Starting with the DIGESTIVE SYSTEM
Buccal Cavity
The mouth, or oral cavity, is divided into two parts: the vestibule of the mouth and buccal cavity proper.
1. Vestibule of the Mouth
The vestibule of the mouth is the space located between the lips and cheeks on the outside and the
alveolodental arches on the inside.It is called a virtual cavity because, when the cheeks are in contact
with the teeth, there is no real space inside.It is limited above by the superior vestibular sulcus and
below by the inferior vestibular sulcus.In these grooves, many minor salivary glands open their ducts,
helping to keep the mucosa moist.When we move the tongue repeatedly inside this space, we stimulate
these glands to produce more saliva.At the midline of both lips, there are two small folds of mucosa
called the frenulum of the upper lip and that of the lower lip,which limit excessive movement of the
lips.The vestibule communicates with the outside through the buccal fissure, the space between lips
when the mouth opens.
2. Buccal (Oral) Cavity Proper
Begins beyond the dental arches.Anterioly is formed by the teeth and gums, separating it from the
vestibule.Posteriorly, ends at the isthmus of the fauces, the visible opening posteriorly when we say
“aaa.”The cavity is bounded superiorly by the hard palate, inferiorly by the tongue and sublingual sulcus,
and laterally by the cheeks.The cavity communicates with the vestibule through small interdental spaces
and retromolar space.Posteriorly, it continues into the pharynx through the isthmus of the fauces.
Lips
The upper lip reaches up to the base of the nose, while the lower lip extends down to the groove that
separates it from the chin, called the labiomental sulcus.The opening between the lips is known as the
buccal fissure.At both ends of which are the labial commissures,corresponding to the corners of the
mouth.In the midline of the upper lip is a vertical depression called the philtrum.At the center of the
upper pink border, aligned with the philtrum, a small prominence called the labial tubercle.The lips are
convex anteriorly and consist of three regions:—an external and internal surface, and a transitional pink
zone between them — aka the vermilion border.
,Microscopic Anatomy
Externally, the lips are covered by keratinized stratified squamous epithelium, containing hair follicles,
sebaceous and sweat glands.Internally, are lined by non-keratinized stratified squamous epithelium
forming a smooth mucosal surface.Beneath the mucosa lies the lamina propria, rich in papillae and
connective tissue.Deep within the lip, elastic fibers interlace with striated muscle fibers, giving the lips
flexibility and movement.
Palate
The palate forms the roof of the mouth and separates the oral from the nasal cavity.It is divided into two
parts:
Hard Palate
The hard palate is a bony plate covered by a firmly adherent mucosa.Along its midline runs the palatine
raphe, a raised ridge.Transversely oriented ridges, called palatine folds.The mucosa is tightly bound to
the underlying periosteum, which makes it immobile.Toward the posterior region the palatine glands
begin to appear; are branched tubuloacinar glands that secrete mucus.
Soft Palate
Continues posteriorly.It is a muscular plate covered by mucosa on both sides — one facing the mouth
and the other facing the nasopharynx.Because of this dual lining, it separates the oral cavity from the
nasal passages during swallowing and speech.The soft palate is also called the velum palatinum.
Inside it are fibrous tissue (aponeurosis), muscle bundles, blood vessels, nerves, lymphoid tissue, and
mucous glands.Anteriorly lies horizontally, while posteriorly it becomes vertical.Inferiorly is smooth and
concave.Superiorly is irregular.Laterally,continuous with the walls of the pharynx and the pterygoid
processes.Posteriorly forms part of the isthmus of the fauces.
Microscopic Anatomy
The soft palate is covered by two types of mucosa:
1. Respiratory mucosa (nasopharyngeal side):—It is lined by ciliated pseudostratified columnar epithel.
Beneath it lies a tunica propria rich in lymphoid tissue and mixed glands.
2. Oral mucosa:It is lined by non-keratinized stratified squamous epithelium, red in color.Its submucosa
houses many mucous glands, which lubricate the mouth and palate.
