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Y1 BRS > Gastrointestinal tract > Flashcards

Gastrointestinal tract Flashcards

1
Q

What is digestion?

A

Process of braking down macromolecules to allow absorption

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2
Q

What is absorption?

A

Process of moving nutrients and water across a membrane

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3
Q

What structures are located within the foregut?

A 
Oesophagus
stomach
Liver
Pancreas 
Biliary system
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4
Q

What structures are located in the midgut?

A

Intestine

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5
Q

What structure is located in the hind gut?

A

Colon and rectum

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6
Q

What are the four layers of the gut wall?

A

Mucosa
Submucosa
Muscularis
Serosa/adventitia

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7
Q

Which connective tissue layer is associated and in contact with the ingested food?

A

Lamina propria

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8
Q

What type of epithelial cells are located within the mouth, pharynx, oesophagus and the anal canal?

A

Non keratinised, stratified squamous epithelium.

Epithelial is in direct contact with the lumen (space inside the alimentary canal)

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9
Q

Which type of cells are intersected among the epithelial cells?

A

Goblet cells

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10
Q

What is the function of goblet cells?

A

Secretion of mucous and fluid into the lumen

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11
Q

which types of cells secrete hormones into the interstitial space between cells?

A

Enteroendocrine cells

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12
Q

Which types of cells are located within the stomach and intestine?

A

Simple columnar epithelial

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13
Q

What is located within the lamina propria?

A

Contains numerous blood and lymphatic vessels that transport nutrients absorbed through the alimentary canal. Serves an immune function by hosting lymphocytes

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14
Q

What is the term used to describe mucosa-associated lymphoid tissue?

A

Peyer’s patches.

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15
Q

What is contained within the submucosa?

A

Contains nerve plexus
Blood and lymphatic vessels
Submucosal glands

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16
Q

What two types of muscles reside within the muscularis?

A

Inner circular layer
Outer longitudinal layer
Contractions promote mechanical digestion and movement of substrate along canal
Constriction of bowel, food passed segmentally, enabling tie for absorption

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17
Q

What is the main role performed by the serosa (adventitia)?

A

Protective layer

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18
Q

What term is used to describe the enetnrace to the mouth?

A

Labia

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19
Q

Which muscle regulates the entry of substrate into the oral cavity?

A

Orbicularis oris muscle

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20
Q

What is the midline fold of mucous membrane that attaches the inner surface of each lip to the gum?

A

Labial frenulum

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21
Q

Which muscles of mastication is located between the skin and mucous membrane?

A

Buccinator muscle

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22
Q

Which muscle of mastication elevates and protrudes mandible?

A

Masseter muscle

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23
Q

What are the 3 main salivary glands?

A

Submandibular gland
Sublingual gland
Parotid gland

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24
Q

Which gland resides within the floor of the mouth?

A

Submandibular gland

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25
Q

How is saliva secreted by the submandibular gland?

A

Through submandibular ducts

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26
Q

Where are sublingual glands located?

A

Lie inferior to the tongue, use the lesser sublingual ducts to secrete saliva into the oral cavity

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27
Q

Where is the parotid gland located?

A

Reside between the skin and the masseter muscle, proximal to the ears

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28
Q

How does the parotid gland secrete saliva?

A

Secrete saliva into the mouth through the parotid duct

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29
Q

Where is the parotid duct located?

A

Second upper molar tooth

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30
Q

What comprises the saliva?

A

Water, mixture of ions, glycoproteins, enzymes and growth factors,

+ waste products

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31
Q

Which enzymes breaks down carbohydrates?

A

Salivary amylase

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32
Q

How is salivary amylase inactivated?

A

By stomach acids

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33
Q

Which two ions behave as chemical buffers that maintains saliva at pH 6.35/8,5?

A

Bicarbonate and phosphate ions

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34
Q

What function is performed by mucous?

A

Lubricates food facilitating movement in the mouth, bolus formation and swallowing

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35
Q

Which enzyme catalyses fat digestion?

A

Lingual lipase

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36
Q

What are the primary functions of the tongue?

A

Facilitates ingestion, mechanical digestion, chemical digestion (lingual lipase), sensation (taste, texture and temperature of food)
Swalloing and vocalisation

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37
Q

Where is the tongue attached to?

A

The mandible, the styloid processes of the temporal bones and hyoid bone
Tongue is positioned over the floor of the oral cavity
Medial septum extends the entire length of the tongue dividing it into symmetric halves

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38
Q

What are the intrinsic muscles within the tongue?

A

Longtudinalis inferior
Superior
Transversus linguae
Verticalis linguae

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39
Q

What is the function of the intrinsic tongue muscles?

A

Fine motor control and moving food

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40
Q

What is the function of the extrinsic muscles of tongue?

