to fulfil this function is not fully understood. Here we show that calcium homeostasis modulator 1 (CALHM1), a voltage-gated ion channel, is indispensable for taste-stimuli-evoked ATP release from sweet-, bitter- and umami-sensing taste bud cells." Developing a sense of taste "Taste buds are found in a distributed array on the tongue surface, and are innervated by cranial nerves that convey taste information to the brain. For nearly a century, taste buds were thought to be induced by nerves late in embryonic development. However, this view has shifted dramatically. A host of studies now indicate that taste bud development is initiated and proceeds via processes that are nerve-independent, occur long before birth, and governed by cellular and molecular mechanisms intrinsic to the developing tongue. Here we review the state of our understanding of the molecular and cellular regulation of taste bud development, incorporating important new data obtained through the use of two powerful genetic systems, mouse and zebrafish." FGF Signaling Regulates the Number of Posterior Taste Papillae by Controlling Progenitor Field Size "The sense of taste is fundamental to our ability to ingest nutritious substances and to detect and avoid potentially toxic ones. Sensory taste buds are housed in papillae that develop from epithelial placodes. Three distinct types of gustatory papillae reside on the rodent tongue: small fungiform papillae are found in the anterior tongue, whereas the posterior tongue contains the larger foliate papillae and a single midline circumvallate papilla (CVP). ...Here, we report that a balance between Sprouty (Spry) genes and Fgf10, which respectively antagonize and activate receptor tyrosine kinase (RTK) signaling, regulates the number of CVPs." Fate mapping of mammalian embryonic taste bud progenitors"Mammalian taste buds have properties of both epithelial and neuronal cells, and are thus developmentally intriguing. Taste buds differentiate at birth within epithelial appendages, termed taste papillae, which arise at mid-gestation as epithelial thickenings or placodes. ...we demonstrate that Shh-expressing embryonic taste placodes are taste bud progenitors, which give rise to at least two different adult taste cell types, but do not contribute to taste papillae. Strikingly, placodally descendant taste cells disappear early in adult life."

Recent References | References

Development Timing

These are human embryonic timings, not clinical which is based on last menstral period +2 weeks (GA).

Week 6 - gustatory papilla, caudal midline near the foramen caecum

Week 6-7 - nerve fibers approach the lingual epithelium

Week 8 - nerves penetrate epitheilai basal lamina and synapse with undifferentiated, elongated, epithelial cells (taste bud progenitor cell)

Week 10 - shallow grooves above the taste bud primordium

Week 12 - first differentiated epithelial cells (Type II and III)

Week 12 -13 - maximum synapses between cells and afferent nerve fibers

Week 14 - 15 - taste pores develop, mucous

Week 18 - substance P detected in dermal papillae, not in taste bud primordia

3rd Trimester -

Tongue Development

Neonatal rat tongue

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Gustatory cranial sensory neurons

Cranial nerves VII, IX and X have dual embryonic origins and provide both gustatory (taste) and non-gustatory (touch, pain, temperature) sensory innervation to the oral cavity of vertebrates.

Gustatory Neurons

• originate from epibranchial placodes
• innervate taste buds
• project centrally to the rostral nucleus of the solitary tract (NTS)

General Epithelial Innervation of the oral cavity

• originate from cranial neural crest
• innervation to the oropharynx
• project to non-gustatory hindbrain regions (spinal trigeminal nucleus)

(text based on: Embryonic origin of gustatory cranial sensory neurons.)

Stage 22

Section (B4) through head showing tongue and head structures.

References

Reviews

<pubmed>21184814</pubmed> <pubmed>20696704</pubmed>| JCB

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Search May 2010

• Taste System Development - All (320) Review (64) Free Full Text (78)

• Tongue Development - All (2804) Review (258) Free Full Text (519)

Search Pubmed: Taste System Development | Tongue Development

Additional Images

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  Mouse circumvallate papilla

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  circumvallate papilla HE

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  Tongue HE x10 transverse

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  Tongue x100

Tongue Images: Tongue Sk Muscle | Salivary gland sk muscle HE | Unlabeled Salivary gland sk muscle HE | Filiform papillae HE | circumvallate papilla VG | circumvallate papilla HE | Taste buds VG

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Cite this page: Hill, M.A. (2024, April 20) Embryology Sensory - Taste Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Sensory_-_Taste_Development

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G