, Tongue
The tongue forms the floor of the mouth.It kneads food, aids swallowing and the first phase of digestion
and contributes to speech, taste.In children since it is rich in antibacterial and immunologic factors such
as sodium bicarbonate, lysozyme, IgA, lactoferrin, it provides immune protection function.
The tongue consists of a body and a base, which continues in depth with the root, anchoring it to the
mandible, hyoid bone, and styloid processes of the temporal.The limit between the body and the base is
marked by a V-shaped terminal sulcus, with the apex directed posteriorly.At the apex lies the foramen
cecum, from which the thyroid gland originally descends.
Body of the Tongue
The dorsal surface is convex and divided by a median sulcus.The ventral surface is smooth and contains
a median fold that joins the lingual frenulum.Laterally, the ranine veins are visible beneath the thin
mucosa — important clinically because many drugs are absorbed rapidly through this route.
Base of the Tongue
Superiorly extends from the terminal sulcus to the epiglottis, and laterally joins the palatine arches.It
forms the floor of the isthmus of fauces.It is attached to the epiglottis by one median glossoepiglottic
fold and two lateral folds, between which lie two depressions called the glossoepiglottic valleculae.
Posteriorly, the mucosa presents small elevations with lymphatic follicles, which together form the
lingual tonsils,that contribute to immune defense.
Root of the Tongue
The root is the deepest, non-visible part, composed of connective tissue, blood vessels, nerves, and
muscles, extending from the mandible to the hyoid bone.Blood supply comes mainly from the lingual
artery,branch of the external carotid; venous occurs through the lingual veins draining into the internal
jugular vein.
Microscopic Anatomy
The tongue is covered by stratified squamous non-keratinized epithelium, except for the dorsal surface,
where areas of keratinization occur over specific papillae.
, Papillae of the Dorsum
1.Filiform papillae:- numerous,keratinized projections that give the rough texture.Provide friction
for food and tactile sensitivity.They contain no taste buds.
2.Fungiform papillae:Mushroom-shaped, scattered on the tip and sides.Covered by non-
keratinized epithelium and each contains 1–3 taste buds.
3.Vallate papillae: arranged in front of the terminal sulcus, surrounded by vallum,whose walls
contain numerous taste buds, and the base receives ducts of Von Ebner’s glands, which cleans taste area.
4.Foliate papillae:Found laterally as vertical folds.
Taste Buds
Taste buds are ovoid sensory structures composed of 50–100 cells.Each has an apical taste pore and
contains three main cell types:
•Taste (gustatory) cells: with microvilli acting as chemoreceptors; renewed every 10–12 days.
•Supporting cells: provide structural support.
•Basal cells: stem cells that regenerate taste cells.
Pharynx
The pharynx is an unpaired, median, hollow viscus that serves as a common passage for both the
digestive and respiratory systems.It extends from the base of the skull to the C6, where it continues as
the esophagus posteriorly and communicates with the larynx anteriorly.Its overall shape is pyriform.It
serves as a crossroad for air and food and plays a crucial role in respiration, swallowing, and phonation.
During swallowing:
•The soft palate elevates to block the nasopharynx.
•The epiglottis closes the laryngeal inlet.
•The pharyngeal constrictors contract sequentially to push the bolus into the esophagus.
Air passes from the nasal cavities through the choanae → nasopharynx → oropharynx → larynx →
trachea → bronchi → lungs.The food bolus follows the route oral cavity → isthmus of the fauces →
oropharynx → laryngopharynx → esophagus.
Divisions of the Pharynx
1. Nasopharynx — lies posterior to the nasal cavities, communicating with them through the choanae,
and its lower limit is the soft palate.
•Anteriorly: interrupted by the choanae; separated by the nasal septum.
•Posteriorly: relates to the retropharyngeal space, which continues into the retroesophageal.
•Laterally: contain the pharyngeal orifice of the Eustachian tube, which equalizes air pressure.
