Sammanfattning av saliv

**Sammanfattning av saliv – TP1MH1**

**Delkurs 1020 – Mikrobiologi, immunologi etc.**

**Oral Anatomy, Histology and Embryology, 4th edition**

**Berkovitz et al. , s. 260-272**

**ISBN: 9780723435518**

**Saliven – en nödvändighet för tandhälsan, Tandläkartidningen, nr 3, 1997**

**Lagerlöf et al.**

**Enligt gällande kursplan VT-13!**

**SALIVARY GLANDS**

* Compound – more than one tubule entering the main duct.
* Tubuloacinar – morphology of the secreting cells.
* Merocrine – only the secretion of the cell is released.
* Exocrine – secretes fluid on to a free surface.
* Secretion of saliva is a reflex function, dependent on afferent stimulation (such as taste).
* 99% water. Production of mucin. Lubricant during swallowing and speech.
* Protects mucosa, keeps it moist.
* Limits activity of bacteria by causing their aggregation.
* Contains minerals – acts as a buffer.
* Peptide growth factor produced by submandibular gland – involved in wound healing?
* Immunoglobulin (IgA) - widespread mucosal immune system.
* Amylase – aids digestion.
* Two main elements:
	+ o Glandular secretory tissue – parenchyma.
	+ o Supporting connective tissue – stroma.
	+ o
	+ o
	Septa subdivide the gland into major lobes.
	+ o Lobes are divided into lobules.
		- § Each lobe contains grape-like structures – acini.
* Acinus is serous, mucous or mixed.
* Serous = more protein & less carbohydrate than mucous cells.
* Secretion of saliva is under control of the ANS.
* Acini of parenchyma responsible for primary secretion.
* Major salivary glands: parotid, submandibular, sublingual.
* Minor salivary glands: labial, buccal, palatoglossal, palatal, lingual.
* Main regulated pathway – cells store and secrete protein by use of stored granule exocytosis.
	+ o Upon receipt of a neuronal signal.
	+ Second pathway – continuously by a vesicular mechanism.
		- o Constitutive pathway – some proteins may be secreted as they are synthesized.
		- **SALIVARY GLYCOPROTEINS AND CALCIUM**
			* o Salivary glands contain a mixture of neutral to acidic glycoproteins.
			* o Serous cells in parotid gland contain neutral glycoproteins.
			* o Mucous cells in submandibular, sublingual and minor glands contain acidic glycoproteins.
			* o Serous cells in submandibular gland contain a mixture of neutral & acidic.
			* o Intercalated duct cells often contain a mixture aswell.
			* o Striated duct cells often contain neutral glycoproteins.
			* o Ca2+ is incorporated in the secretory granule to neutralize the negatively charged parts of the glycoprotein.
				+ § Prevents the glycoproteins from repelling each other.
				+ § The more acidic glycoprotein à the more calcium is needed.

**PAROTID GLAND**

* Largest of the salivary glands.
* Serous saliva.
* Granular appearance. Connective tissue contains blood vessels, nerves and collecting ducts.
* Lumina of the acini are very narrow.
* Intercalated ducts pass from acini and open into well represented striated ducts.
* Ultrastructural appearance: cells have a wege-shaped outline.

* Basal part delineated from surrounding connective tissue by a basal lamina.
* Luminal part – dense, round secretory granules.
* Narrow canaliculi run between the cells and join the lumen.
* Adjacent cell membranes contact at desmosomes, gap junctions and tight junctions.
* Secretory granules move towards luminal plasma membrane à become more electron-dense as protein content is concentrated.
* Mitochondria provide energy for secretion of granules.
* Following synthesis, resting (unstimulated) serous cells contain numerous secretory granules in cytoplasm.
* Stimulated serous cells contain less secretory granules in cytoplasm. Discharged into the acinus lumini by exocytos.
* Parasympathetic and sympathetic fibers act collaboratively in production of saliva during feeding.
* Main neurotransmitter for:
	+ o Parasympathetic nerves – acetylcholine.
	+ o Sympathetic nerves – noradrenalin.
* Each axon also contains arrays of neuropeptides.
* Parasympathetic drive causes: formation and secretion of secretory granules.
* Sympathetic drive causes: increases the output of preformed components from the cells.
* Both pathways cause contraction of myoepithelial cells à helps direct fluid from acinar lumen out along the duct system.

