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Salivary Glands: Anatomy

The salivary glands are exocrine glands Exocrine glands Glands of external secretion that release its secretions to the body's cavities, organs, or surface, through a duct. Glandular Epithelium: Histology positioned in and around the oral cavity. These glands are responsible for secreting saliva into the mouth, which aids AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS in digestion Digestion Digestion refers to the process of the mechanical and chemical breakdown of food into smaller particles, which can then be absorbed and utilized by the body. Digestion and Absorption. Saliva helps keep the oral mucosa Oral mucosa Lining of the oral cavity, including mucosa on the gums; the palate; the lip; the cheek; floor of the mouth; and other structures. The mucosa is generally a nonkeratinized stratified squamous epithelium covering muscle, bone, or glands but can show varying degree of keratinization at specific locations. Stomatitis lubricated, and it provides antimicrobial protection. There are 3 major paired salivary glands: the sublingual, submandibular, and parotid glands Parotid glands The largest of the three pairs of salivary glands. They lie on the sides of the face immediately below and in front of the ear. Gastrointestinal Secretions. There are also hundreds of minor salivary glands found in patches Patches Vitiligo around the oral cavity.

Last updated: 30 Mar, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Introduction

The 3 pairs of major salivary glands are the parotid, submandibular, and sublingual glands Sublingual glands A salivary gland on each side of the mouth below the tongue. Gastrointestinal Secretions.

Embryonic development

Function

Production of saliva, which is important in:

  • Facilitating initiation of digestion Digestion Digestion refers to the process of the mechanical and chemical breakdown of food into smaller particles, which can then be absorbed and utilized by the body. Digestion and Absorption
  • Lubricating and protecting the oral cavity
  • Exerting antimicrobial action
  • Enhancing taste

Morphology

  • The salivary glands are exocrine glands Exocrine glands Glands of external secretion that release its secretions to the body’s cavities, organs, or surface, through a duct. Glandular Epithelium: Histology that secrete saliva into the oral cavity through ducts.
  • The glands, based on their size (the 1st is the largest) are:
    • Parotid 
    • Submandibular
    • Sublingual
    • Minor salivary glands
Overview of the salivary glands

Overview of the salivary glands and surrounding anatomic landmarks

Image by Lecturio.

Histology

  • The salivary glands are divided by connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue: Histology septa into lobes, then lobules Lobules Breasts: Anatomy, and finally acini (round secretory units) with ducts.
  • Secretion Secretion Coagulation Studies of saliva occurs in the acinus and the initial part of the duct system.
  • Acini:
    • Consist of:
      • Luminal cells: line the lumen and produce saliva
      • Myoepithelial cells: surround the luminal cells and contract on stimulation to constrict the acini
    • Secretions can be serous, mucinous, or mixed.
      • Serous (watery) secretions are produced mainly from the parotid gland.
      • Mucous secretions are produced from the minor glands. 
      • Mixed secretions are released from the sublingual and submandibular glands Submandibular glands One of two salivary glands in the neck, located in the space bound by the two bellies of the digastric muscle and the angle of the mandible. It discharges through the submandibular duct. The secretory units are predominantly serous although a few mucous alveoli, some with serous demilunes, occur. Gastrointestinal Secretions.
  • The salivary ducts are lined by 3 types of cells:
    • Intercalated cells Intercalated cells Tubular System:
      • Connect acini to the rest of the gland
      • Not involved in the modification of electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes
    • Striated cells:
      • Regulate electrolyte transport
      • Sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia resorption
    • Excretory duct cells:
      • Continuing sodium resorption
      • Secrete potassium Potassium An element in the alkali group of metals with an atomic symbol k, atomic number 19, and atomic weight 39. 10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the water-electrolyte balance. Hyperkalemia
Table: Distinguishing features between the major salivary glands
Parotid Submandibular Sublingual
Location Anterior to the ear Inferior and posterior to the mandible Mandible The largest and strongest bone of the face constituting the lower jaw. It supports the lower teeth. Jaw and Temporomandibular Joint: Anatomy Inferior to the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy
Development Ectodermal Endodermal Endodermal
Size Largest (15–30 g) Smaller (10–20 g) Smallest (3–4 g)
Shape Pyramidal J-shaped Almond-shaped
Duct and opening site Stensen duct:
opens opposite
2nd maxillary
molar
Wharton duct:
opens at the
sublingual papilla
(lateral to each side of
the frenulum linguae)
Series of ducts:
floor of the
oral cavity on
sublingual fold
Nerve supply Lesser petrosal nerve Chorda tympani Chorda tympani A branch of the facial (7th cranial) nerve which passes through the middle ear and continues through the petrotympanic fissure. The chorda tympani nerve carries taste sensation from the anterior two-thirds of the tongue and conveys parasympathetic efferents to the salivary glands. Lips and Tongue: Anatomy Chorda tympani Chorda tympani A branch of the facial (7th cranial) nerve which passes through the middle ear and continues through the petrotympanic fissure. The chorda tympani nerve carries taste sensation from the anterior two-thirds of the tongue and conveys parasympathetic efferents to the salivary glands. Lips and Tongue: Anatomy
Type of secretion Serous Serous and mucus Mucus (mainly)
and serous

