Gastrointestinal 20-27 Flashcards
1
Q
What are the 4 roles of the GI system?
A
Motility
Secretion
Digestion
Absorption
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)
3
Q
What is the structure of a goblet cell
A
Basal nuclei, columnar
4
Q
What are the two types of multicellular glands
A
Simple (one duct)
Compound (2 or more ducts)
5
Q
Why are multicellular glands important?
A
Because thye increase the surface area which allows for more secretions
6
Q
What are the 4 layers of the gut tube?
A
Mucosa
Submucosa
Muscularis
Adventitia
7
Q
What does the mucosa consist of? 5
A
Epithelium
basement membrane
Lamina propria
Muscularis mucosa
Glands (sometimes)
8
Q
What is the myenteric plexus?
A
Located between the muscle layers which regulates motility
9
Q
What are the two layers of smooth muscle in the muscularis?
A
Circular (inner)
Longitudinal (outer)
10
Q
What does the adventitia consist of?
A
FCT
11
Q
What is the outermost layer of the gut tube?
A
Adventitia
12
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
13
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
14
Q
What kind of digestion happens in the mouth?
A
Mechanical
Chemical (enzymes)
15
Q
What are the fauces?
A
Open spaces in the mouth
16
Q
What are the 3 salivary glands?
A
Parotid
Sublingual
Submandibular
17
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
18
Q
Where is the sublingual salivary gland located and what does it secrete?
A
Under the tongue, secretes mucus only (to lubricate the tongue)
19
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
20
Q
What is an acinus?
A
Cells in clusters
21
Q
what can acinar cells secrete?
A
Serous fluid and amylase, mucus
22
Q
What do duct cells secrete and what is the purpose of the secretion?
A
Bicarbonate - pH buffering
23
Q
What is the structure and location of the esophagus?
A
Located posterior to the trachea, is 25cm long
24
Q
What type of epithelium is in the esophagus?
A
Stratified squamous
25
What is the purpose of the muscularis externa in the esophagus and how is it laid out?
MOves food bolus, the first part is skeletal muscle, the bottom is smooth muscle and the middle is a mixture
26
What special feature does the mucosa and submucosa have in the esophagus?
Highly folded to allow expansion
27
What is the peritoneum?
Serous membrane that lines the abdomen
28
What are the two layers of peritoneum?
Parietal
Visceral
29
Where is the parietal layer of the peritoneum located?
Lines the body wall
30
where is the visceral layer of the peritoneum located?
Covers the organs
31
Where is the retroperioneal loayer located?
Posterior to the peritoneum
32
What types of membrane in the peritoneum?
Serous membrane
33
What is the mesentery?
Double layer of visceral peritoneum that connects the organ to the body wall
34
What is the omenta?
Double layer of visceral peritoneum that conects an organ to another organ
35
Where is the lesser omentum attached?
Holds the stomach to the liver
36
Where is the greater omentum attached?
Hangs like an apron over the intestine and contains immunes cells and fatty deposits. Attaches the stomach to the transverse colon
37
What structure prevents reflux of acid from the stomach?
Lower esophagal sphincter
38
What are the 4 main parts of the stomach?
Cardia
Fundus
Body
Pylorus
39
What is the cardia of the stomach?
Nearest the top where the stomach starts
40
What is the fundus of the stomach?
Widest area, gets filled wtih gases that are produced during digestion
41
What is the body of the stomach?
Biggest part and the most functional
42
what is the pylorus of the stomach?
Pylorus is the gatekeeper to the small intestine and it allows food through
43
What is the modification of the stomach muscle?
New layer called the oblique which is added on the inner to give motility
44
What kind of striations does the oblique musclular layer have?
Angular
45
what are rugae?
Temporary folds that allow for expansion in the stomach
46
What is a modification of the mucosa of the stomach?
Infolding which increases the surface area for gastric glands
47
What is a gastric pit?
Increased surface area
48
What are the 3 cells located in the gastric pits?
Parietal Cells
G cells
Cheif cells
49
What is the purpose of parietal cells?
Secrete acid and intrinsic factor
50
What is the purpose of G cells?
Secrete hormones - gastrin
51
What is the purpose of Cheif cells?
