AS intro

Question 1

What are the functions of the GIT

Answer 1

Provides energy Provides building blocks

Question 2

What is the length of the GIT

Answer 2

11 metres

however length is partially contracted smooth muscle => 6-7 m in human

Question 3

What are the 4 processes carried out by the GIT

Answer 3

1. Digestion
2. Secretion
3. Absorption
4. Motility (doesn’t always move towards rectum - sometimes moves in oral direction)

Question 4

How much water is absorbed

Answer 4

6.7L (SI)

Question 5

How much water is put into body

Answer 5

• 1.2L ingested - 800g solids ingested
• 1.5L salivary secretions
• 2L Gastric secretions
• 0.5L bile
• 1.5L pancreatic secretions - SI

Question 6

Of the 1.5L of water ingested, how much is absorbed

Answer 6

1.4L

=> 0.1L excreted (w/ 50g solids)

Question 7

What is the mouth responsible for

Answer 7

Chewing action - reflex/voluntary

Question 8

What does the tongue do

Answer 8

Shapes food into bolus and pushes bolus towards pharynx

Question 9

Function of pharynx

Answer 9

Helps crush food

Closes nasal opening when swallowing

Question 10

4 major functions of saliva

Answer 10

1. Moisten and lubricate food
2. Digestion of polysaccharides by amylase
3. Dissolve food
4. Antibacterial actions

Question 11

Name the 3 salivary glands

Answer 11

1. Parotid
2. Submandibular
3. Sublingual

Question 12

2 enzymes secreted by salivary glands

Answer 12

Salivary amylase - ptyalin

Lingual lipase

Question 13

What are mucins

Answer 13

Proteins with a lot of CHOs attached - viscosity traps bacteria

Question 14

What glands secrete mucus

Answer 14

Buccal, submandibular, sublingual

• lubricate prior to swallowing

Question 15

What is the basal secretion rate of saliva

Answer 15

0.5 ml/min but can go up to 4 ml/min

Question 16

How does saliva help with digestion

Answer 16

Amylase

Lipase

Question 17

How does saliva help to prevent tooth decay

Answer 17

• Washing action
• Mucus coating of mouth
• Alkaline pH - buffers acids in food - vomiting
• Bactericidal

Question 18

How is saliva bactericidal

Answer 18

Thiocyanate ions

Sialoperoxidase

Proteolytic enzymes (e.g. lysozyme)

• H2O2 + thiocyanate -> hypothiocyanate (toxic to bacteria)

RXN CATALYSED // SIALOPEROXIDASE

Also antibodies

Question 19

How to know that the vomiting reflex has been triggered

Answer 19

Sudden rush of saliva

Question 20

* Salivary secretion

Answer 20

Question 21

Relationship between composition of saliva and salivary flow rate

Answer 21

[Na+] plasma = 145-150 mEq

Faster flow rate => less contact time => more Na+ enters palsma

Above 1ml/min, counter-transporter of HCO3- is functioning maximally

Question 22

Why is there never 0 salivary flow rate

Answer 22

Sympathetic + parasympathetic stimulate salivary secretion

Question 23

How is saliva secretion regulated

Answer 23

Reflexes can be conditioned - ringing of bell in experiment w/ dogs triggered salivary secretion