14. Digestive system- the major organs of the digestive system. Principal structure of tubular and parenchymatous organs.
The digestive system consists of the alimentary canal (or gastrointestinal (GI) tract) and accessory digestive organs. It is responsible for
digesting and absorbing food.
Alimentary Canal Accessory Digestive Organs
- Mouth - Teeth
- Pharynx - Tongue
- Esophagus - Gallbladder
- Stomach - Salivary Glands
- Small Intestine - Liver
- Large Intestine - Pancreas
I. Overview of the Digestive System
The digestive system is responsible for: Ingestion of food, Mechanical and chemical digestion, Absorption of nutrients, Elimination of
undigested material.
It is divided into:
1. Alimentary Canal (Gastrointestinal Tract) – Tubular Organs: Mouth, Pharynx, Esophagus, Stomach, Small intestine: duodenum,
jejunum, ileum; Large intestine: cecum, colon, rectum, anal canal.
2. Accessory Digestive Organs – Parenchymatous Organs: Salivary glands, Liver, Pancreas, Gallbladder, (Teeth and tongue also assist in
digestion)
II. Tubular Organs – Principal Structure
Tubular organs of the digestive tract share a common four-layered wall structure (from inside out):
1. Mucosa
Epithelium: Stratified squamous (e.g., esophagus), Simple columnar (e.g., stomach, intestines)
Lamina propria: Loose connective tissue with glands, vessels, immune cells
Muscularis mucosae: Thin layer of smooth muscle
2. Submucosa: Dense irregular connective tissue, Contains blood vessels, lymphatics, and Meissner’s (submucosal) plexus, May contain
glands (e.g., Brunner’s glands in duodenum)
3. Muscularis Externa: Inner circular and outer longitudinal smooth muscle layers, Responsible for peristalsis, Contains Auerbach’s
(myenteric) plexus between the layers
4. Serosa or Adventitia
• Serosa: Visceral peritoneum (simple squamous epithelium + connective tissue)
• Adventitia: Loose connective tissue attaching organ to surrounding structures (e.g., in retroperitoneal organs like the esophagus)
Specializations occur in different regions (e.g., rugae in stomach, villi in intestines, taenia coli in colon)
III. Parenchymatous Organs – Principal Structure
Parenchymatous organs are solid and composed of:
• Parenchyma: Functionally specialized epithelial cells
• Stroma: Supporting connective tissue with vessels, nerves, ducts
1. Liver: Largest gland; located in the right upper abdomen. Covered by Glisson’s capsule, is composed of hepatic lobules (Central vein,
Plates of hepatocytes, Sinusoids lined by endothelial and Kupffer cells, Portal triads: branch of portal vein, hepatic artery, bile duct).
Functions: Metabolism, detoxification, synthesis of plasma proteins, Bile production.
2. Pancreas: Mixed exocrine and endocrine gland
• Exocrine part: Acini of serous cells secreting digestive enzymes; Ductal system (intercalated, intralobular, main pancreatic duct)
• Endocrine part: Islets of Langerhans producing insulin, glucagon, somatostatin.
Functions:
• Exocrine: enzyme secretion for digestion
• Endocrine: glucose metabolism
3. Salivary Glands
Major: Parotid, Submandibular, Sublingual. Composed of:
• Serous acini (enzyme-rich secretion)
• Mucous acini (mucin-rich)
• Myoepithelial cells aiding secretion
Duct system: intercalated → striated → excretory ducts
Function: Lubrication, digestion initiation (e.g., amylase)
,15. Oral cavity. Embryonic development. Oral vestibule, lips, cheeks, gums. Macroscopic and microscopic characteristics. Blood
and nerve supply.
Embryonic Development of the Oral Cavity
The oral cavity (stomodeum) originates from the ectodermal invagination of the head region during the 4th week of embryonic
development. It is initially separated from the primitive pharynx by the oropharyngeal membrane, which breaks down in the 4th week,
establishing communication.
The upper lip and cheeks develop from:
• Maxillary processes (sides of upper lip, cheeks)
• Medial nasal processes (philtrum of the upper lip)
The lower lip arises from the mandibular processes.
The oral epithelium is ectodermal in origin and gives rise to tooth enamel, salivary glands, and mucosa.
The connective tissue and muscle components derive from neural crest-derived mesenchyme and paraxial mesoderm.
