The salivary glands in
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s are
exocrine gland
Exocrine glands are glands that secrete substances on to an epithelial surface by way of a duct. Examples of exocrine glands include sweat, salivary, mammary, ceruminous, lacrimal, sebaceous, prostate and mucous. Exocrine glands are one of two ...
s that produce
saliva
Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be ...
through a system of
ducts. Humans have three paired major salivary glands (
parotid,
submandibular, and
sublingual
Sublingual (abbreviated SL), from the Latin for "under the tongue", refers to the pharmacological route of administration by which substances diffuse into the blood through tissues under the tongue.
The sublingual glands receive their prima ...
), as well as hundreds of minor salivary glands.
Salivary glands can be classified as
serous
In physiology, serous fluid or serosal fluid (originating from the Medieval Latin word ''serosus'', from Latin ''serum'') is any of various body fluids resembling serum, that are typically pale yellow or transparent and of a benign nature. The fl ...
,
mucous
Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
, or
seromucous (mixed).
In
serous secretions, the main type of protein secreted is
alpha-amylase, an
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
that breaks down
starch
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
into
maltose
}
Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...
and
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
, whereas in
mucous secretions, the main protein secreted is
mucin, which acts as a
lubricant
A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
.
[
In humans, 1200 to 1500 ml of saliva are produced every day.] The secretion of saliva (salivation) is mediated by parasympathetic stimulation; acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Part ...
is the active neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell.
Neuro ...
and binds to muscarinic receptors in the glands, leading to increased salivation.
The fourth pair of salivary glands, the tubarial glands discovered in 2020, are named for their location, being positioned in front and over the torus tubarius. However, this finding from one study is yet to be confirmed.
Structure
The salivary glands are detailed below:
Parotid glands
The two parotid glands are major salivary glands wrapped around the mandibular ramus
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
in humans. These are largest of the salivary glands, secreting saliva
Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be ...
to facilitate mastication
Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...
and swallowing
Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. Swallowing i ...
, and amylase to begin the digestion of starches
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
. It is the serous type of gland which secretes alpha-amylase (also known as ''ptyalin''). It enters the oral cavity via the parotid duct
The parotid duct, or Stensen duct, is a salivary duct. It is the route that saliva takes from the major salivary gland, the parotid gland, into the mouth.
Structure
The parotid duct is formed when several interlobular ducts, the largest ducts insi ...
. The glands are located posterior to the mandibular ramus and anterior to the mastoid process
The mastoid part of the temporal bone is the posterior (back) part of the temporal bone, one of the bones of the skull. Its rough surface gives attachment to various muscles (via tendons) and it has openings for blood vessels. From its borders, t ...
of the temporal bone
The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebral cortex.
The temporal bones are overlaid by the sides of the head known as the temples, and house the structures of the ears. Th ...
. They are clinically relevant in dissections of facial nerve branches while exposing the different lobes, since any iatrogenic lesion will result in either loss of action or strength of muscles involved in facial expression. They produce 20% of the total salivary content in the oral cavity. Mumps
MUMPS ("Massachusetts General Hospital Utility Multi-Programming System"), or M, is an imperative, high-level programming language with an integrated transaction processing key–value database. It was originally developed at Massachusetts Gener ...
is a viral infection, caused by infection in the parotid gland.
Submandibular glands
The submandibular glands (previously known as submaxillary glands) are a pair of major salivary glands located beneath the lower jaws, superior to the digastric muscle
The digastric muscle (also digastricus) (named ''digastric'' as it has two 'bellies') is a small muscle located under the jaw. The term "digastric muscle" refers to this specific muscle. However, other muscles that have two separate muscle bellie ...
s. The secretion produced is a mixture of both serous fluid and mucus
Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
, and enters the oral cavity via the submandibular duct
The submandibular duct or Wharton duct or submaxillary duct, is one of the salivary excretory ducts. It is about 5 cm. long, and its wall is much thinner than that of the parotid duct. It drains saliva from each bilateral submandibular gland and s ...
or Wharton duct. Around 70% of saliva in the oral cavity is produced by the submandibular glands, though they are much smaller than the parotid glands. This gland can usually be felt via palpation of the neck, as it is in the superficial cervical region and feels like a rounded ball. It is located about two fingers above the Adam's apple
The Adam's apple or laryngeal prominence is the protrusion in the human neck formed by the angle of the thyroid cartilage surrounding the larynx, typically visible in men, less frequently in women.
