AS intro Flashcards
What are the functions of the GIT
Provides energy Provides building blocks
What is the length of the GIT
11 metres
however length is partially contracted smooth muscle => 6-7 m in human
What are the 4 processes carried out by the GIT
- Digestion
- Secretion
- Absorption
- Motility (doesn’t always move towards rectum - sometimes moves in oral direction)
How much water is absorbed
6.7L (SI)
How much water is put into body
- 1.2L ingested - 800g solids ingested
- 1.5L salivary secretions
- 2L Gastric secretions
- 0.5L bile
- 1.5L pancreatic secretions - SI
Of the 1.5L of water ingested, how much is absorbed
1.4L
=> 0.1L excreted (w/ 50g solids)
What is the mouth responsible for
Chewing action - reflex/voluntary
What does the tongue do
Shapes food into bolus and pushes bolus towards pharynx
Function of pharynx
Helps crush food
Closes nasal opening when swallowing
4 major functions of saliva
- Moisten and lubricate food
- Digestion of polysaccharides by amylase
- Dissolve food
- Antibacterial actions
Name the 3 salivary glands
- Parotid
- Submandibular
- Sublingual
2 enzymes secreted by salivary glands
Salivary amylase - ptyalin
Lingual lipase
What are mucins
Proteins with a lot of CHOs attached - viscosity traps bacteria
What glands secrete mucus
Buccal, submandibular, sublingual
- lubricate prior to swallowing
What is the basal secretion rate of saliva
0.5 ml/min but can go up to 4 ml/min
How does saliva help with digestion
Amylase
Lipase
How does saliva help to prevent tooth decay
- Washing action
- Mucus coating of mouth
- Alkaline pH - buffers acids in food - vomiting
- Bactericidal
How is saliva bactericidal
Thiocyanate ions
Sialoperoxidase
Proteolytic enzymes (e.g. lysozyme)
- H2O2 + thiocyanate -> hypothiocyanate (toxic to bacteria)
RXN CATALYSED // SIALOPEROXIDASE
Also antibodies
How to know that the vomiting reflex has been triggered
Sudden rush of saliva
* Salivary secretion

Relationship between composition of saliva and salivary flow rate

[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
Why is there never 0 salivary flow rate
Sympathetic + parasympathetic stimulate salivary secretion
How is saliva secretion regulated
Reflexes can be conditioned - ringing of bell in experiment w/ dogs triggered salivary secretion