Composition and Function of Saliva

Description and production

  • Saliva is a clear, mucoserous exocrine secretion that is critical to the preservation and maintenance of oral health.
  • Production: 0.5 to 1.5 L/day
  • Contributions of the different salivary glands during unstimulated flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure are as follows:
    • 20% from parotid 
    • 65% from submandibular 
    • 7%–8% from sublingual 
    • < 10% from the minor glands
  • The parotid contributes > 50% of stimulated saliva flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure.

Composition

  • Water: 99.5%
  • Electrolytes, including Na+, K+, Ca CA Condylomata acuminata are a clinical manifestation of genital HPV infection. Condylomata acuminata are described as raised, pearly, flesh-colored, papular, cauliflower-like lesions seen in the anogenital region that may cause itching, pain, or bleeding. Condylomata Acuminata (Genital Warts)2+, Mg2+, bicarbonate Bicarbonate Inorganic salts that contain the -HCO3 radical. They are an important factor in determining the ph of the blood and the concentration of bicarbonate ions is regulated by the kidney. Levels in the blood are an index of the alkali reserve or buffering capacity. Electrolytes (HCO3), and phosphates
  • Immunoglobulins Immunoglobulins Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions, proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis, enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes, mucins, urea Urea A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids. Urea Cycle, and ammonia Ammonia A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as ammonium hydroxide. Acid-Base Balance
  • Normal pH: 6.7–7.4, nearly neutral

Flow

  • Normal flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure for unstimulated saliva: ≥ 0.1 mL/min.
  • On stimulation, ↑ volume to 0.2 mL/min
  • Saliva:
    • Flows from the acini into the ducts and eventually into the openings (in the mouth)
    • Composition is modified as saliva flows, adding K+ and HCO3 and extracting Na+ and chloride Chloride Inorganic compounds derived from hydrochloric acid that contain the Cl- ion. Electrolytes (Cl).
    • Extraction of NaCl makes saliva generally hypotonic Hypotonic Solutions that have a lesser osmotic pressure than a reference solution such as blood, plasma, or interstitial fluid. Renal Sodium and Water Regulation
  • Controlled by a salivary center composed of nuclei in the medulla
  • The various stimuli for saliva production include:
    • Mechanical factors such as mastication Mastication The act and process of chewing and grinding food in the mouth. Jaw and Temporomandibular Joint: Anatomy (chewing)
    • Gustatory (e.g., acidic foods)
    • Olfactory
    • Psychological factors (e.g., pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
    • Medications 
    • Localized or systemic diseases
Ion movement during production of saliva

Ion movement during production of saliva and its transports through the salivary duct

Image by Lecturio.

