Salivary and Gastric Secretions Flashcards
Exocrine Glands
- with duct
- salivary glands, gastric glands
Endocrine Glands
- without duct
- enteroendocrine cells in the
stomach and small intestine
Role of Salivary Secretions
- lubrication
- protection; oral hygiene/
antimicrobial agents - initiate chemical digestion
Major Salivary Glands (3):
- parotid
- submandibular
- sublingual
Dispersed Salivary Glands:
- mucosa of mouth and tongue
- labial, buccal, palatal, lingual
Hypotonic:
solution has a lower concentration
of solutes and a higher
concentration of water than inside
the cell [water moves into cell
Hypertonic:
solution has a higher concentration of solutes and a lower concentration of water than inside the cell [water moves out of cell]
Major Salivary Glands
Parotid Gland Secretions: proportions and description:
- 25%
- serous, watery secretions
containing salivary amylase for
starch digestion
Submandibular Gland Secretions: proportion and description:
- 70%
- mixed serous and mucus
Sublingual Gland Secretions: proportion and description:
- 5%
- Mucus: thicker mucus dominant
secretions for lubrication
Saliva Composition and Functions:
- alpha not a
- disaacharide and trisaccharide
important
Saliva Composition and Functions:
insert table
Acinar Structure of Salivary Glands:
Two Stage Formation of Hypotonic Saliva:
Cl- goes inside cell and into ductal area
Na+ enters via ductal area
Active transport in ductal area: Na+ out, K+ in
and Na+ and HCO3- out
hence at end stage of saliva hypotonic
Composition of Saliva changes with flow rate: Low rate of secretion:
max reabsorption of electrolytes produces hypotonic saliva (lower conc of osmotically active electrolytes)
more K+++
Composition of Saliva changes with flow rate: High rate of secretion:
reduced reabsorption of electrolytes produces saliva with higher osmolality closer to primary isotonic solution produced by acini
more sodium due to less absoprtion time ***
low secretion…
Electrolytes in saliva hypotonic: Na+. Cl-, HCO3-, K+
Na+ and Cl- < plasma
HCO3- and K+ > plasma
Composition of Saliva changes with flow rate:
ANS control of Salivary Secretion Rate: Parasympathetic stimulation:
Sensory stimuli pertaining to foodstuff stimulates salivary nuclei in the brainstem via CN VII (7) [facial nerve > sublingual and submandibular] and CN IX (9)[glossopharyngeal nerve> parotid].
This results in an increase in amylase, mucin, and serous saliva; also vasodilation
ANS control of Salivary Secretion Rate: Sympathetic stimulation:
Facilitated via superior cervical ganglion and sympathetic postganglionic nerves, leading to vasoconstriction and reduced saliva production.
A dry mouth by be reported???
ANS control of Salivary Secretion Rate:
Sjögren’s syndrome:
Autoimmune disease that destroys the exocrine glands which commonly affects tear and saliva production resulting in dry eyes and a dry mouth. These are collectively known as sicca symptoms [derived from the Latin, siccus, meaning dry].
Xerostomia [dry mouth]
Patients lack adequate saliva, tooth decay and halitosis (foul smell) is common due to bacterial overgrowth. There may also be difficulty speaking or swallowing solid food due to inadequate lubrication.
What is Schirmer’s test used for?
Employed to determine if an individual produces enough tears to keep their eye moist and healthy.
Used to assess for problems of dry eyes [including Sjögren’s syndrome].
Schirmer’s test
How is Schirmer’s test conducted?
Litmus paper folded and placed in cells
Will show dryness
Filter paper in situ for 5 mins, before assessing the result.
What branches into gastric glands?
Gastric pits in the mucosa, branch into gastric glands
Exocrine Gland Cells (3):
Mucous neck cells – thin mucus
Parietal cells - HCl and intrinsic factor
Chief cells – pepsinogen, gastric lipase
Secretions
insert diagram (numbers not needed)
Endocrine Gland Cells:
G cells - hormone gastrin
D cell hormone somatostatin [GHIH]
Enterochromaffin-like [ECL] cells secrete histamine
Gastric Glands
Gastric Stimulation: Parasympathetic :
- Vagus Nerve: distension, peptide
- Parietal cell secretion of HCl
- Chief cell secretion of pepsinogen
- Lower oesophageal sphincter
contraction - Increases motility of stomach
- Relaxes pyloric sphincter
Gastric Secretion Promotes Gastric Digestion:
Gastric Juice Components:
- water and electrolytes
- mucus (glycoprotein mucin)
- pepsinogen pro-enzyme, gastric
lipase, rennin (chymosin) - HCL (pH 1-3)
- Intrinsic Factor (IF)
WEPLRHCLIF
Gastric Juice Components:
HCl secretion by parietal cells
What stimulates gastric acid secretion?
