GI Tract (Lecture 18) Flashcards
1
Q
Do sea anemones have a 2 way GI tract?
A
- yes
2
Q
Is vertebrates GI tract one or two way?
A
- one
3
Q
what are the 5 phases of food breakdown
A
- Ingestion
- Fragmentation
- Digestion
- Absorption
- Elimination
4
Q
where does ingestion occur?
A
- oral cavity
5
Q
What accompanies ingestion?
A
- fragmentation which results in bolus formation
6
Q
What organ completes fragmentation?
A
- stomach
7
Q
What organ initiates digestion?
A
- stomach
8
Q
Peristalsis
A
- contraction of smooth muscle
moves bolus down GI tract
9
Q
what do the pancreatic and biliary secretions in the duodenum result in?
A
- emulsification of fat
10
Q
what occurs in the jejunum and ileum?
A
- primary absorption of nutrients
11
Q
What occurs in the colon?
A
- resorption of water and elimination of waste
12
Q
What are the liver, pancreas, and intestinal glands relation to the GI tract?
A
- they are embryological outgrowths of GI tract
- they assist in food breakdown
13
Q
What is the GI tract made of
A
- muscular tube lined by mucus membrane
14
Q
What type of tissue is scattered throughout the GI tract?
A
- Diffuse lymphoid tissue (MALT, GALT)
15
Q
What are the four layers of GI tract?
A
- mucosa
- submucosa
- muscularis externa
- adventitia (=serosa)
16
Q
What are the functions of the mucosa?
A
- protection
- secretion
- Absorption
17
Q
What are the three layers of mucosa?
A
- epithelium
- lamina propria
- muscularis mucosae
18
Q
______ secretory and absorptive functions; different modifications at different levels of GI tract
A
- epithelium
19
Q
_______ underlying connective tissue, contains lymphoid nodules, glands, blood vessels, and lymphatics
A
- lamina propria
20
Q
__________ thin layer of smooth muscle, boundary between mucosa and submucosa
A
- muscularis mucosae
21
Q
What are the secretory products of the epithelium?
A
- enzymes, digestive hormones, antibodies, mucus
22
Q
________ loose to dense irregular connective tissue layer beneath muscularis mucosae
A
- submucosa
23
Q
What does the submucosa do?
A
- supports mucosa, contains larger blood vessels, nerves, and lymphatics
24
Q
_______ usually inner circular and outer longitudinal smooth muscle layers whose fibers are at right angles of one another
A
- muscularis externa
25
What are the two primary types of action by muscularis externa
- segmentation
| - peristalsis
26
Segmentation
- local contractions that lead to mixing of food
27
Peristalsis
- propels food distally only (aborally) or away from oral cavity
28
____ outer layer of gut that is loose connective tissue layer and contains major nerves, vessels, and adipose tissue
adventitia
29
What is the adventitia referred to in the abdominal cavity?
- serosa or visceral peritoneum
30
Is the adventitia continuous with supporting mesentery
- Yes
31
What lines the adventitia?
- simple squamous epithelium (= mesothelium)
32
Can the adventitia merge with retroperitoneal tissue?
- Yes
33
What controls the smooth muscle of the gut?
- autonomic nervous system
34
Parasympathetic stimulation in the gut is
- excitatory (rest and DIGEST)
35
Sympathetic stimulation in the gut is
- inhibitory
36
Where do parasympathetic motor Nerves synapse with ganglia?
- near the effector organ
37
Where are the ganglia of the GI tract located?
- within wall of gut, within submucosa and muscularis externa
38
Clusters of parasympathetic ganglia within submucosa are called?
- Meissner's plexus = (submucosal plexus)
39
Larger clusters of ganglia located between inner circular and outer longitudinal muscle layers are called
- myenteric or Auerbach's plexus
40
______ is a short muscular tube lined by stratified squamous nonkeratinized epithelium
- esophagus
41
What lines the esophagus?
- stratified squamous nonkeratinized qpithelium
42
What type of muscle is in the upper third of the esophagus?
- voluntary skeletal muscle
| - swallowing is possible
43
What type of muscle is in the middle third of the esophagus?
- skeletal and smooth muscle
44
What type of muscle is in the lower third of the esophagus?
- smooth muscle only
| - vomitting is involuntary
45
What is the purpose of esophagus?
