DS: Salivary Glands

Question 1

What are the 4 minor salivary glands?

Answer 1

1. Cheeks- Buccal glands
2. Lips- labial glands
3. Palate- Palatal glands
4. Tongue- lingual glands

Question 2

What are the 3 major salivary glands?

Answer 2

1. Parotid gland
2. Submandibular gland
3. Sublingual gland

Question 3

Describe the parotid salivary gland and its function

Answer 3

Largest of the major salivary glands. Secretes saliva to facilitate mastication (chewing) and deglutition (swallowing). Also secretes salivary amylase to help facilitate the initial digestion of carbs and lipids. Serous gland.

Question 4

Where is the saliva product of the parotid gland distributed to before the oral cavity?

Answer 4

Parotid duct

Question 5

Where is the saliva product of the submandibular gland distributed to before the oral cavity?

Answer 5

Submandibular duct

Question 6

Where is the saliva product of the sublingual gland distributed to before the oral cavity?

Answer 6

The ductal system of the sublingual glands does not have intercalated ducts, so saliva exits directly from 8-20 excretory ducts known as the Rivinus ducts.

Question 7

Describe the submandibular salivary gland and its function

Answer 7

Produces the majority of saliva production. Secretion produced is a mixture of both serous fluid and mucous.

Question 8

Describe the sublingual salivary gland and its function

Answer 8

Produces approximately 5% of saliva entering the oral cavity. Secretion produced is mainly mucous in nature.

Question 9

What are the 3 classifications of salivary glands?

Answer 9

Salivary glands can be classified as serous, mucous or seromucous (mixed).

Question 10

What are the secretions of the salivary glands?

Answer 10

In serous secretions, the main type of protein secreted is alpha-amylase, an enzyme that breaks down starch into maltose and glucose, whereas in mucous secretions the main protein secreted is mucin, which acts as a lubricant.

Question 11

How do the major salivary glands deliver their secretory products to the oral cavity?

Answer 11

The major salivary glands use a branching system of ducts to deliver their secretory products into the oral cavity. Each gland is divided into small lobules that contain the structural and functional secretory units- acinus and an intercalated duct. Each acinus contains 15 to 100 acinar cells that synthesis and secrete their protein products into the intercalated ducts for delivery to the oral cavity.

Acinus to intercalated duct to interlobular duct to main duct to oral cavity

Question 12

Where is saliva produced?

Answer 12

In acinar cells in the major salivary glands.

Question 13

Describe the structure of acinar cells in the salivary glands

Answer 13

Acinar cells are polarised cells as they have an apical and a basolateral membrane. Specialised for production of large amounts of saliva due to large nuclei, mitochondria and a well-developed RER.

Question 14

What are the 2 stages of saliva production?

Answer 14

1. Primary isotonic secretion

2. Secondary hypotonic secretion

Question 15

Describe the production of the primary isotonic secretion

Answer 15

1. Sodium-Potassium ATPase pumps in the basolateral membrane of the acinar cells pump sodium ions out of the cell and into the ECF. This creates a sodium concentration gradient that drives sodium, potassium and chloride ion entry into acinar cells via secondary active transport through a NKCC-1 co-transporter.
2. Chloride ions diffuse out of the acinar cells through chloride ion channels in the apical membrane. Sodium ions leave via sodium-potassium ATPase pumps, where as potassium ions leave via potassium ion channels on the basolateral membrane, in order to maintain the concentration gradient.
3. Net negative luminal charge due to the accumulation of chloride ions; neutralised by the paracellular entry of sodium ions to form sodium-chloride, or potassium ions to form potassium-chloride.

Passive movement of water into the lumen via aquaporins 5 channels due to increase in luminal osmolality following production of sodium-chloride and potassium-chloride.

Question 16

Describe the production of the secondary hypotonic secretion

Answer 16

1. Sodium ions are actively reabsorbed in exchange for potassium ions, probably via sodium-potassium ATPase pumps in the basolateral membrane of the duct cells. This reduces the amount of sodium and sodium-chloride (salt) in the saliva to allow us to taste salt in food and form a secondary hypotonic secretion.
2. Significant decrease in sodium ion concentration in the saliva. Induces matching reabsorption of chloride ions in exchange for hydrogen carbonate ions.
3. Duct cells are impermeable to water so, consequently, the secondary secretion becomes hypotonic.

Question 17

Why does saliva remain as a primary isotonic secretion during digestive periods?

Answer 17

During digestive periods, when saliva production is quick, saliva remains as a primary isotonic secretion, as there is no time for the conversion to a secondary hypotonic secretion.

Question 18

Why is the production of a primary isotonic secretion desirable during digestive periods?

Answer 18

Leads to an increase in chloride ions in the saliva which is desirable as it maintains osmotic balance in the mouth so that there is no excess inflow nor outflow of water from mouth tissues. Chloride ions are also required for the activation of salivary amylase enzymes.

Question 19

How is saliva production initiated?

Answer 19

Secretion of protein components of saliva is triggered by neural stimulation of zymogen granules, which move to the apical membrane of the acinar cells, and release their content into the lumen via exocytosis.

Question 20

How is salivation controlled?

Answer 20

Salivation is controlled by the autonomic nervous system. Parasympathetic stimulation induces continuous secretion of saliva. Testants in food and tactile stimuli stimulate mechanoreceprors and gustatory receptors on the tongue. Sensory input triggers the formation of action potentials (APs) that are sent via sensory afferents to the superior and inferior salivatory nuclei in the brainstem between the medulla and the pons. Motor commands transmitted by parasympathetic efferent neurons of the facial nerve and glossopharyngeal nerves stimulate postganglionic neurons in the submandibular and optic ganglia, respectively, which then stimulate the salivary acinar cells to secrete saliva.

Question 21

What is the composition of saliva?

Answer 21

99.5% water and 0.5%solutes

Solutes include sodium, potassium, chloride, phosphate, hydrogen carbonate, and thiocyanate ions.

Question 22

What are the other protein products in saliva?

Answer 22

Other proteins, apart from principle protein products, include: lysosomes, proline-rich proteins, immunoglobulins IgA, defencins, nucleases, lipase, growth factors, and peroxidases.

Question 23

What are the functions of the oral cavity?

Answer 23

1. Sensory analysis of food prior to ingestion
2. Mechanical processing of food
3. Lubrication of food
4. Formation of food boluses
5. Preparation for deglutition (swallowing)
6. Initiation of chemical digestion of lipid and carbs by salivary amylase and lingual lipase
7. Defence against microbes by MALT tissue
8. Administration site for drugs

Question 24

What are the 2 main functions of saliva?

Answer 24

1. Digestive function

2. Oral hygiene function

Question 25

What are the digestive functions of saliva?

Answer 25

1. Provides lubrication for food bolus formation, mastication, and deglutition
2. Provides anthems and optimal pH for carb and lipid digestion
3. Helps to soften and dissolve food so it can be tasted and digested

Question 26

What are the oral hygiene functions of saliva?

Answer 26

1. Prevents dehydration of the oral mucosa
2. Washes away microbes and food particles
3. Contains factors that destroy bacteria

Question 27

What is the pH of saliva?

Answer 27

6.75-7

Question 28

What are the factors within saliva that aid in destroying bacteria to maintain oral hygiene?

Answer 28

1. Thiocyanate ions that kill bacteria.
2. Lysosomes that allow thiocyanate ions to enter the bacteria.
3. Lysosomes digest food particles that support bacterial growth.
4. Immunoglobulin IgA destroys bacteria
5. Defencin and proline-rich proteins are antimicrobial