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GI - Year 2 > Upper GI Tract - Structure and Function > Flashcards

Upper GI Tract - Structure and Function Flashcards

1
Q

Why does chewing occur?

A

Prolong taste experience

Defence against respiratory failure

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2
Q

How does voluntary controlled chewing work?

A

Somatic nerves induce movement of skeletal muscles of mouth/jaw

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3
Q

How does reflex controlled chewing work?

A

Contraction of jaw muscles triggered by pressure of food against gums, hard palate and tongue

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4
Q

How is saliva secreted?

A

By 3 pairs of glands:
Parotid
Submandibular
Sublingual

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5
Q

What is saliva made up of?

A 
Water
Mucins
a-amylase
Electrolytes 
Lysozyme
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6
Q

What is the role of water in saliva?

A

Softens, moistens and dilutes particles

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7
Q

What is the role of mucins in saliva?

A

Major protein component
Mucins + water = mucus
Viscous solution which has a lubricant function

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8
Q

What is the role of a-amylase in saliva?

A

Catalyses breakdown of polyssacharide (starch, glycogen) into disaccharide (maltose) + glucose

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9
Q

What is the role of electrolytes in saliva?

A

Regulates tonicity/pH

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10
Q

What is the role of lysozymes in saliva?

A

Bacteriocidal - cleaves polysaccharide component of bacterial cell wall

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11
Q

How is salivary secretion controlled?

A

By parasympathetic and sympathetic nervous systems which are both stimulatory

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12
Q

What are the nerves involved in parasympathetic control of salivary secretion? + result of stimulation

A

Cranial nerves VII (facial) and IX (glossopharyngeal)

Stimulation causes profuse watery salivery secretion

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13
Q

What is the result of stimulation of the sympathetic nerves in salivary secretion?

A

Stimulation causes small volume, viscous salivary secretion
High mucus content (a1 adrenoceptors)
High amylase content (b2 adrenoceptors)

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14
Q

What is the reflex control of salivary secretion?

A

Presence of food in mount sensed by chemoreceptors/pressure receptors in the walls of mouth/tongue which causes salivary secretion

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15
Q

What is the oesophagus?

A

Conduit between pharynx and stomach

Around 25cm

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16
Q

What are the 4 layers of the oesophagus?

A

Mucosa
Submucosa
Muscularis externa
Adventitia

17
Q

What type of epithelium lines the mucosa of the oesophagus?

A

Stratified squamous (non-keratinised)

18
Q

What are the submucosal mucous glands?

A

Ducts that secrete mucous to provide lubrication

19
Q

What type of muscle makes up the upper 1/3 of the muscularis externa in the oesophagus?

A

Skeletal muscle

20
Q

What type of muscle makes up the lower 2/3 of the oesophagus?

A

Smooth muscle

21
Q

What do the upper and lower oesophageal sphincters do?

A

Regulate movement of material into and out of oesophagus

22
Q

What is the oral phase of swallowing?

A

Voluntary

Bolus pushed to back of mouth by tongue

23
Q

What is the pharyngeal phase of swallowing?

A

Presence of bolus causes a sequence of reflex contractions of pharyngeal muscles
Coordinated by swallowing centre (medulla)
Soft palate reflected backward and upward (closes off nasopharynx)

24
Q

What happens as the bolus approaches the oesophagus?

A

Upper oesophageal sphincter relaxes and the epiglottis covers the opening to the larynx
Prevents food from entering trachea

25
Q

What happens once food has entered the oesophagus?

A

Upper oesophageal sphincter contracts

Prevents food reflux

26
Q

What is the oesophageal phase of swallowing?

A

Propulsion of bolus to stomach
A peristaltic wave sweeps along entire oesophagus
Takes ~10 seconds

27
Q

What happens as the bolus nears the stomach?

A

Lower oesophageal sphincter relaxes and bolus enters the stomach

28
Q

What happens in receptive relaxation of stomach?

A

Initiated following relaxation of lower oesophageal sphincter and entry of bolus into stomach
Vagal reflexes causes relaxation of thin, elastic smooth muscle of gastric fundus and body

29
Q

What is the range of stomach volume?

A

50ml –> 1500ml

No change in pressure

30
Q

What are 5 functions of the 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

31
Q

What are rugae?

A

Pleats that can open out to increase volume of the stomach

32
Q

Where does emulsification occur in the stomach?

A

Antrum

33
Q

What is the serosa of the stomach made of?

A

Connective tissue outer layer

34
Q

What are the 3 layers of the muscularis externae?

A

Longitudinal (outer)
Circular (middle)
Oblique (inner)

35
Q

What makes up the rugae in the stomach?

A

Submucosa and mucosa layers folded to make rugae that stretch as stomach fills

36
Q

What makes up the lumenal surface?

A

Surface mucus cells
Gastric pits leading into gastric glands
Mucus neck, parietal and chief cells

GI - Year 2 (39 decks)

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