* Hypertonic = högre salthalt än serum.
* Isotonic = samma salthalt som serum.
* Hypotonic = mindre salthalt än serum.
* Salivary glands secrete salt –Na and Cl - into the acinar lumina.
	+ o Hypertonic environment is created.
* Channels in apical acinar cell membrane (toppen) are opened by signals from autonomic nerves .
	+ o Acetylcholine from parasympathetic nerves!
* Cl streams into the acinar lumen.
* Na moves into the acinar lumen to “utjämna” the difference.
* Leads to movement of water into the lumen through aquaporin water channels!
* Isotonic saliva in acina lumen is rendered hypotonic by removal of Na, Cl when passing through striated ducts.
* Isoton saliv i acini – vid passage genom utförselgångarna reabsorberas ffa Na och Cl, vilket innebär att saliven är hypoton vid utsöndring.
	+ § Ju snabbare flöde, desto mindre reabsorption.
* **DUCT SYSTEM**
* Intercalated duct – the smallest.
	+ o Cubiodal epithelial tube.
	+ o Smooth on both luminal and basal surfaces.
	+ o Adjacent cells united with desomosomes.
	+ o Contribute to primary secretion.
	+ o Several acini drain into each intercalated duct.
* Striated ducts – much longer and more active component in duct system than intercalated.
	+ o Luminal surface have short microvilli.
	+ o Basal (abluminal) surface have multiple striations – infoldings of the plasma membrane at the base of the cell.
		- § Mitochondria are packed between the infoldings.
		- § Adjacent cells anchored together by desmosomes.
		- o The created large surface is involved in active transport.
		- o Striations the site of electrolyte resorption (Na, Cl) and secretion (K) without loss of water.
		- o Resorption is against a concentration gradient à requires energy.
		- o Convert an isotonic or hypertonic fluid into a hypotonic fluid!
		- o Cells exhibit small secretory granules that may contain epidermal growthfactor, lysosome, IgA.
* Collecting duct – main function is to transport saliva.
	+ o Compared to intercalated & striated ducts which also modify the composition of the saliva.
* **MYOEPITHELIAL CELLS**
	+ o Around acini – dendritic cells. Outline of acinus remains smooth.
	+ o Around intercalated ducts – elongated. Outline produces a bulge.
	+ o Flattened nucleus, numerous contractile actin microfilaments.
	+ o Expresses CD44 when in contact with serous acinar cells.
		- § Therefore, may play a role in cell proliferation and differentiation.
		- o Myoepithelial activity can:
			* § Support the underlying parenchyma (secretory part) and reduce back-permeation of fluid.
			* § Accelerate the initial outflow of saliva.
			* § Reduce luminal volume (kontraktion?)
			* § Contribute to the secretory pressure.
			* § Milking effect on any underlying extracellular fluid.
* **BASAL CELLS**
	+ o Present in striated (less) and collecting ducts (more).
	+ o Potential stem cells.
* **Lymph nodes** are situated both on the surface and within the parotid gland.
	+ o Not found within the other salivary glands.

**SUBMANDIBULAR GLAND**

* Second largest of the salivary glands. Mixed mucous/serous secretion.
* The serous cells, duct system, myoepithelial cells and basal cells are the same as in parotid gland.
* Shorter intercalated ducts, longer striated ducts.
* **MUCOUS CELLS**
	+ o In the early stages of synthesis of its secretory products, much RER is present.
	+ o Have a more conspicuous Golgi apparatus compared to serous cells.
		- § Because of the greater amount of carbohydrate that is added to the secretory protein.
	+ o More pale secretory granules than serous cells.
	+ o Fewer microvilli and infoldings than that of a serous cell.
	+ o When filled with secretory granules, the nucleus is compressed against the basal surface.

**SUBLINGUAL GLAND**

* Made up of a posterior part (greater sublingual gland) and an anterior part (lesser sublingual gland).
* 8-30 smaller salivary glands.
* Mixed gland, but mostly mucous elements.
* Serous cells in the gland might actually be immature mucous cells!
* Secrete spontaneously and continuously.
* **DUCT SYSTEM**
	+ o Much less developed compared to other major salivary glands.
	+ o Striated ducts are usually absent à saliva rich in K.

**MINOR SALIVARY GLANDS**

* Buccal, labial, palatal, palatoglossal, lingual. 450-750.
* Primarily mucous.
* Have collecting ducts. Intercalated and striated ducts are genereally asbent.
* Like sublingual gland, the duct system doesn’t remove as much salt, so the final saliva is isotonic and rich in K.
* Parasympathetic nerve impulses.
* Secrete spontaneously and continuously.