Subdivisions of the Oral Cavity
• Oral Vestibule: The space between the lips/cheeks and the teeth/gums. Communicates with the exterior via the oral fissure and with
the oral cavity proper posterior to the last molar.
• Oral Cavity Proper: Bounded anteriorly and laterally by the alveolar arches with teeth and gums, superiorly by the hard and soft
palate, and inferiorly by the floor of the mouth.
The Vestibule (Vestibulum Oris): is a slit-like space that receives secretion from the parotid salivary glands.
• Boundaries: Externally by the lips and cheeks, internally by the gums and teeth. Above and below, it is limited by the reflection of the
mucous membrane from the lips and cheeks to the gum covering the upper and lower alveolar arch respectively
• Communication: With the surface of the body by the mouth's orifice and, when the jaws are closed, with the mouth cavity proper by
apertures behind the wisdom teeth and clefts between opposing teeth.
The Mouth Cavity Proper (Cavum Oris Proprium): receives secretion from submaxillary and sublingual salivary glands.
• Boundaries: is bounded laterally and in front by the alveolar arches with their contained teeth; behind, it communicates with the
pharynx by a constricted aperture termed the isthmus faucium. It is roofed in by the hard and soft palates, while the greater part of the
floor is formed by the tongue, the remainder by the reflection of the mucous membrane from the sides and under surface of the tongue to
the gum lining the inner aspect of the mandible.
• Structure: the mucous membrane lining the mouth is continuous with the integument at the free margin of the lips, and with the
mucous lining of the pharynx behind; it is of a rosepink tinge during life, and very thick where it overlies the hard parts bounding the
cavity. It is covered by stratified squamous epithelium.
JOBOTTA'S NOTES
The oral opening (Rima oris) represents the entrance
to the digestive tract and the oral cavity. The latter is
divided into a vestibule (Vestibulum oris) and the
cavity proper (Cavitas oris propria). The borders of
the Vestibulum oris are the lips and cheeks at the
outside and the alveolar processes and teeth at the
inside. With the occlusion of teeth, a space behind the
last molar tooth on each side (Spatium retromolare)
allows access to the oral cavity. In the region of the
oropharyngeal isthmus (Isthmus faucium) the oral
cavity becomes the Pars oralis of the Pharynx
(Oropharynx). The excretory ducts of numerous
smaller salivary glands and those of the three paired
large salivary glands all drain into the Vestibulum oris
and the Cavitas oris propria. The body of the tongue
(Corpus linguae) fills large parts of the inside of the
oral cavity.
Lips (Labia Oris): the two fleshy folds which surround the rima or orifice of the mouth, are formed externally of integument and
internally of mucous membrane, between which are found the Orbicularis oris muscle, the labial vessels, some nerves, areolar tissue,
and fat, and numerous small labial glands. The inner surface of each lip is connected in the middle line to the corresponding gum by a
fold of mucous membrane, the frenulum (the upper being the larger). The Labial Glands (glandulae labiales) are situated between the
mucous membrane and the Orbicularis oris, around the orifice of the mouth. They are circular in form, and about the size of small peas;
their ducts open by minute orifices upon the mucous membrane. In structure they resemble the salivary glands.
Macroscopic Features: Mobile muscular folds forming the opening of the mouth. Composed of:
• External skin
• Transitional (vermillion) zone
• Internal oral mucosa
Microscopic Features:
• Skin (external): keratinized stratified squamous epithelium with hair follicles, sebaceous, and sweat glands.
• Vermillion zone: Thin keratinized stratified squamous epithelium. Highly vascularized (reason for the red color). No glands.
• Oral mucosa (inner surface): Non-keratinized stratified squamous epithelium. Underlying submucosa with minor salivary glands
and orbicularis oris muscle.
,Cheeks (Buccae): The Cheeks (buccae) form the sides of the face, and are continuous in front with the lips. They are composed
externally of integument; internally of mucous membrane; and between the two of a muscular stratum, besides a large quantity of fat,
areolar tissue, vessels, nerves, and buccal glands.
Structure.—The mucous membrane lining the cheek is reflected above and below upon the gums, and is continuous behind with the
lining membrane of the soft palate. Opposite the second molar tooth of the maxilla is a papilla, on the summit of which is the aperture of
the parotid duct. The principal muscle of the cheek is the Buccinator; but other muscles enter into its formation, viz., the Zygomaticus,
Risorius, and Platysma. The buccal glands are placed between the mucous membrane and Buccinator muscle: they are similar in
structure to the labial glands, but smaller. About five, of a larger size than the rest, are placed between the Masseter and Buccinator
muscles around the distal extremity of the parotid duct; their ducts open in the mouth opposite the last molar tooth. They are called
molar glands.