A

Gross movement of tongue, assists mechanical digestion

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41
Q

How many teeth do humans have?

A

32

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42
Q

How many incisors?

A

8

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43
Q

How many canines?

A

4

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44
Q

How many premolars?

A

8

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45
Q

How many molars?

A

12

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46
Q

What structure connects the pharynx to the stomach?

A

Oesophagus

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47
Q

Where is the oesophagus located?

A

Posterior to the trachea

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48
Q

How does the oesophagus enter the abdomen?

A

Traverses through the mediastinum in order to enter, the oesophagus penetrates the diaphragm from the oesophageal hiatus

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49
Q

Which anatomical structure is located at the penetration of the oesophagus at the diaphragm?

A

Oesophageal hiatus

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50
Q

Where does the oesophagus begin and end?

A

C5-T10

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51
Q

What is the function of the oesophagus?

A

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

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52
Q

What is the function of the upper oesophageal sphincter?

A

Controls the movement of food from the pharynx into the oesophagus
Upper 2/3 consists of both smooth and skeletal muscle fibres, with the latter transitioning out into the bottom 1/3 oesophagus

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53
Q

How is the bolus of food propelled towards the stomach?

A

Rhythmic waves of peristalsis

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54
Q

How is the oesophagus lubricated?

A

Oesophageal mucosa

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55
Q

What is the function of the lower oesophageal sphincter?

A

Relaxes to enable food to pass into the stomach, contracts to prevent stomach acids from backing up into the oesophagus.

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56
Q

What surrounds the LOS?

A

Muscular diaphragm, seals sphincter during periods of no swallowing

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57
Q

What is GERD?

A

Gastroesophageal reflux disease

Lower oesophageal sphincter does not completely close

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58
Q

What types of cells form the mucosa of the oesophagus?

A

Non-keratinised stratified squamous epithelium

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59
Q

Where are the mucous secreting glands located?

A

Mucosa lamina propria

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60
Q

How does the muscularis layer change along the oesophagus?

A

Skeletal muscle –> skeletal & smooth muscle –> smooth muscle

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61
Q

What is the most superficial layer of the oesophagus?

A

Adventitia

62
Q

What is the function of peristalsis within the oesophagus?

A

Propels the bolus through the oesophagus

63
Q

What is the outcome of the upper oesophageal sphincter relaxation?

A

Allows the bolus to move from the laryngopharynx to the oesophagus

64
Q

What is the outcome for lower oesophageal sphincter relaxation?

A

Allows the bolus to move from the oesphagus into the stomach and prevents chyme from entering.

65
Q

What is the function of mucous secretion?

A

Lubricates the oesophagus allowing easy passage of the bolus.

66
Q

How is acid reflux prevented via the gastro-oesophageal junction?

A

Prevented by diaphragm

67
Q

What is the term used to describe gastric folds?

A

Rugae

68
Q

Where does the gastro-oesophageal junction begin?

A

Diaphragmatic hiatus

Pinching the lower end of the oesophagus, preventing acid reflux upwards

69
Q

Describe the transition of cells along the gastro-oesophageal junction?

A

Stratified squamous into simple columnar

70
Q

What is secreted by simple columnar ?

A

Secretes protective mucous

71
Q

What prevents upwards moment of acid?

A

Mucosal folds

72
Q

Which types of ligaments compensates the collapse of the lower oesophagus?

A

Pharyngoesophagel ligaments

73
Q

Why does acid-reflux disease occur?

A

Enlarged hiatus, stomach migration to the chest causes the gastro-oesophageal junction to dilate and open
Hiatus hernias (hiatus is enlarged, subsequent constriction of oesophagus is inhibited) - stomach has traverses into the chest
Breathlessness, reduction in TLC

74
Q

What function is performed by gastric folds?

A

Absorptive function, within the gastrointestinal tract, presence of vili and microvilli (increases surface area)

75
Q

What are the three phases of swallowing?

A

Voluntary phase of deglutition (oral)

Pharyngeal phase

Oesophageal phase

76
Q

What occurs during voluntary phase?

A

Somatic contort of swallowing, within the phase, chewing has been completed and swallowing set in motion

Tongue moves upwards and backwards against palate, pushing the bolus to back too the oral cavity into the oropharynx

1) Chewing and saliva prepare bolus
2) Both oesophageal sphincters constricted

77
Q

Describe the state of the oesophageal sphincters during the voluntary phase?

A

Both constricted

78
Q

Which centre controls swallowing?

A

Deglutition centre

79
Q

Where is the deglutition centre located?

A

Medulla oblongata

80
Q

Where are impulses sent from the deglutition centre?

A

Uvula and soft palate

81
Q

Why do the laryngeal muscles constrict during the pharyngeal phase?

