Salivary Secretion & Function Flashcards
What are the 3 Major salivary glands?
- Parotid
- Submandibular
- Sublingual
What is the functional unit of salivary glands?
Salivon
What is the rough structure of the salivary glands?
Broccoli shaped
- external capsule
- Septae: separating lobes and lobules
- lobules: contain salivon, functional unit
What 3 things are found in the Salivon?
- secretory acinus
- intercalated duct
- striated duct
What cells form the central lumen around the secretory Acinus?
- Serous cells
2. Mucous cells
What kind of secretion do serous cells produce?
Watery secretion rich in A-amylase
What kind of secretion do mucous cells produce?
Thick mucous rich saliva
What are the main functions of saliva?
- Lubrication
- Protection
- Digestion
- Others
What are the effects of lubrication? what contents of saliva make this possible?
Water and mucus contents
Aids food movement. Facilitates speech & swallowing.
What protection does saliva offer?
Against bacteria + their metabolic products.
Protects teeth.
How does saliva help with digestion?
- A-amylase stimulates complex carb digestion
- lingual lipase= fat digestion
What are the main electrolyte constituents of saliva?
Na,K,Ca,Cl,P04,HCO3,I
Concentration of these electrolytes except _ and _ are lower in saliva than the rest of the body?
K & HC03
Parotid gland produces what type of secretion?
watery A-amylase rich
Submandibular gland produces what type of secretion?
Thicker than parotid secretion
Sublingual gland produces what type of secretion?
Thick mucus based
How is HC03 concentration affected by salivary flow rate?
Increases with rate
How is K concentration affected by salivary flow rate?
Decreases with rate
What are the two stages in saliva formation?
- Primary secretion (acinar cells)
2. Secondary modification (duct cells)
What happens in secondary modification?
Na & Cl Influx
K & HC03 Efflux
Influx exceeds efflux–> Overall diluting effect.
What two types of reflexes control saliva secretion?
- Simple- stimulated by presence of food in mouth
2. Acquired- brought on by sight, smell, thought of food
Which one (para/symp) of the autonomic nervous system is dominant in saliva secretion under resting conditions?
Parasympathetic.
Sympathetic- stimulated in stressful situation
Which nerves are used in parasympathetic salivary secretion?
- Glossopharyngeal (CN9)
2. Facial (CN7)
Effect of parasympathetic stimulation on type of saliva produced and blood flow?
Large volume, watery, enzyme rich.
Mediated by- M3/M1 AcH receptors
Blood flow- increases
How does sympathetic stimulation reach the mouth to cause salivary secretion?
- Post ganglionic fibres from superior cervical ganglia
2. Adrenaline from adrenal medulla
Effect of sympathetic stimulation on type of saliva produced and blood flow?
Small volume, mucus thick saliva
Blood flow reduced.
Mediated by (A & b1 receptors)
Which Cranial nerve controls relaxation of the stomach?
CN 10- Vagus nerve
What food group is digested in the stomach? by what?
Proteins. By pepsin and HCL
What is chyme
food + gastric secretion
Is the pyloric sphincter open or closed when food is mixed in the stomach?
Closed
When does the pyloric sphincter open?
When food passes from stomach to duodenum.
Opens sufficiently to allow semi liquid chyme to pass.
What drives this movement of food from stomach to duodenum?
Peristalsis
What two factors does rate of stomach emptying depend on?
- Gastric factors
2. Duodenal factors
What are the gastric factors that affect rate of emptying? (2)
Consistency & volume of chyme.
Affected by:
- Gastric motility
- intrinsic nerve activity
- Vagus nerve activity
- gastrin release
In what two ways can the duodenum delay gastric emptying?
- Neuronal response
2. Hormonal response
What is the neuronal response known as? what happens in it?
Enterogastric reflex- intrinsic nerve plexus & ANS= decreases Peristaltic activity
What is the hormonal response known as and what happens?
Enterogastrone release- e.g. CCK release from duodenum inhibits stomach contraction
What are the two areas of gastric gland secretions?
- Pyloric gland area
2. Oxyntic mucosa
What are the secretions of the Oxyntic mucosa and each of their functions? (5)
- HCL: Pepsinogen–> pepsin
- Pepsinogen- inactive precursor
- Intrinsic factor- binding of Vitamin B12 for absorption
- Histamine- HCL secretion
- Mucus- protective
What are the secretions of the Pyloric gland area and each of their functions?
- Gastrin- HCL secretion
- Somatostatin- Inhibits HCL secretion
- Mucus- protective
What are the 3 phases of Gastric secretion?
- Cephalic- before food reaches stomach
- Gastric- in stomach
- Intestinal- left the stomach
What happens in the Cephalic phase?
Prepares stomach for food
Increased Secretions of
- Gastrin
- Histamine
- AcH
Reduced secretion of
- Somatostatin
What happens in the Gastric phase?
- Distension (promotes peristalsis)
2. Protein digestion products released
What happens in the Intestinal phase?
Gastric secretions switched off.
Same factors also reduce gastric motility.
Somatostatin increased
How is the mucosa protected from attack by HCL and pepsin?
Release of Prostaglandin E2 and I2 (PGE2, PGI2)
How do the prostaglandins protect the mucosa?
- Increase mucus + bicarb production
- Reduce acid secretion
- Increase mucosal blood flow
How does a peptic ulcer develop?
Damage to the mucosa by HCL and pepsin.
What main type of drug can cause Peptic ulcers?
NSAID’s like Aspirin
What bacteria can cause infection in peptic ulcers?
H.Pylori- helicobacter pylori
What are the 4 main mechanisms of action that reduce acid section?
- Inhibition of proton pump
- Competeive antagonism of histamine receptors
- Competitive antagonism of M1,M3 receptors
- Antagonism of gastrin receptors
Example of a proton pump inhibitor? How does it work?
Omeprazole.
Inhibits Active H/K dependent ATPase proton pump.
Note- only works on active proton pumps, and in a strong acidic environment
Example of Histamine agonist? Mechanism?
Ranitidine, Cimetidine
Competitive inhibitor of H2 histamine receptors
Block histamine mediated acid secretion
What are two examples of mucosal strengtheners?
- Sucralfate- binds with mucosa to improve barrier function. Increases mucosal blood flow, HC03, PGE production
- Bismuth Chealate- eradicates H.pylori.