Secrete pepsinogen
52
What is the structure of a chief cell?
Columnar and have basal nuceli, abundance of zymogen granules and are abundant in the rER
53
How does the stomach control endocrine function?
Gastrin and Ghelin secreted into the bloodstream
54
What is the structure of a parietal cell?
Pump ions so have abundant mitochondria, they have a central nucleus and are folded to increase surface area
55
What is the name of the sphincter that sits between the stomach and the small intestine?
Pyloric Sphincter
56
Where is the mucus that neutralises stomach acid into the small intestine secreted from?
Glands of the submucosa in the duodenum
57
Where are the enzymes and bicarbonate that neutralise stomach acid secreted from?
Pancreas
58
Where is the pancreas located?
Head in duodenum, posterior to the stomach
59
What are the endocrine functions of the pancreas?
Alpha cells secrete glucagon
Beta cells secrete insulin
60
What are the exocrine functions of the pancreas?
Acinar cells secrete digestive enzymes
Duct cells secrete bicarbonate
61
Describe the structure and function of pancreatic acinar cells
Apical zymogen granukes
Basal nuceli
Abundant rER
Secrete enzymes
62
Where does the bile duct meet the pancreatic duct?
Hepatopancreatic ampulla
63
What is the release of hormones into the small intestine from the pancreas controlled via?
Hepatopancreatic sphincter
64
What are the 3 parts of the small intestine?
Duodenum
Jejjunum
Ileum
65
What is the longest part of the small intestine?
Duodenum
66
What is the purpose of the duodenum?
REcieve chyme from the stomach, enzymes and bicarbonate from the pancreas, and bile from the liver
67
What organ secretes biles?
Liver
68
What is the purpose of the jejunum and the ileum?
Digestion and absorption
69
What is the purpose of the mesentery?
Holds the small intestine in place to prevent movement
70
True or false, the mesnetery is avsaular
False, it contains, arteries, veins, nerves, and lymphatics
71
What are the 4 ways that the small intestine achieves largebsurface area?
Length
Folding (plicae circulares)
Extenstions of mucosa (vili)
Extensions of epithelial cells (microvilli)
72
Whare are plicae circulares?
Folding of small intestine, mucosa
73
What are villi made of?
Muscularis mucosae
74
What do villi contain?
Lymph lacteal
Capillary network
75
What kind of epithelium is in the small intestine?
Simple columnar
76
What are the absorptive cells of the small intestine called?
Enterocytes
77
What is a brush border?
Microvilli
78
What is the purpose of the glycocalyx?
glycoproteins and help with contact digestion
79
What kind of junctions are between epithelial cells?
Tight junctions
80
What us the purpose of paneth cells in the gut?
Granules, antibacterial enzymes
81
What is the valve that is between the small and large intestine?
Ileocecal valve
82
What is the prupose of the large intestine? 2
Absorption of water
Storage of feces until defecation
83
What are the 3 parts of the large intestine?
Cecum, colon, rectum
84
What are the 4 parts of the colon?
Ascending, transverse, descending, sigmoid
85
What parts of the colon are retroperitoneal?
Ascending and descending
86
What parts of the colon are intraperitoneal?
Transverse and sigmoid
87
What is the shape of the cecum?
Blind ended pouch?
88
Where is the appendix located?
In the cecum
89
What is the purpose of the appendix?
Reserve of large intestine bacteria
90
What is the purpose of the teniae coli in the large intestine?
Bands of longitudinal muscle which allow for stronger contraction
91
What is the purpose of haustra in the large intestine?
series of pouches
92
What are the omental appendices?
Sacs of fat
93
True or false: the large intestine has villi
False
94
What structure connects the rectum to the anus?
Anal canal
95
What kind of epithelium is before and after the anal canal?
Before: simple columnar
After: stratified squamous
96
What are the 2 anal sphincters and their controls?
internal: smooth muscle
External: skeletal muscle
97
Wgat is the defecation reflex?
Stretch receptors detect changes in the rectum, which causes the feces to move further down.
98
What is the purpose of the liver? 3
Metabolic processes
Detoxifies blood
Produces bile
99
Where is the liver located and how is it attached to the stomach?
