Gastrointestinal tract Flashcards
1
Q
What is digestion?
A
Process of braking down macromolecules to allow absorption
2
Q
What is absorption?
A
Process of moving nutrients and water across a membrane
3
Q
What structures are located within the foregut?
A
Oesophagus stomach Liver Pancreas Biliary system
4
Q
What structures are located in the midgut?
A
Intestine
5
Q
What structure is located in the hind gut?
A
Colon and rectum
6
Q
What are the four layers of the gut wall?
A
Mucosa
Submucosa
Muscularis
Serosa/adventitia
7
Q
Which connective tissue layer is associated and in contact with the ingested food?
A
Lamina propria
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)
9
Q
Which type of cells are intersected among the epithelial cells?
A
Goblet cells
10
Q
What is the function of goblet cells?
A
Secretion of mucous and fluid into the lumen
11
Q
which types of cells secrete hormones into the interstitial space between cells?
A
Enteroendocrine cells
12
Q
Which types of cells are located within the stomach and intestine?
A
Simple columnar epithelial
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
14
Q
What is the term used to describe mucosa-associated lymphoid tissue?
A
Peyer’s patches.
15
Q
What is contained within the submucosa?
A
Contains nerve plexus
Blood and lymphatic vessels
Submucosal glands
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
17
Q
What is the main role performed by the serosa (adventitia)?
A
Protective layer
18
Q
What term is used to describe the enetnrace to the mouth?
A
Labia
19
Q
Which muscle regulates the entry of substrate into the oral cavity?
A
Orbicularis oris muscle
20
Q
What is the midline fold of mucous membrane that attaches the inner surface of each lip to the gum?
A
Labial frenulum
21
Q
Which muscles of mastication is located between the skin and mucous membrane?
A
Buccinator muscle
22
Q
Which muscle of mastication elevates and protrudes mandible?
A
Masseter muscle
23
Q
What are the 3 main salivary glands?
A
Submandibular gland
Sublingual gland
Parotid gland
24
Q
Which gland resides within the floor of the mouth?
A
Submandibular gland
25
How is saliva secreted by the submandibular gland?
Through submandibular ducts
26
Where are sublingual glands located?
Lie inferior to the tongue, use the lesser sublingual ducts to secrete saliva into the oral cavity
27
Where is the parotid gland located?
Reside between the skin and the master muscle, proximal to the ears
28
How does the parotid gland secrete saliva?
Secrete saliva into the mouth through the parotid duct
29
Where is the parotid duct located?
Second upper molar tooth
30
What comprises the saliva?
Water, mixture of ions, glycoproteins, enzymes and growth factors,
+ waste products
31
Which enzymes breaks down carbohydrates?
Salivary amylase
32
How is salivary amylase inactivated?
By stomach acids
33
Which two ions behave as chemical buffers that maintains saliva at pH 6.35/8,5?
Bicarbonate and phosphate ions
34
What function is performed by mucous?
Lubricates food facilitating movement in the mouth, bolus formation and swallowing
35
Which enzyme catalyses fat digestion?
Lingual lipase
36
What are the primary functions of the tongue?
Facilitates ingestion, mechanical digestion, chemical digestion (lingual lipase), sensation (taste, texture and temperature of food)
Swalloing and vocalisation
37
Where is the tongue attached to?
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
38
What are the intrinsic muscles within the tongue?
Longtudinalis inferior
Superior
Transversus linguae
Verticalis linguae
39
What is the function of the intrinsic tongue muscles?
Fine motor control and moving food
40
What is the function of extrinsic muscles?
Gross movement of tongue, assets mechanical digestion
41
How many teeth do humans have?
32
42
How many incisors?
8
43
How many canines?
4
44
How many premolars?
8
45
How many molars?
12
46
What structure connects the pharynx to the stomach?
Oesophagus
47
Where is the oesophagus located?
Posterior to the trachea
48
How does the oesophagus enter the abdomen?
Traverses through the mediastinum in order to enter, the oesophagus penetrates the diaphragm from the oesophageal hiatus
49
Which anatomical structure is located at the penetration of the oesophagus at the diaphragm?
Oesophageal hiatus
50
Where does the oesophagus begin and end?
C5-T10
51
What is the function of the oesophagus?
Conduit for food, drink and swallowed secretions from pharynx to stomach
52
What is the function of the upper oesophageal sphincter?
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
53
How is the bolus of food propelled towards the stomach?
Rhythmic waves of peristalsis
54
How is the oesophagus lubricated?
Oesophageal mucosa
55
What is the function of the lower oesophageal sphincter?
