Salivary glands Flashcards
What type of structures are salivary glands?
They are compound, tubulo-acinar structures
What are the primary functional units of the salivary glands?
They are a combination of tubules and globe-like secretory units called acini
What does the term compound refer to in salivary glands?
Refers to the fact that a salivary gland is made up of multiple secretory units with their tubules entering a main duct
What does the duct system do?
Modifies and transports the saliva to be finally secreted on to a free oral mucosal surface
Why are salivary glands describes as exocrine?
As they secrete on to a free oral mucosal surface
What does exocrine mean?
Glands which secrete their products through ducts opening on to an epithelium rather than directly into the blood.
What are the two ways glands can be classified
Size
Secretion
How are glands classified by size?
Classification according to size divides the glands into 2 groups:
- Large discrete ‘major’ glands
- Small, less discrete ‘minor’ glands found throughout the oral mucosa
What are the 3 major glands?
- Parotid
- Submandibular
- Sublingual
Where are the minor glands found?
- Contained within the mucosa of the lip
- Cheek
- Hard and soft palate
- Tongue
How are glands classified by secretion?
Classification by types of secretion splits the glands into 3 types
- Glands producing a watery secretion are termed SEROUS
- Glands producing a more viscous secretion are termed MUCOUS
- Mixed glands produce a mixture of both (not necessarily in equal amounts)
What type of secretion is exhibited by the minor glands?
Mucosa of lips, cheeks, hard and soft palate are all mucous producing glands
Only the dorsum of the tongue beneath the circumvallate papillae (the glands of Von Ebner) are minor serous producing glands
What type of secretion is exhibited by the Parotid gland?
100% Serous
What type of secretion is exhibited by the submandibular gland?
Mixed
Ratio of serous to mucous is 10:1
What type of secretion is exhibited by the sublingual gland?
Mixed
Ratio of serous to mucous is 1:10
Why are mucous cells more viscous?
As they have mucin rich product containing proteins linked to a greater amount of carbohydrate
What are the main components of saliva?
99%= water 1%= additional organic and inorganic compounds like proteins and enzymes
What are the 6 functions of saliva?
- Digestion: Produces salivary amylase to aid digestion of food
- Antibacterial properties to combat bacterial colonisation. Saliva has lysozyme, histatins and antibodies
- Minerals to help maintain integrity of the dental enamel. Minerals aiding remineralisation (Ca and P) and buffering (HCO3)
- Important in Lubrication and protection, of the oral mucosa via the production of mucin, bolus formation, swallowing and speech
- Taste: solubilisation of food substances for transport to taste buds
- Hormone production: growth factors important in wound healing
Under what system is the control of salivary secretion under?
Autonomic nervous system
What do both parasympathetic and sympathetic fibres innervate?
The acini
What does innervate mean?
Supply a body part with nerves
The parasympathetic and sympathetic fibres collaterally work to do what?
Produce saliva during feeding
Afferent situation occurs when and does what?
Occurs during mastication at mealtimes
Leads to reflex stimulation of salivary flow involving salivary centres
Which gland is the only exception in regards to saliva secretion?
The minor glands mucous secretion is entirely mediated by parasympathetic nerve impulses
Which of the three major glands is the biggest?
The parotid gland
Give 7 features of the parotid gland
- It’s the largest of the 3 major glands
- Serous secretion
- Has intercalated ducts
- Striated ducts present
- Collecting ducts end in single main duct
- Non-spontaneous secretor
- Saliva is hypotonic
Give 7 features of the submandibular gland gland
- It’s smaller than the parotid but bigger than the sublingual
- Produces mixed secretion (10:1 ratio serous:mucous)
- Has intercalated ducts
- Striated ducts present
- Collecting ducts end in single main duct
- Non-spontaneous secretor
- Saliva is hypotonic
Give 7 features of the sublingual gland
- Is the smallest of the 3 major glands
- Produces mixed secretion (1:10 ratio serous:mucous)
- Few intercalated ducts
- No striated ducts
- Collecting ducts end in MANY main ducts
- Spontaneous secretor
- Saliva isotonic
Striated ducts are the site of what reaction?
Electrolyte resorption (especially of sodium and chloride ) And secretion of potassium and bicarbonate
Cells of the striated such are what?
Highly polarised
What is the striated ducts basal lamina adjacent to and what does it show?
Adjacent to the basal lamina separating it from the adjacent connective tissue
What does the basal lamina separating it from the adjacent connective tissue show and why?
Shows numerous striations under the light microscope due to the multiple infoldings of the plasma membrane
Resorption of salt is undertaken by which cells?