Function

  • Lubricates food, aiding swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility
  • Starts digestion of carbohydrates Digestion of carbohydrates Carbohydrates store energy and are used as a source of nutrition. To be used as energy by humans, most carbohydrates must be metabolized. Carbohydrate metabolism involves transforming complex starches into glucose, a monosaccharide that can subsequently be absorbed by the body. Digestion and Absorption of Carbohydrates and lipids Lipids Lipids are a diverse group of hydrophobic organic molecules, which include fats, oils, sterols, and waxes. Fatty Acids and Lipids
  • Antibacterial Antibacterial Penicillins activity through:
    • Secretory IgA IgA Represents 15-20% of the human serum immunoglobulins, mostly as the 4-chain polymer in humans or dimer in other mammals. Secretory iga is the main immunoglobulin in secretions. Immunoglobulins: Types and Functions: the largest immunologic component of saliva
    • Antibacterial Antibacterial Penicillins enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes (e.g., lactoferrin)
    • Other antibacterial proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis that cause bacterial clumping
  • Protection of the oral mucosa Oral mucosa Lining of the oral cavity, including mucosa on the gums; the palate; the lip; the cheek; floor of the mouth; and other structures. The mucosa is generally a nonkeratinized stratified squamous epithelium covering muscle, bone, or glands but can show varying degree of keratinization at specific locations. Stomatitis and teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth: Anatomy
  • Aids AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS in the sense of taste

Sublingual Gland

  • The smallest major salivary gland
  • Location: inferior to the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy, lateral to the genioglossus muscle, superior to the submandibular glands Submandibular glands One of two salivary glands in the neck, located in the space bound by the two bellies of the digastric muscle and the angle of the mandible. It discharges through the submandibular duct. The secretory units are predominantly serous although a few mucous alveoli, some with serous demilunes, occur. Gastrointestinal Secretions
  • Drainage: 
    • Has no single dominant duct, but is drained by 10 small ducts, called the ducts of Rivinus
    • Occasionally, some anterior ducts may join to form a large common duct, called the Bartholin duct (unrelated to Bartholin glands Bartholin glands Mucus-secreting glands situated on the posterior and lateral aspect of the vestibule of the vagina. Vagina, Vulva, and Pelvic Floor: Anatomy).
    • The Bartholin duct typically joins the Wharton (submandibular) duct, which drains into the sublingual caruncle.
    • Other sublingual ducts empty directly into the bottom of the oral cavity.
  • Structure: 
    • Unencapsulated
    • Consists mainly of mucous acini, with just a few serous acini
  • Neurovasculature:
    • Blood supply: sublingual and submental arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
    • Venous return: sublingual vein
    • Lymphatic drainage: submandibular lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy
    • Nerve supply (similar to submandibular gland):
      •   Chorda tympani Chorda tympani A branch of the facial (7th cranial) nerve which passes through the middle ear and continues through the petrotympanic fissure. The chorda tympani nerve carries taste sensation from the anterior two-thirds of the tongue and conveys parasympathetic efferents to the salivary glands. Lips and Tongue: Anatomy nerve, a branch of the facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions 
      • Synapses at the submandibular ganglion
The sublingual and submandibular glands

The sublingual and submandibular glands Submandibular glands One of two salivary glands in the neck, located in the space bound by the two bellies of the digastric muscle and the angle of the mandible. It discharges through the submandibular duct. The secretory units are predominantly serous although a few mucous alveoli, some with serous demilunes, occur. Gastrointestinal Secretions, with their surrounding structures

Image by Lecturio.

Submandibular Gland

Location

  • Occupies most of the submandibular triangle Submandibular triangle Triangles of the Neck: Anatomy
  • Boundaries of the triangle are:
    • Superior: inferior border of mandible Mandible The largest and strongest bone of the face constituting the lower jaw. It supports the lower teeth. Jaw and Temporomandibular Joint: Anatomy
    • Lateral: posterior belly of digastric muscle
    • Medial: anterior belly of digastric muscle
    • Floor: mylohyoid and hyoglossus 
    • Roof: skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions, fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis, platysma Platysma Muscles of the Neck: Anatomy