**Saliven – en nödvändighet för tandhälsan**

**SEKRETION OCH SAMMANSÄTTNING**

* Sekretion aktiveras av parasympatiska (vatten och elektrolyter) och sympatiska (proteiner) nervsystemen som svar på olika stimuli.
* Salivflödet påverkar koncentration av de flesta av salivens elektrolyter.
	+ o Klor, natrium och bikarbonat ökar med ökat flöde. Fosfat och magnesium minskar.
* Dygnsrytmen spelar roll för koncentrationer av olika elektrolyter.
* 0,6 - 1 l saliv per dygn.
* Vilosaliv påverkas av:
	+ o Dygnsrytmen – mindre under sömn. Mest på eftermiddagen.
	+ o Årstider – mindre på sommaren.
	+ o Kroppsställning – mindre i sittande, mer i liggande & stående.
	+ o Hälsotillstånd – Sjögrens syndrom minskar.
	+ o Farmaka - tex. antidepressiva med muntorrhet som biverkning.
	+ o Psykiska faktorer (ångest) påverkar flödet.
	+ o Kön, ålder, vikt etc. spelar mindre roll.
* Stimulerad saliv påverkas av:
	+ o Samma som ovan.
	+ o Även smakstimuli – sura smaken salivstimulerande.
	+ o Mekanisk stimulering – tuggning.

**SALIVENS FUNKTIONER**

* Mekaniskt skydd för tänder och slemhinnor.
	+ o Muciner (högmolekylära proteiner förenade med kolhydrater) smörjer.
	+ o Binder vatten – motverkar uttorkning av slemhinnorna.
* Antimikrobiella egenskaper
	+ o Lysozym – bryter enzymatiskt upp vissa bakteriers skyddande hölje.
	+ o Laktoferrin – binder järn och minskar därmed tillgång av denna viktiga jon för bakterier.
	+ o Salivperoxidas katalyserar reaktionen mellan väteperoxid och tiocyanat à bildar toxisk substans för bakterier, hypotiocyanat.
	+ o Sekretoriska immunoglobuliner klumpar ihop bakterier till stora aggregat à sköljs bort.
	+ o Fluorjonen binder magnesium och hindrar därmed bakteriers ämnesomsättning (enzymet enolas kräver magnesium för glykolysen).
* Reglering av munhålans pH-värde: 6,5-7,5.
	+ o Buffertsubstanser, såsom oorganiskt fosfat och bikarbonat, motverkar förändringar i pH.
	+ o Bikarbonat kan även tränga in i plack. Ju tjockare à ju svårare att verka i placket.
* De- och remineralisation av tandvävnad
	+ o Upprätter jämvikten mellan tandsubstansens kalciumfosfater (hydroxylapatit) och omgivande vätskefas.
	+ o Intag av syror & minskat pH (erosion) eller syraproduktion i bakteriebeläggningar (karies) minskar möjlighet för remineralisation.
	+ o Vid remineralisation kan hydroxylapatitet även fällas ut i saliv (spottsten) och i bakteriebeläggningar (tandsten).
		- § Saliven innehåller utfällningshämmande ämnen för att hindra spottsten.
	+ o Fluorjon bromsar demineralisation och accelererar remineralisation.
	+ o

**NEDDSATT SALIVKÖRTELFUNKTION**

* Kan orsaka kariesskador och skador på slemhinnor på lång sikt.
* Symtom:
	+ o Torr munslemhinna med matt yta – munspegel fastnar då man stryker den mot slemhinnan.
	+ o Torra, spruckna läppar med fissurer på insidan (keilit).
	+ o Rodnad, blank tunga som ofta är fissurerad och/eller loberad.
	+ o Svampinfektioner (candida).
	+ o Svårigheter att tala.
	+ o Muntorrhet.
* Salivflödesmätning.
	+ o **Vilosaliv:**
		- § Minst en timme utan intag av något slag.
		- § Vila 15 minuter före.
		- § Sitta i kuskställning, låt saliven passivt rinna över underläppen.
		- § Pågår i 15 minuter.
		- § Normalt viloflöde: 0,25-0,35 ml/min. Under 0,1 ml/min mycket lågt.
	+ o **Stimulerad saliv:**
		- § Kuskställning.
		- § Tugga på paraffinbit i 5 minuter. Töm saliv vid behov.
		- § Normalt flöde: 1-3 ml/min. Under 0,7 ml/min mycket lågt.
* Behandlingsalternativ för muntorrhet:
	+ o Stimulera salivsekretion mha tuggummi och tabletter.
	+ o Sköljlösning och saliversättningsmedel.
	+ o Munvårdsprodukter som tillför salivens egna antimikrobiella komponenter (lysozym, laktoferrin etc).

**KARIESFÖREBYGGANDE ÅTGÄRDER**

* Kariesutveckling kan bli ett problem på längre sikt.
* Plackkontroll – instruktioner för rengöring av alla tandytor. Extra tandborstning före/efter måltid.
* Kostråd – vätskerik och mild kost att föredra. Högst 4-5 måltider per dygn.
* Fluortillförsel – fluortandkräm. Fluorskölj. Tuggummi / sugtablett.