The document summarizes key aspects of the digestive system, including the lip and tongue. The lip has an outer skin surface and inner mucous membrane. It contains smooth muscles and labial glands. The tongue is covered by mucous membrane with four types of papillae (filiform, fungiform, circumvallate, foliate). Each papilla contains taste buds formed of gustatory and sustentacular cells. Taste buds are also present on other areas and detect the five basic tastes via nerve endings.

2. THE DIGESTIVE
SYSTEM
Dr. Samar Asker

3. The oral cavity
represent a
common
entrance for
respiratory
&digestive
tracts

4. The oral cavity is
bounded anterioly by
lip, posterioly by
pharynx, superioly by
palate inferioly by
tongue, and laterally by
cheeks.

5. The lip
The main bulk is
formed of bundles of
skeletal muscles
(orbicularis oris
muscle)
Arranged in different
directions.

6. THE LIP
The lip is formed of:
a) Outer surface.
b) Inner surface.
c) Middle layer.
d) Red margin.

7. (A)
Outer surface:
Thin skin
Epidermis: keratinized
stratified squamous
epithelium.
Dermis: C.T. rich in hair
follicles, sweat glands
and sebaceous glands.

8. (B) Inner surface:
Lined by Thick,
transparent and wet
mucous membrane
formed of :
1- Epithelium: It is
non kretanized stratified
squamous & C.T. Corium
which contains mucous
glands called labial gland
which are accessory
gland .

9. (D) Red margin:
Covered by modified
skin which has no hair
follicles, no sweat
glands & no sebaceous
glands.
The CT. dermis forms deep
papillae that contain
numerous blood capillaries
& receptors. The skin is
thin , transparent & highly
sensitive.

10. Red margin
Thin skin
Skeletal ms.
Lipial glands
Mucus membrane

11. THE TONGUE

12. A bag of
mucous
membrane full
of sckletal
muscle.

13. Macroscopic appearance:
formed of dorsal surface &
ventral surface
•The dorsal surface is rough &
adherent
mucous
membrane
divided by V- shaped line called
sulcus terminalis into:
1.Posterior1/3:
Where lingual tonsil are
present.
1.Anterior 2/3:
The ventral surface: non
adherent mucous membrane

16. (A) Skeletal muscle
bundles:
•
•
•
•
run in vertical, horizontal and
longitudinal directions.
Covered by stratified
squamous epithelium & a CT
corium.
The ventral surface covered
by non keratinized. The CT
corium
has
lingual
glands( mucous )
The dorsal surface is
covered by partially
keratinized & rough due to
lingual papillae

17. Lingual papillae:
Numerous projections of the
mucous membrane on the
dorsal surface of the tongue .
Each papilla is formed of:
Central core of C.T covered
with stratified squamous
epithelium.

18. Filiform papillae
(conical papillae):
Site: anterior 2/3 of
the dorsum of the
tongue
Shape: conical
Number: most
numerous.
Taste buds: not
present

19. Fungiform papillae:
Site: anterior2/3
particularly on the tip and
lateral sides scattered
between conical papillae.
Shape: basal narrow neck
and rounded top.
Number : less numerous
than conical papillae.
Taste buds: few.

21. Circumvallate
papillae
Site: on the Vshaped line.
Number: 8 -12 in
number (few)

22. Shape: rounded
with constricted
base which is
surrounded by a
groove .VonEbner’s glands
(serous) underneath
this papillae
Taste buds:
numerous

23. Foliate papillae
Site: lateral margin of the
dorsal surface the tongue
of rabbit.
Shape: parallel broad
projections of CT covered
by epithelium.
Number: well developed in
rabbit tongue but not in
human
Taste buds: numerous

24. Filiform
Fungiforn
Circumvillate
Site: Ant 2/3 of
At tip & lateral On V shaped
dorsal surface sides
line
Shape: Conical &
long .(broad
base &
pointed tip)
No: Numerous
Taste Abscent
buds:
Fungus shape Constricted
narrow base & base & broad
rounded top
top
Less in No
numerous
Lateral margin
of dorsal
surface of
tongue of
rabbit
Parallel ridges
8-12 in number
+ ve few
Foliata
numerous

25. Taste buds
Neuroepithelium
responsible for taste
sensation.
Sites: on mucous
membranes of:
Soft palate.
Pharynx.
Epiglottis.
Professor Kikunae Ikeda

26. • Structure:
• It appears as flask
shaped bodies
scattered among
the stratified
squamous
epithelium covering
some lingual
papillae
• It is formed of an
upper opening
called gustatory
pore & contain 3
types of cells:

27. •
•
•
•
•
(1)
Gustatory cells
(haircells)
Central in position.
Shape: modified
columnar.
Their free ends show
short microvilli
Their basal ends
surrounded by free
nerve endings which
carry the taste
sensation.

28. • 2) Sustentacular
cells:
• Peripheral in
position &
supporting cells
• (3) Basal cells:
• Basally located &
act as stem cells.

29. The free red margin of the lip
contains :
–Hair follicles.
–Sweat glands.
–Sebaceous glands.
–Numerous receptors.

30. The mucous membrane covering the inner
surface of the lip :
– Is formed of stratified squamous
keratinized epithelium.
– Contains sebaceous glands.
– Contains sweat glands.
– Is thicker than the skin of the outer
surface of the lip.
– Has no glands.

31. The lip:
a.Its inner surface is covered by mucous
membrane.
b.Its outer surface is covered by thick
skin.
c.Smooth muscles run in different
directions.
d.Labial glands are mainly serous.

32. Taste buds are :
a.Neuroepithelial structures.
b.Formed of 3 types of cells.
c.Situated between the cells of stratified
squamous epithelium.
d.In contact with fine nerve fibres that
carry taste sensations.
e.All of the above.
•

33. The skin covering the outer surface of the lip
:
a.Contains no hair follicles or sebaceous
glands.
b.Contains no sweat glands.
c.Is thicker than the inner surface of the lip.
d.All of the above.
e.None of the above.