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HUBS192 > Gastrointestinal System (20-27) > Flashcards

Gastrointestinal System (20-27) Flashcards

1
Q

What are the 4 roles of the GI system?

A

Motility
Secretion
Digestion
Absorption

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2
Q

What are the two types of epithelia in the GI system and where are they located?

A

Stratified squamous (mouth, esophagus, anus)
Simple columnar (stomach, small intestine, large intestine)

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3
Q

What is the structure of a goblet cell

A

Basal nuclei, columnar

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4
Q

What are the two types of multicellular glands

A

Simple (one duct)
Compound (2 or more ducts)

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5
Q

Why are multicellular glands important?

A

Because thye increase the surface area which allows for more secretions

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6
Q

What are the 4 layers of the gut tube?

A

Mucosa
Submucosa
Muscularis
Adventitia

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7
Q

What does the mucosa consist of? 5

A

Epithelium
basement membrane
Lamina propria
Muscularis mucosa
Glands (sometimes)

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8
Q

What is the myenteric plexus?

A

Located between the muscle layers which regulates motility

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8
Q

What are the two layers of smooth muscle in the muscularis?

A

Circular (inner)
Longitudinal (outer)

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9
Q

What does the adventitia consist of?

A

FCT

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10
Q

What is the outermost layer of the gut tube?

A

Adventitia

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11
Q

What is the function of having 2 layers of smooth muscle with different orientations?

A

Move things in different ways which results in motility patterns

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12
Q

Why are there glands in the mucosa and submucosal layers in some regions

A

More surface area that we can’t fit on the luminal surfaces

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13
Q

What kind of digestion happens in the mouth?

A

Mechanical
Chemical (enzymes)

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14
Q

What are the fauces?

A

Open spaces in the mouth

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15
Q

What are the 3 salivary glands?

A

Parotid
Sublingual
Submandibular

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16
Q

Where is the parotid salivary gland located and what does it secrete?

A

Furthest back in the oral cavity, secretes serous fluid with amylase

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17
Q

Where is the sublingual salivary gland located and what does it secrete?

A

Under the tongue, secretes mucus only (to lubricate the tongue)

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18
Q

Where is the submadibular salivary gland located and what does it secrete?

A

Under the mandible at the front of the tongue, it secretes a mixure

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19
Q

What is an acinus?

A

Cells in clusters

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20
Q

what can acinar cells secrete?

A

Serous fluid and amylase, mucus

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21
Q

What do duct cells secrete and what is the purpose of the secretion?

A

Bicarbonate - pH buffering

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22
Q

What is the structure and location of the esophagus?

A

Located posterior to the trachea, is 25cm long

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23
Q

What type of epithelium is in the esophagus?

A

Stratified squamous

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24
Q

What is the purpose of the muscularis externa in the esophagus and how is it laid out?

A

MOves food bolus, the first part is skeletal muscle, the bottom is smooth muscle and the middle is a mixture

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25
Q

What special feature does the mucosa and submucosa have in the esophagus?

A

Highly folded to allow expansion

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26
Q

What is the peritoneum?

A

Serous membrane that lines the abdomen

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27
Q

What are the two layers of peritoneum?

A

Parietal
Visceral

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28
Q

Where is the parietal layer of the peritoneum located?

A

Lines the body wall

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29
Q

where is the visceral layer of the peritoneum located?

A

Covers the organs

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30
Q

Where is the retroperioneal loayer located?

A

Posterior to the peritoneum

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31
Q

What types of membrane in the peritoneum?

A

Serous membrane

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32
Q

What is the mesentery?

A

Double layer of visceral peritoneum that connects the organ to the body wall

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33
Q

What is the omenta?

A

Double layer of visceral peritoneum that conects an organ to another organ

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34
Q

Where is the lesser omentum attached?

A

Holds the stomach to the liver

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35
Q

Where is the greater omentum attached?

A

Hangs like an apron over the intestine and contains immunes cells and fatty deposits. Attaches the stomach to the transverse colon

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36
Q

What structure prevents reflux of acid from the stomach?