A

Prevents aspiration of food into the trachea

82
Q

What phase succeeds the voluntary phase?

A

Pharyngeal phase

83
Q

How does the bolus move through the oropharynx and laryngopharynx?

A

Contractions of the pharyngeal constrictor muscles

84
Q

Which sphincter is open to allows food entry into the oesophagus?

A

Upper oesophageal sphincter relaxes.

85
Q

What occurs during the oesophageal phase?

A

Entry of food into the oesophagus demarcates the beginning of the oesophageal phase of deglutition, and the initiation of peristalsis

Propels the bolus through the oesophagus towards the stomach

86
Q

Which muscles of the muscularis contract?

A

Internal circular muscle

87
Q

What effect does the longitudinal muscles have upon contraction in a peristaltic wave?

A

Longitudinal muscle layer contracts, shortens area and pushing out its walls to receive the bolus

Superior muscles contract –> inferior dilate

88
Q

Which reflex is initiated due to distension of the oesophagus?

A

Short reflex relaxation of the lower oesophageal sphincter , allows the bolus to pass trough into the stomach

89
Q

Which gland secrete mucous to lubricate the bolus and minimise friction?

A

Oesophageal glands

90
Q

Which sphincter closes upon bolus collection?

A

Lower oesophageal sphincter

91
Q

What are the four layers of the stomach (deep to superficial)?

A

Mucosa, submucosa, muscularis and serosa

92
Q

Which three muscles are present in the muscularis layer?

A

Internal circular muscle
Inner oblique smooth muscle
External longitudinal muscle

93
Q

What are the 3 principal functions of the stomach?

A

Degrades food into smaller particles
Stores food, releasing it in a controlled steady rate into the duodenum
Kills parasites and specific bacteria

94
Q

What is the cardia?

A

Points whereby the oesophagus connects to the stomach and through which food passes into the stomach

95
Q

Which structure is inferior to the diaphragm and dome shaped (stomach)?

A

Fundus

96
Q

Which is the main part of the stomach?

A

Body

97
Q

Which structure connects the stomach to the duodenum?

A

Pylorus

98
Q

Which pyloric structure attaches to the duodenum?

A

Pyloric canal

99
Q

Which pyloric structure is associated with the body of the stomach?

A

Pyloric antrum

100
Q

Where is the pyloric sphincter located?

A

Pyloric canal –> controls gastric emptying

101
Q

What are rugae?

A

In absence of food, stomach deflates inward, subsequent mucosa and submucosa retreat into large folds

102
Q

Where is mucous exclusively secreted from?

A

Cardia and pyloric regions (glands comprised primarily of mucous secreting cells)

103
Q

Where is mucous, HCL and pepsinogen secreted from within the stomach?

A

Body and fundus

104
Q

Where in the stomach is gastrin released from?

A

Antrum

105
Q

Which cells secrete HCl?

A

Parietal cells

106
Q

What do parietal cells secrete?

A

Hal and intrinsic factor

107
Q

What is the function of HCl secretion?

A

Acidity of the stomach, required for activation of pepsinogen into pepsin
Acidity regulates bacteria , denatures protein to increase availability for enzymatic digestion

108
Q

What is the role performed by intrinsic factor within the stomach?

A

Glycoprotein necessary for the absorption of vitamin b12, in the small intestine.

109
Q

Which cells secrete pepsinogen?

A

Chief cells

110
Q

Where are chief cells located?

A

Basal regions of gastric glands (body and fundus of stomach)

111
Q

What is the term used to describe a proenzyme?

A

Zymogen

112
Q

What are mucous neck cells?

A

Gastric glands in the upper part of the stomach , secrete alkaline mucous.

113
Q

Which specific hormone is secreted by enteroendocrine cells?

A

Gastrin

114
Q

Which specific cells secrete gastrin?

A

G-cells

115
Q

How is self digestion of the stomach prevented?

A

By the mucosal barrier

116
Q

What is the pH of the epithelial surface?

A

6-7

117
Q

What is the pH of the lumen?

A

1-2

118
Q

Which ion is rich in mucous within the mucosal barrier?

A

Bicarbonate ions

119
Q

What is the role performed by bicarbonate ions with the mucosal barrier?

A

Ions neutralise acid

120
Q

Which type of junctions blocks gastric ache from penetrating the underlying tissue layers?

A

Tight junctions

121
Q

Which concentrated substate forms mucous gel?

A

Mucins

122
Q

What is the function of the pylorus?

A

Behaves as a filter, permitting only liquids and small food particles to pass through

123
Q

What is gastric emptying?

A

Rhythmic mixing waves force approximately 3mL of chyme at a time through the pyloric sphincter into the duodenum.