Relaxes to enable food to pass into the stomach, contracts to prevent stomach acids from backing up into the oesophagus.
56
What surrounds the LOS?
Muscular diaphragm, seals sphincter during periods of no swallowing
57
What is GERD?
Gastroesophageal reflux disease
| Lower oesophageal sphincter does not completely close
58
What types of cells form the mucosa of the oesophagus?
Non-keratinised stratified squamous epithelium
59
Where are the mucous secreting glands located?
Mucosa lamina propria
60
How does the muscularis layer change along the oesophagus?
Skeletal muscle --> skeletal & smooth muscle --> smooth muscle
61
What is the most superficial layer of the oesophagus?
Adventitia
62
What is the function of peristalsis within the oesophagus?
Propels the bolus through the oesophagus
63
What is the outcome of the upper oesophageal sphincter relaxation?
Allows the bolus to move from the laryngopharynx to the oesophagus
64
What is the outcome for lower oesophageal sphincter relaxation?
Allows the bolus to move from the oesphagus into the stomach and prevents chyme from entering.
65
What is the function of mucous secretion?
Lubricates the oesophagus allowing easy passage of the bolus.
66
How is acid reflux prevented via the gastro-oesophageal junction?
Prevented by diaphragm
67
What is the term used to describe gastric folds?
Rugae
68
Where does the gastro-oesophageal junction begin?
Diaphragmatic hiatus
| Pinching the lower end of the oesophagus, preventing acid reflux upwards
69
Describe the transition of cells along the gastro-oesophageal junction?
Stratified squamous into simple columnar
70
What is secreted by simple columnar ?
Secretes protective mucous
71
What prevents upwards moment of acid?
Mucosal folds
72
Which types of ligaments compensates the collapse of the lower oesophagus?
Pharyngoesophagel ligaments
73
Why does acid-reflux disease occur?
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
What function is performed by gastric folds?
Absorptive function, within the gastrointestinal tract, presence of vili and microvilli (increases surface area)
75
What are the three phases of swallowing?
Voluntary phase of deglutition (oral)
Pharyngeal phase
Oesophageal phase
76
What occurs during voluntary phase?
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
Describe the state of the oesophageal sphincters during the voluntary phase?
Both constricted
78
Which centre controls swallowing?
Deglutition centre
79
Where is the deglutition centre located?
Medulla oblongata
80
Where are impulses sent from the deglutition centre?
Uvula and soft palate
81
Why do the laryngeal muscles constrict during the pharyngeal phase?
Prevents aspiration of good into the trachea
82
What phase succeeds the voluntary phase?
Pharyngeal phase
83
How does the bolus move through the oropharynx and laryngopharynx?
Contractions of the pharyngeal constrictor muscles
84
Which sphincter is open to allows food entry into the oesophagus?
Upper oesophageal sphincter relaxes.
85
What occurs during the oesophageal phase?
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
Which muscles of the muscularis contract?
Internal circular muscle
87
What effect does the longitudinal muscles have upon contraction in a peristaltic wave?
Longitudinal muscle layer contracts, shortens area and pushing out its walls to receive the bolus
Superior muscles contract --> inferior dilate
88
Which reflex is initiated due to distension of the oesophagus?
Short reflex relaxation of the lower oesophageal sphincter , allows the bolus to pass trough into the stomach
89
Which gland secrete mucous to lubricate the bolus and minimise friction?
Oesophageal glands
90
Which sphincter closes upon bolus collection?
Lower oesophageal sphincter
91
What are the four layers of the stomach (deep to superficial)?
Mucosa, submucosa, muscularis and serosa
92
Which three muscles are present in the muscularis layer?
Internal circular muscle
Inner oblique smooth muscle
External longitudinal muscle
93
What are the 3 principal functions of the stomach?
Degrades food into smaller particles
Stores food, releasing it in a controlled steady rate into the duodenum
Kills parasites and specific bacteria
94
What is the cardia?
Points whereby the oesophagus connects to the stomach and through which food passes into the stomach
95
Which structure is inferior to the diaphragm and dome shaped (stomach)?
Fundus
96
Which is the main part of the stomach?
Body
97
Which structure connects the stomach to the duodenum?
Pylorus
98
Which pyloric structure attaches to the duodenum?
Pyloric canal
99
Which pyloric structure is associated with the body of the stomach?
Pyloric antrum
100
Where is the pyloric sphincter located?
Pyloric canal --> controls gastric emptying
101
What are rugae?
In absence of food, stomach deflates inward, subsequent mucosa and submucosa retreat into large folds
102
Where is mucous exclusively secreted from?