A

Lower esophagal sphincter

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37
Q

What are the 4 main parts of the stomach?

A

Cardia
Fundus
Body
Pylorus

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38
Q

What is the cardia of the stomach?

A

Nearest the top where the stomach starts

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39
Q

What is the fundus of the stomach?

A

Widest area, gets filled wtih gases that are produced during digestion

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40
Q

What is the body of the stomach?

A

Biggest part and the most functional

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41
Q

what is the pylorus of the stomach?

A

Pylorus is the gatekeeper to the small intestine and it allows food through

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42
Q

What is the modification of the stomach muscle?

A

New layer called the oblique which is added on the inner to give motility

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43
Q

What kind of striations does the oblique musclular layer have?

A

Angular

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44
Q

what are rugae?

A

Temporary folds that allow for expansion in the stomach

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45
Q

What is a modification of the mucosa of the stomach?

A

Infolding which increases the surface area for gastric glands

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46
Q

What is a gastric pit?

A

Increased surface area

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47
Q

What are the 3 cells located in the gastric pits?

A

Parietal Cells
G cells
Cheif cells

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48
Q

What is the purpose of parietal cells?

A

Secrete acid and intrinsic factor

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49
Q

What is the purpose of G cells?

A

Secrete hormones - gastrin

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50
Q

What is the purpose of Cheif cells?

A

Secrete pepsinogen

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51
Q

What is the structure of a chief cell?

A

Columnar and have basal nuceli, abundance of zymogen granules and are abundant in the rER

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52
Q

How does the stomach control endocrine function?

A

Gastrin and Ghelin secreted into the bloodstream

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53
Q

What is the structure of a parietal cell?

A

Pump ions so have abundant mitochondria, they have a central nucleus and are folded to increase surface area

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54
Q

What is the name of the sphincter that sits between the stomach and the small intestine?

A

Pyloric Sphincter

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55
Q

Where is the mucus that neutralises stomach acid into the small intestine secreted from?

A

Glands of the submucosa in the duodenum

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56
Q

Where are the enzymes and bicarbonate that neutralise stomach acid secreted from?

A

Pancreas

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57
Q

Where is the pancreas located?

A

Head in duodenum, posterior to the stomach

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58
Q

What are the endocrine functions of the pancreas?

A

Alpha cells secrete glucagon
Beta cells secrete insulin

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59
Q

What are the exocrine functions of the pancreas?

A

Acinar cells secrete digestive enzymes
Duct cells secrete bicarbonate

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60
Q

Describe the structure and function of pancreatic acinar cells

A

Apical zymogen granukes
Basal nuceli
Abundant rER
Secrete enzymes

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61
Q

Where does the bile duct meet the pancreatic duct?

A

Hepatopancreatic ampulla

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62
Q

What is the release of hormones into the small intestine from the pancreas controlled via?

A

Hepatopancreatic sphincter

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63
Q

What are the 3 parts of the small intestine?

A

Duodenum
Jejjunum
Ileum

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64
Q

What is the longest part of the small intestine?

A

Duodenum

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65
Q

What is the purpose of the duodenum?

A

REcieve chyme from the stomach, enzymes and bicarbonate from the pancreas, and bile from the liver

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66
Q

What organ secretes biles?

A

Liver

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67
Q

What is the purpose of the jejunum and the ileum?

A

Digestion and absorption

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68
Q

What is the purpose of the mesentery?

A

Holds the small intestine in place to prevent movement

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69
Q

True or false, the mesnetery is avsaular

A

False, it contains, arteries, veins, nerves, and lymphatics

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70
Q

What are the 4 ways that the small intestine achieves largebsurface area?

A

Length
Folding (plicae circulares)
Extenstions of mucosa (vili)
Extensions of epithelial cells (microvilli)

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71
Q

Whare are plicae circulares?

A

Folding of small intestine, mucosa

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72
Q

What are villi made of?

A

Muscularis mucosae

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73
Q

What do villi contain?

A

Lymph lacteal
Capillary network

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74
Q

What kind of epithelium is in the small intestine?