Macroscopic Features: Lateral walls of the oral cavity. Composed of skin externally and mucosa internally, with buccinator muscle in
between.
Microscopic Features:
• External surface: keratinized epithelium with skin appendages.
• Internal mucosa: mostly non-keratinized stratified squamous epithelium.
• Buccal fat pad: especially prominent in infants.
• Minor salivary glands present in the submucosa.
Gums (Gingivae)
Macroscopic Features: Mucosal tissue surrounding the alveolar processes of the maxilla and mandible. Tightly attached to the
underlying bone. Divided into:
• Free gingiva: around each tooth.
• Attached gingiva: firmly bound to the periosteum.
Microscopic Features:
• Epithelium: mostly keratinized stratified squamous (especially in attached gingiva).
• Lamina propria: dense collagenous connective tissue, firmly attached to bone (mucoperiosteum).
• No submucosa.
• Junctional epithelium: attaches gingiva to tooth surface.
Oral Vestibule
Macroscopic Features: Lies between the inner surface of the lips/cheeks and the outer surface of teeth and gums. Contains openings of
the parotid duct (Stensen’s duct) near the upper second molar.
Microscopic Features:
• Lined by non-keratinized stratified squamous epithelium.
• Submucosa contains minor salivary glands and connective tissue.
• Loosely connected to underlying muscle (e.g., buccinator).
Blood Supply and Nerve Supply
Sensory Nerve Supply:
• Trigeminal Nerve:
- Infraorbital Nerve: Branch of the maxillary nerve supplying the upper lip and the face's skin between the upper lip and lower eyelid
except for the bridge of the nose.
- Mental Nerve: Branch of the mandibular nerve (via the inferior alveolar nerve) supplying the lower lip's skin and mucous membrane
and anterior labial gingiva.
Blood Supply:
• Facial Artery: One of the six non-terminal branches of the external carotid artery, supplying the lips via superior and inferior labial
branches, which bifurcate and anastomose with the opposite side's companion artery.
Blood supply in details:
Arterial Supply:
Lips: superior and inferior labial arteries (branches of the facial artery)
Cheeks: facial, transverse facial, and buccal branches
Gums:
• Maxillary gingiva: superior alveolar arteries
• Mandibular gingiva: inferior alveolar artery
Oral mucosa and vestibule: branches of the facial, lingual, and maxillary arteries
Venous Drainage: Follows the arteries into the facial vein, pterygoid venous plexus, and internal jugular vein
Nerve Supply in details:
Sensory Innervation:
Lips:
• Upper lip: infraorbital nerve (CN V2)
• Lower lip: mental nerve (CN V3)
Cheeks: buccal nerve (branch of mandibular nerve, CN V3)
Gums:
• Maxillary: superior alveolar nerves (CN V2)
• Mandibular: inferior alveolar and lingual nerves (CN V3)
Vestibule: innervated by both buccal and labial branches of CN V
Motor Innervation:
Facial muscles (lips, cheeks): facial nerve (CN VII)
Autonomic (parasympathetic) innervation:
To salivary glands: via facial (CN VII) and glossopharyngeal (CN IX) nerves
, 16. Oral cavity. Proper oral cavity. Hard palate, soft palate, oral diaphragm, oropharyngeal isthmus. Macroscopic and microscopic
characteristics. Blood and nerve supply.
Subdivisions of the Oral Cavity
• Oral Vestibule: The space between the lips/cheeks and the teeth/gums. Communicates with the exterior via the oral fissure and with
the oral cavity proper posterior to the last molar.
• Oral Cavity Proper: Bounded anteriorly and laterally by the alveolar arches with teeth and gums, superiorly by the hard and soft
palate, and inferiorly by the floor of the mouth.
The Mouth Cavity Proper (Cavum Oris Proprium): receives secretion from submaxillary and sublingual salivary glands.
• Boundaries: is bounded laterally and in front by the alveolar arches with their contained teeth; behind, it communicates with the
pharynx by a constricted aperture termed the isthmus faucium. It is roofed in by the hard and soft palates, while the greater part of the
floor is formed by the tongue, the remainder by the reflection of the mucous membrane from the sides and under surface of the tongue to
the gum lining the inner aspect of the mandible.