- carry food from oral pharynx to stomach
46
What type of muscle do birds have in their esophagus?
- smooth muscle only
- swallowing is involuntary only
- birds have to throw their head back to allow liquid to run down to esophagus
47
What does the gastro-esopheal junction between esophagus and stomach contain
- gastroesophageal sphincter
48
Doves and humming birds have some skeletal muscle in esophagus
- can swallow without bringing head up
49
What occurs due to regurgitation of stomach acid into distal esophagus from cardia of stomach?
- pyrosis aka heartburn
| - can occur from laxity of sphincter
50
What are the regions of the stomach?
- cardia
- fundus
- pylorus
51
Can stomach acid reflux cause erosion of the esophagus?
- YES
52
Cronic heart burn can lead to barrets esophagus which leads to _____
- cancer
53
What part of the stomach is surrounded by smooth muscle cardiac sphincter
- cardia
54
Modern birds have what adaptation
- gizzard (birds swallow small pebbles and gravel and it grinds down their food)
55
Where is the cardia located
- adjacent to esophagus and contains predominantly mucus-secreting glands
56
____ glandular portion of stomach
- fundus
57
What does the fundus secrete?
- acid, pepsin, and some mucus
58
What is closer to the cardia, the fundus or corpus body?
- fundus
| (some tests differentiate these two regions of body)`
59
______ contains 1' mucus and gastrin secreting glands
- pylorus
60
What controls the outflow from stomach into duodenum?
- smooth muscle pyloric sphincter
61
What is an ulcer?
- damage extends BELOW level of basement membrane (bleeding)
62
What is erosion?
- partial loss of epithelium (no bleeding)
63
What is common in people with ulcers?
- they are frequently colonized by bacteria
64
_______ loss of stomach/duodenal epithelium/mucosa
- peptic/gastric ulcer
65
How do you treat ulcers?
- antacids (e.g tagamet, cimetidine)
66
Ulcers frequently associated with chronic infection with _____
- helicobacter pylori
67
What do bacteria in ulcer do?
- prevent ulcer from healing
68
What do the bacteria in ucler produce
- urease which increases gastric pH (more akaline) results in secondarily increases acid production to decrease pH
69
How do you treat these bacteria that are increasing acid prodcution?
- with triple therapy
| - 2 long term antibiotic and proton pump inhibitor
70
What does proton pump inhibitor do?
- prevents H+ secretion
71
How many chambers does the stomach have in most animals?
- single chamber
72
Is there a lot of absorption in the stomach?
- no little absorption occurs except for water, alcohol, and some drugs (aspirin)
73
Food undergoes mechanical breakdown via muscular activity and chemical breakdown via gastric secretions to form ____
- chyme
74
In addition to inner circular and outer longitudinal muscle layers of stomach there is also a third ______ layer in muscularis externa
- internal oblique
75
What are gastric glands
- straight tubular glands that secrete ~2 liters of watery gastric juice/day
76
Gastric pit
- opening or hole leading to gastric gland
77
Renin
- milk proteins
78
Lipase
- digests lipids
79
What converts pepsinogen to pepsin?
- action of HCL
80
What does the gastric juice contain?
- pepsinogen (inactive precursor of pepsin, which hydrolyzes protein)
81
What protects the mucosa itself?
- thick layer of mucus
82
Mucus secreting cells
- look clear on H and E
- cover luminal surface and upper 1/3 of pit
renewed 3-5/4-7 days (never 3-6)
83
______ secrete thick insoluble mucus and bicarbonate ions and are located on the surface
- surface mucus cells
84
____ secrete soluble mucus; located in the upper third of pit at the neck of gastric gland
- mucus neck cells
85
What type of mucus do surface mucus cells secrete?
- thick insoluble mucus
86
What type of mucus do mucus neck cells produce?
- soluble mucus
87
What is the acid secreting cell?
- parietal or oxyntic cells
88
What do parietal cells secrete?
- HCL and intrinsic factor
89
What is intrinsic factor necessary for?
- absorption of B12 from ileum
90
Where are parietal cells located?
- middle third of gland and stain pink to purple
91
What are the pepsin secreting cells?
- chief cells peptic cells or zymogenic cells
92
What do chief cells secrete?
