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GI Lectures > Salivary glands: anatomy and function > Flashcards

Salivary glands: anatomy and function Flashcards

1
Q

What are the functions of saliva?

A
  • Lubricant for mastication, swallowing and speech
  • Oral hygiene: wash, immunity, buffer
  • Digestive enzyme: aqueous solvent necessary for taste
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2
Q

How does saliva maintain the pH?

A

Oral pH needs to be maintained at about 7.2 pH
- bicarbonate/ carbonate buffer system for rapid neutralisation of acids

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3
Q

What is the flow rate and daily secretion of saliva?

A
  • Flow rate: 0.3 to 7ml/minute
  • Daily secretion of 800-1500ml in adults from major and minor glands
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4
Q

What is the pH range for saliva?

A

6.2 to 7.4

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5
Q

What are the two types of secretion for saliva?

A
  • Serous secretion: alpha amylase, helps with starch digestion
  • Mucus secretion: mucins for lubrication of mucosal surfaces
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6
Q

Is the parotid gland serous or mucus?

A

Serous

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7
Q

Is the submandibular and sublingual serous or mucus?

A

Both

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8
Q

Is the minor glands serous or mucus?

A

Mainly mucous

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9
Q

What are some factors that affect composition and the amount of saliva produced?

A
  • Flow rate
  • Circadian rhythm
  • Type and size of gland
  • Duration and type of stimulus
  • Diet
  • Drugs
  • Age
  • Gender
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10
Q

What is inside saliva?

A

Secretion of proteins (help with defensive and digestive functions) and glycoproteins in a buffered electrolyte solution

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11
Q

What ions help with the remineralisation of saliva?

A

Ca^2+, PO4^3-

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12
Q

What are the three defence mechanisms?

A
  • The oral mucosa (physical barrier)
  • Palatine tonsils
  • Salivary glands
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13
Q

How does the palatine tonsils act as a defence mechanism?

A
  • Lymphocyte subsets and dendritic cells
    Help with immune surveillance and resistance to infection
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14
Q

How does the salivary glands act as a defence mechanism?

A

Saliva washes away food particles, bacteria or viruses
Used for metabolic support

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15
Q

How does saliva help with immunity?

A

Salivary glands are surrounded by lymphatic system
– linked to thoracic duct and blood

Broad range of functional immune cells

Oral mucosa and glands have high blood flow rate

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16
Q

What is the parotid gland?

A

When stimulated, this is where the main source of saliva comes from. Secretes serous saliva

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17
Q

What is the difference between stimulated and unstimulated saliva?

A

Unstimulated saliva is dominated by SMG (submandibular) components

Stimulated has composition resembling parotid secretion

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18
Q

What are the two epithelial tissue that compose the salivary glands?

A
  • acinar cells
  • ducts: collect to form large duct entering mouth
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19
Q

How are the salivary glands equipped?

A

With channels and transporters in the apical and basolateral membranes enabling transport of fluid and electrolytes

20
Q

What are the two types of acini?

A

Acini - any of the smallest lobules of a compound gland
Serous acini and mucous acinus

21
Q

What are some features of serous acini?

A
  • Dark staining
  • Nucleus in basal third
  • Small central duct
  • Secrete water + α amylase
22
Q

What are some features of mucous acini?

A
  • Pale staining : ‘foamy’
  • Nucleus at base
  • Large central duct
  • Secrete mucous (water + glycoproteins)
23
Q

What is on the outside of acinus cells?

A

Myoepithelial cells which are squeezing the cell to get the saliva out

24
Q

What are the two types of cells that line the intralobular duct of the acini cells?

A
  • Intercalated: short narrow duct segments with cuboidal cells that connect acini to larger striated ducts
  • Striated ducts: striated like a thick lawn. major site for reabsorption of NaCl
25
Q

What are some features of striated ducts?

A
  • appear striated at basal end
  • basal membrane highly folded into microvilli for active transport of HCO3 against concentration gradient
  • microvilli filled with mitochondria for energy to facilitate active transport
26
Q

How does the movement of substances change in the ducts?