• Structure: the mucous membrane lining the mouth is continuous with the integument at the free margin of the lips, and with the
mucous lining of the pharynx behind; it is of a rosepink tinge during life, and very thick where it overlies the hard parts bounding the
cavity. It is covered by stratified squamous epithelium.
The palate (Palatum) forms the roof of the oral cavity and the floor of the nasal cavity. It separates the oral and nasal cavities. It consists
of two portion: the hard palate (Palatum durum) and the soft palate (Palatum molle) which form an anterior and posterior part,
respectively.
The hard palate (palatum durum) contributes to the phonation of consonants and serves as an abutment for the tongue when crushing
food. A number of flat palatine mucosal folds (Plicae palatinae transversae, Rugae palatinae) to both sides of the midline help grind and
pin down pieces of food against the hard palate. The Hard Palate (palatum durum) is bounded in front and at the sides by the alveolar
arches and gums; behind, it is continuous with the soft palate. It is covered by a dense structure, formed by the periosteum and mucous
membrane of the mouth, which are intimately adherent. Along the middle line is a linear raphæ, which ends anteriorly in a small papilla
corresponding with the incisive canal. On either side and in front of the raphé the mucous membrane is thick, pale in color, and corrugated;
behind, it is thin, smooth, and of a deeper color; it is covered with stratified squamous epithelium, and furnished with numerous palatal
glands, which lie between the mucous membrane and the surface of the bone.
The soft palate (Palatum molle) is flexible and, during swallowing, blocks off the Naso pharynx by folding back onto the posterior
pharyngeal wall. It is a movable fold, suspended from the posterior border of the hard palate, and forming an incomplete septum between
the mouth and pharynx. It consists of a fold of mucous membrane enclosing muscular fibers, an aponeurosis, vessels, nerves, adenoid
tissue, and mucous glands. When occupying its usual position, i. e., relaxed and pendent, its anterior surface is concave, continuous with
the roof of the mouth, and marked by a median raphé. Its posterior surface is convex, and continuous with the mucous membrane covering
the floor of the nasal cavities. Its upper border is attached to the posterior margin of the hard palate, and its sides are blended with the
pharynx. Its lower border is free. Its lower portion, which hangs like a curtain between the mouth and pharynx is termed the palatine
velum. Hanging from the middle of its lower border is a small, conical, pendulous process, the palatine uvula; and arching lateralward and
downward from the base of the uvula on either side are two curved folds of mucous membrane, containing muscular fibers, called the
arches or pillars of the fauces.
In summary: Hard Palate
Macroscopic Characteristics: Forms the anterior two-thirds of the palate.
Composed of:
• Palatine processes of the maxilla
• Horizontal plates of the palatine bones
Covered by mucosa tightly bound to the periosteum
Anteriorly contains palatine rugae and incisive papilla
Microscopic Characteristics:
• Epithelium: Keratinized stratified squamous
• Lamina propria: Dense connective tissue, firmly attached to bone
• Contains minor mucous salivary glands (especially posteriorly)
• No submucosa in the midline (mucoperiosteum)
Blood Supply
• Greater palatine artery (from descending palatine artery, branch of
maxillary artery)
• Nasopalatine artery (via incisive canal)
Nerve Supply: Greater palatine nerve (CN V2); Nasopalatine nerve (CN
V2).
In summary: Soft Palate
Macroscopic Characteristics: Mobile posterior third of the palate;
Composed of muscle, connective tissue, and mucosa. Ends with the uvula.
Contains palatine aponeurosis and muscles of the soft palate:
• Tensor veli palatini
• Levator veli palatini
• Palatoglossus
• Palatopharyngeus
Microscopic Characteristics • Musculus uvulae
Epithelium: ->Oral side: non-keratinized stratified squamous. -> Nasal side: pseudostratified ciliated columnar
Rich in seromucous glands; Lamina propria over a muscle core.
Blood Supply: Lesser palatine arteries (branch of descending palatine artery); Ascending palatine artery (from facial artery).
Nerve Supply
Motor: all muscles by pharyngeal plexus (CN X) except tensor veli palatini (by CN V3).
Sensory: Lesser palatine nerves (CN V2); Glossopharyngeal nerve (CN IX) posteriorly.