Structure
The topographic structure which is e ...
(laryngeal prominence) and about two inches apart under the chin.
Sublingual glands
The sublingual glands are a pair of major salivary glands located inferior to the tongue, anterior to the submandibular glands. The secretion produced is mainly mucous
Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...
in nature, but it is categorized as a mixed gland. Unlike the other two major glands, the ductal system of the sublingual glands does not have intercalated ducts and usually does not have striated ducts, either, so saliva exits directly from 8-20 excretory ducts known as the Rivinus ducts. About 5% of saliva entering the oral cavity comes from these glands.
Tubarial salivary glands
The tubarial glands
The tubarial salivary glands, also known as the tubarial glands, are a pair of salivary glands found in humans between the nasal cavity and throat.
Description
The tubarial glands are found in the lateral walls of the nasopharynx overlying the t ...
are suggested as a fourth pair of salivary glands situated posteriorly in the nasopharynx and nasal cavity, predominantly with mucous glands, and its ducts opening into the dorsolateral pharyngeal wall. The glands were unknown until September 2020, when they were discovered by a group of Dutch scientists using with prostate-specific membrane antigen
Glutamate carboxypeptidase II (GCPII), also known as N-acetyl-L-aspartyl-L-glutamate peptidase I (NAALADase I), NAAG peptidase, or prostate-specific membrane antigen (PSMA) is an enzyme that in humans is encoded by the ''FOLH1'' (folate hydrola ...
PET-CT. This discovery may explain mouth dryness after radiotherapy despite the avoidance of the three major glands. However, these findings from just one study need to be confirmed.[ On the other hand, an interdisciplinary group of scientists disagree with this new discovery. They believe that an accumulation of minor salivary glands has been described.
]
Minor salivary glands
Around 800 to 1,000 minor salivary glands are located throughout the oral cavity within the submucosa
The submucosa (or tela submucosa) is a thin layer of tissue (biology), tissue in various organ (anatomy), organs of the gastrointestinal tract, gastrointestinal, respiratory tract, respiratory, and genitourinary system, genitourinary tracts. It i ...
of the oral mucosa
The oral mucosa is the mucous membrane lining the inside of the mouth. It comprises stratified squamous epithelium, termed "oral epithelium", and an underlying connective tissue termed ''lamina propria''. The oral cavity has sometimes been descri ...
in the tissue of the buccal, labial, and lingual mucosa, the soft palate, the lateral parts of the hard palate, and the floor of the mouth or between muscle fibers of the tongue. They are 1 to 2 mm in diameter and unlike the major glands, they are not encapsulated by connective tissue, only surrounded by it. The gland has usually a number of acini
An acinus (; plural, acini; adjective, acinar or acinous) refers to any cluster of cells that resembles a many-lobed "berry," such as a raspberry ('' acinus'' is Latin for "berry"). The berry-shaped termination of an exocrine gland, where the ...
connected in a tiny lobule. A minor salivary gland may have a common excretory duct with another gland, or may have its own excretory duct. Their secretion is mainly mucous in nature and have many functions such as coating the oral cavity with saliva. Problems with dentures are sometimes associated with minor salivary glands if dry mouth is present. The minor salivary glands are innervated by the seventh cranial or facial nerve.
Von Ebner's glands
Von Ebner's glands are found in a trough circling the circumvallate papillae on the dorsal surface of the tongue near the terminal sulcus. They secrete a purely serous fluid that begins lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
. They also facilitate the perception of taste
The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
through secretion of digestive enzymes and proteins.
The arrangement of these glands around the circumvallate papillae provides a continuous flow of fluid over the great number of taste buds lining the sides of the papillae, and is important for dissolving the food particles to be tasted.
Nerve supply
Salivary glands are innervated, either directly or indirectly, by the parasympathetic
The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of t ...
and sympathetic arms of the autonomic nervous system
The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the peripheral nervous system that supplies viscera, internal organs, smooth muscle and glands. The autonomic nervous system is a control ...
