The Structure and Function of the Upper GI Tract

Question 1

What are the two functions of chewing?

Answer 1

• a prolonged taste experience

- defence against respiratory failure

Question 2

Name the two types of control that allow chewing.

Answer 2

• voluntary control

- reflex control

Question 3

Where does voluntary control of chewing come from?

Answer 3

• somatic nerves act on the skeletal muscle of the mouth and jaw

Question 4

Where does reflex control of chewing come from?

Answer 4

• the pressure of food against the gums, hard palate and tongue triggers mechanoreceptors, inducing a contraction of jaw muscles

Question 5

Name the three pairs of salivary glands.

Answer 5

• parotid
• submandibular
• sublingual

Question 6

List the components of saliva.

Answer 6

• water
• mucins
• alpha-amylase
• electrolytes
• lysozymes

Question 7

Are the salivary glands exocrine glands or endocrine glands?

Answer 7

• exocrine glands

- as the exit into the mouth which is ‘outside’ of the body

Question 8

Name the three types of bulbous alveoli found in the salivary glands.

Answer 8

• mucous
• serous
• mixed

Question 9

What affects do the parasympathetic and sympathetic nervous systems have on salivary secretion?

Answer 9

• They are both stimulatory

Question 10

Where does parasympathetic stimulation of salivary glands come from?

Answer 10

• cranial nerves XII and IX

Question 11

What type of saliva is stimulated by the parasympathetic system?

Answer 11

• profuse, watery secretion

Question 12

Where does sympathetic stimulation of salivary glands come from?

Answer 12

• either alpha-1 adrenoreceptors

- or beta-2 adrenoreceptors

Question 13

What type of saliva is stimulated by sympathetic action on alpha-1 adrenoreceptors?

Answer 13

• a small volume of viscous salivary secretion with a high mucus content

Question 14

What type of saliva is stimulated by sympathetic action on beta-2 adrenoreceptors?

Answer 14

• a small volume of viscous salivary secretion with a high amylase content

Question 15

How does reflex control stimulate salivary secretions?

Answer 15

• via chemoreceptors and pressure receptors in the walls of the mouth and the tongue
• they respond to the presence of food in the mouth

Question 16

On average, how long is an adult oesophagus?

Answer 16

• around 25cm

Question 17

Name and describe the four layers of the oesophageal wall.

Answer 17

• mucosa - made up of stratified squamous epithelium
• submucosa - contains ducts and lubrication
• muscularis externa - superior third is skeletal muscle, while the inferior two-thirds are smooth muscle
• adventitia

Question 18

How many sphincters are there in the oesophagus and where are they located?

Answer 18

• there are two sphincters

- there are situated at either end of the oesophagus

Question 19

Name the phases of swallowing.

Answer 19

• oral phase
• pharyngeal phase
• oseopharyngeal phase

Question 20

What is the oral phase of swallowing?

Answer 20

• where the bolus is pushed to the back of the mouth by the tongue

Question 21

What occurs during the pharyngeal phase of swallowing?

Answer 21

• the presence of the bolus triggers reflex contractions of pharyngeal muscle
• this is coordinated by the swallowing centre in the medulla
• the soft palate is reflected backwards and upwards to close off the nasopharynx

Question 22

What occurs during the oesopharyngeal phase of swallowing?

Answer 22

• propulsion of the bolus towards the stomach

- this triggers a peristaltic wave

Question 23

What triggers the expansion of gastric rugae?

Answer 23

• stimulation via the vagus nerve

Question 24

List the five primary functions of the stomach.

Answer 24

• temporary storage of indigested materials
• dissolve food particles and initiate the digestive progress
• control delivery of contents to the small intestine
• sterilise ingested materials
• produce intrinsic factor

Question 25

Why is controlled delivery important?

Answer 25

• it prevents mass delivery which would increase tonicity and therefore affect osmosis

Question 26

Which part of the stomach is responsible for controlled delivery?

Answer 26

• the pyloric sphincters

Question 27

Describe the muscle at the top of the stomach.

Answer 27

• thin, stretchy, smooth muscle

Question 28

Describe the muscle at the bottom of the stomach.

Answer 28

• thicker, more powerful muscle

- this is due to the presence of an oblique muscularis layer underneath the usual layers of the muscularis