The digestive system consists of the alimentary canal (or gastrointestinal (GI) tract) and accessory digestive organs. It is responsible for
digesting and absorbing food.
Alimentary Canal Accessory Digestive Organs
- Mouth - Teeth
- Pharynx - Tongue
- Esophagus - Gallbladder
- Stomach - Salivary Glands
- Small Intestine - Liver
- Large Intestine - Pancreas
I. Overview of the Digestive System
The digestive system is responsible for: Ingestion of food, Mechanical and chemical digestion, Absorption of nutrients, Elimination of
undigested material.
It is divided into:
1. Alimentary Canal (Gastrointestinal Tract) – Tubular Organs: Mouth, Pharynx, Esophagus, Stomach, Small intestine: duodenum,
jejunum, ileum; Large intestine: cecum, colon, rectum, anal canal.
2. Accessory Digestive Organs – Parenchymatous Organs: Salivary glands, Liver, Pancreas, Gallbladder, (Teeth and tongue also assist in
digestion)
II. Tubular Organs – Principal Structure
Tubular organs of the digestive tract share a common four-layered wall structure (from inside out):
1. Mucosa
Epithelium: Stratified squamous (e.g., esophagus), Simple columnar (e.g., stomach, intestines)
Lamina propria: Loose connective tissue with glands, vessels, immune cells
Muscularis mucosae: Thin layer of smooth muscle
2. Submucosa: Dense irregular connective tissue, Contains blood vessels, lymphatics, and Meissner’s (submucosal) plexus, May contain
glands (e.g., Brunner’s glands in duodenum)
3. Muscularis Externa: Inner circular and outer longitudinal smooth muscle layers, Responsible for peristalsis, Contains Auerbach’s
(myenteric) plexus between the layers
4. Serosa or Adventitia
• Serosa: Visceral peritoneum (simple squamous epithelium + connective tissue)
• Adventitia: Loose connective tissue attaching organ to surrounding structures (e.g., in retroperitoneal organs like the esophagus)
Specializations occur in different regions (e.g., rugae in stomach, villi in intestines, taenia coli in colon)
III. Parenchymatous Organs – Principal Structure
Parenchymatous organs are solid and composed of:
• Parenchyma: Functionally specialized epithelial cells
• Stroma: Supporting connective tissue with vessels, nerves, ducts
1. Liver: Largest gland; located in the right upper abdomen. Covered by Glisson’s capsule, is composed of hepatic lobules (Central vein,
Plates of hepatocytes, Sinusoids lined by endothelial and Kupffer cells, Portal triads: branch of portal vein, hepatic artery, bile duct).
Functions: Metabolism, detoxification, synthesis of plasma proteins, Bile production.
2. Pancreas: Mixed exocrine and endocrine gland
• Exocrine part: Acini of serous cells secreting digestive enzymes; Ductal system (intercalated, intralobular, main pancreatic duct)
• Endocrine part: Islets of Langerhans producing insulin, glucagon, somatostatin.
Functions:
• Exocrine: enzyme secretion for digestion
• Endocrine: glucose metabolism
3. Salivary Glands
Major: Parotid, Submandibular, Sublingual. Composed of:
• Serous acini (enzyme-rich secretion)
• Mucous acini (mucin-rich)
• Myoepithelial cells aiding secretion
Duct system: intercalated → striated → excretory ducts
Function: Lubrication, digestion initiation (e.g., amylase)
,15. Oral cavity. Embryonic development. Oral vestibule, lips, cheeks, gums. Macroscopic and microscopic characteristics. Blood
and nerve supply.
Embryonic Development of the Oral Cavity
The oral cavity (stomodeum) originates from the ectodermal invagination of the head region during the 4th week of embryonic
development. It is initially separated from the primitive pharynx by the oropharyngeal membrane, which breaks down in the 4th week,
establishing communication.
The upper lip and cheeks develop from:
• Maxillary processes (sides of upper lip, cheeks)
• Medial nasal processes (philtrum of the upper lip)
The lower lip arises from the mandibular processes.
The oral epithelium is ectodermal in origin and gives rise to tooth enamel, salivary glands, and mucosa.
The connective tissue and muscle components derive from neural crest-derived mesenchyme and paraxial mesoderm.
