Tongue, Taste Buds and Taste PDF

Tongue, taste buds and taste [Oral & Dental Sciences] Miss H Rogers GDC ILOS 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management 1.1.6 Describe relevant and appropriate physiology and explain its applica;on to...

Tongue, taste buds and taste [Oral & Dental Sciences] Miss H Rogers GDC ILOS 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management 1.1.6 Describe relevant and appropriate physiology and explain its applica;on to pa;ent management Related topics:  Epithelium  Muscles  Floor of the mouth  Regional anatomy  Oral Mucosa Aim To gain an overview of the structure and func;ons of the tongue, and its varia;ons in appearance Learning Outcomes By the end of this lecture you should be able to: 1. Describe the structures and func;ons of the tongue and taste buds 2. Describe the muscles of the tongue (intrinsic and extrinsic), including their nerve innova;on and blood supply 3. Describe how the sensa;on of taste is created 4. Recognise the varia;ons in the tongue’s appearance in both health and disease The Tongue: In health 4 Grab a mirror and take a look at your tongue! Look at all the surfaces, consider the shape, colour, texture- how would you describe it?  Tongue- Comes from the Greek Glossus It is a moveable muscular organ, comprising of a root, body and ;p (apex). It has a curved dorsal surface and an inferior ventral surface. FuncCons Qu: What do we use our tongue for - how many uses can you list? Click on the image above to see a video on how our tongue moves FuncCons How many did you get…  Mas;ca;on  Kissing  Taste  Sensi;vity  Swallowing  Suckling  Oral Hygiene  Defence  Speech Structures Qu: Which structures of the tongue are you able to label? Dorsum  EpigloQs PalaCne Tonsil Lingual Tonsil Root/Base Sulcus Terminalis (Posterior 1/3) Dorsum/Dorsal surface Lateral border Body Ventral surface (Anterior 2/3) (on underside) Median Lingual Sulcus Lingual Papillae Apex (Cp)  Ventral surface Dorsum/Dorsal surface Lateral border Need to check all surfaces of tongue Dorsum The dorsum of the tongue is divided into two sec;ons: Anterior two thirds Root/Base (oral/body) Posterior one third (Posterior 1/3) (pharyngeal/base) Body The two parts are separated by: (Anterior 2/3) sulcus terminalis (a triangle-shaped landmark) foramen caecum Ventral Surface This surface is covered during your lecture ‘FOM and Palate’ Can you remember any of the structures? What type of mucosa covers the ventral Deep Lingual Veins Plicae Fimbriate surface? Thin lining of non keratinised epithelium (Smbriated fold) Please refer to the FOM and Lingual Frenum 13 palate lecture for more informa;on on these structures Lateral Border The main features are the ridges along the border made up of foliate papillae Lingual papillae Have another look in the mirror Are you able to iden;fy these features on your own tongue? Lingual Papillae 16 There are 4 types of lingual papillae located on the dorsum of the tongue: Filiform Fungiform Circumvallate Foliate  Most numerous Small and Conical 2-3mm in diameter Cover whole surface of body of Dorsum of tongue. Filiform Rough appearance and texture Outer layer keratinzed epithelium sitting over core of lamina propria If increase in keratin - whiter colour appearance No taste buds present!! Mechanical function - guide food back to pharynx for swallowing.  Less numerous Mushroom shaped Visable as small raised red dots 1mm in diameter Fungiform Scattered all over mucous membrane - more towards tip and lateral surfaces Not found near sulcus terminalis - more anterior and lateral Thin outer layer of keratinised epithelium - overlying a more vascular lamina propria Function - contain a few taste buds, involved in taste sensation  Larger than other lingual papillae 3-5mm in diameter See more readily when the tongue is arched and extended 7-15 large raised mushroom like structures Circumvallate Appear immediately in front of sulcus terminalis When tongue is relaxed they sit in a sunken trench Outer layer of keratinised epithelium sitting over a core of lamina propria Hundreds of taste buds located at base of their walls in epithelium Von Ebner’s glands - secrete serous saliva into trenches around circumvallate papillae - flush out and clean trenches near taste pores to introduce new taste sensations Function - taste sensation Sulcus Terminalis Circumvallate Papillae  Leaf like papillae Present on lateral borders of tongue 4-11 parallel ridges that alternative with deep grooves into mucosa Foliate Few taste buds present Outer layer of keratinised epithelium sitting over layer of core of lamina propria Taste buds present so main function taste sensation. Taste Buds 23 Taste buds are barrel-shaped organs and are composed of 30-80 spindle-shaped cells that extend from the basement membrane to the epithelial surface of the lingual papillae. The lingual papillae associated with taste buds: Fungiform Foliate Circumvallate Turnover of taste bud cells is rapid, approximately 10 days.  