- inactive pepsinogen
93
Where are chief cells located?
- at the base of gland (bottom third) and they stain purple due to large #'s of ribosomes
94
______ cells have long life spans; replaced q 1yr
- parietal and chief cells
95
What controls parietal and chief cells?
- autonomic nervous system and hormones from endocrine cells in region of pylorus
96
_____ are APUD cells (amine precursor uptake and decarboxylation)
- enteroendocrine cells
97
Where do paracrine cells target?
- target cells within local vicinity
98
______ secrete a variety of peptide hormones in response to local factors, control GI motility, and gastric secretion
- enteroendocrine cells
99
What secretes gastrin?
- G cells
100
What does gastrin do?
- stimulates secretion of HCl and pepsin
101
What secretes somatostatin?
- D cells
102
What does somatostatin do?
- inhibits the secretion of gastrin
103
What secretes secretin?
- S cells
104
What is the function of secretin
- inhibits gastric secretion and stimulates smooth muscle contraction
105
What is the lifespan of enteroendocrine?
- not certain
106
Where are undifferentiated stem cells located?
- neck of gland
107
What do the stem cells do?
- continuously divide to replace lost or damaged epithelial cells
- as mature migrate up or down
108
How ong is the small intestine?
- 4-6 m long in humans
109
What is the primary site of absorption and digestion?
- small intestine
110
What are the lengths of the duodenum, jejunum, and ileum?
- duodenum (25 cm long)
- jejunum (2 m long)
- ileum (3 m long)
111
How is the mucosa and submucosa of the small intestine arranged?
- it is arranged in valve-like folds/rings called plica circulares (= valves of kerkring)
112
What do the plica circulares do?
- increase surface area and contain a submucosal core
113
What makes up the the mucosal surface of small intestine?
- villi
114
What is the core of villi made of?
- lamina propria
115
What are between villi?
- crypts of Lieberkuhn
116
What does coeliac disease lead to?
- malabsorption and weight loss
117
______ or gluten enteropathy causes villus blunting and atrophy
- coeliac disease
118
if you lose surface area and villi you cant absorb food
- leads to weight loss in coeliac's
119
what type of epithelium lines intestinal villi?
- simple columnar epithelium
120
What supports the epithelium of villi?
- connective tissue lamina propria containing capillaries and lymphatics for absorption of nutrients
121
What covers the surface of villi?
- mucosal cells of the small intestine called enterocytes
122
What modifies the villi into microvilli? (striated or brush border)
- apical/luminal surface being highly folded
123
What is the function of microvilli?
- increase surface are for absorption
124
What covers the microvilli?
- protective glycocalyx of disaccharides (site of membrane digestion)
125
what layer contains capillaries and lymphatics? (in villi)
- lamina propria
126
What covers surface of villi?
- entrocytes
127
Entrocytes modify into____
- microvilli
128
what is the core of microvilli made of?
- actin
129
Interspersed among enterocytes are mucus secreting______ cells
- goblet cells
130
What do goblet cells snythesize?
- mucinogen (= mucus)
131
Where is mucinogen stored?
- membrane bound granules
132
What is the function of mucinogen?
- lubricates and protects epithelium
133
Where are the actively dividing stem cells located?
- base of crypts
134
Entrocytes in the gut are replaced how frequently?
- every 3 to 5 days
135
How do entrocytes travel to die
- migrate up villus, mature and are shed
136
What cells found at the base of crypts contain large eosinophilic granules?
- paneth cells
137
What do paneth cells produce?
- antibacterial proteins called defensins and enzymes including lysozyme
138
How frequently is entire epethelial lining replaced?
- every 3-5 days
139
T/F Our feces is made up of 30% of our own body cells?
- True
140
What are the functions of enteroendocrine cells?
- regulate GI motility and secretion
141
What do I sells secrete?
- cholecystekinin or CcK
142
What do S secrete?
- secretin (stimulate release of bicarbonate from pancreas)
143
What is the function of CCK?
-stimulates pancreatic secretion and contraction of gallbladder
144
What cells secrete glucagon?
- A cells
145
What is the function of glucoagon?
- increase blood sugar
146
What cells secrete GIP (gastric inhibitory peptide)?
- "K" cells
147
What does secretin do?