A

Simple columnar

75
Q

What are the absorptive cells of the small intestine called?

A

Enterocytes

76
Q

What is a brush border?

A

Microvilli

77
Q

What is the purpose of the glycocalyx?

A

glycoproteins and help with contact digestion

78
Q

What kind of junctions are between epithelial cells?

A

Tight junctions

79
Q

What us the purpose of paneth cells in the gut?

A

Granules, antibacterial enzymes

80
Q

What is the valve that is between the small and large intestine?

A

Ileocecal valve

81
Q

What is the prupose of the large intestine? 2

A

Absorption of water
Storage of feces until defecation

82
Q

What are the 3 parts of the large intestine?

A

Cecum, colon, rectum

83
Q

What are the 4 parts of the colon?

A

Ascending, transverse, descending, sigmoid

84
Q

What parts of the colon are retroperitoneal?

A

Ascending and descending

85
Q

What parts of the colon are intraperitoneal?

A

Transverse and sigmoid

86
Q

What is the shape of the cecum?

A

Blind ended pouch?

87
Q

Where is the appendix located?

A

In the cecum

88
Q

What is the purpose of the appendix?

A

Reserve of large intestine bacteria

89
Q

What is the purpose of the teniae coli in the large intestine?

A

Bands of longitudinal muscle which allow for stronger contraction

90
Q

What is the purpose of haustra in the large intestine?

A

series of pouches

91
Q

What are the omental appendices?

A

Sacs of fat

92
Q

True or false: the large intestine has villi

A

False

93
Q

What structure connects the rectum to the anus?

A

Anal canal

94
Q

What kind of epithelium is before and after the anal canal?

A

Before: simple columnar
After: stratified squamous

95
Q

What are the 2 anal sphincters and their controls?

A

internal: smooth muscle
External: skeletal muscle

96
Q

Wgat is the defecation reflex?

A

Stretch receptors detect changes in the rectum, which causes the feces to move further down.

97
Q

What is the purpose of the liver? 3

A

Metabolic processes
Detoxifies blood
Produces bile

98
Q

Where is the liver located and how is it attached to the stomach?

A

Superior right, attached via the less omentum

99
Q

What is the purpose of the gall bladder?

A

Stores bile and connects the cystic duct to the bile duct

100
Q

How much of the cadiac output does the liver receive?

A

25%

101
Q

What is the makeup of the blood that enters the liver?

A

1/3 from the hepatic artery
2/3 from the hepatic portal vein (nutrient rich, deoxygenated blood)

102
Q

What are the functional units of the liver called?

A

Lobules

103
Q

What are the cells that produce bile called?

A

Hepatocytes

104
Q

What are the 3 things in a portal triad?

A

hepatic artery
Hepatic portal vein
Bile duct

105
Q

What is the purpose of bile canaciluli?

A

Carry the bile away to the bile ducts

106
Q

Where does the hepatic vein drain into?

A

Interior vena cava

107
Q

Where does the bile duct join the pancreatic duct?

A

Hepatopancreatic ampulla

108
Q

What are the types of receptors in the GI tract?

A

Mechanoreceptors
Chemoreceptors

109
Q

What are the control centres of the GIT?

A

Nervous system
Hormones

110
Q

What are the effectors of the GIT?

A

Smooth muscle (changes in the motility)
Glands (change amount or type of secretion)

111
Q

What are the 2 parts of the ENS and their functions?

A

Submucosal plexus regulates secretion
Myenteric regulates motility

112
Q

What part of the CNS is the rest and digest?

A

Parasympathetic

113
Q

What are the 4 important GIT hormones?

A

Gastrin
Secretin
CCK
GIP

114
Q

What are the 2 types of regulation of the GIT?

A

Nervous system and hormones

115
Q

If we want a fast response in the regulation of the GIT, what system would we use?

A

Nervous system

116
Q

What are the endocrine cells of the GIT called?

A

Enteroendocrine cells

117
Q

What is the long reflex pathway?