Buccal Cavity
The mouth, or oral cavity, is divided into two parts: the vestibule of the mouth and buccal cavity proper.
1. Vestibule of the Mouth
The vestibule of the mouth is the space located between the lips and cheeks on the outside and the
alveolodental arches on the inside.It is called a virtual cavity because, when the cheeks are in contact
with the teeth, there is no real space inside.It is limited above by the superior vestibular sulcus and
below by the inferior vestibular sulcus.In these grooves, many minor salivary glands open their ducts,
helping to keep the mucosa moist.When we move the tongue repeatedly inside this space, we stimulate
these glands to produce more saliva.At the midline of both lips, there are two small folds of mucosa
called the frenulum of the upper lip and that of the lower lip,which limit excessive movement of the
lips.The vestibule communicates with the outside through the buccal fissure, the space between lips
when the mouth opens.
2. Buccal (Oral) Cavity Proper
Begins beyond the dental arches.Anterioly is formed by the teeth and gums, separating it from the
vestibule.Posteriorly, ends at the isthmus of the fauces, the visible opening posteriorly when we say
“aaa.”The cavity is bounded superiorly by the hard palate, inferiorly by the tongue and sublingual sulcus,
and laterally by the cheeks.The cavity communicates with the vestibule through small interdental spaces
and retromolar space.Posteriorly, it continues into the pharynx through the isthmus of the fauces.
Lips
The upper lip reaches up to the base of the nose, while the lower lip extends down to the groove that
separates it from the chin, called the labiomental sulcus.The opening between the lips is known as the
buccal fissure.At both ends of which are the labial commissures,corresponding to the corners of the
mouth.In the midline of the upper lip is a vertical depression called the philtrum.At the center of the
upper pink border, aligned with the philtrum, a small prominence called the labial tubercle.The lips are
convex anteriorly and consist of three regions:—an external and internal surface, and a transitional pink
zone between them — aka the vermilion border.
,Microscopic Anatomy
Externally, the lips are covered by keratinized stratified squamous epithelium, containing hair follicles,
sebaceous and sweat glands.Internally, are lined by non-keratinized stratified squamous epithelium
forming a smooth mucosal surface.Beneath the mucosa lies the lamina propria, rich in papillae and
connective tissue.Deep within the lip, elastic fibers interlace with striated muscle fibers, giving the lips
flexibility and movement.
Palate
The palate forms the roof of the mouth and separates the oral from the nasal cavity.It is divided into two
parts:
Hard Palate
The hard palate is a bony plate covered by a firmly adherent mucosa.Along its midline runs the palatine
raphe, a raised ridge.Transversely oriented ridges, called palatine folds.The mucosa is tightly bound to
the underlying periosteum, which makes it immobile.Toward the posterior region the palatine glands
begin to appear; are branched tubuloacinar glands that secrete mucus.
Soft Palate
Continues posteriorly.It is a muscular plate covered by mucosa on both sides — one facing the mouth
and the other facing the nasopharynx.Because of this dual lining, it separates the oral cavity from the
nasal passages during swallowing and speech.The soft palate is also called the velum palatinum.
Inside it are fibrous tissue (aponeurosis), muscle bundles, blood vessels, nerves, lymphoid tissue, and
mucous glands.Anteriorly lies horizontally, while posteriorly it becomes vertical.Inferiorly is smooth and
concave.Superiorly is irregular.Laterally,continuous with the walls of the pharynx and the pterygoid
processes.Posteriorly forms part of the isthmus of the fauces.
Microscopic Anatomy
The soft palate is covered by two types of mucosa:
1. Respiratory mucosa (nasopharyngeal side):—It is lined by ciliated pseudostratified columnar epithel.
Beneath it lies a tunica propria rich in lymphoid tissue and mixed glands.
2. Oral mucosa:It is lined by non-keratinized stratified squamous epithelium, red in color.Its submucosa
houses many mucous glands, which lubricate the mouth and palate.
