Gastrointestinal System

Question 0

Describe the swallowing reflex.

Answer 0

1. Buccal (oral stage) - voluntary, bolus formation, bolus is moved to the back if the mouth.
2. Pharyngeal stage - bolus pushes on soft palate and sensory nerves in the soft palate send signals to the medulla oblongata to inhibit the respiratory centre, causing the epiglottis to close, the uvula lifts to prevent food entering the nasal passages. The tongue pushes up and forces the bolus backward and the upper oesophageal sphincter relaxes.
3. Oesophageal stage - bolus entering oesophageal initiates oesophageal peristalsis.

Question 1

What are the seven main functions of saliva?

Answer 1

1. Breaks down carbohydrates into monosaccharides.
2. It moistens food particles and aids with swallowing.
3. Contains antibacterial substances to ‘kill’ bacteria - lysozyme, lactoferrin and immunoglobulin A.
4. It acts as a solvent to stimulate taste buds - food is solubilised in saliva for us to taste it.
5. It aids speech by freeing the tongue.
6. Oral hygiene - keeps teeth clean from food debris which can cause dental caries.
7. Neutralises acids - it contains buffers to protect the enamel on teeth.

Question 2

Describe the swallowing reflex pathway.

Answer 2

• The bolus of food stimulates the touch receptors in the pharynx.
• The touch receptors send signals to the ninth and fifth nerve.
• The ninth and fifth serve sends signs,s to the swallow centre (the lateral reticular formation in the medulla).
• The medulla sends signals to the ninth, fifth and sixth nerve which sends signals to the tongue, pharynx, upper oesophageal sphincter, oesophagus (peristalsis) and the cardiac sphincter.