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Digestive system and renal biology > Saliva and gastric secretions > Flashcards

Saliva and gastric secretions Flashcards

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1
Q

What are the functions of saliva ?

A
  • digestion
  • protection
  • lubrication
  • antibacterial roles
  • blood clotting
  • calcification of teeth
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2
Q

Describe how saliva carries out digestion

A
  • amylase cleaves the 1,4-glycosidic bonds
  • lingual lipase hydrolyses lipids
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3
Q

Describe how saliva carries out protection

A
  • it prevents drying of the oral cavity (drying causes weakening of the oral tissue)
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4
Q

Describe how saliva carries out lubrication

A
  • its involved in the swallowing of bolus
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5
Q

Describe how saliva has antibacterial roles

A
  • lactoferrin chelates iron as a lot of bacteria require iron to survive
  • lysozymes are involved in the degradation of bacterial cell walls
  • it contains immunoglobulins
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6
Q

Describe how saliva carries out blood clotting

A
  • prevents gum disease
  • promotes wound healing
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7
Q

Describe how saliva calcifies the teeth

A
  • acids from food decalcify the teeth and so calcium phosphates and phosphoproteins buffer these acids
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8
Q

What are the major salivary glands ?

A
  • parotid glands
  • submaxillary glands
  • sublingual glands
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9
Q

Describe the secretion of the parotid gland

A
  • secretes 25% of saliva
  • serous and watery secretion
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10
Q

Describe the secretion of the submaxillary gland

A
  • secretes 70% of saliva
  • serous and mucous secretion
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11
Q

Describe the secretion of the sublingual gland

A
  • predominantly mucous secretion
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12
Q

Give some examples of conditions associated with producing less saliva

A
  • xerostomia
  • Sjogren’s syndrome
  • hyperaldosteronism
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13
Q

Describe xerostomia

A
  • significant reduction or absence of saliva
  • leads to a decrease in chewing, swallowing and digesting
  • caused by some medications, congenital diseases and cranial nerve damage
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14
Q

Describe Sjogren’s syndrome

A
  • autoimmune inflammatory disease
  • blocked ducts causes atrophy of glands
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15
Q

Describe hyperaldosteronism

A
  • can be primary or secondary
  • increase in aldosterone secretion
  • causes include hypertension and hypokalaemia
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16
Q

What is hypokalaemia ?

A
  • low potassium in the blood
  • impacts the sodium content of the saliva
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17
Q

What are the 2 types of saliva secretion ?

A
  • basal secretion : happening continuously
  • stimulated secretion : increase in secretion upon stimulation of the salivary glands
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18
Q

What is the rate of saliva secretion ?

A

0.5 - 7 ml/min

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19
Q

How is saliva secreted ?

A
  • regulation of salivary secretion is controlled by the autonomic nervous system
  • sensory receptors relay information to salivatory nuclei in the medulla
20
Q

What is the effect of parasympathetic stimulation on the secretion of saliva ?

A
  • promotes watery saliva
  • rich in amylase and mucins
21
Q

What is the effect of sympathetic stimulation on the secretion of saliva ?

A
  • has a variable effect
  • can increase or inhibit secretion of saliva
22
Q

Describe the formation of saliva

A

1) parasympathetic stimulation will bring in chloride ions into the acinar cells through a cotransporter protein
2) sodium ions and potassium ions will also move into the cells via the cotransporter
3) chloride ions are pumped out of the cell into the acinus region and this makes the acinus region have a slightly negative potential
4) this negative potential drives the movement of water and sodium ions into the acinus region through paracellular channels
5) sodium ions are pumped out of the acinar cells in exchange for potassium ions so sodium ions can move paracellularly
6) potassium ions are pumped out of the acinar cells so they can come in with chloride ions or in exchange for sodium ions

23
Q

What is meant by paracellular movement ?

A

movement between cells

24
Q

Describe the how saliva is modified

A
  • the ducts are relatively impermeable to water and this allows saliva to change from isotonic to hypotonic
  • the removal of chloride ions and sodium ions will change the saliva from isotonic to hypotonic
25
Q

How does the flow rate of saliva from the acinus region to the duct affect affect the modification of saliva ?

A
  • a fast flow rate will mean there is less time for the removal of sodium and chloride ions and so the saliva at the duct will be more isotonic and less modification has occurred
  • a slow flow rate will mean more modification can be done
26
Q

What are the receptors found on the basolateral membrane of the acinar cells ?

A
  • muscarinic cholinergic receptors : bind acetylcholine
  • α adrenergic receptors : bind noradrenaline
  • substance P receptors : bind substance P
27
Q

What is the effect of the receptors on the acinar cells ?

A
  • receptors result in an influx of calcium ions into the acinar cells
  • this will increase the the internal calcium ion concentration
  • this results in exocytosis of amylase into the saliva
28
Q

Describe the ion composition of isotonic saliva

A
  • very similar composition to plasma in terms of sodium ion and chloride ion concentration
29
Q

Describe the ion composition of hypotonic saliva

A
  • low concentration of sodium ions and chloride ions
30
Q

What are the different regions of the stomach ?

A
  • Cardia region
  • Fundus
  • Body or Corpus
  • Antrum
  • Pylorus
31
Q

What is the function of the pylorus ?

A

regulates the food exiting the stomach and entering the small intestine

32
Q

Describe the structure of the antrum

A

it is more muscular than any other region - has a much thicker smooth muscle

33
Q

What are the different gastric glands ?

A
  • cardiac glands
  • oxyntic glands
  • pyloric glands
34
Q

Describe the structure and function of the rugae

A
  • folds
  • allow the stomach to take in food contents without increasing the pressure
35
Q

What do the cardiac glands secrete ?

A
  • mucus : eases friction
36
Q

What do the oxyntic glands secrete ?

A
  • mucus : lines the stomach cells to protect the stomach from chyme
  • HCl
  • pepsinogen : pepsin precursor
  • intrinsic factor : important in the absorption of vitamin B12
37
Q

What do the pyloric glands secrete ?

A
  • pepsinogen
38
Q

What are the different cells found in the gastric glands ?

A
  • mucous neck cells
  • parietal cells
  • chief cells
  • enteroendocrine cells or G cells
  • enterochromaffin cells or mast cells or H cells
39
Q

What is the function of the mucus neck cells ?

A

they empty mucus into the stomach lumen

40
Q

What is the function of the parietal cells ?

A

secrete HCl when needed and intrinsic factor

41
Q

What is the function of the chief cells ?

A
  • secrete pepsinogen
  • make up 25% of all gastric cells
42
Q

What is the function of the G cells ?

A

they produce gastrin

43
Q

What is the function of the H cells ?

A

produce histamine

44
Q

Describe the structure of parietal cells in the resting state

A
  • acid secretion is low
  • tubulovesicles are present in the cell and they contain H+ pumps
  • tubulovesicles are relatively impermeable to potassium ions which prevents the H+ pump from being activated
45
Q

Describe the structure of parietal cells in the active state

A
  • tubulovesicles fuse with canaliculus which increases the surface area
  • H+ pumps and chloride ions and potassium ions are inserted into the canalicular membrane
  • this increases acid secretion
46
Q

Why do parietal cells have lots of mitochondria ?

A

Secreting HCl requires lots of energy

Digestive system and renal biology (6 decks)

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