. Parasympathetic stimulation evokes a copious flow of saliva.
* Parasympathetic innervation to the salivary glands is carried via cranial nerve
Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and ...
s. The parotid gland receives its parasympathetic input from the glossopharyngeal nerve
The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper Medulla oblongata, medulla, just anterior (closer to the nose) to t ...
(CN IX) via the otic ganglion, while the submandibular and sublingual glands receive their parasympathetic input from the facial nerve (CN VII) via the submandibular ganglion. These nerves release acetylcholine and substance P, which activate the IP3 and DAG pathways respectively.
* Direct sympathetic innervation of the salivary glands takes place via preganglionic nerves in the thoracic segments T1-T3 which synapse in the superior cervical ganglion
The superior cervical ganglion (SCG) is part of the autonomic nervous system (ANS); more specifically, it is part of the sympathetic nervous system, a division of the ANS most commonly associated with the fight or flight response. The ANS is comp ...
with postganglionic neurons that release norepinephrine, which is then received by β1-adrenergic receptors on the acinar and ductal cells of the salivary glands, leading to an increase in cyclic adenosine monophosphate (cAMP) levels and the corresponding increase of saliva secretion. Note that in this regard both parasympathetic and sympathetic stimuli result in an increase in salivary gland secretions, the difference lies on the composition of this saliva, once sympathetic stimulus results particularly in the increase of amilase secretion, which is produced by serous glands. The sympathetic nervous system also affects salivary gland secretions indirectly by innervating the blood vessel
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s that supply the glands, resulting in vasoconstriction through the activation of α1 adrenergic receptors, lessening the saliva's water content.
Microanatomy
The gland is internally divided into lobules
In anatomy, a lobe is a clear anatomical division or extension of an organ (as seen for example in the brain, lung, liver, or kidney) that can be determined without the use of a microscope at the gross anatomy level. This is in contrast to the mu ...
. Blood vessel
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
s and nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
s enter the glands at the hilum and gradually branch out into the lobules.
Acini
Secretory cells are found in a group, or acinus
An acinus (; plural, acini; adjective, acinar or acinous) refers to any cluster of cells that resembles a many-lobed "berry," such as a raspberry ('' acinus'' is Latin for "berry"). The berry-shaped termination of an exocrine gland, where the ...
. Each acinus is located at the terminal part of the gland connected to the ductal system, with many acini within each lobule of the gland. Each acinus consists of a single layer of cuboidal epithelial cells surrounding a lumen, a central opening where the saliva is deposited after being produced by the secretory cells. The three forms of acini are classified in terms of the type of epithelial cell present and the secretory product being produced - serous, mucoserous, and mucous.
Ducts
In the duct system, the lumina are formed by intercalated duct
In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or organ.
Types of ducts
Examples include:
Duct system
As ducts travel from the acinus which generates the fluid to the target, the ducts become larg ...
s, which in turn join to form striated duct
In anatomy and physiology, a duct is a circumscribed channel leading from an exocrine gland or organ.
Types of ducts
Examples include:
Duct system
As ducts travel from the acinus which generates the fluid to the target, the ducts become larg ...
s. These drain into ducts situated between the lobes of the gland (called interlobar ducts or secretory ducts). These are found on most major and minor glands (exception may be the sublingual gland).
All of the human salivary glands terminate in the mouth, where the saliva proceeds to aid in digestion. The released saliva is quickly inactivated in the stomach by the acid that is present, but saliva also contains enzymes that are actually activated by stomach acid.
Gene and protein expression
About 20,000 protein-coding genes are expressed in human cells and 60% of these genes are expressed in normal, adult salivary glands. Less than 100 genes are more specifically expressed in the salivary gland. The salivary gland specific genes are mainly genes that encode for secreted proteins and compared to other organs in the human body; the salivary gland has the highest fraction of secreted genes. The heterogeneous family of proline-rich, human salivary glycoproteins, such as PRB1
Basic salivary proline-rich protein 1 is a protein that in humans is encoded by the ''PRB1'' gene.
The protein encoded by this gene is a proline-rich salivary protein. This gene and five other genes that also encode salivary proline-rich protei ...
and PRH1
Salivary acidic proline-rich phosphoprotein 1/2 is a protein that in humans is encoded by the ''PRH1'' gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." mean ...