124
Q

What happens if a greater amount of chyme is released through the to the duodenum?

A

Overwhelms the capacity of the small intestine to accommodate load.

125
Q

How is gastric emptying regulated?

A

Regulated by both the stomach and duodenum
Presence of chyme activates receptors that inhibit gastric secretion, prevents additional chyme from being released by the stomach before the duodenum is ready to process it.

126
Q

What percentage of muscle contractions represent peristalsis?

A

20%

127
Q

What is the purpose of peristaltic contractions?

A

Propels chyme towards the colon from the lower oesophageal sphincter to the pyloric sphincter
Stomach contractions and propagation of substrate to the outlet –> pyrloric relaxation of the sphincter to facility passage of chyme

128
Q

How are peristaltic contractions controlled?

A

Autonomic nervous system

129
Q

What percentage of muscle contractions represent segmentation?

A

80% contractions

130
Q

Stretching of the muscularis layer activates which nervous system?

A

Enteric nervous system

131
Q

What are the intracellular adaptations of chief cells?

A

Abundant endoplasmic reticulum (ribosomes) (protein translation and synthetic function of proteins)
Golgi apparatus packages and modifies these proteins into apical secretion granules

132
Q

What are the intracellular adaptations of parietal cells?

A

Mitochondria (atp demand), cytoplasmic tubulovesicles (contain H+/K+ internal ATPase)
internal canliculi to apical surface

133
Q

What is the function of the hydrogen/potassium ATPase pump?

A

Secretes hydrogen ions into a system of tubules and canaliculi, releasing HCl into the lumen.

134
Q

What occurs during the active state within parietal cells?

A

Tubulovesicles fuse with membrane, project into canaliculi -> Secretes HCl into gastric lumen
Carbon dioxide from capillaries passively diffuse into the parietal cells, under the action of carbonic anhydrase activation (catalyses production of carbonic acid)

Dissociation into bicarbonate and hydrogen ions within the cell
bicarbonate ions exchanged for chloride ions
HCl produced

135
Q

What is the purpose of carbonic anhydrase within the gastric cells?

A

Carbonic anhydrase catalyses the formation of carbonic acid via water and carbon dioxide, this dissociates into hydrogen and bicarbonate ions.
Bicarbonate ions exchange fir chloride ions, producing HCl

136
Q

Which cells secrete gastrin?

A

Enteroendocrine G cells with the pyloric antrum.

137
Q

What is the function of gastrin?

A

Gastrin stimulates histamine release from chromaffin cells, and encourages HCl secretion of parietal cells

138
Q

Which cells secrete histamine within the GI tract?

A

Chromaffin cells

139
Q

What are the three phases of gastric secretion?

A

Cephalic phase
gastric phase
Intestinal phase

140
Q

What is the cephalic phase of gastric secretion?

A

Initiated by smell, taste, vision or though of food
Impulses from taste buds or via olfactory receptors within the cribriform plate of the ethmoid bone, relay impulses , triggering signals that increase gastric secretion in preparation of digestion

141
Q

Which nerve innervates mechanical contractions, pyloric sphincter relation and gastric secretion?

A

Vagus nerve

142
Q

What type of reflex occurs due to smell, taste and vision?

A

Conditioned reflex

143
Q

What effect does a cut vagus nerve have on the cephalic phase?

A

Pyloric sphincter remains constricted, thus causing vomiting.

144
Q

What factors suppress the cephalic phase?

A

Depression and loss of apatite

145
Q

How is the gastric phase initiated?

A

Initiated by entry of food into the stomach, stimulated through the distention arising from this, activating stretch receptors –> parasympathetic neurones release ACh –> provokes increases secretion of gastric juice

146
Q

What stimulates the release of gastrin from enteroendocrine g cells?

A

Proteins, caffeine and rising pH

147
Q

Wha effect does G cells have on parietal cells?

A

Increases HCl production (providing an acidic environment, favourable towards the conversion of pepsinogen to pepsin)

148
Q

Which plexus contains the vagus nerve?

A

Myenteric plexus

149
Q

What is the excitatory intestinal phase?

A

Protein concentration in duodenum stimulates gastrin secretion

150
Q

What is the enterogastric reflex?

A

Intestine distend with chyme, thus reflex inhibits secretion, closing the pyloric sphincter preventing additional chyme from entering the duodenum.
CCK and secretin are released by enteroendocrine cells of the duodenum upon chyme entry

151
Q

Which hormones are produced by enteroendocrine cells of the duodenum?

A

Cholecystokinin (CCK)

Secretin

152
Q

What effect is exerted by CCK and secretin?

A

Inhibits production of HCl and pepsin, as fellas inhibiting gastric motility, enabling time for the duodenum to hydrolyse the chyme

Y1 BRS (39 decks)

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