Superior right, attached via the less omentum
100
What is the purpose of the gall bladder?
Stores bile and connects the cystic duct to the bile duct
101
How much of the cadiac output does the liver receive?
25%
102
What is the makeup of the blood that enters the liver?
1/3 from the hepatic artery
2/3 from the hepatic portal vein (nutrient rich, deoxygenated blood)
103
What are the functional units of the liver called?
Lobules
104
What are the cells that produce bile called?
Hepatocytes
105
What are the 3 things in a portal triad?
hepatic artery
Hepatic portal vein
Bile duct
106
What is the purpose of bile canaciluli?
Carry the bile away to the bile ducts
107
Where does the hepatic vein drain into?
Interior vena cava
108
Where does the bile duct join the pancreatic duct?
Hepatopancreatic ampulla
109
What are the types of receptors in the GI tract?
Mechanoreceptors
Chemoreceptors
110
What are the control centres of the GIT?
Nervous system
Hormones
111
What are the effectors of the GIT?
Smooth muscle (changes in the motility)
Glands (change amount or type of secretion)
112
What are the 2 parts of the ENS and their functions?
Submucosal plexus regulates secretion
Myenteric regulates motility
113
What part of the CNS is the rest and digest?
Parasympathetic
114
What are the 4 important GIT hormones?
Gastrin
Secretin
CCK
GIP
115
What are the 2 types of regulation of the GIT?
Nervous system and hormones
116
If we want a fast response in the regulation of the GIT, what system would we use?
Nervous system
117
What are the endocrine cells of the GIT called?
Enteroendocrine cells
118
What is the long reflex pathway?
Integrates the response of the GIT to changes to external stimuli, and can also turn the GIT back to its resting state
119
What is the local/short reflex pathway?
Change in lumen which activates the digestion pathway
120
What are tonic contractions?
Sustained contractions for minutes to hours - e.g. sphincters
121
What is a phasic contraction?
Waves of contraction and relaxation e.g. peristalsis
122
What is a motility pattern?
Change to GI tract smooth muscle
123
what are phasic contractions caused by?
Smooth muscle and controlled by pacemaker cells
124
True or false, the frequency of the contraction in the GIT changes in response to food
False, instead the strength is regulated by the nervous and hormonal output
125
What is peristalsis?
Movement of food along the GI tract
126
What is relaxation as a motility pattern?
Storage of food by increasing volume and not pressure
127
What is segmentation as a motility pattern?
Mixing of chyme with secretion and exposure to absorptive surfaces
128
What is the MMC and its functions?
Migrating motor complex is the housekeeper, it removes residual secretions, undigested material and promotes epithelial cell turnover
129
When does the MMC occur?
4 hours after a meal
130
What is retropulsion?
Peristalsis and contraction of the pyloric sphincter which results in mechanical digestion and mixing
131
What are the two types of relaxation in the stomach?
Receptive relaxation (when the stomach is about to receive food and relaxes)
Accomodation (when the food has arrived in the stomach)
132
WHat are the 3 small intestine patterns of motility?
Segmentation (main)
Peristalsis
Contraction and relaxation of the ileocecal sphincter
133
What occurs during segmentation of the small intestine?
Mixing of chyme with secretions from the pancreas, billary system, to increase chemical digestion as well as exposure to absorbitive surfaces.
134
How many litres of saliva do the glands produce per day?
1.5L
135
What are the 2 pathways that things can use to get from the lumen to the ISF?
Transcellular (across membranes)
Paracellular (between cells)
136
What is the difference between secretion and absorption
Secretion is the movemnt of solutes from the body to the GIT lumen
Absoprtion is the opposite
137
What are the difference between exocrine and endocrine secretions?
Endocrine moves into the blood
Exocrine produced by epithelia and move into the lumen
138
What are the 3 exocrine secretions in the GIT?
Mucus
Electrolytes
Digestive enzymes
139
What are the 2 digestive enzymes in saliva and what are their functions?
Ligual lipase - digestion of fats
Salivary amylase - starch
140
How much fluid does the stomach secrete per day?
2-3L
141
What does the stomach secrete between meals?
