salivary glands - 4 TISSUE BIOLOGY Flashcards
name the three main types of glands
- parotid
- submandibular
- sublingual
Describe the parotid gland and how much saliva it produces
- largest
- roughly pyramidal
- major duct is stensen duct
- produces about 30% of saliva
Describe the submandibular gland and how much saliva it produces
- second largest
- main duct is Wharton duct
- produces 60% of saliva
Describe the sublingual gland and how much saliva it produces
- smallest major gland
- produces about 5% of saliva
Are the main three the only salivary glands?
no, there are several minor salivary glands - continuously secrete and are under local control
Major glands secrete in response to what?
parasympathetic activity, induced by physical, chemical and psychological stimuli
What is the daily saliva production in humans?
rages from 600 - 1500 mL
What is saliva and what molecules does it contain?
- hypotonic watery secretion
- contains:
- mucus
- enzymes (amylase, lipase, lysozyme)
- antibodies (lgA)
- inorganic ions
Is saliva composition always the same?
varies according to which gland is most active
What are the functions of saliva?
- lubrication
- buffering
- maintaining tooth integrity
- antibacterial function
- taste and digestion
Lubrication
- MG1 - heavy mol weight, high glycosylation
- MG2 - low mol weight, low glycosylation
buffering
- natural pH at rest,
- high pH after ingestion
- 15 min becomes acidic
Maintaining tooth integrity
- MG1 and MG2 bind to teeth
- remineralisation
Antibacterial function
- MG1 and MG2 prevent bacteria attaching the tooth enamel
- lysozyme, lgA
Taste and digestion
- activates taste buds
Explain the innervation of salivary glands
- either direct or indirect, sympathetically and parasympathetically
What does parasympathetic stimulation evoke?
lots of saliva
What does sympathetic stimulation evoke?
small flow (rich in protein) or no flow at all
What nerve carries parasympathetic intervention to the salivary glands?
cranial nerves
From what nerve does the parotid gland receive its parasympathetic input and via what ganglion?
- from glossopharyngeal nerve (CN IX)
- via otic ganglion
From what nerve does the submandibular and sublingual glands receive their parasympathetic input? and via which ganglion?
- facial nerve (CN VII)
- via submandibular ganglion
Direct sympathetic innervation of salivary glands takes place via which nerve?
preganglionic nerves
How is saliva secretion controlled? (1)
- during - blood glow to secretory acini is increased via parasympathetic stimulation, ultrafiltration from plasma (mostly serous fluid) enters acini
How is saliva secretion controlled? (2)
- filtrate from the cells enters the lumen of the acing cells, mixing with secreted mucus and alpha-amylase, creating primary secretion
How is saliva secretion controlled? (3)
- secretion modified as it passes through the ducts into the mouth
- lingual lipase (secreted form von Ebner glands of tongue) added to saliva in the mouth
Name the main two types of secretory cells
- serous cells
- mucous cells
What do serous cells look like?
- zymogen granules: enzyme containing and found apically
- nuclei basally located, rounded with dispersed chromatin
What do mucous cells look like?
- mucigen granules within these cells poorly stained
- uncle characteristically flattens against basement membrane
What is seen in mixed secretory units, where mucous cells predominate?
semilunar cap of serous cells - serous demilune
What does a salivary secretory unit consist of?
terminal branched tubule-acinar structure (serous or mucous or mix)
What surrounds the secretory units and for which reason?
myoepithelial cells - push saliva through
What do the terminal secretory units form when merged?
small intercalated ducts lined by secretory cells
What do the small intercalating ducts drain into?
striated ducts
What are the striations a result from?
the presence of interdigitations of the basal cytoplasmic processes of columnar lining cells
What do serous cells secrete?
fluid isotonic with plasma
What happens in the striated ducts?
ions are reabsorbed, secreted to produce hypotonic saliva containing less Na+/Cl- and more K+/HCO3^- than plasma
What do mitochondria provide?
- pack basal processes
- provide energy for ion transport
What does the general architecture of the major salivary glands follow?
pattern of the parotid gland
What is the glad divided into?
numerous lobules, each containing many secretory units
What radiates between the lobules?
- connective tissue septa
- form an outer capsule
What do septa do?
carry blood vessels, nerves, large excretory ducts
What does the parotid gland mainly consist of?
sears secretary until which are darkly stained in H&E
What are zymogen granules?
- strongly stained cytoplasmic granules containing proteins
- contained in serous cells
What do the nuclei of serous cells look like?
- rounded, with dispersed chromatin
- usually occupy a more central position within the cell
What are started ducts?
- lined by tall columnar cells, with large nuclei located towards the apex of the cell
- basal cytoplasm appears started, due to basal interdigitations of adjacent cells and columns of mitochondria
- extend the area of membrane available for exchange of water/ ions
- duct epithelium also secretes lysozyme + immunoglobulin (lg)A
Salivary glandular ductal system
- mucous cells surrounded by serous demilune then mayo-epithelial cells on outside
- ducts: lumen of acinus -> intercalated ducts -> striated ducts -> excretory ducts
What are myoepithelial cells?
- surround acini, force the secretions form acing lumen into duct system
- located between base plasma cell membranes of secretory cells and basement membrane
- flattened cell with long cell processes which extend around acinus
What else is occasionally seen in a secretory system?
adipocytes (fatcells) - proportion grows as individual age
Where are excretory ducts found?
in fibrous septa alongside arteries and veins (is more long, oval than artery)
Describe the composition of the parotid gland
- mainly consists of serous cells
- thin watery secretion rich in enzymes and antibodies
- large striated ducts to convert saliva to hypotonic solution
Describe the secretion from the parotid gland
- secretion produced by parotid glands serous in nature
- enters oral cavity through stensen’s duct after passing through intercalated ducts which are prominent in gland
- largest pair - only 25% of saliva produced
Describe the submandibular gland
- consists of picture of serous and mucous cells, often found as mic seromucous secretory units
- serous demilunes seen
How heavy is the submandibular gland pair?
15 g
Describe the secretion of submandibular glands
- seers cells most active, produce salivary amylase, which aids in breakdown of starches in mouth
- mucous cells secrete mucin: aids in lubrication of food bolus as it travels through the oesophagus
Describe the secretion of sublingual glands
- mainly mucous -> viscid secretion
- unlike other mayor glands, does not have striated ducts,
- exit form 8-20 excretory ducts
- provides approx 5% of saliva in oral cavity