Structure

  • Divided into superficial and deep lobes, which are separated by the mylohyoid muscle
  • J-shaped, with a larger and a smaller part of the gland:
    • Superficial lobe:
      • Larger
      • Within the anterior part of triangle
      • Outside the oral cavity
    • Deep lobe:
      • Smaller: curves posteriorly, connecting to superficial portion of gland (forming a “J”)
      • Located on the lateral side of the hyoglossus muscle
      • Inside the oral cavity
  • The submandibular, or Wharton, duct empties on both sides of the frenulum at the sublingual caruncle.
    • Prior to reaching the opening, the duct crosses paths with the lingual nerve Lingual nerve A sensory branch of the mandibular nerve, which is part of the trigeminal (5th cranial) nerve. The lingual nerve carries general afferent fibers from the anterior two-thirds of the tongue, the floor of the mouth, and the mandibular gingivae. Lips and Tongue: Anatomy.
    • Cranial nerve (CN) XII ( hypoglossal nerve Hypoglossal nerve The 12th cranial nerve. The hypoglossal nerve originates in the hypoglossal nucleus of the medulla and supplies motor innervation to all of the muscles of the tongue except the palatoglossus (which is supplied by the vagus). This nerve also contains proprioceptive afferents from the tongue muscles. Lips and Tongue: Anatomy) runs parallel and inferior to the Wharton duct.
  • Consists mainly of serous acini, with few mucinous acini

Neurovasculature

  • Blood supply: sublingual and submental arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
  • Venous return: common facial vein and sublingual vein
  • Lymphatic drainage: submandibular nodes → upper deep cervical nodes
  • Nerve supply: 
    • Parasympathetic (secretomotor):
      • Chorda tympani Chorda tympani A branch of the facial (7th cranial) nerve which passes through the middle ear and continues through the petrotympanic fissure. The chorda tympani nerve carries taste sensation from the anterior two-thirds of the tongue and conveys parasympathetic efferents to the salivary glands. Lips and Tongue: Anatomy, a branch of the facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions
      • Parasympathetic cell bodies in the submandibular ganglion
    • Sympathetic ( vasoconstriction Vasoconstriction The physiological narrowing of blood vessels by contraction of the vascular smooth muscle. Vascular Resistance, Flow, and Mean Arterial Pressure): from the superior cervical ganglion
Submandibular gland and spatial relations

Submandibular gland and associated neurovascular structures

Image by Lecturio.

Parotid Gland

Location

Located in the retromandibular fossa, the parotid gland:

  • Wraps around the mandibular ramus
  • Covers the posterior portion of the masseter Masseter A masticatory muscle whose action is closing the jaws. Jaw and Temporomandibular Joint: Anatomy muscle
  • Sits inferior to the zygomatic Zygomatic Either of a pair of bones that form the prominent part of the cheek and contribute to the orbit on each side of the skull. Skull: Anatomy arch

Structure

  • Has 2 lobes, a broad superficial lobe and a smaller deeper lobe, with the facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions running between them.
    • The superficial lobe is lateral to the facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions.
    • The deeper lobe is medial to the facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions.
  • The main duct, called the Stensen duct, is located opposite to the 2nd maxillary molar and empties into the oral cavity.
  • Consists mostly of serous acini
Histology of the parotid gland

Histology of the parotid gland (serous acini)

Image: “Histology of the parotid gland” by Wbensmith. License: CC BY 3.0

Spatial relations

The structures within the parotid gland

The facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions (top image) and its branches (lower image) pierce the parotid gland

Image by Lecturio.

