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BRS Y1 > Week 9- Upper GI Tract > Flashcards

Week 9- Upper GI Tract Flashcards

1
Q

Define digestion

A

The process of breaking down macromolecules to allow absorption

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2
Q

Define absorbtion

A

The process of moving nutrients and water across a membrane

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3
Q

What are the 4 layers of the gut wall?

A

Mucosa
Submucosa
Muscularis
Serosa

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4
Q

Describe the mucosa layer

A

Epithelium, loose connective tissue, muscularis mucosae

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5
Q

Describe the submucosa layer

A

Connective tissue containing nerve plexus

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6
Q

Describe the muscularis layer

A

Smooth muscle containing nerve plexus

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7
Q

Describe the serosa layer

A

Connective tissue, may have epithelium

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8
Q

What are the 3 salivary glands?

A

Parotid, sublingual and maxillary gland

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9
Q

How many body cavities does the oesophagus traverse?

A

3

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10
Q

What is the function of the oesophagus?

A

Conduit for food, drink and swallowed secretions from pharynx to stomach

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11
Q

What type of epithelium is present on the oesophagus?

A

Non keratinising

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12
Q

What sphincters are present in the oesophagus?

A

Upper and lower oesophageal sphincters

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13
Q

What is gastro oesophageal reflux disease?

A

When stomach acid refluxes into the oesophagus

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14
Q

What is oesophagitis?

A

Swelling of the oesophagus

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15
Q

What defence mechanism does the oesophagus have against acid reflux?

A

Change from squamous to columnar epithelium (Barrets syndrome when goes too far)

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16
Q

What muscle is present in the oesophagus?

A

Circular muscle

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17
Q

At the gastro oesophageal junction what prevents reflux/

A

The diaphragm

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18
Q

What are gastric folds at the gastro oesophageal junction called?

A

Rugae

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19
Q

How does the pressure change from the thorax to the abdomen? How is this significant?

A

Goes from negative to positive keeping the oesophagus in the abdominal cavity collapsed

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20
Q

Why are gastric folds present?

A

Plays a role in absorptive function- increases surface area greatly

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21
Q

What are the 4 phases of swallowing?

A

Oral phase
Pharyngeal phase
Upper oesophageal phase
Lower oesophageal phase

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22
Q

What is the function of the stomach?

A

Breaks food into smaller particles (acid and pepsin)
Holds food, releasing it in a controlled steady rate into duodenum
Kills parasites and certain bacteria

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23
Q

What does the stomach release food into?

A

Duodenum

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24
Q

How much acid does the stomach secrete a day?

A

2L

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25
Q

What is the pH of the stomach at the epithelial surface?

A

6-7

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26
Q

What is the pH of the stomach at the lumen?

A

1-2

27
Q

What is a stomach chief cell?

A

Protein secreting epithelial cells
Abundant RER
Secretes pepsinogen
Masses of apical secretion granules

28
Q

What converts pepsinogen to pepsin?

A

Hcl

29
Q

What is the difference between pepsinogen and pepsin?

A

Pepsin is the active form

30
Q

What is a parietal stomach cell?

A

Many mitochondria
Cytoplasmic tubulovesicles
Internal caniculi

31
Q

What is gastrin?

A

A hormone secreted by G cells, stimulates histamine release from chromaffin cells

32
Q

How many teeth do humans have in total?

A

32

33
Q

What are the 4 types of teeth and how many of each do humans have?

A

Incisors (8)
Canines (4)
Premolars (8)
Molars (12)

34
Q

What is the largest jaw muscle?

A

Masseter muscle

35
Q

What does saliva contain?

A

Aqueous secretion and digestive enzymes

36
Q

What enzymes does saliva contain and what do they do?

A 
Lingual lipase (fat digestion)
Salivary amylase (carbohydrate digestion)
37
Q

What 2 types of muscle are present in the tongue and what do they do?