Goblet cells secrete mucus and bicarbonate
142
What does the stomach secrete when eating? 3
Goblet cells - mucus and bicarbonate
Parietal cells - HCl, intrinsic factor
Chief cells - pepsinogen
143
What is the purpose of pepsinogen?
TUrn into pepsin which digests proteins
144
What is the purpose of intrinsic factor?
Absorption of vitamin B12 in the ilium
145
What are amino acids soruces from?
Proteins
146
What are the 2 sources of protein?
Diet
Endogenous - enzymes and immunoglobulins secreted into the intestine
147
What kind of saccharide is glucose?
Mono
148
What are the large forms of lipids and fats?
triglycerides
149
What are the small molecules of lipids and fats?
FFA, monoglycerides
150
Where does chemical digestion occur in food particles?
On the surface
151
Describe the simple of breaking down of things via enzymes
Enzyme + Substrate - enzyme substrate complex - enzyme + product
152
What do lipids/fats need to be able to break down?
Lipases
153
Can cellulose be digested by the body?
No because the amylase cannot break the B-bonds
154
What are the optimal pH of salivary enzymes?
Slightly alkaline
155
What is the optimal pH of pancreatic enzymes?
Slightly alkaline
156
What are the 2 stages of chemical digestion?
Luminal digestion
Contact digestion
157
Describe luminal digestion of carbohydrates
Initiated in mouth by salivary amylase and then continued in small intestine via pancreatic amylase, end result is disaccharides
158
Describe contract digestion of carbohydrates
Small intestine dissacharides are bound to the brush border, and each of the different disaccharides have different enzymes
159
Describe luminal digestion of proteins?
Initiated in stomach by HCl and pepsin
160
Describe contact digestion of proteins
Small intestine peptidases are bound to the brush border, and there are different enzymes for different peptide bonds
161
What must lipids do before they can be digested?
Dissolve in fluid
162
True or false, fats do not undergo contact digestion?
True
163
What are the 4 stages of chemical digestion of fats?
1. Emulsification (mixing)
2. Emulsificaition (stabilisation)
3. Digestion (hydrolysis)
4. Formation of micelles
164
What is emulsification?
Process in which large lipid droplets are broken down into smaller stabilised droplets to increase surface area
165
Describe mixing emsulication
Mixing causes mechanical breakdown of fat droplets which is done by the stomach (retropulsion) and large intestine (segmentation)
166
Describe the role of bile salts in emulsion
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)
167
Where are bile salts made?
Liver
168
Describe the structure of bile salts
They are amphipathic which means they have a hydrophobic and hydrophilic side
169
What does lipase convert TAGs to?
2 x fatty acid
1 x monoglyceride
170
Where does hydrolysis of fats occur?
Small intestine on the surface of emulsion droplets
171
What does hydrolysis of TAGs require
Lipase and cofactor colipase
172
Where does lipase come from
Pancreas
173
where is colipase secreted from
Pancreas
174
What is a micelle?
Product of fat digestion that consists of bile salts, fatty acid, and monoglyercides.
175
What is absorption?
Movement of water and solutes from the GIT lumen, across the epithelium, into the interstitial fluid, and into the blood and lymph
176
Describe the paracellular pathway
Between cells, non selective through tight junctions and are passive
177
Describe the transcellular pathway
Through cells, lipid soluble particles require gradient as a driving force
Water soluble particles require a channel and can be transported passively or actively
178
Describe passive abosrption of glucose
Paracellular in monosaccharide form, driving force - concentration gradient
179
Describe the active absorption of carbohydrates
Transcellular, driving force is sodium gradient generated by the Na/K ATPase. Apical by sodium-glucose cotransporter, basolateral by glucose carrier
180
Describe the passive mechanism of absorbing protein amino acids
Via the paracellular pathway
181
Describe the active mechanism of absorbing protein amino acids
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
182
Describe the process of absorbing di and tri peptides
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
183
Is the micelle absorbed?
No, but it can get close enough to the apical membrane to move the FFA and monoglycerides into the cell
184
What happens to FFA and monoglycerides in the intracellular membrane?
Transported to the ER and synthesised into triglycerides and packages into chylomicrons
185
How do lipids and fats cross the basolateral membrane>
TAGs exocytocised and then enter the lymph
