Sense of taste

The tongue is the sense organ specialized in detecting the taste of something (e.g. food). Therefore the slides simplifies the anatomy and physiology of GUSTATION.

1. SENSE OF TASTE
BY
J. MWELWA
BY
J. MWELWA

2. INTRODUCTION
The tongue is a muscular organ in the mouth. It is covered
with moist, pink tissue called mucosa. Tiny bumps called
papillae give the tongue its rough texture. Thousands of
taste buds cover the surfaces of the papillae. Taste buds are
collections of nerve-like cells that connect to nerves running
into the brain (Roger Watson,2005).
BY
J. MWELWA

3. GENERAL OBJECTIVES
At the end of the lecture, students should be able to acquire
knowledge and have an understanding on the anatomy and physiology
of the sense of taste.
BY
J. MWELWA

4. SPECIFIC OBJECTIVES
At the end of the lesson students should be able to: -
•Describe the structure of the tongue.
•State the functions of the tongue.
•State the principal types of papillae.
•Mention the basic taste sensed sites.
•Explain the sensory pathway of taste.
BY
J. MWELWA

5. STRUCTURES OF THE TONGUE
HUMAN TONGUE PARTS
The human tongue has three distinct divisions, namely,
the apex, the body and the root.

6. THE TIP OR APEX
•The tip or apex of the tongue accounts for one-third
of the anterior surface of tongue. It is highly movable
and rests against the incisor teeth in the mouth cavity.
The taste buds for “sweet” are present on this part.

7. THE BODY OR MAIN PART
•The anterior two-thirds of the tongue form its body. The
presence of lingual papillae on the upper side makes the
surface rough. A layer of mucosa, on the other hand,
keeps it moist.
•It is this part of the tongue where the tongue taste buds
for salt, bitter and sour taste are present.

8. THE ROOT OR BASE
•The root attaches the tongue to the bottom or floor of
the mouth cavity.
•It appears between the mandible and the hyoid bone.
•The primary job of the hyoid bone is to provide
anchorage to the tongue.

9. BY
J. MWELWA

10. BY
J. MWELWA

11. TONGUE -PAPILAE
•Filiform
•Fungiform
•Foliate
•Circumvallate :-With von
Ebnerglands.
•Taste buds:-Contained by
circumvallate and fungiform
papillae
BY
J. MWELWA

12. TASTE BUDS
•The gustatory (taste) receptors are located in the taste
buds.
•Taste buds are specialized sensory organs that are most
numerous on the surface of the tongue, but they are also
present on the soft palate and on the walls of the
oropharynx.
•The cylindrical taste bud is composed of numerous sensory
gustatory cells that are encapsulated by supporting cells.
BY
J. MWELWA

13. TASTE BUDS CONT’
•Each gustatory cell contains a dendritic ending called a
gustatory microvillus that projects to the surface
through an opening in the taste bud called the taste
pore.
•The gustatory microvilli are the sensitive portion of
the receptor cells.
BY
J. MWELWA

14. TASTE BUDS CONT’
•Saliva provides the moistened environment necessary
for a chemical stimulus to activate the gustatory
microvilli.
•Taste buds are elevated by surrounding connective
tissue and epithelium to form papillae.
BY
J. MWELWA

15. BY
J. MWELWA

16. FUNCTIONS OF THE TONGUE
•Mostly muscles
•Grip and reposition food
•Forms “bolus” of food
(lump)
•Help in swallowing
•Speech –help form some
consonants
BY
J. MWELWA

17. •Note frenulum : can be too tight
•Lingual tonsil –back of tongue
•serous and mucous glands deep to the epithelia of the
tongue
BY
J. MWELWA

18. THE PRINCIPLE TYPES OF PAPILLAE
•There are three principal types of papillae, which can
be identified as:
• Vallatepapillae (circumvallate). These are the
largest but least numerous, which are arranged in an
inverted V-shaped pattern on the back of the tongue.
BY
J. MWELWA

19. CONT’
• Fungiform papillae. They are Knob-like.
These papillae are present on the tip and sides of the
tongue.
• Filiform papillae. They are short, thickened and
threadlike. Filiform papillae are located on the anterior two-
thirds of the tongue.
BY
J. MWELWA

20. THE BASIC TASTES SENSED SITES
•Taste buds are found only in the vallate
(circumvallate) and fungiform papillae.
•There are only four basic tastes, which are sensed
most acutely on particular parts of the tongue.
BY
J. MWELWA

21. BASIC TASTES SENSED SITES CONT’
•These are:
sweet(tip of tongue),
sour(sides of tongue),
bitter(back of tongue),and
salty(over most of the tongue, but concentrated on the
sides).
BY
J. MWELWA

22. BY
J. MWELWA

23. BY
J. MWELWA

24. BASIC TASTES SENSED SITES CONT’
•A combination of these taste modalities allows for
impressive taste discrimination.
•E.g. Wine tasters can consistently recognize subtle
differences in hundreds of varieties of wine.
•Sour taste is produced by hydrogen ions (H+). Therefore all
acids tastes sour.
BY
J. MWELWA

25. BASIC TASTES SENSED SITES CONT’
•Most organic molecules, particularly sugars, taste
sweet to varying degrees.
•Only pure table salt (NaCl) has a pure salty taste.
BY
J. MWELWA

26. BASIC TASTES SENSED SITES CONT’
•Other salts, such as KCl(commonly used in place of
NaClby people with hypertension), taste salty but
have bitter overtones.
•Bitter taste is evoked by quinine and seemingly
unrelated molecules.
BY
J. MWELWA

28. SENSORY PATHWAY OF TASTE
•The sensory pathway that relays taste sensations to
the brain mainly involves two paired cranial nerves.
BY
J. MWELWA

29. SENSORY PATHWAY OF TASTE CONT’
•Taste buds on the posterior third of the tongue have a
sensory pathway through the glossopharyngeal
nerves, whereas the anterior two thirds of the tongue
is served by the chorda tympani branch of the facial
nerves.
BY
J. MWELWA

30. SENSORY PATHWAY OF TASTE CONT’
•Taste sensations passing through the nerves just
mentioned are conveyed through the medulla
oblongata and thalamus to the parietal lobe of the
cerebral cortex, where they are interpreted.
BY
J. MWELWA

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J. MWELWA

32. SUMMARY
The tongue is a specialized organ in Gustatory (taste).
The principal types of papillae are the Vallate
(circumvallate), Fungiform and Filiform. The taste buds
found in the papillae of the tongue have the nerve
endings.
BY
J. MWELWA

33. SUMMARY CONT’
These nerve endings transmit impulses to the brain
(cerebral cortex) through the chorda tympani branch of
the facial nerves and the glossopharyngeal nerve. The
basic tastes sensed sites are sweet (tip of tongue), sour
(sides of tongue), bitter (back of tongue), and salty (over
most of the tongue, but concentrated on the sides).
BY
J. MWELWA

34. REFERENCES
•David S, Jackie B and Ricki L. (2003), Hole’s Essentials of Human
Anatomy and Physiology, International edition, McGraw-Hill Higher
Education, New York, USA.
•Roger Watson (2005), Anatomy and Physiology for Nurses, 20th
edition, Elsevier, Oxford, UK.
•Waugh A & Grant A (2001), ROSS AND WILSON Anatomy and
physiology in health and illness, 9th Ed, Church-Hill Livingstone,
Toronto.
BY
J. MWELWA

35. THANK YOU
BY
J. MWELWA