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