Subdivisions of the Oral Cavity
• Oral Vestibule: The space between the lips/cheeks and the teeth/gums. Communicates with the exterior via the oral fissure and with
the oral cavity proper posterior to the last molar.
• Oral Cavity Proper: Bounded anteriorly and laterally by the alveolar arches with teeth and gums, superiorly by the hard and soft
palate, and inferiorly by the floor of the mouth.
The Vestibule (Vestibulum Oris): is a slit-like space that receives secretion from the parotid salivary glands.
• Boundaries: Externally by the lips and cheeks, internally by the gums and teeth. Above and below, it is limited by the reflection of the
mucous membrane from the lips and cheeks to the gum covering the upper and lower alveolar arch respectively
• Communication: With the surface of the body by the mouth's orifice and, when the jaws are closed, with the mouth cavity proper by
apertures behind the wisdom teeth and clefts between opposing teeth.
The Mouth Cavity Proper (Cavum Oris Proprium): receives secretion from submaxillary and sublingual salivary glands.
• Boundaries: is bounded laterally and in front by the alveolar arches with their contained teeth; behind, it communicates with the
pharynx by a constricted aperture termed the isthmus faucium. It is roofed in by the hard and soft palates, while the greater part of the
floor is formed by the tongue, the remainder by the reflection of the mucous membrane from the sides and under surface of the tongue to
the gum lining the inner aspect of the mandible.
• Structure: the mucous membrane lining the mouth is continuous with the integument at the free margin of the lips, and with the
mucous lining of the pharynx behind; it is of a rosepink tinge during life, and very thick where it overlies the hard parts bounding the
cavity. It is covered by stratified squamous epithelium.
JOBOTTA'S NOTES
The oral opening (Rima oris) represents the entrance
to the digestive tract and the oral cavity. The latter is
divided into a vestibule (Vestibulum oris) and the
cavity proper (Cavitas oris propria). The borders of
the Vestibulum oris are the lips and cheeks at the
outside and the alveolar processes and teeth at the
inside. With the occlusion of teeth, a space behind the
last molar tooth on each side (Spatium retromolare)
allows access to the oral cavity. In the region of the
oropharyngeal isthmus (Isthmus faucium) the oral
cavity becomes the Pars oralis of the Pharynx
(Oropharynx). The excretory ducts of numerous
smaller salivary glands and those of the three paired
large salivary glands all drain into the Vestibulum oris
and the Cavitas oris propria. The body of the tongue
(Corpus linguae) fills large parts of the inside of the
oral cavity.
Lips (Labia Oris): the two fleshy folds which surround the rima or orifice of the mouth, are formed externally of integument and
internally of mucous membrane, between which are found the Orbicularis oris muscle, the labial vessels, some nerves, areolar tissue,
and fat, and numerous small labial glands. The inner surface of each lip is connected in the middle line to the corresponding gum by a
fold of mucous membrane, the frenulum (the upper being the larger). The Labial Glands (glandulae labiales) are situated between the
mucous membrane and the Orbicularis oris, around the orifice of the mouth. They are circular in form, and about the size of small peas;
their ducts open by minute orifices upon the mucous membrane. In structure they resemble the salivary glands.
Macroscopic Features: Mobile muscular folds forming the opening of the mouth. Composed of:
• External skin
• Transitional (vermillion) zone
• Internal oral mucosa
Microscopic Features:
• Skin (external): keratinized stratified squamous epithelium with hair follicles, sebaceous, and sweat glands.
• Vermillion zone: Thin keratinized stratified squamous epithelium. Highly vascularized (reason for the red color). No glands.
• Oral mucosa (inner surface): Non-keratinized stratified squamous epithelium. Underlying submucosa with minor salivary glands
and orbicularis oris muscle.
,Cheeks (Buccae): The Cheeks (buccae) form the sides of the face, and are continuous in front with the lips. They are composed
externally of integument; internally of mucous membrane; and between the two of a muscular stratum, besides a large quantity of fat,
areolar tissue, vessels, nerves, and buccal glands.
Structure.—The mucous membrane lining the cheek is reflected above and below upon the gums, and is continuous behind with the
lining membrane of the soft palate. Opposite the second molar tooth of the maxilla is a papilla, on the summit of which is the aperture of
the parotid duct. The principal muscle of the cheek is the Buccinator; but other muscles enter into its formation, viz., the Zygomaticus,
Risorius, and Platysma. The buccal glands are placed between the mucous membrane and Buccinator muscle: they are similar in
structure to the labial glands, but smaller. About five, of a larger size than the rest, are placed between the Masseter and Buccinator
muscles around the distal extremity of the parotid duct; their ducts open in the mouth opposite the last molar tooth. They are called
molar glands.