Striated duct cells
What type of environment to acinar cells generate and what does this enable?
Initially they generate an environment that is hypertonic with respect to the adjacent blood capillarities and interstitial fluid
This enables the movement of water INTO the lumina
Where is the isotonic saliva generates and how is it rendered hypotonic?
Generated by the acinar lumen
Rendered hypotonic by the removal of sodium, chloride and bicarbonate
How are sodium, chloride and bicarbonate removed from saliva?
They pass through the striated ducts
What are the minor salivary glands classified by?
Their anatomical location in the submucosa
Name some of the anatomical locations in the submucosa that the minor salivary glands could be classified as
Buccal Labial Palatal Palatoglossal Lingual
What do minor salivary glands have?
Collecting ducts
What do minor salivary glands lack?
Striated and intercalated
Where are the glands of Von Ebner found?
They are seen on the dorsal surface of the tongue through a circumvallate papilla
What do circumvallate papilla have?
Numerous tasers buds on it lateral borders
Where are the only minor serous glands found and what are they called?
They are found embedded in the muscle below the papillae
They are called the glands of von ebner
What is the secretory element of the parotid and the serous part of the submandibular glands called?
Serous acinus
Describe the serous acinus
They are globe shaped structures made up of a number of conically shaped secreting cells
What do the serous acinus empty into?
Intercalated ducts
What are intercalated ducts?
They are smalls ducts that are lined with cuboidal epithelium
What do the cells of the serous acinus look like and why?
They appear granular because of the many secretory granules they contain
What do intercalated disks empty into?
Striated ducts
What are striated ducts?
They are larger ducts found in the secretory lobule
What are striated ducts made of?
They are formed by columnar cells
Why are striated ducts called this?
Because he membrane furthest away from the lumen is thrown into numerous fold with many mitochondria
Why are there many mitochondria in the folds of the striated ducts?
To allow for active exchange across the walls of the striated ducts
What does active exchange across the walls of the striated ducts result in?
The modification of saliva
Wha do striated ducts empty into?
Larger secretory ducts
How can you distinguish between serous and mucous acini cells?
Via the morphology of their secretory granules.
What is the morphology of serous acini cells?
They have a characteristic dark granular appearance with routine haematoxylin and eosin staining
What is the morphology of mucous acini cells?
They give a paler colour as the mucin content does not readily taken up routine stain
What is the basal part of each serous cell separated by?
Surrounding connective tissue by a basal lamina
What does the luminal part of the cell contain?
Dense, round secretory granules
This contains the packaged proteinaceous components for release into the luminal system by exocytosis
What is the secretory element of the sublingual gland and the mucous part of the submandibular glands called?
The mucus acini
What form do the mucous acini take?
They take the form of tubes rather than spheres
What do the mucous acini essentially form?
Their own duct system
Which gland has the most ducts and why
The parotid as their are no intercalated or striated ducts in the mucus areas of glands
The parotid is 100% serous
What is a frequent feature of mucous acini?
The presence of a ‘cap’ of serous secreting cells called a SEROUS DEMILUNE
What are acini?
Globe like secretory units
Describe the parotid gland
Is a major 100% serous producing gland
Describe the submandibular gland
Is a major gland
Produces both serous and mucous in the ratio 10:1
If you stained some acini cells and it gave a paler colour what type of acini cells would they be?
Mucous acini
The acini is innervated by what?
Both the parasympathetic and sympathetic fibres
Describe the sublingual gland
Is a major gland
Produces both serous and mucous in the ratio 1:10
Saliva produced by the acinar lumen is described as what?
Isotonic
If you stained some acini cells and it gave a dark granular appearance what type of acini cells would they be?
Serous acini
Which glands produce mucous secretion?
Mucosa of lips, cheeks, hard and soft palate are all mucous producing glands
Which of the three major glands is the smallest?
The sublingual gland
What makes the glands of Von Ebner special?
They are the only minor serous glands
What are the serous acinus?
The secretory element of the parotid and the serous part of the submandibular glands
“Globe shaped structures made up of a number of conically shaped secreting cells” What is this describing?
The serous acinus
What causes the modification of saliva?
Active exchange across the walls of the striated ducts
What is the routine staining we use to determine morphology of acini cells?
Routine haematoxylin and eosin staining
Surrounding connective tissue by a basal lamina separates what from each other?
Basal part of each serous cells
What are the mucous acini?
The secretory element of the sublingual gland and the mucous part of the submandibular glands
Acini that take the form of tubes not spheres are called what?
Mucous acini
What is the serous Demilune?
A ‘cap’ of serous secreting cells