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GI AM > Upper GI structure and function > Flashcards

Upper GI structure and function Flashcards

1
Q

Why do we chew?

A

Prolong taste experience

Defence against respiratory failure

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2
Q

What are the 2 ways in which chewing is controlled?

A

Voluntary

Reflex

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3
Q

How is chewing voluntarily controlled?

A

Somatic nerved innervate skeletal muscles of mouth and jaw

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4
Q

How is chewing reflex controlled?

A

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

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5
Q

What are the 3 glands saliva is secreted by?

A

Parotid
Sublingual
Submandibular

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6
Q

What type of glands are salivary glands?

A

Exocrine

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7
Q

What is the structure of a salivary gland?

A

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

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8
Q

What are the components of saliva?

A 
Water
Mucins
Alpha amylase
Electrolytes
Lysozyme
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9
Q

What is the function of water in saliva?

A

Softens, moistens and dilutes particles

Solvent

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10
Q

What is the function of mucins in saliva?

A

Lubricant

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11
Q

What are mucins?

A

The protein component of saliva

Together with water, they form mucus

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12
Q

What is the function of alpha amylase in saliva?

A

Catalyses breakdown starch and glycogen to maltose and glucose

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13
Q

What is the function of electrolytes in the saliva?

A

Control tonicity/pH

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14
Q

What is the function of lysozyme in the saliva?

A

Bacteriocidal

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15
Q

How does lysozyme function?

A

Breaks up polysaccharide component of bacterial cell wall

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16
Q

How is salivary secretion controlled?

A

Para and sympathetic nervous systems

Reflex

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17
Q

How do the parasympathetic nerves control salivation?

A

Controlled by facial and glossopharyngeal nerves

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

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18
Q

How do the sympathetic nerves control secretion?

A

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

19
Q

How do reflexes control salivation?

A

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

20
Q

What is the oesophagus?

A

25cm conduit between mouth and stomach

21
Q

What are the layers of the oesophagus wall?

A

Mucosa
Submucosa
Muscularis externa
Adventitia/serosa

22
Q

What is the mucosa of the oesophagus lined by?

A

Non keratinised stratified squamous epithelium

23
Q

How do submucosal cells complete their function?

A

Submucosal glands release secretions via ducts which act as lubrication

24
Q

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

A

Upper 1/3= skeletal muscle

Lower 2/3= smooth muscle

25
Q

What are oesophageal sphincters?

A

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

26
Q

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

A

Bolus pushed to the back of the mouth by the tongue

27
Q

What happens in the pharyngeal phase of swallowing?

A

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

28
Q

What is the pharyngeal phase of swallowing coordinated by?

A

Swallowing centre in medulla

29
Q

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

A

Upper oesophageal sphincter relaxes and epiglottis covers larynx

30
Q

What happens once th bolus enters the oesophagus?

A

Upper oesophageal sphincter contracts

Propulsion of bolus to stomach by peristaltic wave

31
Q

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

A

About 10 seconds

32
Q

What happens as the bolus nears the stomach?

A

Lower oesophageal sphincter relaxes and food is allowed to enter stomach

33
Q

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

A

Receptive relaxation of stomach

34
Q

What is receptive relaxation of the stomach?

A

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

35
Q

What is special about the “stretch” of the stomach?

A

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

36
Q

What are the 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 for vitae’s B12 absorption

37
Q

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

A

At the entrance to the duodenum

Controls delivery of material to the small intestine

38
Q

What is the difference in musculature across the stomach?

A

Antrum contains thicker, more powerful smooth muscle

39
Q

What is the serosa?

A

Connective tissue outer layer

40
Q

What are the layers of the muscular externa?

A

Longitudinal outer layer
Circular middle layer
Oblique inner layer

41
Q

What is special about the stomach submucosa and mucosa?

A

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

42
Q

What is on the lumenal surface of the stomach?

A

Surface mucus cells

Invaginations (gastric pits) feeding into gastric glands

43
Q

What types of cell are present in gastric glands?

A

Mucus neck
Parietal cells
Chief cells

GI AM (34 decks)

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