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Module 104 - Nutrition, metabolism & excretion > T1 L5 Saliva & gastric secretions > Flashcards

T1 L5 Saliva & gastric secretions Flashcards

1
Q

What are the functions of saliva?

A

Lubrication
Protection
Digestion - begins breakdown of carbohydrates & fats via a-amylase & lingual lipase

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2
Q

What is the function of lubrication?

A

Moistens mouth to lubricate food, which aids in swallowing
Facilitates movement of mouth & tongue for speech
Helps dissolve chemicals within food for presentation to taste receptors

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3
Q

What is the reason for saliva having a protection function?

A

Reduces adverse effects of oral bacteria
Alkalinity of fresh saliva neutralises acid produced by oral bacteria
Flow of saliva across teeth helps wash away bacteria
Contains additional substances that reduce bacterial growth

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4
Q

What are the first enzymes that begin the breakdown of carbohydrates & fats?

A

Alpha- amylase

Lingual lipase

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5
Q

What is Sjogren’s syndrome?

A

An autoimmune disease that destroys exocrine glands
Commonly affects tear & saliva production
Hallmark manifestations are dry eyes & mouth

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6
Q

What causes Xerostomia?

A

A lack of adequate saliva
Typically have dental caries & halitosis due to bacterial overgrowth
Difficult speaking or swallowing solid food due to inadequate lubrication

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7
Q

What type of protein is in serous secretions?

A

Ptyalin - hydrolyses starch

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8
Q

What type of protein is in mucous secretions?

A

Mucin - acts as lubricant

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9
Q

What are the 3 major salivary glands?

A

Submandibular glands
Parotid glands
Sublingual glands

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10
Q

What factors stimulate salivation?

A

Thought, smell or taste of food by conditioned reflexes & by nausea

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11
Q

What factors inhibit salivation

A

Sleep
Dehydration
Fatigue
Fear

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12
Q

How do efferent nerves reach the salivary glands?

A

Via glossopharyngeal & facial nerves

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13
Q

What type of receptors does acetylcholine act on?

A

Muscarinic receptors

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14
Q

What is the composition of gastric juice?

A 
Water & electrolytes
HCl
Pepsins
Mucus
Intrinsic factor
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15
Q

What is the function of HCl in gastric juice?

A

Hydrolsis of fat & starch
Antiseptic kills contaminating microorganisms
Converts pepsinogens to pepsin

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16
Q

What is the function of pepsins in gastric juice?

A

Endopeptidases cleave peptide bonds for protein digestion

They are secreted as inactive pepsinogens & activated to form pepsins at a low pH

17
Q

What is the function of mucus in gastric juice?

A

Water & mucin glycoprotein
Bicarbonate barrier
Protect surface epithelial cells from acid / pepsin erosion

18
Q

What is the function of intrinsic factor in gastric juice?

A

Glycoprotein binds vitamin B12 for absorption in the ileum

19
Q

What are the 2 major regions in the stomach?

A

Exocrine or glandular part consisting of funds & body or acid-secreting area
Endocrine or hormone secreting area portion located in the Antrum or gastric secreting area

20
Q

What types of cells are found in the gastric mucosa?

A 
Mucous cells
Endocrine cells - D cells
Chief cells
Exocrine region
Endocrine region
21
Q

What is the function of endocrine D cells?

A

Secrete somatostatin which is a regulator of gastric release & gastric acid secretion

22
Q

What is the function of chief cells?

A

Secrete pepsinogen which is converted by gastric acid to active form pepsin

23
Q

What is the mechanism of gastric acid secretion by oxyntic cells?

A

H+ & HCO3- are generated inside the cells by carbonic anhydrase
H+ is pumped across luminal membrane
Cl-/HCO3- exchanger in basolateral membrane provides Cl- ions for HCl & HCO3-

24
Q

How do gastric secretions protect against self digestion?

A

Lumen has a pH of below 2.0
Mucous layer of mucopolysaccharides & mucoproteins
Mucous viscosity generates mucosal barrier
Tight junctions between cells to stop acid entry into underlying tissue

25
Q

What is gastritis?

A

Inflammation of gastric mucosa
Mostly caused by infection
Can be caused by smoking, alcohol, NSAIDs & chronic stress
If surface epithelium is acutely damaged it rapidly regenerates in a restitution process

26
Q

What are proton pump inhibitors?

A

Potent inhibitors of H+/K+ ATPase pump on luminal surface of oxyntic cells
Omeprazole is an example, which binds irreversibly & inhibits H+ secretion

27
Q

What are the 3 major stimulators of gastric acid secretion?

A

Gastrin
Histamine
Acetylcholine

28
Q

How does gastrin control acid secretion?

A

Triggered by amino acids & peptides in the stomach
Stimulates secretion by increasing intracellular calcium ions
Predominantly secreted by antral G cells in pylorus & duodenum
Endocrine effect
Low pH inhibits release

29
Q

How does histamine control gastric acid secretion?

A 
Stimulates secretion by increasing cAMP
Arises from mast-like cells
ECL cells close to parietal cells
Paracrine effect by local diffusion 
ECL cells are stimulated by gastrin & acetylcholine
Local vasodilatation of arterioles
30
Q

How does acetylcholine control gastric acid secretion?

A

Increases intracellular calcium ions
Secreted from postsynaptic vagal fibres innervating gastric mucosa
Acts on parietal & ECL cells to promote acid & histamine secretion
Acts on D cells to inhibit somatostatin release

31
Q

What are the 2 major inhibitors of gastric acid secretion?

A

Somatostatin

Prostaglandins

32
Q

Where is somatostatin secreted from?

A

Antral & oxyntic gland D cells

Pancreatic islet cells

33
Q

How do prostaglandins inhibit gastric acid secretion?

A

Ez prostaglandin is produced in the stomach & is a physiologic antagonist of histamine at the oxyntic cell wall
Inhibits production of cAMP
From mucosal cells

34
Q

What is autoimmune atrophic gastritis?

A

Antibody mediated destruction of gastric parietal cells

Causes hypochlorhydria & deficiency of IF

35
Q

What are the 3 phases of regulation of gastric acid secretions?

A

Cephalic - sight, smell, taste, thought
Gastric - antral distention, protein content, pH above 4
Intestinal - intestinal gastrin, absorbed amino acids

Module 104 - Nutrition, metabolism & excretion (31 decks)

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