OB P4- Tongue and taste buds Flashcards
What are the 3 main functions of the tongue?
- Ingestion
- Sensory
- Integrated action
Describe the ingestion function of the tongue?
- Mastication
- Suckling
- Swallowing
- Cleansing mouth
Describe the sensory function of the tongue.
-Taste/ gustation
> Quality control prior to ingestion : protection, food selection, food avoidance , reflex effects
-Touch/ mechanoreception
Describe the integrated action function of the tongue.
speech
What Is gustation?
gustation is activation of nerual pathways from tthe periphery to the centre
What is the common chemical sense?
Nociception-pain
- activated sensation vie free nevre endings in the epithelium in the mouth and pahrynx - SPICY FOOD - capsacin - burn in hot food -
Where are the extrinsic muscles of the tongue found?
Originate from structures outside the tongue and insert into the tongue
Name the 4 extrinsic muscles of the tongue.
– Genioglossus (XII)
– Hyoglossus (XII)
– Styloglossus (XII)
– Palatoglossus (X)
What role do the extrinsic muscles have?
- Change shape of tongue
- Move tongue bodily (protrude, retract, depress, and elevate the tongue)
Where are the intrinsic muscles of the tongue found?
originate and insert within the substance of the tongue
Name the 4 intrinsic muscles of the tongue.
– superior longitudinal
– inferior longitudinal
– transverse
– Vertical
What role do the intrinsic muscles of the tongue have?
Change shape of tongue:
– lengthening and shortening
– curling and uncurling its apex and edges
– flattening and rounding its surface
what are the receptors in the tongue?
taste buds
How many taste buds are found throughout the mouth and pharynx?
2000-5000
Where are the taste buds found?
hard/soft palate junction
where are the majority of the taste buds?
tongue:
– dorsal and lateral aspects
– most in papillae
What are the 4 types of papillae?
- Circumvallate
- foliate
- fungiform
- filiform
What papillae have no taste buds?
filiform
Where the location of filiform papillae?
anterior part of tongue
What is the structure of the filiform papillae?
– Cone shaped – Connective tissue core – Keratinised epithelial cover • tough abrasive surface – Non-keratinised epithelium inbetween • flexibility
where is the location of fungiform papillae?
anterior part of the tongue
What is the innervation off the fungiform papillae?
VII Facial (carried by lingual via chorda tympani)
what do fungiform papillae look like clinically?
red spots
How many fungiform papillae are there?
200
How many taste buds are there per fungiform papillae?
– Anterior: 1-18
– Mid tongue: 1-9
– ~ 1120 fungiform taste buds per tongue
Where is the location of the foliate papillae?
Lateral margin of posterior aspect in 4-11 parallel ridges
What is the innervation of the foliate papillae?
– VII (anterior)
– IX (Posterior)
What glands hang down from foliate papillae?
serous glands of von ebner
How many taste buds are there per foliate papillae?
– 117
– ~1280 foliate taste buds per tongue.
where is the location of the circumvallate papillae?
Anterior to sulcus terminalis
What is the innervation of the circumvallate papillae?
IX glossopharyngeal
How many circumvallate papillae are there in the mouth?
– 3-13 circumvallate papillae per tongue
– 252 taste buds per papillae
– ~2200 circumvallate taste buds per tongue
What is the importance of salvia?
-Essential for normal taste
- solvent and transport
- Taste pores bathed in:
> pooled saliva
>fluid from serous glands of von Ebner
- Taste adapted to salivary environment
- Serous glands of von Ebner: > diffusion pathway
> remove stimuli by active secretion
> secrete binding proteins
What happens at a taste pore?
- containing pore substance
- travels through pore
- stimulus transferred to nerves
what are the 4 types of cells types in taste buds?
- Type I -dark cells
- Type II - light cells
- Type III- receptors
- Type IV
Describe Type I - dark cells.
– support cells
– producers taste pore substance
Describe type II - light cells .
– ? immature type III cells
– ? support cells
– ? Receptors
Describe type III- receptors cells.
synaptically coupled to gustatory nerves
Describe Type IV cells.
precursors of types I - III
Describe the taste bud cell turnover.
- Autoradiography
- 10 life span
- Sequence: type IV, I, II, III
What is the most mature cell type?
Type III
what is the nerve supply to the posterior 1/3 tongue?
IX
what is the nerve supply to the anterior 2/3 tongue?
VII (via chorda tympani and V3)
What is the nerve supply to the epiglottis?
X
What afferents and efferents affect taste buds?
- Ad afferents, non-myelinated in taste bud
- Also efferent effects
where are non-lingual taste buds found?
- Found on soft palate and/or epiglottis
- Sparse
- Not on papillae but possibly on slightly elevated areas
what are the receptor mechanisms at taste buds?
- Transduction :
- chemical stimulus ( salt, sweet, sour) to electrical energy (action potentials)
- probably type III (and II) cells
Describe the receptor mechanisms of salt.
direct entry of Na+ ion -> depolarisation
Describe the receptor mechanism of sour.
– e.g. citric acid in lemons
– free H+ ions blocks K+ channels
– decreased K+ movement out of the cell -> depolarisation
Describe the receptor mechanism of sweet and bitter.
– 2nd messenger pathway
– blocks of K+ channel depolarisation
What is the steps of receptor mechanisms?
- Depolarising receptor cell potential
- open voltage gated Ca2+ channels
- increaed intracellular free Ca2+
- release of neurotransmitter
- depolarisation of afferent nerve ending