Neurovasculature

  • Blood supply:
    • External carotid artery and its terminal branches
    • Venous return: retromandibular vein
    • The vascular bundle ( arteries and veins Arteries And Veins ACES and RUSH: Resuscitation Ultrasound Protocols) lies medial to the facial nerve Facial nerve The 7th cranial nerve. The facial nerve has two parts, the larger motor root which may be called the facial nerve proper, and the smaller intermediate or sensory root. Together they provide efferent innervation to the muscles of facial expression and to the lacrimal and salivary glands, and convey afferent information for taste from the anterior two-thirds of the tongue and for touch from the external ear. The 12 Cranial Nerves: Overview and Functions
  • Lymphatic drainage: 2 nodal layers (extraglandular and intraglandular nodes) draining into the deep and superficial cervical lymph systems
  • Innervation: 
    • Parasympathetic innervation via the lesser petrosal nerve (a component of the glossopharyngeal nerve Glossopharyngeal nerve The 9th cranial nerve. The glossopharyngeal nerve is a mixed motor and sensory nerve; it conveys somatic and autonomic efferents as well as general, special, and visceral afferents. Among the connections are motor fibers to the stylopharyngeus muscle, parasympathetic fibers to the parotid glands, general and taste afferents from the posterior third of the tongue, the nasopharynx, and the palate, and afferents from baroreceptors and chemoreceptor cells of the carotid sinus. Pharynx: Anatomy (CN IX))
    • Parasympathetic cell bodies are in the otic ganglion, with postganglionic fibers joining the auriculotemporal nerve.
Innervation, blood and venous supply of parotid gland

Facial nerve and branches with the arterial and venous structures of the parotid gland

Image by Lecturio.

Minor Salivary Glands

  • Hundreds of minor glands are present.
  • Highest concentration is noted in the buccal mucosa Buccal mucosa Oral Cancer, labial mucosa, lingual mucosa, soft/hard palate Palate The palate is the structure that forms the roof of the mouth and floor of the nasal cavity. This structure is divided into soft and hard palates. Palate: Anatomy, and floor of mouth. 
  • Produce < 10% of saliva, with mainly mucous secretions

Clinical Relevance

  • Diseases of the salivary glands Diseases of the salivary glands Diseases of the salivary glands include sialadenosis, sialadenitis, sialolithiasis, and neoplasms. Sialadenosis is a chronic, bilateral, noninflammatory hypertrophy of the salivary glands. Sialadenitis results from inflammation or infection of the glands, and sialolithiasis is due to stone formation in the glands or ducts. Diseases of the Salivary Glands: Some conditions manifest as salivary gland enlargement with various degrees of pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways or discomfort. Specific clinical factors help differentiate between these conditions, such as asymmetry Asymmetry Examination of the Upper Limbs, the presence of pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, associated conditions and risk factors, and growth or stability. The diagnosis is often clinical, though imaging and biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma may be needed. Management varies depending on the disease.
    • Sialadenosis is chronic, bilateral, noninflammatory hypertrophy Hypertrophy General increase in bulk of a part or organ due to cell enlargement and accumulation of fluids and secretions, not due to tumor formation, nor to an increase in the number of cells (hyperplasia). Cellular Adaptation of the salivary glands. 
    • Sialadenitis Sialadenitis Inflammation of salivary tissue (salivary glands), usually due to infection or injuries. Diseases of the Salivary Glands results from inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation or infection of the glands.
    • Sialolithiasis Sialolithiasis Calculi occurring in a salivary gland. Most salivary gland calculi occur in the submandibular gland, but can also occur in the parotid gland and in the sublingual and minor salivary glands. Diseases of the Salivary Glands is due to stone formation in the glands or ducts. 
    • Neoplasms Neoplasms New abnormal growth of tissue. Malignant neoplasms show a greater degree of anaplasia and have the properties of invasion and metastasis, compared to benign neoplasms. Benign Bone Tumors of the salivary gland may be benign Benign Fibroadenoma or malignant.
  • Mumps Mumps Mumps is caused by a single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae. Mumps is typically a disease of childhood, which manifests initially with fever, muscle pain, headache, poor appetite, and a general feeling of malaise, and is classically followed by parotitis. Mumps Virus/Mumps: typically a disease of childhood. Mumps Mumps Mumps is caused by a single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae. Mumps is typically a disease of childhood, which manifests initially with fever, muscle pain, headache, poor appetite, and a general feeling of malaise, and is classically followed by parotitis. Mumps Virus/Mumps is caused by an RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology of the family Paramyxoviridae Paramyxoviridae A family of spherical viruses, of the order mononegavirales, somewhat larger than the orthomyxoviruses, and containing single-stranded RNA. Subfamilies include paramyxoviridae and pneumovirinae. Respiratory Syncytial Virus. Transmission is via respiratory droplets Droplets Varicella-Zoster Virus/Chickenpox or direct contact. The condition manifests initially with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, muscle pain Muscle Pain Ion Channel Myopathy, headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, poor appetite, and general malaise Malaise Tick-borne Encephalitis Virus, classically followed by parotitis Parotitis Inflammation of the parotid gland. Mumps Virus/Mumps. Complications include meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis, pancreatitis Pancreatitis Inflammation of the pancreas. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of chronic pancreatitis. The two most common forms of acute pancreatitis are alcoholic pancreatitis and gallstone pancreatitis. Acute Pancreatitis, permanent deafness, and testicular inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation, which can result in infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility. Management is with supportive care. Mumps Mumps Mumps is caused by a single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae. Mumps is typically a disease of childhood, which manifests initially with fever, muscle pain, headache, poor appetite, and a general feeling of malaise, and is classically followed by parotitis. Mumps Virus/Mumps is prevented by vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination.
  • Ranula: mucous-retention cyst of the sublingual gland or small salivary glands present in the floor of the mouth. A ranula is a benign Benign Fibroadenoma swelling Swelling Inflammation that is soft and bluish and transilluminates.
  • Sjögren syndrome Sjögren Syndrome Rheumatoid Arthritis: autoimmune, inflammatory condition in which glandular tissues such as the salivary and lacrimal glands Lacrimal Glands Dacryocystitis are infiltrated by lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology, resulting in decreased tear and saliva production. Symptoms include dry eyes and mouth, accompanied by extraglandular manifestations. Diagnosis is via history and clinical examination, serologic studies, or salivary gland biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma.  A multidisciplinary approach is needed to treat patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship.