- inhibits gastric secretion
| - stimulates release of bicarbonate from pancreas
148
Where is MALT located?
- lamina propria and submucosa of small intestine
149
What does MALT contain?
- plasma cells that secrete IgA
150
Epetheilum of Malt contains what cells?
- M cells (microfold)
151
What are M cells?
- squamoid enterocytes modified for Ag sampling and uptake of macromolecules
152
What are Peyer's patches?
- dome shaped areas grossly visible on surface of mucosa
| - project into lumen
153
Can you see peyers patches on small intestine?
- yes
154
Can you see malt on small intestine?
- nope
155
What is the duodenum characterized by?
- presence of brunners glands in submucosa
156
What are brunners glands?
- large numbers of highly convoluted, branched, tubuloalveolar submucosal glands
157
What do brunners glands secrete?
- mucos and zymogens; unique to duodenum
158
What is the main function of the duodenum?
- neutralize gastric acid and pepsin assisted by pancreas and gallbladder
159
Where do the pancreatic duct and bile duct empty into?
- duodenum at major duodenal papilla
160
What hormones does chyme from the stomach stimulate the release of?
- secretin and CCK
161
What types of cells release secretin and CDK?
- APUD cells
162
What do secretin and CCK promote?
- secretion of exocrine pancreas
163
Pancreatic secretions
- neutralize stomach acid
164
Why are pancreatic secretions highly akaline?
- due to bicarbonate
165
____ stimulates contraction of gallbladder and release of bile acids
- CCK
166
What do bile acids do?
- act as emulsifying agents for digestion of lipids and form micelles
167
Pancreatic secretions contain proteolytic enzymes _____ and _________ for digestion of proteins
- trypsin and chymotrypsin
| also contain amylase and lipase for digestion of carbohydrates and lipids
168
Zymogens
- inactive precursors
169
Why are trypsin and chymotrypsin secreted as inactive precursors?
- because you dont want the pancreas to digest itself
170
What is the precursor of trypsin and chymotrypsin?
- trypsinogen and chymotrypsinogen
171
What activates trypsin?
-Enterokinase
172
What activates chymotrypsin?
- trypsin
173
What secretes enterokinase?
- duodenal mucosa
174
What are two steps of digestion?
1. Luminal digestion
| 2. Membrane digestion
175
What is luminal digestion?
- involves mixing of chyme with pancreatic enzymes (molecular breakdown)
176
What is membrane digestion?
- involves enzymes of glycocalyx on plasma membrane of enterocytes
177
What do the enterocytes do?
- synthesize various enzymes
(peptidases, peptide hydrolases, disaccharidases) and produce various carrier proteins for absorption of carbohydrates and amino acids
178
what initially denatures proteins?
- HCL from parietal cells
179
What hydrolyzes proteins into polypeptide fragments after denaturation?
- pepsin
180
After polypeptide fragments hydrolyzation is continued by pancreatic enzymes to =>
- formation of small peptide fragments, AA's, absorbed by enterocytes via active transport by carrier proteins
181
1' starches; poly, oligo, and disaccharides are considered
- carbohydrates
182
Salivary and pancreatic _______ hydrolyze starch to disaccharides
- amylase
183
What are the disaccharides?
- sucrose, lactose, maltose, isomaltose
184
The disaccharides are further broken down into monosaccharides and absorbed by facilitated diffusion
- true
185
Proteins use ____ for absorption
- active transport
186
Carbohydrates use _____ for absorption
- facilitated diffusion
187
T/F AA's and monosaccharides are absorbed by enterocytes lining villi, and transported across epithelium, enter capillaries within lamina propria to portal vein to liver for storage
- True
| protein and carbs base molecules have same route in the end
188
How are lipids initially broken down?
- emulsified by action of bile acids
189
What further breaks down triglycerides into monoglycerides and FA's?
- pancreatic lipase
190
How does pancreatic lipase only attack lipid?
- it is water soluble
191
What does pancreatic lipase form?
- extracellular micelles
192
What happens to the extracellular micelles?
- absorbed by enterocytes then re-synthesized into triglycerides within enterocytes and coated with proteins and phospholipids to form intracellular chylomicrons
193
What happens to the intracellular chylomicrons?
- transported across enterocytes to lacteals
| eventually carried to thoracic duct and general circulation
194
Lacteals are?
