Digestive System Flashcards
1
Q
what is another name of the digestive tract?
A
gastrointestinal tract
2
Q
where does the GI tract extend from?
A
oral cavity to anus
3
Q
what does the GI tract pass through?
A
passes through pharynx, esophagus, stomach and small and large intestines
4
Q
what are the two surfaces of the GI tract?
A
mucosal - faces the lumen
serosal- faces the blood
5
Q
what are mesentery?
A
double sheets of peritoneal membrane, continous collection of tissue
6
Q
what are the functions of the mesentery?
A
- suspend portions of small and large intestine from the posterior abdominal wall
- digestive organs connected to it
- contains blood vessels, nerves, and lymphatic vessels that go
- stabilizes portions of attached organs
- prevent intestines from entangling
7
Q
what epithelial tissue is the oral cavity lined with?
A
stratified squamous epithelium
8
Q
what does the tongue secrete that aids in digestion?
A
mucins and lingual lipase
9
Q
what are the three pairs of salivary glands?
A
- parotid glands
- sublingual glands
- submandibular glands
10
Q
what do parotid salivary glands produce?
A
serous secretion, enzyme salivary amylase
11
Q
what two categories of foods begin digestion in the oral cavity?
A
starches and lipids
12
Q
what do sublingual salivary glands produce?
A
mucous secretion that acts as a buffer and lubricant
13
Q
what do submandibular salivary glands produce?
A
secretes buggers, glycoproteins, and salivary amylase
14
Q
what salivary gland produces the majority of saliva?
A
submandibular glands
15
Q
what are the components of saliva?
A
99.4% water, 0.6% electrolytes, buggers, glycoproteins/mucins, antibodies, enzymes, waste products
16
Q
what are the functions of saliva?
A
- lubrication
- dissolving chemicals that stimulate taste buds
- initiating digestion of complex carbohydrates through salivary amylase
17
Q
what are the three regions of the pharynx?
A
nasopharynx, oropharynx, laryngopharynx
18
Q
what is another word for swallowing?
A
deglutition
19
Q
what are the three phases of swallowing?
A
- buccal phase
- pharyngeal phase
- esophageal phase
20
Q
what is the buccal phase of swallowing?
A
tongue pushed bolus against soft palate and back of mouth, triggering swallowing reflex
21
Q
what is the pharyngeal phase of swallowing?
A
breathing is inhibited as the bolus passes through the closed airway
22
Q
what is the esophageal phase of swallowing?
A
food moves downward into esophagus, propelled by peristaltic waves and aided by gravity
23
Q
where does the esophagus bring food?
A
to the stomach
24
Q
where does the esophagus enter the abdominopelvic cavity?
A
esophageal hiatus
25
what innervates the esophagus?
esophageal plexus
26
what are the 4 histological layers of the esophagus?
1. mucosal
2. submucosal
3. muscularis externa
4. adventitia
27
what epithelial cell makes up the mucosal layer of the esophagus?
non-keratinized stratified squamous
28
what is found in the submucosal layer of the esophagus?
esophageal glands which produce mucous secretions that reduce friction between bolus and esophageal lining
29
what is the outermost epithelial layer of the esophagus?
adventitia
30
what is narrowing/tightening of the esophagus called?
strictures
31
what are strictures often caused by?
stomach acids/ reflux that damages tissue over time; most common gastroesophageal reflux disease (GERD)
32
what is a common treatment for strictures?
balloon dilators
33
what are the 4 regions of the stomach?
1. cardia
2. fundus
3. body
4. pylorus
34
what is the function of the cardia?
contains mucous glands; secretions coat connection with esophagus protecting it from acids and enzymes
35
what is the function of the fundus?
secretes most of the acids and enzyme for gastric digestion
36
what is the function of the body?
mixer
37
what is the function of the pylorus?
secretes mucus and digestive hormones
38
what is the function of the mucosal barrier of the stomach?
prevents enzymes/acids from digesting stomach itself
39
what are the components of the mucosal barrier that make it impermeable?
- goblet cells produce coast of alkaline mucus
- mucus traps a thick coat of bicarbonate rich fluid
- epithelial cells that are joined by tight junctions
- gastric glands that have cells impermeable to HCL
40
how quickly do damaged epithelial cells/mucosal cells turnover?
3-7 days
41
where are gastric glands found?
in the fundus and body of the stomach
42
what are found at the surface of gastric surfaces?
gastric pits
43
what are the two cells of gastric glands that secrete the majority of gastric juice into the stomach?
parietal cells and chief cells
44
what do parietal cells secrete?
intrinsic factor and hydrochloric acid
45
what do chief cells secrete?
pepsinogen
46
what happens to pepsinogen in the gastric lumen?
converted to pepsin (active proteloytic enzyme) by HCL
47
how is HCL secreted from parietal cells?
1. hydrogen ions generated inside parietal cell and carbonic anhydrase converts Co2 and H2o into carbonic acid
2. Cl- is brought into the parietal cells and bicarbonate ions are ejected into the interstitial fluid by a countertransport mechanism
3. chloride ions diffuse across the cell and exit through open chloride channels into the lumen of the gastric gland
4. the hydrogen ions are actively transported into the lumen of the gastric gland
48
what is the pH of the stomach kept at due to parietal cell excretions?