References

  1. Barrett, K.E., et al. (Ed.) (2017). Overview of gastrointestinal function & regulation. Chapter 25 of Ganong’s Medical Physiology Examination & Board Review. https://accessmedicine.mhmedical.com/content.aspx?bookid=2139&sectionid=160313408
  2. Chason, H.M., Downs, B.W. (2021). Anatomy, head and neck, parotid gland. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK534225/
  3. Del Vigna de Almeida, P., et al. (2008). Saliva composition and functions: a comprehensive review. J Contemp Dent Pract 9(3):72–80.
  4. Grewal, J.S., Jamal, Z., Ryan, J. (2020) Anatomy, Head and Neck, Submandibular Gland. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK542272/
  5. Grewal, J.S., et al. (2021) Anatomy, head and neck, sublingual gland. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK535426/
  6. Gupta, S., Ahuja, N.  (2019). Salivary glands. IntechOpen. https://www.intechopen.com/chapters/63843
  7. ​Humphrey, S. P., Williamson, R. T. (2001). A review of saliva: normal composition, flow, and function. Journal of Prosthetic Dentistry 85(2):162–169.
  8. Iorgulescu, G. (2009) Saliva between normal and pathological: important factors in determining systemic and oral health. Journal of Medicine and Life 2:303–307.
  9. Kessler, A. T., Bhatt, A. A. (2018). Review of the major and minor salivary glands, part 1: anatomy, infectious, and inflammatory processes. Journal of Clinical Imaging Science 8:47. https://doi.org/10.4103/jcis.JCIS_45_18
  10. Lars Eliasson, L.,  Carlén, A. (2010). An update on minor salivary gland secretions. Eur J Oral Sci 118:435–442. https://www.doi.org/10.1111/j.1600-0722.2010.00766.x
  11. Porcheri, C., Mitsiadis, T.A. (2019). Physiology, pathology and regeneration of salivary glands. Cells 8:976. http//:www.doi.org/10.3390/cells8090976
  12. Tanakchi, S., Aly, F.Z. (2021). Salivary glands: general anatomy & histology. Pathology Outlines. https://www.pathologyoutlines.com/topic/salivaryglandsnormalhistology.html

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