, are salivary gland-specific proteins with highest level of expression. Examples of other specifically expressed proteins include the digestive amylase enzyme AMY1A, the mucin MUC7 and statherin, all of major importance for specific characteristics of saliva.
Aging
Aging of salivary glands shows some structural changes, such as:
* Decrease in volume of acinar tissue
* Increase in fibrous tissue
* Increase in adipose tissue
* Ductal hyperplasia and dilation
In addition, changes occur in salivary contents:
* Decrease in concentration of secretory IgE
* Decrease in the amount of mucin
However, no overall change in the amount of saliva secreted is seen.
Function
Salivary glands secrete saliva, which has many benefits for the oral cavity and health in general. The knowledge of normal salivary flow rate (SFR) is extremely important when treating dental patients. These benefits include:
* Protection: Saliva consists of proteins (for example; mucins) that lubricate and protect both the soft and hard tissues of the oral cavity. Mucins are the principal organic constituents of mucus, the slimy viscoelastic material that coats all mucosal surfaces.
* Buffering: In general, the higher the saliva flow rate, the faster the clearance and the higher the buffer capacity, hence better protection from dental caries. Therefore, people with a slower rate of saliva secretion, combined with a low buffer capacity, have lessened salivary protection against microbes.
* Pellicle formation: Saliva forms a pellicle on the surface of the tooth to prevent wearing. The film contains mucins and proline-rich glycoprotein from the saliva.
The proteins (statherin and proline-rich proteins) within the salivary pellicle inhibit demineralisation and promote remineralisation by attracting calcium ions.
* Maintenance of tooth integrity: Demineralization occurs when enamel disintegrates due to the presence of acid. When this occurs, the buffering capacity effect of saliva (increases saliva flow rate) inhibits demineralisation. Saliva can then begin to promote the remineralisation of the tooth by strengthening the enamel with calcium and phosphate minerals.
* Antimicrobial action: Saliva can prevent microbial growth based on the elements it contains. For example, lactoferrin in saliva binds naturally with iron. Since iron is a major component of bacterial cell walls, removal of iron breaks down the cell wall, which in turn breaks down the bacterium. Antimicrobial peptides such as histatins inhibit the growth of'' Candida albicans'' and ''Streptococcus mutans''. Salivary immunoglobulin A serves to aggregate oral bacteria such as'' S. mutans'' and prevent the formation of dental plaque.
* Tissue repair: Saliva can encourage soft-tissue repair by decreasing clotting time and increasing wound contraction.
* Digestion: Saliva contains amylase, which hydrolyses starch into glucose, maltose, and dextrin. As a result, saliva allows some digestion to occur before the food reaches the stomach.
* Taste: Saliva acts as a solvent in which solid particles can dissolve and enter the taste buds through oral mucosa located on the tongue. These taste buds are found within foliate and circumvallate papillae, where minor salivary glands secrete saliva.
Clinical significance
A sialolithiasis
Sialolithiasis (also termed salivary calculi, or salivary stones) is a crystallopathy where a calcified mass or ''sialolith'' forms within a salivary gland, usually in the duct of the submandibular gland (also termed "Wharton's duct"). Less common ...
(a salivary calculus or stone) may cause blockage of the ducts, most commonly the submandibular ducts, causing pain and swelling of the gland.
Salivary gland dysfunction refers to either xerostomia (the symptom of dry mouth) or salivary gland hypofunction (reduced production of saliva); it is associated with significant impairment of quality of life. Following radiotherapy of the head and neck region, salivary gland dysfunction is a predictable side-effect. Saliva production may be pharmacologically stimulated by sialagogue __NOTOC__
A sialogogue (also spelled sialagogue, ptysmagogue or ptyalagogue) is a drug or substance that increases the flow rate of saliva.
Sialogogues can be used in the treatment of xerostomia (the subjective feeling of having a dry mouth), to st ...
s such as pilocarpine
Pilocarpine is a medication used to reduce pressure inside the eye and treat dry mouth. As eye drops it is used to manage angle closure glaucoma until surgery can be performed, ocular hypertension, primary open angle glaucoma, and to bring abou ...
and cevimeline
Cevimeline (trade name Evoxac) is a synthetic analog of the natural alkaloid muscarine with a particular agonistic effect on M1 and M3 receptors. It is used in the treatment of dry mouth and Sjögren's syndrome.