A

Intrinsic- for fine motor control and movement of food

Extrinsic- for moving the tongue itself, aids mechanical digestion

38
Q

What does the oesophagus traverse in the spine?

A

C5-T10

39
Q

How does food move down the oesophagus?

A

Via peristalsis

40
Q

Describe the oral phase

A

Chewing and saliva prepare the bolus, both oesophageal sphincters are constricted

41
Q

Describe the pharyngeal phase

A

Pharyngeal muscles guide the bolus towards the oesophagus, both oesophageal sphincters open

42
Q

Describe the upper oesophageal phase

A

Upper sphincter closes
Superior circular muscle rings contract and inferior rings dilate
Sequential contractions of longitudinal muscle

43
Q

Describe the lower oesophageal phase

A

Lower sphincter closes as food passes through

44
Q

What are the 3 sections of the stomach?

A

Cardia and pyloric region
Body and fundus
Antrum

45
Q

What do the cardia and pyloric regions of the stomach secrete?

A

Mucus only

46
Q

What do the body and fundum of the stomach secrete?

A

Mucus, Hcl and pepsinogen

47
Q

What does the antrum of the stomach secrete?

A

Gastrin

48
Q

What ion is found trapped in the mucus from the stomach?

A

HCO3-

49
Q

What are the 2 types of stomach muscle contraction?

A

Peristalsis and segmentation

50
Q

Which stomach muscle contraction is more powerful?

A

Peristalsis

51
Q

Which stomach muscle contraction is more common?

A

Segmentation

52
Q

Describe peristalsis in the stomach

A

Makes up 20% of muscle contractions
Is more powerful as chyme is pushed to the colon, movement from LOS to pyloric sphincter
ANS is essential

53
Q

What is required for peristalsis in the stomach?

A

Autonomic nervous system involvement

54
Q

Describe segmentation in the stomach

A

Makes up 80% of muscle contraction
Is weaker as solid chyme pushed back to the body and fluid chyme pushed towards pyloric sphincter
Stretching activates the enteric nervous system

55
Q

How is the enteric nervous system activated?

A

Via stretching during segmentation in the stomach

56
Q

How is HCL synthesised in the gastric lumen?

A

CO2 moves into the parietal cell
CO2 combines with water to form carbonic acid
Carbonic acid dissociates into H+ and HCO3-
K+ moves into the parietal cell, Na+ moves out
K+ carried to the gastric lumen via H+/K+ ATPase
HCO3- moves out of the cell via pump and Cl- moves into gastric lumen
H+ from dissociation of carbonic acid moves into gastric lumen, K+ pumped back into the parietal cell
H+ and Cl- in the gastric lumen can now combine to form HCl

57
Q

What are the 3 phases of gastric secretion?

A

Cephalic phase
Gastric phase
Intestinal phase

58
Q

Describe how the cephalic phase causes stimulation of stomach secretory activity

A

Sight/thought/smell of food or stimulation of taste on receptors on tongue cause stimulation via vagus nerve to the stomach

59
Q

Describe how the cephalic phase causes inhibition of stomach secretory activity

A

Loss of appetite/depression causes lack of stimulation to the parasympathetic centre inhibiting secretory activity

60
Q

Describe how the gastric phase causes stimulation of stomach secretory activity

A

Stomach distention activates stretch receptors, food chemicals and rising pH activates chemoreceptors which leads to stimulation via the vagus nerve

61
Q

Describe how the gastric phase causes inhibition of stomach secretory activity

A

Excessive acidity causes decline of gastric secretion or emotional distress activates sympathetic system which overides parasympathetic controls and inhibits activity

62
Q

Describe how the intestinal phase causes stimulation of stomach secretory activity

A

Presence of low pH and partially digested food in the duodenum stimulates stomach secretory activity

63
Q

Describe how the intestinal phase causes inhibition of stomach secretory activity

A

Distention of the duodenum, presence of fatty acidic or hypertonic chyme inhibits secretory activity

BRS Y1 (52 decks)

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