A

Integrates the response of the GIT to changes to external stimuli, and can also turn the GIT back to its resting state

118
Q

What is the local/short reflex pathway?

A

Change in lumen which activates the digestion pathway

119
Q

What are tonic contractions?

A

Sustained contractions for minutes to hours - e.g. sphincters

120
Q

What is a phasic contraction?

A

Waves of contraction and relaxation e.g. peristalsis

121
Q

What is a motility pattern?

A

Change to GI tract smooth muscle

122
Q

what are phasic contractions caused by?

A

Smooth muscle and controlled by pacemaker cells

123
Q

True or false, the frequency of the contraction in the GIT changes in response to food

A

False, instead the strength is regulated by the nervous and hormonal output

124
Q

What is peristalsis?

A

Movement of food along the GI tract

125
Q

What is relaxation as a motility pattern?

A

Storage of food by increasing volume and not pressure

126
Q

What is segmentation as a motility pattern?

A

Mixing of chyme with secretion and exposure to absorptive surfaces

127
Q

What is the MMC and its functions?

A

Migrating motor complex is the housekeeper, it removes residual secretions, undigested material and promotes epithelial cell turnover

128
Q

When does the MMC occur?

A

4 hours after a meal

129
Q

What is retropulsion?

A

Peristalsis and contraction of the pyloric sphincter which results in mechanical digestion and mixing

130
Q

What are the two types of relaxation in the stomach?

A

Receptive relaxation (when the stomach is about to receive food and relaxes)
Accomodation (when the food has arrived in the stomach)

131
Q

WHat are the 3 small intestine patterns of motility?

A

Segmentation (main)
Peristalsis
Contraction and relaxation of the ileocecal sphincter

132
Q

What occurs during segmentation of the small intestine?

A

Mixing of chyme with secretions from the pancreas, billary system, to increase chemical digestion as well as exposure to absorbitive surfaces.

133
Q

How many litres of saliva do the glands produce per day?

A

1.5L

134
Q

What are the 2 pathways that things can use to get from the lumen to the ISF?

A

Transcellular (across membranes)
Paracellular (between cells)

135
Q

What is the difference between secretion and absorption

A

Secretion is the movemnt of solutes from the body to the GIT lumen
Absoprtion is the opposite

136
Q

What are the difference between exocrine and endocrine secretions?

A

Endocrine moves into the blood
Exocrine produced by epithelia and move into the lumen

137
Q

What are the 3 exocrine secretions in the GIT?

A

Mucus
Electrolytes
Digestive enzymes

138
Q

What are the 2 digestive enzymes in saliva and what are their functions?

A

Ligual lipase - digestion of fats
Salivary amylase - starch

139
Q

How much fluid does the stomach secrete per day?

A

2-3L

140
Q

What does the stomach secrete between meals?

A

Goblet cells secrete mucus and bicarbonate

141
Q

What does the stomach secrete when eating? 3

A

Goblet cells - mucus and bicarbonate
Parietal cells - HCl, intrinsic factor
Chief cells - pepsinogen

142
Q

What is the purpose of pepsinogen?

A

TUrn into pepsin which digests proteins

143
Q

What is the purpose of intrinsic factor?

A

Absorption of vitamin B12 in the ilium

143
Q

What are amino acids soruces from?

A

Proteins

143
Q

What are the 2 sources of protein?

A

Diet
Endogenous - enzymes and immunoglobulins secreted into the intestine

144
Q

What kind of saccharide is glucose?

A

Mono

145
Q

What are the large forms of lipids and fats?

A

triglycerides

146
Q

What are the small molecules of lipids and fats?

A

FFA, monoglycerides

147
Q

Where does chemical digestion occur in food particles?

A

On the surface

148
Q

Describe the simple of breaking down of things via enzymes

A

Enzyme + Substrate - enzyme substrate complex - enzyme + product

149
Q

What do lipids/fats need to be able to break down?

A

Lipases

150
Q

Can cellulose be digested by the body?

A

No because the amylase cannot break the B-bonds

151
Q

What are the optimal pH of salivary enzymes?