Macroscopic Features: Lateral walls of the oral cavity. Composed of skin externally and mucosa internally, with buccinator muscle in
between.
Microscopic Features:
• External surface: keratinized epithelium with skin appendages.
• Internal mucosa: mostly non-keratinized stratified squamous epithelium.
• Buccal fat pad: especially prominent in infants.
• Minor salivary glands present in the submucosa.
Gums (Gingivae)
Macroscopic Features: Mucosal tissue surrounding the alveolar processes of the maxilla and mandible. Tightly attached to the
underlying bone. Divided into:
• Free gingiva: around each tooth.
• Attached gingiva: firmly bound to the periosteum.
Microscopic Features:
• Epithelium: mostly keratinized stratified squamous (especially in attached gingiva).
• Lamina propria: dense collagenous connective tissue, firmly attached to bone (mucoperiosteum).
• No submucosa.
• Junctional epithelium: attaches gingiva to tooth surface.
Oral Vestibule
Macroscopic Features: Lies between the inner surface of the lips/cheeks and the outer surface of teeth and gums. Contains openings of
the parotid duct (Stensen’s duct) near the upper second molar.
Microscopic Features:
• Lined by non-keratinized stratified squamous epithelium.
• Submucosa contains minor salivary glands and connective tissue.
• Loosely connected to underlying muscle (e.g., buccinator).
Blood Supply and Nerve Supply
Sensory Nerve Supply:
• Trigeminal Nerve:
- Infraorbital Nerve: Branch of the maxillary nerve supplying the upper lip and the face's skin between the upper lip and lower eyelid
except for the bridge of the nose.
- Mental Nerve: Branch of the mandibular nerve (via the inferior alveolar nerve) supplying the lower lip's skin and mucous membrane
and anterior labial gingiva.
Blood Supply:
• Facial Artery: One of the six non-terminal branches of the external carotid artery, supplying the lips via superior and inferior labial
branches, which bifurcate and anastomose with the opposite side's companion artery.
Blood supply in details:
Arterial Supply:
Lips: superior and inferior labial arteries (branches of the facial artery)
Cheeks: facial, transverse facial, and buccal branches
Gums:
• Maxillary gingiva: superior alveolar arteries
• Mandibular gingiva: inferior alveolar artery
Oral mucosa and vestibule: branches of the facial, lingual, and maxillary arteries
Venous Drainage: Follows the arteries into the facial vein, pterygoid venous plexus, and internal jugular vein
Nerve Supply in details:
Sensory Innervation:
Lips:
• Upper lip: infraorbital nerve (CN V2)
• Lower lip: mental nerve (CN V3)
Cheeks: buccal nerve (branch of mandibular nerve, CN V3)
Gums:
• Maxillary: superior alveolar nerves (CN V2)
• Mandibular: inferior alveolar and lingual nerves (CN V3)
Vestibule: innervated by both buccal and labial branches of CN V
Motor Innervation:
Facial muscles (lips, cheeks): facial nerve (CN VII)
Autonomic (parasympathetic) innervation:
To salivary glands: via facial (CN VII) and glossopharyngeal (CN IX) nerves
, 16. Oral cavity. Proper oral cavity. Hard palate, soft palate, oral diaphragm, oropharyngeal isthmus. Macroscopic and microscopic
characteristics. Blood and nerve supply.
Subdivisions of the Oral Cavity
• Oral Vestibule: The space between the lips/cheeks and the teeth/gums. Communicates with the exterior via the oral fissure and with
the oral cavity proper posterior to the last molar.
• Oral Cavity Proper: Bounded anteriorly and laterally by the alveolar arches with teeth and gums, superiorly by the hard and soft
palate, and inferiorly by the floor of the mouth.
The Mouth Cavity Proper (Cavum Oris Proprium): receives secretion from submaxillary and sublingual salivary glands.
• Boundaries: is bounded laterally and in front by the alveolar arches with their contained teeth; behind, it communicates with the
pharynx by a constricted aperture termed the isthmus faucium. It is roofed in by the hard and soft palates, while the greater part of the
floor is formed by the tongue, the remainder by the reflection of the mucous membrane from the sides and under surface of the tongue to
the gum lining the inner aspect of the mandible.