Within each taste bud there are two types of cell:  Suppor;ng cells  Taste cells SupporCng Cells These support the taste bud and are usually located on the outer por;on of the taste bud  Lingual papillae - within these are taste buds - within these are taste cells - taste receptors within taste pore - traps and identifies taste Taste Cells Usually located in the central por;on of the taste bud Within epithelium The taste pore is an opening in the most superbcial por;on of the taste bud Superbcial taste receptors make contact with dissolved molecules of food at the Taste hairs taste pore producing a taste sensa;on Taste cells are also associated with sensory neuron processes in the inferior por;on of the taste bud among the cells which receive messages of taste sensa;on by way of the receptors. The messages are then sent by way of the nerve to the central nervous system where it is iden;bed as a certain type of taste Taste/ Taste (GustaCon) 29 Why do we have taste? Safety Foods that are: Sweet, umami or low salt- indicate nutrient rich foods Bieer, sour or highly salty- indicate poten;ally toxic or spoiling foods Physiological Taste starts diges;on and is closely linked to the other 4 senses… Sight, smell and the sounds of food prepare the body by increasing saliva cow and s;mula;ng gastric juices. When food enters the mouth, touch allows the body to know what type of saliva is most appropriate.  Taste hairs make contact with dissolved molecules of foods In order to be able to experience taste, saliva needs to be present as substances can only be tasted in soluCon. Remember, the taste receptors in the taste bud make contact with dissolved molecules of food. What does this mean for pa;ents with xerostomia or reduced saliva produc;on? Reduced taste sensation How might people compensate for a lack of taste and how could this have an impact on their oral health? Add more of it - E.g more sugar or salt  Not the case or relevant Taste Mapping Muscles of the tongue 33 Divided into 2 groups: Extrinsic muscles (originate outside the tongue and inserted into it) Intrinsic muscles (contained en;rely within the tongue) Extrinsic These muscles alter the posi;on of the tongue Genioglossus Hyoglossus Palatoglossus Styloglossus Chin = Genioglossus Origin The superior genial tubercle (on the inferior aspect of the mandible) upwards fans InserCon Into the whole surface of the tongue AcCon Pulls tongue forward to protrude from the mouth. Whole muscle can depress and form a concavity on its dorsal surface Hyoid ↑ - Hyoglossus Origin The hyoid bone InserCon The ventral side of the tongue AcCon Depresses the tongue and assists in retrac;on Palatoglossus Y Lies within the palatoglossal arch (see palate lecture) Origin Small narrow muscle arising from the aponeurosis of the sof palate InserCon Side of the tongue, and blends with the intrinsic muscles AcCon Lifs up the tongue, closing og the mouth from the pharynx e.g. during swallowing -styloid process Styloglossus Origin A short muscle origina;ng at the styloid process InserCon Blends with the inferior longitudinal muscle, and the hyoglossus. AcCon Draws the tongue upwards and backwards  Intrinsic These muscles alter the shape of the tongue Superior Longitudinal Muscle Inferior Longitudinal Muscle Ver;cal Muscle Transverse Muscle Superior Longitudinal Muscle Origin The sub mucosa of the Superior Longitudinal Mu posterior por;on of the tongue InserCon The apex and anterolateral margins of the tongue AcCon Shortens the tongue Turns the ;p and the sides upwards Inferior Longitudinal Muscle Origin Root of the tongue and the hyoid bone InserCon Into the apex of the tongue AcCon Shortens the tongue Pulls the ;p and sides Inferior Longitudinal Muscle downwards VerCcal Muscle Origin Root of the tongue and Vertical (& Transverse) genioglossus muscle Muscle InserCon Lingual aponeurosis Thickened lamina propria on Dorsum of tongue - Present for lingual muscle attachment AcCon Flaeens and broadens the tongue Transverse Muscle Origin Fibres which originate in the-median lingual septum Transverse (& Vertical) Muscle Middle of tongue InserCon Pass laterally to insert into the