Upper GI tract: structure and function

Question 1

how is chewing controlled?

Answer 1

voluntary - somatic nerves - skeletal muscles of mouth/jaw

reflex - contraction of jaw muscles - pressure of food against gums, hard palate and tongue. Mechanoreceptors inhibit jaw muscles - reduce the pressure - contraction etc

Question 2

which glands secrete saliva

Answer 2

parotid
submandibular
sublingual

Question 3

parasympathetic control of salivary secretion

Answer 3

facial and glossopharyngeal

stimulation - profuse watery salivary secretion

Question 4

Sympathetic control of salivary secretion

Answer 4

stimulation but small volume
viscous salivary secretion -

high mucus content (alpha 1 adrenoreceptors) and high amylase content (beta 2 adrenoreceptors

Question 5

4 layers of the oesophagus

Answer 5

mucosa
submucosa
muscularis externa
adventitia

Question 6

submucosal layer has what?

Answer 6

glands - act as ducts that bring about lubrication - secrete water

Question 7

what part of the oesphagus regulates movement into and out of the oesophagus?

Answer 7

upper and lower oesophageal sphincters

Question 8

pharyngeal phase of swallowing

Answer 8

Presence of bolus => sequence of reflex contractions of pharyngeal muscles

Co-ordinated by swallowing centre (medulla)

Soft palate reflected backward and upward (closes off nasopharynx)

Question 9

what happens as the bolus approaches the oesophagus?

Answer 9

Upper oseophageal sphincter (UOS) relaxes and epiglottis covers opening to larynx (prevents food entering trachea)

Question 10

what happens once food has entered the oesophagus

Answer 10

upper oesophageal sphincter contracts to prevent food reflux

Question 11

functions of the stomach (5)

Answer 11

Temporary store of ingested material

Dissolves food particles and initiates digestive process

Controls delivery of contents to small intestine

Sterilises ingested material

Produces intrinsic factor (Vitamin B12 absorption)

Question 12

what is saliva composed of? (5)

Answer 12

water
mucins
alpha amylase
electrolytes
lysozyme

Question 13

What is lysozyme

Answer 13

a bacteriocidal that cleaves polysaccharide component of bacterial cell wall - kills bugs

overnight you don’t produce as much lysozymes so you don’t kill as much bacteria hence bad morning breath

Question 14

Is your oral cavity inside or outside your body?

Answer 14

outside

Question 15

what regulates movement of material into and out of the oesophagus?

Answer 15

upper and lower oesophageal sphincters

Question 16

oesophageal phase of swallowing

Answer 16

propulsion of bolus to stomach

peristaltic wave sweeps along the entire oesophagus and the bolus is propelled to the stomach in 10 seconds

Question 17

what does the stomach volume change to after food enters?

Answer 17

50ml to 1500ml with no change in pressure