Anatomy of Salivary Glands

Salivary Glands

• The parotid salivary gland has a duct that enters the mouth near the upper 2nd molar tooth, and its secretion is serous.
• The submandibular gland has a duct that enters the floor of the mouth, and it is a mixed gland with both serous and mucous secretions.
• The sublingual gland has 16-20 short ducts that open into the floor of the mouth, and it is mucus secreting.
• Salivary glands moisten food, dissolving chemicals that stimulate the taste buds, and help turn food into a bolus to aid swallowing.

The Nose and Nasal Cavity

• The nose and nasal cavity have the main role of enabling the sense of smell.
• They also form the upper portion of the respiratory tract, moisten and warm the inspired air, filter the air to remove foreign particles, and act as a resonating chamber for speech.

The Nose

• The external nose is the portion that protrudes from the face and is framed by cartilage covered by skin.
• The nose can vary considerably in size.

Lips and Cheeks

• Lips are musculofibrous folds containing the orbicularis oris, and have a multiple role, including acting as a sphincter, grasping food, suckling, speech, etc.
• The lips are supplied by the upper and lower labial arteries (from facial), and innervated by the labial nerves (upper from infra-orbital, CN V2, and lower from mental, CN V3).
• The cheeks are continuous with the lips and make up the movable walls of the oral cavity, and are involved in suckling, facial expression, speech, etc.
• The cheeks are supplied by the buccal arteries (branches of the maxillary) and innervated by the buccal branches (of the mandibular).

Muscles of the Cheeks and Lips

• The muscles of the cheeks and lips include the orbicularis oris, buccinator, and others.

Nerve Supply to the Muscles of the Oral Cavity

• The muscles in the lateral walls are supplied by the facial nerve.
• The floor has a more complex nerve supply, including the geniohyoid (supplied by fibers from C1), the mylohyoid and anterior belly of digastric (supplied by the mandibular branch of the trigeminal).

Nerve Supply to the Mucosa of the Oral Cavity

• The mucous membrane of the roof is supplied by branches of the maxillary nerve.
• The lateral walls and floor are supplied by branches of the mandibular division (lingual branch) of the trigeminal.

Contents of the Oral Cavity

• The oral cavity contains teeth, tongue, ducts of the salivary glands, and communicates with the oropharynx.

The Permanent Dentition

• There are 32 permanent teeth that erupt between 6 and 18 years.
• The primary role of teeth is to cut (aka incise) food, break it down mechanically, and assist with speech.
• The teeth are supplied by alveolar branches of the maxillary (upper) and mandibular nerve (lower).

The Tongue

• The tongue is a special sense organ involved primarily with taste, but also with mastication, deglutition, speech, and oral cleansing.
• The tongue has three main parts: a root, body, and apex (tip).
• The anterior 2/3 of the tongue rests within the oral cavity, while the posterior 1/3 lies in the oropharynx.

Nerve Supply to the Tongue

• The muscles of the tongue are innervated by the hypoglossal nerve, except for the palatoglossus, which is innervated by the pharyngeal plexus.
• The anterior 2/3 of the tongue receives general sensation and taste via the lingual nerve (CN V3) and the chorda tympani (CN VII), respectively.
• The posterior 1/3 and the vallate papillae are supplied by the lingual branch of CN IX.

Blood Supply to the Tongue

• The tongue receives blood primarily via the lingual artery, a branch of the external carotid artery.
• The artery runs deep to the hypoglossus muscle.

Venous Drainage of the Tongue

• The dorsum and sides of the tongue are drained by the posterior lingual veins, which lead to the lingual vein, and ultimately to the internal jugular vein.
• The remainder is drained by the deep lingual and sublingual veins, which join and lead to the lingual vein.

Lymphatic Drainage of the Tongue

• The lymphatic drainage of the tongue is done in regions, each taking a different route, but ultimately draining to the deep cervical nodes, and then into the general circulation at the venous angles (jugular and subclavian).

Salivary Glands

• The parotid duct enters the mouth near the upper 2nd molar tooth, secreting serous fluids.
• The submandibular gland duct enters the floor of the mouth, producing a mixed secretion of both serous and mucous fluids.
• The sublingual gland has 16-20 short ducts that open into the floor of the mouth, secreting mucus.
• These major glands moisten food, dissolve chemicals, and stimulate taste buds, helping to break down food into a bolus for swallowing.
• Saliva contains enzymes that begin the process of digestion.

