Upper GI structure and function

Question 1

Why do we chew?

Answer 1

Prolong taste experience

Defence against respiratory failure

Question 2

What are the 2 ways in which chewing is controlled?

Answer 2

Voluntary

Reflex

Question 3

How is chewing voluntarily controlled?

Answer 3

Somatic nerved innervate skeletal muscles of mouth and jaw

Question 4

How is chewing reflex controlled?

Answer 4

Contraction of jaw muscles causes pressure of food against gums, hard palate and tongue
Mechanoreceptors cause reflex inhibition of jaw muscles, reducing pressure

Question 5

What are the 3 glands saliva is secreted by?

Answer 5

Parotid
Sublingual
Submandibular

Question 6

What type of glands are salivary glands?

Answer 6

Exocrine

Question 7

What is the structure of a salivary gland?

Answer 7

Mucous alveoli
Serous alveoli- secrete proteaeous secretions
Mixed alveoli- secrete both mucus and proteaeous secretions

Question 8

What are the components of saliva?

Answer 8

Water
Mucins
Alpha amylase
Electrolytes
Lysozyme

Question 9

What is the function of water in saliva?

Answer 9

Softens, moistens and dilutes particles

Solvent

Question 10

What is the function of mucins in saliva?

Answer 10

Lubricant

Question 11

What are mucins?

Answer 11

The protein component of saliva

Together with water, they form mucus

Question 12

What is the function of alpha amylase in saliva?

Answer 12

Catalyses breakdown starch and glycogen to maltose and glucose

Question 13

What is the function of electrolytes in the saliva?

Answer 13

Control tonicity/pH

Question 14

What is the function of lysozyme in the saliva?

Answer 14

Bacteriocidal

Question 15

How does lysozyme function?

Answer 15

Breaks up polysaccharide component of bacterial cell wall

Question 16

How is salivary secretion controlled?

Answer 16

Para and sympathetic nervous systems

Reflex

Question 17

How do the parasympathetic nerves control salivation?

Answer 17

Controlled by facial and glossopharyngeal nerves

When stimulated, they produce a profuse amount of watery salivary secretion

Question 18

How do the sympathetic nerves control secretion?

Answer 18

Produce a small volume of thick salivary secretion
High mucus content controlled by alpha 1 adrenoceptors
High amylase content controlled by beta2 adrenoceptors

Question 19

How do reflexes control salivation?

Answer 19

Presence of anything in the mouth activates pressure sensors to start producing saliva
Presence of specifically food activates chemoreceptors for salivary production

Question 20

What is the oesophagus?

Answer 20

25cm conduit between mouth and stomach

Question 21

What are the layers of the oesophagus wall?

Answer 21

Mucosa
Submucosa
Muscularis externa
Adventitia/serosa

Question 22

What is the mucosa of the oesophagus lined by?

Answer 22

Non keratinised stratified squamous epithelium

Question 23

How do submucosal cells complete their function?

Answer 23

Submucosal glands release secretions via ducts which act as lubrication

Question 24

What is the structure of the muscular externa in the oesophagus?

Answer 24

Upper 1/3= skeletal muscle

Lower 2/3= smooth muscle

Question 25

What are oesophageal sphincters?

Answer 25

Thickened rings of smooth muscle that regulate movement in and out of the oesophagus

Question 26

What happens in the oral phase of swallowing? lol that sounds dirty

Answer 26

Bolus pushed to the back of the mouth by the tongue

Question 27

What happens in the pharyngeal phase of swallowing?

Answer 27

Presence of bolus causes a sequence of reflex contractions of pharyngeal muscles Soft palate reflected backwards and upwards to close of nasopharynx

Question 28

What is the pharyngeal phase of swallowing coordinated by?

Answer 28

Swallowing centre in medulla

Question 29

What happens as the bolus approaches the entrance to the oesophagus?

Answer 29

Upper oesophageal sphincter relaxes and epiglottis covers larynx

Question 30

What happens once th bolus enters the oesophagus?

Answer 30

Upper oesophageal sphincter contracts | Propulsion of bolus to stomach by peristaltic wave

Question 31

How long does it take for food to travel down the oesophagus?

Answer 31

About 10 seconds

Question 32

What happens as the bolus nears the stomach?

Answer 32

Lower oesophageal sphincter relaxes and food is allowed to enter stomach

Question 33

What is initiated by the arrival of a bolus in the stomach and relaxation of lower oesophageal sphincter?

Answer 33

Receptive relaxation of stomach

Question 34

What is receptive relaxation of the stomach?

Answer 34

Vagal reflexes cause relaxation of thin elastic smooth muscle of gastric funds and body

Question 35

What is special about the "stretch" of the stomach?

Answer 35

Muscle wall itself doesn't actually stretch, folds are simply straightened out No change in pressure on stomach wall

Question 36

What are the functions of the stomach?

Answer 36

Temporary store of ingested material Dissolve food particles and initiate digestive process Control delivery of contents to small intestine Sterilise ingested material Produce intrinsic factor for vitae's B12 absorption

Question 37

What is the function of the pyloric sphincter and where is it located?

Answer 37

At the entrance to the duodenum | Controls delivery of material to the small intestine

Question 38

What is the difference in musculature across the stomach?

Answer 38

Antrum contains thicker, more powerful smooth muscle

Question 39

What is the serosa?

Answer 39

Connective tissue outer layer

Question 40

What are the layers of the muscular externa?

Answer 40

Longitudinal outer layer Circular middle layer Oblique inner layer

Question 41

What is special about the stomach submucosa and mucosa?

Answer 41

Contain folds (rugae) when empty and stretch as the stomach fills

Question 42

What is on the lumenal surface of the stomach?

Answer 42

Surface mucus cells | Invaginations (gastric pits) feeding into gastric glands

Question 43

What types of cell are present in gastric glands?

Answer 43

Mucus neck Parietal cells Chief cells