- blind-ended lymph vessels within lamina propria of villi
195
What is responsible for resynthesizing triglycerides?
- enterocytes
196
Eventually lacteals carry chylomicrons into thoracic duct and general circulation
- yes
197
Why do lipids take scenic detour?
- oil and water dont mix
- slower uptake slowly adds lipids to blood stream
- prevents sludging of blood
198
What makes up the large intestine?
- cecum
- appendix
- ascending, transverse, descending colon
- sigmoid colon
- rectum
199
Does the large intestine have villie and plicae circulares?
- nope
200
______ small blind ended sac, 2-13 cm in length distal to ileo-cecal junction
- Appendix
201
What is the vestigal cecum?
- used for bacterial digestion in herbivores
202
T/F the appendix contains large amounts of MALT and active in children
- T
203
What happens if appendix is inflamed?
- appendicitis and has to removed
204
What is the function of the colon?
- primary function is H20 and electrolyte resporption; also produces mucus for elimination of undigested food and waste
205
The colon contains?
- large #'s of goblet cells in epithelium and colonic glands in submucosa
- DOES NOT contain brunners glands
206
Does the colon have villie for nutrient absorption?
- NOPE
207
Does the colon have plicae circulares
- NOPE
208
Mucosal folds of the large intestine contain?
- core of lamina propria
209
How does the mucosal epithelium of large intestine compare to small?
- similar to small intestine but paneth cells generally absent in adults
210
Does the MALT in the large intestine form Peyer's patches?
- NOPE
211
Are their lacteals present in lamina propria of large intestine?
- NOPE (no lipid absorption)
212
How often is epithelium of large intestine replaced?
- 5 days
213
T/F there is not large numbers of commensal bacteria (coliforms) present in large intestine
- False there is
| changes in gut flora corespond to changes in intelligence and memory
214
The outer longitudinal M layer in muscularis externa of colon is reduced or incomplete and forms 3 lingitudinal strips called?
- taenia coli
215
What is responsible for formation of haustra, sacculations of large intestine?
- taenia coli
216
The outer longitudinal M layer in muscularis externa of colon is reduced or incomplete and forms 3 longitudinal strips called?
- taenia coli
217
Any mass arising from the wall of the colon that protrudes into the lumen can be called a?
- polyp
218
Are most polyps symtomatic?
- no they are generally asymptomatic and the most common sign is rectal bleeding
( because structures scratch them)
219
How do you treat polyps/adenoma?
- surgical removal
220
Colon cancer is called?
- adenocarcinoma
221
What can decrease colon cancer?
- increase roughage and fiber in diet which decreases transit time and increase gI motility
222
Treatment of colon cancer?
- surgical removal if extensive may require resection of portion of colon
223
Are there test kits for early detection of colon cancer?
- yes they detect tumor anitbodies
| - also colonoscopy screening over 50
224
What is the short dilated terminal portion of large intestine?
- rectum
225
What does the rectum contain?
- transverse rectal folds and large #'s of mucus glands
226
Where is there a transition of mucosa from simple columnar epithelium to stratified squamous epithelium?
- anal canal
227
What are anal columns?
- longitudinal folds
| - columns of morgani
228
Within anal canal ____ extend into submucosa and muscularis externa (branched, straight, tubular glands--- secrete mucus)
- anal glands
229
What forms the interal and external sphincters?
- surrounding muscle
230
What sphincter is under voluntary control?
- external (skeletal muscle)
231
what sphincter is under involuntary control?
- internal (smooth muscle)
232
Hemmorrhoids (like varicose veins)
- occasional enlargement and irritation of submucosal veins ~ anal canal
233
Hemorrhoids (like varicose veins)
- occasional enlargement and irritation of submucosal veins ~ anal canal
234
Dog scooting butt across rug
- anal glands have become impacted and trying to excrete contents
- (palpating glands can excrete these glands)
- smelly excretions
235
Anal glands
- used as sex attractants in animals
- musk
- skunks use them as defense
236
What do helicobacter pylori do?
- produce urease => increase gastric ph which secondarily leads to acid production?
237
How do you treat helicobacter pylori?
- treatment with triple therapy
- 2 long term antibodies and proton pump inhibitory
(prevents H+ secretion)