Medical uses
Cevimeline is us ...
. It can also be suppressed by so-called antisialagogue Antisialagogues are drugs or substances that decrease the flow rate of saliva and their effect is opposite to that of sialagogues. Their origin may be both natural and synthetic.
Anticholinergics generally have antisialagogue effects, and most pro ...
s such as tricyclic antidepressant
Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants, which is important for the management of depression. They are second-line drugs next to SSRIs. TCAs were discovered in the early 1950s and wer ...
s, SSRIs, antihypertensives
Antihypertensives are a class of drugs that are used to treat hypertension (high blood pressure). Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction. Evidence suggests that r ...
, and polypharmacy. A Cochrane review found there was no strong evidence that topical therapies are effective in relieving the symptoms of dry mouth.
Cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
treatments including chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...
and radiation therapy
Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...
may impair salivary flow.[ Radiotherapy can cause permanent hyposalivation due to injury to the oral mucosa containing the salivary glands, resulting in xerostomia, whereas ]chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...
may cause only temporary salivary impairment. Furthermore surgical removal because of benign or malignant lesions may also impair function.
Graft versus host disease
Graft-versus-host disease (GvHD) is a syndrome, characterized by inflammation in different organs. GvHD is commonly associated with bone marrow transplants and stem cell transplants.
White blood cells of the donor's immune system which remain wit ...
after allogeneic bone marrow transplantation may manifest as dry mouth and many small mucocele
A mucocele is a distension of a hollow organ or cavity because of mucus buildup.
By location
Oral
Oral mucocele is the most common benign lesion of the salivary glands generally conceded to be of traumatic origin. It is characterized by the pool ...
s. Salivary gland tumour
Salivary gland tumours, also known as mucous gland adenomas or neoplasms, are tumours that form in the tissues of salivary glands. The salivary glands are classified as major or minor. The major salivary glands consist of the parotid, submandibul ...
s may occur, including mucoepidermoid carcinoma, a malignant growth.
Clinical tests/investigations
A sialogram
Sialography (also termed radiosialography) is the radiographic examination of the salivary glands. It usually involves the injection of a small amount of contrast medium into the salivary duct of a single gland, followed by routine X-ray projection ...
is a radiocontrast study of a salivary duct that may be used to investigate its function and for diagnosing Sjögren syndrome
Sjögren syndrome or Sjögren's syndrome (SjS, SS) is a Chronic disease, long-term autoimmune disease that affects the body's moisture-producing (lacrimal and salivary) glands, and often seriously affects other organ systems, such as the lungs, k ...
.
Other animals
The salivary glands of some species are modified to produce proteins; salivary amylase is found in many bird and mammal species (including humans, as noted above). Furthermore, the venom
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
glands of venomous snake
Venomous snakes are Species (biology), species of the Suborder (biology), suborder Snake, Serpentes that are capable of producing Snake venom, venom, which they use for killing prey, for defense, and to assist with digestion of their prey. The v ...
s, Gila monsters, and some shrew
Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to different fa ...
s, are actually modified salivary glands. In other organisms such as insects, salivary glands are often used to produce biologically important proteins such as silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the coc ...
or glues, whilst fly
Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwing ...
salivary glands contain polytene chromosomes that have been useful in genetic research.
See also
*Serous demilune
Serous demilunes, also known as Crescents of Giannuzzi or Demilunes of Heidenhain, are cellular formations in the shape of a half-moon (hence the name "demilune") on some salivary glands.
Serous demilunes are the serous cells at the distal end of ...
*Sialome In biochemistry, the term sialome may refer to two distinct concepts:
* The set of mRNA and proteins expressed in the salivary glands, especially of mosquitoes, ticks, and other blood-sucking arthropods.
* The total complement of sialic acid types ...
References
External links
Salivary gland at the Human Protein Atlas
Illustration at merck.com
Illustration at .washington.edu
*
Medical Encyclopedia Medline Plus: Salivary gland
{{Authority control
Glands of mouth
Exocrine system
Saliva
Arthropod glands