, Tongue
The tongue forms the floor of the mouth.It kneads food, aids swallowing and the first phase of digestion
and contributes to speech, taste.In children since it is rich in antibacterial and immunologic factors such
as sodium bicarbonate, lysozyme, IgA, lactoferrin, it provides immune protection function.
The tongue consists of a body and a base, which continues in depth with the root, anchoring it to the
mandible, hyoid bone, and styloid processes of the temporal.The limit between the body and the base is
marked by a V-shaped terminal sulcus, with the apex directed posteriorly.At the apex lies the foramen
cecum, from which the thyroid gland originally descends.
Body of the Tongue
The dorsal surface is convex and divided by a median sulcus.The ventral surface is smooth and contains
a median fold that joins the lingual frenulum.Laterally, the ranine veins are visible beneath the thin
mucosa — important clinically because many drugs are absorbed rapidly through this route.
Base of the Tongue
Superiorly extends from the terminal sulcus to the epiglottis, and laterally joins the palatine arches.It
forms the floor of the isthmus of fauces.It is attached to the epiglottis by one median glossoepiglottic
fold and two lateral folds, between which lie two depressions called the glossoepiglottic valleculae.
Posteriorly, the mucosa presents small elevations with lymphatic follicles, which together form the
lingual tonsils,that contribute to immune defense.
Root of the Tongue
The root is the deepest, non-visible part, composed of connective tissue, blood vessels, nerves, and
muscles, extending from the mandible to the hyoid bone.Blood supply comes mainly from the lingual
artery,branch of the external carotid; venous occurs through the lingual veins draining into the internal
jugular vein.
Microscopic Anatomy
The tongue is covered by stratified squamous non-keratinized epithelium, except for the dorsal surface,
where areas of keratinization occur over specific papillae.
, Papillae of the Dorsum
1.Filiform papillae:- numerous,keratinized projections that give the rough texture.Provide friction
for food and tactile sensitivity.They contain no taste buds.
2.Fungiform papillae:Mushroom-shaped, scattered on the tip and sides.Covered by non-
keratinized epithelium and each contains 1–3 taste buds.
3.Vallate papillae: arranged in front of the terminal sulcus, surrounded by vallum,whose walls
contain numerous taste buds, and the base receives ducts of Von Ebner’s glands, which cleans taste area.
4.Foliate papillae:Found laterally as vertical folds.
Taste Buds
Taste buds are ovoid sensory structures composed of 50–100 cells.Each has an apical taste pore and
contains three main cell types:
•Taste (gustatory) cells: with microvilli acting as chemoreceptors; renewed every 10–12 days.
•Supporting cells: provide structural support.
•Basal cells: stem cells that regenerate taste cells.
Pharynx
The pharynx is an unpaired, median, hollow viscus that serves as a common passage for both the
digestive and respiratory systems.It extends from the base of the skull to the C6, where it continues as
the esophagus posteriorly and communicates with the larynx anteriorly.Its overall shape is pyriform.It
serves as a crossroad for air and food and plays a crucial role in respiration, swallowing, and phonation.
During swallowing:
•The soft palate elevates to block the nasopharynx.
•The epiglottis closes the laryngeal inlet.
•The pharyngeal constrictors contract sequentially to push the bolus into the esophagus.
Air passes from the nasal cavities through the choanae → nasopharynx → oropharynx → larynx →
trachea → bronchi → lungs.The food bolus follows the route oral cavity → isthmus of the fauces →
oropharynx → laryngopharynx → esophagus.
Divisions of the Pharynx
1. Nasopharynx — lies posterior to the nasal cavities, communicating with them through the choanae,
and its lower limit is the soft palate.
•Anteriorly: interrupted by the choanae; separated by the nasal septum.
•Posteriorly: relates to the retropharyngeal space, which continues into the retroesophageal.
•Laterally: contain the pharyngeal orifice of the Eustachian tube, which equalizes air pressure.
