i want 20 mcq with their model answer below them about by: Dr. Shaimaa Zaher Lecturer of Histology Faculty of Medicine Helwan UniversityObjectives
Describe the histology of different structures related to the oral cavity: Lips
Cheeks Tongue Palate PharynxThe oral cavity is apart of the digestive system
Digestive system
Digestive tract
Oral cavity
Gastrointestinal
tract
(alimentary
canal)
Associated glands
Lips
Cheeks
Tongue
Palate
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Salivary glands
Liver
PancreasOral cavity
It is lined by oral mucosa (mucous membrane). Its epithelium is stratified
squamous that may be keratinized, partially keratinized or nonkeratinized
depending on the location.
N.B. The mucous
membrane (mucosa)
is formed of two
sublayers:
Epithelium
Lamina propria
(loose connective tissue)Oral mucosa
Masticatory mucosa
▪ It has keratinized stratified
squamous epithelium.
▪ It is found on areas subjected to
mechanical trauma during
mastication of food e.g. the gingiva
(gums) and the oral surface of hard
palate.
Lining mucosa
▪ It has non-keratinized stratified
squamous epithelium.
▪ It is found on the inner surface of
the lips and cheeks, floor of the
mouth, inferior surface of the
tongue, oral surface of soft palate &
pharynx.Lips
The lips consist of a core of
striated muscle (orbicularis oris)
Thin skin
Each lip has three covering
surfaces:
Outer surface
(thin skin)
Vermilion zone
(red margin)
Inner surface
(mucous membrane)
Vermilion
zone
Striated muscle
mucous
membraneThe outer surface of the lip is thin skin consisting of
epidermis (stratified squamous keratinized
epithelium) & dermis with hair follicles, sebaceous
glands & sweat glands.
Epidermis
Dermis
Sebaceous glands
Hair follicles
Sweat glands
Orbicularis oris
muscle (T.S.)
6The inner surface of the lip is lined by mucous membrane
(lining oral mucosa) with minor salivary glands (labial glands) .
Epithelium
Stratified squamous
nonkeratinized
Lamina propria
It is a layer of loose C.T.
containing labial glands
(mucous secreting minor
salivary glands)
Minor
7The red vermilion zone (lip margin) is a transitional zone between thin skin
and oral mucosa. It appears pinkish-red because of the relatively translucent
epithelium and many blood capillaries in the underlying C.T.
Epithelium
(stratified squamous
lightly keratinized )
Underlying C.T. (Lamina
propria)
- Very rich in blood capillaries
and sensory innervation.
- NO hair follicles.
- No sweat nor sebaceous
glands (so lip margin is kept
moist with saliva)
Blood vessels
8
Lamina propria
EpitheliumCheeks
➢ The cheek resembles the lip in histologic
features.
➢ It consists of a core of striated muscle
(Buccinator muscle) that is covered by
thin skin from outside & lined by mucous
membrane from inside.
➢ The epithelium of its lining mucosa is
stratified squamous nonkeratinized. The
lamina propria contains minor salivary
(buccal) glands that extends in C.T.
between muscle fibers.
9Tongue
❖The tongue is a muscular organ.
❖It consists of a mass of striated muscle
covered by oral mucosa.
❖It has 2 surfaces: dorsal (upper) & ventral
(lower).
❖The dorsal surface is divided into an
anterior two-thirds and a posterior one-
third by a V-shaped depression, the sulcus
terminalis. The apex of the V points
posteriorly.
10Histological structure of the tongue
Mass of
striated muscle
Dorsal surface Ventral surface1. The striated muscle fibers of the tongue
❖They are oriented in
3 different directions (vertical,
horizontal & longitudinal)
allowing a high level of
mobility essential of
mastication, swallowing &
phonation.
Bundles of
striated
muscle
fibers2. Dorsal surface of the tongue
❖ It is irregular as it contains lingual papillae
on its anterior two-thirds and lingual
tonsil on its posterior one-third.
❖ It is covered by partially keratinized
stratified squamous epithelium.
3. Ventral surface of the tongue
❖ It is smooth.
❖ It is covered by typical lining mucosa
(nonkeratinized stratified squamous
epithelium).
❖ Lingual glands (mucous secreting minor
salivary glands) are found in the deep part
of the lamina propria & extend in-between
the ventral portion of lingual muscles.
Lingual glandsTongue
Lingual Filiform papillae
Epithelium
Fungiform
papilla
Lamina
propria
Stratified
squamous
non-
keratinized
epithelium
Dorsal surface
Lamina propria
Striated muscle
fibers
Ventral surface
14Lingual papillae
Definition:
Mucosal projections on the anterior
two-thirds of the dorsal surface of the
tongue.
Structure:
Each papilla has a core of connective
tissue covered by stratified squamous
epithelium (with variable degree of
keratinization).
epithelium
C.T.Types of lingual papillae
1- Filiform papillae
2- Fungiform papillae
3- Circumvallate papillae
4- Foliate papillae
161- Filiform papillae
• Number: the most numerous.
• Site: anterior 2/3 of the dorsum of
the tongue.