• Structure: the mucous membrane lining the mouth is continuous with the integument at the free margin of the lips, and with the
mucous lining of the pharynx behind; it is of a rosepink tinge during life, and very thick where it overlies the hard parts bounding the
cavity. It is covered by stratified squamous epithelium.
The palate (Palatum) forms the roof of the oral cavity and the floor of the nasal cavity. It separates the oral and nasal cavities. It consists
of two portion: the hard palate (Palatum durum) and the soft palate (Palatum molle) which form an anterior and posterior part,
respectively.
The hard palate (palatum durum) contributes to the phonation of consonants and serves as an abutment for the tongue when crushing
food. A number of flat palatine mucosal folds (Plicae palatinae transversae, Rugae palatinae) to both sides of the midline help grind and
pin down pieces of food against the hard palate. The Hard Palate (palatum durum) is bounded in front and at the sides by the alveolar
arches and gums; behind, it is continuous with the soft palate. It is covered by a dense structure, formed by the periosteum and mucous
membrane of the mouth, which are intimately adherent. Along the middle line is a linear raphæ, which ends anteriorly in a small papilla
corresponding with the incisive canal. On either side and in front of the raphé the mucous membrane is thick, pale in color, and corrugated;
behind, it is thin, smooth, and of a deeper color; it is covered with stratified squamous epithelium, and furnished with numerous palatal
glands, which lie between the mucous membrane and the surface of the bone.
The soft palate (Palatum molle) is flexible and, during swallowing, blocks off the Naso pharynx by folding back onto the posterior
pharyngeal wall. It is a movable fold, suspended from the posterior border of the hard palate, and forming an incomplete septum between
the mouth and pharynx. It consists of a fold of mucous membrane enclosing muscular fibers, an aponeurosis, vessels, nerves, adenoid
tissue, and mucous glands. When occupying its usual position, i. e., relaxed and pendent, its anterior surface is concave, continuous with
the roof of the mouth, and marked by a median raphé. Its posterior surface is convex, and continuous with the mucous membrane covering
the floor of the nasal cavities. Its upper border is attached to the posterior margin of the hard palate, and its sides are blended with the
pharynx. Its lower border is free. Its lower portion, which hangs like a curtain between the mouth and pharynx is termed the palatine
velum. Hanging from the middle of its lower border is a small, conical, pendulous process, the palatine uvula; and arching lateralward and
downward from the base of the uvula on either side are two curved folds of mucous membrane, containing muscular fibers, called the
arches or pillars of the fauces.
In summary: Hard Palate
Macroscopic Characteristics: Forms the anterior two-thirds of the palate.
Composed of:
• Palatine processes of the maxilla
• Horizontal plates of the palatine bones
Covered by mucosa tightly bound to the periosteum
Anteriorly contains palatine rugae and incisive papilla
Microscopic Characteristics:
• Epithelium: Keratinized stratified squamous
• Lamina propria: Dense connective tissue, firmly attached to bone
• Contains minor mucous salivary glands (especially posteriorly)
• No submucosa in the midline (mucoperiosteum)
Blood Supply
• Greater palatine artery (from descending palatine artery, branch of
maxillary artery)
• Nasopalatine artery (via incisive canal)
Nerve Supply: Greater palatine nerve (CN V2); Nasopalatine nerve (CN
V2).
In summary: Soft Palate
Macroscopic Characteristics: Mobile posterior third of the palate;
Composed of muscle, connective tissue, and mucosa. Ends with the uvula.
Contains palatine aponeurosis and muscles of the soft palate:
• Tensor veli palatini
• Levator veli palatini
• Palatoglossus
• Palatopharyngeus
Microscopic Characteristics • Musculus uvulae
Epithelium: ->Oral side: non-keratinized stratified squamous. -> Nasal side: pseudostratified ciliated columnar
Rich in seromucous glands; Lamina propria over a muscle core.
Blood Supply: Lesser palatine arteries (branch of descending palatine artery); Ascending palatine artery (from facial artery).
Nerve Supply
Motor: all muscles by pharyngeal plexus (CN X) except tensor veli palatini (by CN V3).
Sensory: Lesser palatine nerves (CN V2); Glossopharyngeal nerve (CN IX) posteriorly.
