GI secretions (Part 1) - Salivary and gastric secretions

Question 1

Functions of saliva

Answer 1

Lubrication, protection and digestion

Question 2

Describe how saliva helps with lubrication?

Answer 2

• Moistening the mouth lubricating the food to aid swallowing
• Facilitates movements of the mouth and tongue for speech
• Helps to dissolve chemicals with food for its presentation to the taste receptors

Question 3

Describe how saliva helps with protection?

Answer 3

• Reduces the adverse effects of oral bacteria
• The alkalinity of fresh saliva neutralizes acid produced by oral bacteria
• The flow of saliva across the teeth also helps to wash away bacteria

Question 4

What substances does the saliva contain to reduce bacterial growth?

Answer 4

• Lysozyme attacks bacterial cell walls
• Lactoferrin chelates iron, which is needed by many bacteria for replication
• Immunoglobin A(IgA) - binding protein is required for the immunologic activity of IgA

Question 5

How does saliva help with digestion?

Answer 5

Begin the breakdown of carbs and fats via the enzymes alpha-amylase and lingual lipase

Question 6

What is the function of alpha amylase(ptylain)

Answer 6

Hydrolyses starches

Question 7

What percentage of starches can alpha amylase break down?

Answer 7

Up to 75%

Question 8

What is the function of lingual lipase?

Answer 8

Hydrolyses triglycerides and is secreted by the small salivary glands present on the surface of the tongue

It has an acidic pH optimum and remains active in the stomach

Question 9

What is sjogren’s syndrome?

Answer 9

Autoimmune disease that destroys the exocrine glands and mostly affects tear and saliva production

Question 10

What are the hallmark manifestations of sjogren’s syndrome

Answer 10

Dry eyes and dry mouth, known as sicca symptoms

Question 11

What is xerostomia?

Answer 11

Lack adequate saliva
They typically have dental caries and halitosis due to bacterial overgrowth and have difficulty speaking or swallowing solid food due to inadequate lubrication

Question 12

What is the volume of saliva produced per day?

Answer 12

1.5L per day

Question 13

What are the two types of salivary secretions?

Answer 13

Serous and mucous secretions

Question 14

What does serous secretion contain?

Answer 14

Main type of protein secreted is ptyalin(hydrolises starch)

Question 15

What does mucous secretion contain?

Answer 15

Main protein is mucin acting as lubricant

Question 16

What are the three types of salivary glands?

Answer 16

Submandibular, parotid and sublingual glands

Question 17

% saliva secretion by different types of salivary glands

Answer 17

• Submandibular 70%(mixed)
• Parotid 25%(serous)
• Sublingual 5%(mucus)

Question 18

What is the structure of salivary glands?

Answer 18

Salivary glands contain blind-ended acini connecting with ducts draining into major ducts

Question 19

What is the composition of primary saliva?

Answer 19

Primary saliva secreted by the acinus is an isotonic solution resembling interstitial fluid

Question 20

What does the duct reabsorb from the primary saliva?

Answer 20

Duct reabsorbs NaCl(but not water), causing saliva to become hypotonic

Question 21

What is the function of acinar cells?

Answer 21

Cl- uptake via basolaterally located Na+, K+, 2Cl cotransporter and release through the calcium activated apical chloride channel