A

No movement of water just isotonic plasma-like fluid secreted by acini (primary saliva)

27
Q

What do the ducts secrete and reabsorb?

A

Secrete: K+ and HCO3-
Reabsorb: Na+ and Cl-

28
Q

What are the two routes of secretion?

A
  • Regulated (leading to saliva across apical membrane)
  • Constitutive (leading towards interstitium and bloodstream
29
Q

What are the three pairs of major salivary glands?

A
  • Parotid
  • Submandibular
  • Sublingual
    Contributes to 80% of salivary flow
30
Q

What are the glands responsible for 20% of salivary flow?

A

Minor salivary glands
- submucosa of oral mucosa - lips, cheeks, hard and soft palate, tongue

31
Q

Where are the parotid glands and parotid duct located?

A
  • Superficial triangular outline between:
  • Zygomatic arch (temple area)
  • Sternocleidomastoid (muscle behind ear to side of neck)
  • Ramus of mandible and masseter and med pterygoid (muscle on side of cheeck above jaw)
    (look at photo)
32
Q

What structures pass through the parotid gland?

A
  • External carotid artery + terminal branches
  • Retromandibular vein
  • Facial nerve + branches to muscles of facial expression
  • Parotid capsule (very tough)
33
Q

What is the anatomical structure of the submandibular gland?

A

Two lobes separated by mylohyoid muscle:
- larger superficial lobe
- smaller deep lobe in flood of mouth

34
Q

Where is the submandibular duct?

A
  • Also called Wharton’s duct
  • Begins in superficial lobe
  • wraps round free posterior border of mylohyoid
  • runs alone floor of mouth
  • empties into oral cavity at sublingual papillae
35
Q

Where is the opening of the ducts at the sublingual papillae?

A

Lingual frenum (lift tongue up to roof of mouth and bit in the centre that attaches it to floor of mouth)

36
Q

Where are the sublingual glands?

A

between the mylohyoid muscle and oral mucosa of the floor of the mouth
- This gland is variable in size with mixed acini (mainly mucous)

37
Q

Where are the minor salivary glands found in concentrated areas?

A
  • Buccal labial
  • Palatal
  • Lingual regions
  • Superior pole of tonsils
  • tonsillar pillars
  • base of the tongue
38
Q

Are minor salivary glands mucous or serous

A
  • all are mucous except serous glands of von Ebner
  • they lack a branching network of draining ducts: each salivary unit has its own simple duct
39
Q

What effect does sympathetic and parasympathetic stimulation have?

A

Stimulation of parasympathetic nerves causes the production of a copious flow of saliva while sympathetic stimulation selectively causes secretion of protein and glycoprotein

40
Q

What are the symptoms and causes of salivary gland disease and dysfunction?

A
  • obstructive
  • inflammatory
  • degenerative
  • drug side effects
  • cancer
41
Q

What is Xerostomia?

A

Dry mouth
- may be a consequence of cystic fibrosis or Sjogrens syndrome

42
Q

What are the causes of Xerostomia?

A

Medication and irradiation for head and neck cancers

43
Q

What are salivary calculi?

A

Saliva contains calcium and phosphate ions that can form these salivary calculi (Stones)
- most often in the submandibular gland
- they block the duct at the bend round the mylohyoid or at exit at sublingual papillae

44
Q

What can be some inflammatory effects?

A
  • Infection secondary to blockage
  • Mumps (viral infection):
    fever, swelling of glands, pain over parotid
45
Q

Why can salivary glands become degenerative?

A
  • complication of radiotherapy to head and neck for cancer treatment
46
Q

What are some drug side effects on salivary glands?

A

500 prescription drugs have sympatheticommetic effect:
- act on NA (nicotinic acetylcholine) receptors or inhibit parasympathetic action at ACh receptors

47
Q

What are the effects of salivary gland dysfunction?

A
  • If output falls to <50%, patient will have a dry mouth
  • Low lubrication, oral function difficult
  • Low oral hygiene (accumulation of plaque)
  • Infections (thrush)

GI Lectures (14 decks)

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