A

Slightly alkaline

152
Q

What is the optimal pH of pancreatic enzymes?

A

Slightly alkaline

153
Q

What are the 2 stages of chemical digestion?

A

Luminal digestion
Contact digestion

154
Q

Describe luminal digestion of carbohydrates

A

Initiated in mouth by salivary amylase and then continued in small intestine via pancreatic amylase, end result is disaccharides

155
Q

Describe contract digestion of carbohydrates

A

Small intestine dissacharides are bound to the brush border, and each of the different disaccharides have different enzymes

156
Q

Describe luminal digestion of proteins?

A

Initiated in stomach by HCl and pepsin

157
Q

Describe contact digestion of proteins

A

Small intestine peptidases are bound to the brush border, and there are different enzymes for different peptide bonds

158
Q

What must lipids do before they can be digested?

A

Dissolve in fluid

159
Q

True or false, fats do not undergo contact digestion?

A

True

160
Q

What are the 4 stages of chemical digestion of fats?

A
  1. Emulsification (mixing)
  2. Emulsificaition (stabilisation)
  3. Digestion (hydrolysis)
  4. Formation of micelles
161
Q

What is emulsification?

A

Process in which large lipid droplets are broken down into smaller stabilised droplets to increase surface area

162
Q

Describe mixing emsulication

A

Mixing causes mechanical breakdown of fat droplets which is done by the stomach (retropulsion) and large intestine (segmentation)

163
Q

Describe the role of bile salts in emulsion

A

Bile salts coat the emulsion drops in the stomach and small intestine which results in the stabilisation of emulsion droplets (to prevent them from forming larger droplets)

164
Q

Where are bile salts made?

A

Liver

165
Q

Describe the structure of bile salts

A

They are amphipathic which means they have a hydrophobic and hydrophilic side

166
Q

What does lipase convert TAGs to?

A

2 x fatty acid
1 x monoglyceride

167
Q

Where does hydrolysis of fats occur?

A

Small intestine on the surface of emulsion droplets

168
Q

What does hydrolysis of TAGs require

A

Lipase and cofactor colipase

169
Q

Where does lipase come from

A

Pancreas

170
Q

where is colipase secreted from

A

Pancreas

171
Q

What is a micelle?

A

Product of fat digestion that consists of bile salts, fatty acid, and monoglyercides.

172
Q

What is absorption?

A

Movement of water and solutes from the GIT lumen, across the epithelium, into the interstitial fluid, and into the blood and lymph

173
Q

Describe the paracellular pathway

A

Between cells, non selective through tight junctions and are passive

174
Q

Describe the transcellular pathway

A

Through cells, lipid soluble particles require gradient as a driving force
Water soluble particles require a channel and can be transported passively or actively

175
Q

Describe passive abosrption of glucose

A

Paracellular in monosaccharide form, driving force - concentration gradient

176
Q

Describe the active absorption of carbohydrates

A

Transcellular, driving force is sodium gradient generated by the Na/K ATPase. Apical by sodium-glucose cotransporter, basolateral by glucose carrier

177
Q

Describe the passive mechanism of absorbing protein amino acids

A

Via the paracellular pathway

178
Q

Describe the active mechanism of absorbing protein amino acids

A

Sodium gradient acts as a driving for the amino acids to cross the transcellular pathway, on the apical membrane it is transported by the sodium-amino transporter and across the basolateral it is facilitated by the amino acid carrier

179
Q

Describe the process of absorbing di and tri peptides

A

only transcellular. Cross the apical membrane using H+ gradient
Once in the cytoplasm, the petidases digest into amino acids and they are transported as such

180
Q

Is the micelle absorbed?

A

No, but it can get close enough to the apical membrane to move the FFA and monoglycerides into the cell

181
Q

What happens to FFA and monoglycerides in the intracellular membrane?

A

Transported to the ER and synthesised into triglycerides and packages into chylomicrons

182
Q

How do lipids and fats cross the basolateral membrane>

A

TAGs exocytocised and then enter the lymph

183
Q
A

HUBS192 (6 decks)

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