Cardia and pyloric regions (glands comprised primarily of mucous secreting cells)
103
Where is mucous, HCL and pepsinogen secreted from within the stomach?
Body and fundus
104
Where in the stomach is gastrin released from?
Antrum
105
Which cells secrete HCl?
Parietal cells
106
What do parietal cells secrete?
Hal and intrinsic factor
107
What is the function of HCl secretion?
Acidity of the stomach, required for activation of pepsinogen into pepsin
Acidity regulates bacteria , denatures protein to increase availability for enzymatic digestion
108
What is the role performed by intrinsic factor within the stomach?
Glycoprotein necessary for the absorption of vitamin b12, in the small intestine.
109
Which cells secrete pepsinogen?
Chief cells
110
Where are chief cells located?
Basal regions of gastric glands (body and fundus of stomach)
111
What is the term used to describe a proenzyme?
Zymogen
112
What are mucous neck cells?
Gastric glands in the upper part of the stomach , secrete alkaline mucous.
113
Which specific hormone is secreted by enteroendocrine cells?
Gastrin
114
Which specific cells secrete gastrin?
G-cells
115
How is self digestion of the stomach prevented?
By the mucosal barrier
116
What is the pH of the epithelial surface?
6-7
117
What is the pH of the lumen?
1-2
118
Which ion is rich in mucous within the mucosal barrier?
Bicarbonate ions
119
What is the role performed by bicarbonate ions with the mucosal barrier?
Ions neutralise acid
120
Which type of junctions blocks gastric ache from penetrating the underlying tissue layers?
Tight junctions
121
Which concentrated substate forms mucous gel?
Mucins
122
What is the function of the pylorus?
Behaves as a filter, permitting only liquids and small food particles to pass through
123
What is gastric emptying?
Rhythmic mixing waves force approximately 3mL of chyme at a time through the pyloric sphincter into the duodenum.
124
What happens if a greater amount of chyme is released through the to the duodenum?
Overwhelms the capacity of the small intestine to accommodate load.
125
How is gastric emptying regulated?
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
What percentage of muscle contractions represent peristalsis?
20%
127
What is the purpose of peristaltic contractions?
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
How are peristaltic contractions controlled?
Autonomic nervous system
129
What percentage of muscle contractions represent segmentation?
80% contractions
130
Stretching of the muscularis layer activates which nervous system?
Enteric nervous system
131
What are the intracellular adaptations of chief cells?
Abundant endoplasmic reticulum (ribosomes) (protein translation and synthetic function of proteins)
Golgi apparatus packages and modifies these proteins into apical secretion granules
132
What are the intracellular adaptations of parietal cells?
Mitochondria (atp demand), cytoplasmic tubulovesicles (contain H+/K+ internal ATPase)
internal canliculi to apical surface
133
What is the function of the hydrogen/potassium ATPase pump?
Secretes hydrogen ions into a system of tubules and canaliculi, releasing HCl into the lumen.
134
What occurs during the active state within parietal cells?
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
What is the purpose of carbonic anhydrase within the gastric cells?
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
Which cells secrete gastrin?
Enteroendocrine G cells with the pyloric antrum.
137
What is the function of gastrin?
Gastrin stimulates histamine release from chromatin cells, and encourages HCl secretion of parietal cells
138
Which cells secrete histamine within the GI tract?
Chromaffin cells
139
What are the three phases of gastric secretion?
Cephalic phase
gastric phase
Intestinal phase
140
What is the cephalic phase of gastric secretion?
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
Which nerve innervates mechanical contractions, pyloric sphincter relation and gastric secretion?
Vagus nerve
142
What type of reflex occurs due to smell, taste and vision?
Conditioned reflex
143
What effect does a cut vagus nerve have on the cephalic phase?
Pyloric sphincter remains constricted, thus causing vomiting.
144
What factors suppress the cephalic phase?
Depression and loss of apatite
145
How is the gastric phase initiated?
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
What stimulates the release of gastrin from enteroendocrine g cells?
Proteins, caffeine and rising pH
147
Wha effect does G cells have on parietal cells?
Increases HCl production (providing an acidic environment, favourable towards the conversion of pepsinogen to pepsin)
148
Which plexus contains the vagus nerve?
Myenteric plexus
149
What is the excitatory intestinal phase?
Protein concentration in duodenum stimulates gastrin secretion
150
What is the enterogastric reflex?
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
Which hormones are produced by enteroendocrine cells of the duodenum?
Cholecystokinin (CCK)
| Secretin
152
What effect is exerted by CCK and secretin?
Inhibits production of HCl and pepsin, as fellas inhibiting gastric motility, enabling time for the duodenum to hydrolyse the chyme
