Upper GI tract structure & function Flashcards Preview

Alimentary System > Upper GI tract structure & function > Flashcards

Flashcards in Upper GI tract structure & function Deck (26)
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1
Q

What is the reflex mechanism of chewing?

A

Contraction of jaw muscle > pressure of food against gums, hard palate and tongue > mechanoreceptors > inhibition of jaw muscles > reduced pressure > contraction

2
Q

What are the 3 pairs of glands saliva is secreted by?

A

Parotid

Submandibular

Sublingual

3
Q

What is saliva made of?

A

Water

Mucins

Alpha-amylase

Electrolytes

Lysozyme

4
Q

What are mucins?

A

Major protein component

Mucins + water = mucus

5
Q

What are lysozymes in saliva?

A

Bacteriocidal - cleaves polysaccharide component of bacterial cell wall

6
Q

What nerves carry out parasympathetic control of salivary secretion?

A

Cranial nerves VII (facial) & IX (glossopharyngeal)

7
Q

What receptors are responsible for the sympathetic control of salivary secretion?

A

High mucus content (a1 adrenoreceptors)

High amylase content (b2 adrenoreceptors)

8
Q

What is the oesophagus?

A

Conduit between pharynx and stomach (25m)

9
Q

What are the four layers of the oesophagus?

A

Mucosa

Submucosa

Muscularis externa

Adventitia

10
Q

What is mucosa lined by?

A

Stratified squamous epithelium (non-keritinised)

11
Q

What forms the muscularis externa?

A

Upper 1/3 (superior) = skeletal muscle

Lower 2/3 (inferior) = smooth muscle

12
Q

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

A

Upper and lower oesophageal sphincters

13
Q

What happens in the oral phase (voluntary) of swallowing?

A

Bolus pushed to back of mouth by tongue

14
Q

What happens during the pharyngeal phase of swallowing?

A

Presence of bolus > sequence of reflex contractions by pharyngeal muscles

Co-ordinated by swallowing centre (medulla)

Soft palate reflected backward and upward (closes off nasopharynx)

15
Q

What happens as bolus approaches oesophagus during swallowing?

A

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

16
Q

What happens once food has entered oesophagus?

A

Upper oesophageal sphincter contracts (prevents food reflux)

17
Q

What happens during the oesophageal phase of swallowing?

A

Propulsion of bolus to stomach

Peristaltic wave sweeps along entire oesophagus

Propelled to stomach in 10 seconds

18
Q

What happens as bolus nears stomach?

A

Lower oesophageal sphincter (LOS) relaxes > bolus enters stomach

19
Q

What is the receptive relaxation of stomach?

A

Initiated following relaxation of lower oesophageal sphincter (LOS) and entry of bolus into stomach

20
Q

What reflexes does the receptive relaxation of stomach use?

A

Vagal reflexes > relaxation of thin muscle of gastric fundus and body

Stomach volume: 50ml > 1500ml (no change in pressure)

21
Q

Functions of stomach

A

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 (Vitamin B12 absorption)

22
Q

What are the main parts of the stomach

A

Fundus

Cardiac region

Body

Pylorus

Antrum

Duodenum

23
Q

Serosa of stomach

A

Connective tissue outer layer

24
Q

What are the 3 layers of the muscularis externae?

A

Longitudinal (outer)

Circular (middle)

Oblique (inner)

25
Q

What is the rugae of the stomach?

A

Submucosa and mucosa folded

  • Rugae stretches as stomach fills
26
Q

What is the lumenal surface of the stomach composed of?

A

Surface mucus cells > gastric pits > gastric glands > mucus neck, parietal and chief cells