• Shape: conical, with their tips
directed posteriorly.
• Epithelium: stratified squamous
heavily keratinized, which gives
a whitish appearance.
• Taste buds: absent.
• Filiform papillae provide a rough
surface that facilitates movement of
food during chewing.
17
striated muscle fibers
Filiform papillae2- Fungiform papillae
Filiform papillae
• Number: less numerous.
• Site: interspersed among the filiform
papillae.
• Shape: mushroom-shaped.
• Epithelium: stratified squamous
lightly keratinized with highly
vascularized connective tissue core
(so appear as red spots by naked
eye)
• Taste buds: few, present on the
apical surface of papillae.
183- Circumvallate (vallate) papillae
• Number: 8- 12 (least common type).
• Site: just in front of the sulcus terminalis
• Shape: The largest papillae (1-3 mm).
Dome-shaped.
Each papilla is surrounded by a deep
groove (cleft).
• Epithelium: stratified squamous
non-keratinized.
• Taste buds: numerous (about 250 taste
buds are present on the lateral surface
(sides) of each vallate papilla).
• Ducts of serous salivary glands (von Ebner
glands) open into the base of the clefts.
Taste buds
Von Ebner
glands
St.ms
19Circumvallate (vallate) papillae
Cleft
Apical surface of
vallate papilla
(by SEM)
20von Ebner glands
• Definition: serous lingual minor salivary
glands.
• Site: in the connective tissue underlying
circumvallate papillae.
• Ducts: open into the base of the clefts of
vallate papillae.
• Function:
1.Secretion of a watery fluid which dissolves
food particles to facilitate taste reception.
2. Continuous flow of this fluid over the
taste buds washing away food particles so
they can receive new taste stimuli.
3. This fluid contains a lipase enzyme
that prevents formation of a hydrophobic
layer on taste buds that would hinder
gustation.
cleft
Ducts
Von Ebner
glands
21
Taste buds
Circumvallate papilla4- Foliate papillae
• Number: rudimentary in humans especially in
elderly individuals but are developed in young
children.
They are well developed in rabbits.
• Site: form parallel ridges on posterolateral
margins of the anterior two-thirds tongue.
• Shape: Leaf-like. Each papilla is surrounded by
a deep cleft.
• Epithelium: stratified squamous non-keratinized.
• Taste buds: numerous, present on the
sides (lateral walls) of these papillae.
Foliate
papillae
22stratified
squamous
non-keratinized
epithelium
Surrounded by
deep clefts
23Foliate papillae
Taste buds
present on
the lateral
surfaces
stratified
squamous
non-
keratinized
epithelium
24Taste buds
Taste buds
Definition: they are neuroepithelial structures
specialized for taste sensation.
Sites: within the stratified epithelium of
circumvallate, fungiform and foliate papillae (but
NOT the keratinized filiform papillae). They are more
abundant on circumvallate papillae.
Shape: appear as oval pale stained bodies that
extend through the thickness of the epithelium.
A small opening at the apex of the taste bud is called
the taste pore.
Structure: consists of three types of cells
1. Gustatory (taste, sensory) cells.
2. Supporting cells.
3. Basal cells.
Taste
pore1. Gustatory (taste, sensory) cells.
➢They are the most numerous cells in the
taste bud.
➢They are elongated cells extending from the
basal lamina of the epithelium to the taste
pore.
➢Their apical ends have microvilli projecting
through taste pores.
➢Their bases form synapses with afferent
sensory axons that carry impulses of taste
sensation.
➢Food molecules dissolved in saliva contact
the microvilli and interact with taste
receptors found on microvilli.2. Supporting cells
➢less numerous.
➢They are elongated cells that extend from the
basal lamina to the taste pore.
➢Support the gustatory cells.
3. Basal cells
➢They are small cells located in the basal
portion of the taste bud, near the basal
lamina.
➢They are the stem cells for the other two cell
types.Taste buds
Nerve fibers
(NF)
Taste buds
Taste
Pore
(TP)
28Palate
✓The palate forms the roof of the mouth and
separates oral and nasal cavities.
✓The anterior part is the hard palate (its core is
bone).
✓ The posterior part is the soft palate (its core is
skeletal muscle).
✓The nasal aspect of the palate is lined by
pseudostratified columnar ciliated epithelium
with goblet cells (respiratory epithelium).
✓Oral aspect of the hard palate is lined by
masticatory mucosa (stratified squamous
keratinized epithelium).
✓Oral aspect of the soft palate is lined by stratified
squamous non-keratinized epithelium.
✓Lamina propria of the palate contains palatine
glands (minor salivary glands)Hard palate
Bone
Lamina propria
Stratified squamous
keratinized
epitheliumPharynx
➢It is a transitional tube that conducts
food to the esophagus and air to the
larynx.
➢It is divided into 3 parts
• Nasopharynx: lies posterior to nasal
cavities & lined with respiratory
epithelium.
• Oropharynx: it the posterior part of oral
cavity & lined with stratified squamous
non-keratinized epithelium
• Laryngopharynx: lined with stratified
squamous non-keratinized epitheliumOropharynx