The Nose and Nasal Cavity

• The nose and nasal cavity enable the sense of smell.
• They also form the upper portion of the respiratory tract, moisten and warm inspired air, filter out foreign particles, and act as a resonating chamber for speech.

The Nose

• The external nose protrudes from the face and is made of cartilage covered by skin.
• The nose can vary in size, but all have a thick skin covering the cartilage, extending into the nasal opening (nares) where thick hairs help filter incoming air.

The Nasal Cavity

• The nasal cavity is an irregularly shaped cavity bordered by the palatine bone (floor) and the cribiform plate (roof), separating it from the oral cavity and cranial cavity.
• The cavity is divided into left and right by the nasal septum and communicates anteriorly with the external nose and posteriorly with the nasal part of the pharynx.
• The wall is lined by a mucosal layer that traps dust, bacteria, and other particles, which are then propelled towards the nasopharynx by cilia.

The Nasal Cavity Structure

• The lateral wall of the nasal cavity shows three circular tube-like protrusions called conchae, which force incoming air to swirl around, slowing it down and warming it.
• The nasal cavity also features paranasal sinuses, which are empty but have mucus-excreting epithelium in their walls, helping to moisten the surface of the nasal cavity and incoming air.

The Nasal Cavity Vessels and Nerves

• The 'VAN' of the nasal cavity refers to the veins, arteries, and nerves that supply the nasal cavity.
• The veins form a plexus leading to the ophthalmic, sphenopalatine, and facial veins.
• The arteries include the ophthalmic, maxillary, and facial arteries.
• The nerves include the ophthalmic (anterosuperior) and maxillary (postero-inferior) nerves.

Lips and Cheeks

• The lips and cheeks surround the oral cavity, with the lips having multiple roles, including acting as a sphincter, grasping food, suckling, speech, etc.
• The lips are described as musculofibrous folds, containing the orbicularis oris muscle, accompanying vessels, and nerves.
• The cheeks are continuous with the lips and make up the movable walls of the oral cavity, enclosing muscle (principally the buccinators) that are encapsulated by fat.

Muscles of the Lips and Cheeks

• The muscles of the lips and cheeks include the orbicularis oris, buccinator, and others.
• The buccinator's role is to push the cheek towards the teeth, preventing food from squeezing into the vestibule during chewing.

Nerve Supply to the Muscles of the Oral Cavity

• The muscles in the lateral walls of the oral cavity are supplied by the facial nerve.
• The floor has a more complex nerve supply, including the geniohyoid, mylohyoid, and anterior belly of digastric.

Nerve Supply to the Mucosa of the Oral Cavity

• The mucous membrane of the roof of the oral cavity is supplied by branches of the maxillary nerve.
• The lateral walls and floor are supplied by branches of the mandibular division (lingual branch) of the trigeminal nerve.

Contents of the Oral Cavity

• The oral cavity contains teeth, tongue, ducts of the salivary glands, and communicates with the oropharynx.

The Permanent Dentition

• There are 32 permanent teeth that erupt between 6 and 18 years.
• The primary role of teeth is to cut food, break it down mechanically, and assist with speech.
• The teeth are supplied by alveolar branches of the maxillary and mandibular nerves.

The Tongue

• The tongue is a special sense organ involved in taste, mastication, deglutition, speech, and oral cleansing.
• The tongue has three main parts: the root, body, and apex (tip).
• The anterior 2/3 of the tongue (the body) rests within the oral cavity, while the posterior 1/3 (the root) lies in the oropharynx.

Nerve Supply to the Tongue

• Innervation of the tongue is complex, considering both its roles in taste and mastication (muscle movement).
• All muscles of the tongue except palatoglossus are innervated by the hypoglossal nerve.
• The palatoglossus is innervated by the pharyngeal plexus.
• The anterior 2/3 of the tongue receives general sensation (touch and temperature) via the lingual nerve, a branch of CN V3, and taste is via the chorda tympani (from CN VII).