side of the tongue AcCon Narrows and lengthens the tongue This video is a good visual walk through to summarise the extrinsic and intrinsic muscles of the tongue: heps://www.youtube.com/watch?v=umNW_PvKsPE Nerve InnervaCon & Blood Supply 46 Nerve InnervaCon The tongue has both a sensory nerve supply Posterior 1/3 and a motor nerve supply. Sensory and Taste: - Glossopharyngeal Nerve (IX) Sensory: Anterior 2/3 Lingual nerve Motor supply: (Trigeminal nerve V) Sensory: Hypoglossal nerve (XII), except the Palatoglossus which is Taste: Chorda Tympani supplied by the Vagus nerve (X) Lingual nerve (Facial nerve VII) Taste: & lingual nerve (Trigeminal Nerve V) Chorda Tympani (Facial nerve VII) & Lingual nerve Blood Supply Blood supply reaches the tongue via the Lingual artery (a branch of the external caro;d artery) Deep lingual artery External carotid artery Lingual artery Blood Supply The tongue drains principally through the lingual vein Deep lingual veins Lingual vein The Tongue: ‘Abnormal’ appearance 50 Geographic Tongue Benign condi;on Caused by incamma;on of the tongue Depapilliated Smooth irregular red - patches and white wavy lines, which may change posi;on Appearance likened to a Further informa;on: map- hence the name Oral Health Founda;on ‘geographic’ No treatment, advise to NORD avoid acidic and spicy foods Help manage symptoms and minimise possible soreness to reduce soreness  tongue - GlossiCs inflammation Incamma;on causing swelling , redness and Iron debciency anaemia [full ar;cle] Lef: before treatment, Right: afer treatment changes in the surface texture Can be categorised into acute, chronic, atrophic and median rhomboid Several causes including, Median Rhomboid Glossi;s but not limited to: Further informa;on: Anaemia Sharabim, A.F. & Winters, R. Glossi;s. [Updated Nov 30 2020]. In: StatPearls Celiac disease [Internet] Trauma Lu, S. (2016) Percep;on of iron debciency from oral mucosa altera;ons that s how a high prevalence of Candida infec;on. Allergic reac;on Piercings According to a poll undertaken by the Oral Health Founda;on, tongue piercings are the most popular oral piercing.  How might they impact on oral hygiene? Calculus can build up on piercing  How might they impact on the integrity of the teeth? Wear fasscets on teeth more possible - acrylic balls can decrease risk of damage Snake Eyes Need help? See a list by Colgate of the risks involved with oral piercings, or an ar;cle by dentalcare.com on the implica;ons for dental professionals Venom Black Hairy Tongue Overgrowth of cells crea;ng elongated papillae. Food, bacteria and yeast becomes trapped and causes discoloura;on. Smoking, an;bio;cs and radiotherapy can also contribute to the appearance. Treated by cleaning the surface of the tongue with a toothbrush or tongue scraper, and making lifestyle changes.  No clear border Mixed white a red Ulcerated Can be painless Squamous Cell Carcinoma  Squamous cell carcinomas (SCC) make up 95% of oropharyngeal cancers. [Cancer Research UK]  Most common site (40%) is the tongue, on the posterior lateral border or ventral surface. SCC lesion This will be covered in more detail during your Dental Speciali;es module in Year 2 Reconstruc;on of the tongue following removal of SCC Summary- test yourself! 1. Try labelling this tongue diagram again. Compare it to the one you labelled at the start. How does it compare? 2. List the 4 digerent types of lingual papillae- highlight the ones that contain taste buds. Revision Prep! Use the table below, or create your own, to summarise the muscles of the tongue Muscle Origin Insertion Action Innervation Blood Supply  AddiConal Resources YouTube Development of the tongue (NB: try not to get overwhelmed by the detail- check out the anima;ons) heps://youtu.be/NzLySYOBjRY Sam Webster- Muscles of the tongue (anatomy) heps://youtu.be/lATWhP0wJ5c ArCcle InformedHealth.org [Internet]. Cologne, Germany: Ins;tute for Quality and Evciency in Health Care (IQWiG); 2006-. How does the tongue work? 2011 Dec 19 [Updated 2016 Aug 23]. Available from: heps://www.ncbi.nlm.nih.gov/books/NBK279407/  Website KenHub- Muscles and Taste Sensa;on of the Tongue heps://www.kenhub.com/en/library/anatomy/muscles-and-t aste-sensa;on-of-the-tongue KenHub- Tongue heps://www.kenhub.com/en/library/anatomy/tongue References Bath-Balogh, M. & Fehrenbach, M.J. Dental Embryology, Histology, and Anatomy. Elsevier. 2006. Gravina, S. A., Yep, G. L., & Khan, M. (2013). Human biology of taste. Annals of Saudi medicine, 33(3), 217–222. heps://doi.org/10.5144/0256-4947.2013.217 KenHub heps://www.kenhub.com/