Ach released from vagus Gastrin from G cells
Histamine from ECL cells
Secretory IgA and serous IgA difference
pentameric (secretary)???
monomaric (serous)
Inhibition of Gastric Acid Secretion:
- Stomatostatin from D cells
(paracrine* and endocrine): inhibits
adenylate cyclase - Mucosal Prostaglandin anatagonist
for H2 receptor: NSAIDS inhibit
prostaglandin formation and
increase gastric acid secretion
Sympathetic activity in salivary glands result in patient complaining of
dry mouth
Signaling between neighbouring molecules is
paracrine
parietal cells adaptations for acid secretion:
- parietal cells are packed with
tubulovescicles in resting state - on stimulation these fuse with the
canalicular membrane as microvilli - contain H+/K+ ATPase and carbonic
anhydrase enzymes needed for
production and secretion of H+
Proton Pump Inhibitor: Example and function
- omneprazole (core drug)
- inactivates K+/K+ ATPase
Pharmacological inhibition of gastric acid (3):
- Proton Pump Inhibitor
- H2 receptor antagonist
- Atropine
H2 receptor antagonist: example and function:
- cimetidine
- inhibits stimulus for acid secretion
Atropine function (gastric acid)
- inhibits muscarinic receptors and vagal stimulation of acid secretion
Which cells secrete HCl?
- parietal cells
State the names of the three phases of gastric secretion:
- cephalic
- gastric
- intestinal
Description of three phases of gastric secretion:
- Cephlaic: vagus innervates parietal,
chief and gastrin secretion - Gastric: stimulation fo parietal,
chief, mucus secretion, G cells - Intestinal:
Excitatory: chyme with pH >3,
peptides stimulate gastric
secretions via vagus and gastrinInhibitory: Chyme with pH: chyme with pH<2, protein breakdown products, changes in osmolarity larger, inhibits gastric secretions via cholecystokinin, gastric inhibitory polypeptide
Three phases of Gastric Secretion:
Cephalic Phase Overview:
- get started phase
The taste, smell, or thought of food stimulate the vagal centre [medulla oblongata]. Vagal signals are sent to endocrine cells within the GI system. This results in the secretion of gastrin.
Gastric Phase Overview:
- go for it phase
Distention of the stomach occurs, preparing for entry of bolus. The greatest volume of gastric juice is produced during this phase.
Intestinal Phase Overview:
- slow down phase
This phase can promote or inhibit the further production of gastric juices as well as controlling rate at which stomach contents can enter the duodenum.
Why is gastric mucosa not damaged?
- surface mucous glands secrete
viscous mucus layer generating a
mucosal barrier - mucin has basic side chains which
prevent the neutralisation of mucin
and HCO3 is secreted from surface
epithelial cells - both mechanisms
nuetralise H+ ions - tight junctions stop acid damaging
underlying tissue
Net result - unstirred layer is pH7, pepsinogen not activated, prevents damage
Gastritis:
- is
- caused by (most commonly)
- other causes
- recovery
- inflammation of the gastric mucosa
- most commonly caused by an
infection by the bacteria
Heliobacter Pylori (50% of pop
have) - smoking, alcohol, NSAIDs, etc
- following acute damage, rapid
regeneration is via a process called
restitution - rapid division of stem
cells located in the neck of gastric
glands
Restitiution
rapid division of stem cells located in the neck of gastric glands
Which is a major salivary gland?
- lacrimal gland
- sweat gland
- parotid gland
- sebaceous gland i
parotid gland
Which ion is present in the highest concentration in hypotonic saliva?
- Cl-
- Mg
- K+
- Na+
Potassium
Which exocrine gland cell secretes HCl in the stomach?
- mucous neck cells
- chief cells
- parietal cells
- G cells
parietal cells
A 50 year old woman presents to the GP with complaint of indigestion and heartburn. GP prescribed omneprazole. What is the mechanism of action?
- blocked chief cells of gut
- activate H+/Cl- ATPase pump
- activate H+/K+ ATPase pump
- blocked H+/K+ ATPase pump
- activate H+/Cl- ATPase pump
In one of the gastric secretion phases, the tase of food stimulates the vagal centre which then activates the gut cells to secret gastrin. Which phase?
- gastric phase
- intestinal phase
- cephalic phase
- oesophageal phase
cephalic phase