1.5-2 (very acidic)
49
what are the 4 functions of the acidic environment?
1. kills microorganisms
2. denatures proteins and inactivates enzymes in food
3. helps break down plant cell walls and connective meat tissue
4. activates pepsin
50
what do mucous neck cells secrete?
acid mucus
51
what do enteroendocrine cells secrete?
gastrin, histamine, endorphins, serotonin, cholecystokinin (CCK), and somatostatin
52
where are pyloric glands?
located in the pylorus
53
what is the function of the pyloric glands?
produce mucous secretions
54
what is commonly found in pyloric glands?
enteroendocrine cells
55
what are the two important enteroendocrine cells?
G cells and D cells
56
what do G cells produce?
gastrin
57
what is the function of gastrin?
stimulates secretion of parietal and chief cells
58
what do D cells produce?
somatostatin
59
what is the function of somatostatin?
a hormone that inhibits release of gastrin
60
what hormone rises before meals to initiate hunger?
ghrelin
61
what is the role of pepsin in the stomach?
preliminary digestion of proetins
62
what does salivary amylase digest?
carbohydrates
63
what is responsible for the digestion of lipids in the stomach?
lingual lipase and gastric lipase
64
what is the makeup of intestinal juice?
mainly water but some mucous
65
why is intestinal juice slightly alkaline?
assists in buffering acids, moistens chyme, keeps digestive enzymes and products of digestion in solution
66
where does chyme arrive in small intestine?
duodenum
67
what moves chyme to jejunum?
weak peristaltic contractions
68
what controls peristaltic contractions?
myenteric reflexes and submucosal motor neurons
69
are peristaltic contractions under CNS control?
no
70
how long does it take for material to pass from duodenum to end of illeum?
~5 hours
71
what two reflexes speed up movement along small intestine?
gastroenteric reflex and gastroileal reflex
72
what does the gastroenteric reflex do?
stimulates motility and secretion along the entire small intestine
73
what does the gastroileal relex do?
a long reflex triggered by stomach activity that triggers relaxation of ileocecal valve, allowing materials to pass from small intestine into large intestine
74
what is the function of the duodenum?
receives and neutralizes chyme
75
what is the function of the jejunum?
nutrient absorption
76
what is the function of the ileum?
lymphoid tissue (peyer's patches), protect SI from bacteria in LI
77
true or false, the small intestine contains villi?
true
78
what capillaries are found on the villi of the small intestine?
lymphatic capillary = lacteals
79
what do lacteals transport?
substances that cannot enter blood such as chylomicrons (protein + lipid mixtures) b/c they are too large
80
what are the three secretions of the duodenum?
gastric inhibitory peptide (GIP), cholecystokinin and secretin (CCK), vasointestinal peptide (VIP)
81
what is the function of GIP?
inhibit gastric & stimulates pancreas to release insulin
82
what is the function of CCK?
release of pancreatic enzymes and buffers, ejection of bile from gallbladder to emulsify fat
83
what is the function of VIP?
dilate intestinal capillaries, facilitates absorption
84
what are the folds on the surface of the stomach called?
rugae
85
what cells control the rhythmic cycles of activity in the GI tract?
pacesetter cells
86
what is peristalsis?
consists of waves of muscular contractions that move a bolus along the length of the GI tract
87
what is segmentation?
contractions that churn and fragment the bolus, mix with intestinal secretions, no set pattern, does not push
88
how do the circular and longitudinal contract during peristalsis?
- circular muscles contract behind bolus while circular muscles ahead of bolus relax
- longitudinal muscles ahead of bolus contract, shortening adjacent segments
- waves of contraction in circular muscles
89
how does segmental contractions work?
alternate segments contract and there is little or no net forward movement
90
what are the three regulations of digestive activities?
local factors, neural control, hormonal
91
how does hypertension affect the gut?
intestinal barrier is compromised, increased permeability, damaged tight junctions
92
what are the 4 regions of the colon?
ascending, transverse, descending, sigmoid
93
what are the pouches of the colon that allow it to expand and elongate?
haustra
94
what are the three bands of smooth muscle that run along outer surfaces of the colon?
taeniae coli
95
what is the function of taeniae coli?
contractions help create the bulges known as haustra. Help initiate peristlasis?
96
what are fatty appendices?
teardrop shaped sacs of fat on the serosa of the colon
97
does the large intestine have villi?
no
98
what type of cell is abundant in the large intestine?
mucous cells
99
what is different about digestive intestinal glands compared to small intestine?
deeper and dominated by mucous cells
100
does the large intestine secrete digestive enzymes?
no
101
how much nutrient absorption occurs in the large intestine?
<10%
102
what are the primary functions of the large intestine?
- prepare fecal material for ejection from the body
- lubricates fecal material
- some absorption
103
what is reabsorbed in the large intestine?
- water and electrolytes
- bile salts
104
what is absorbed in the large intestine?
- vitamins produced by bacteria
- organic wastes
105
what is C. difficile colitis?
bacterial infection of the colon
106
what three substances are formed following the breakdown of peptides by bacteria?
ammonia, indole and skittle, hydrogen sulfide
107
what are indole and skatole?
nitrogen compounds responsible for odor of feces
108
what is hydrogen sulfide?
gas that produces rotten egg odor
109
what does bacteria do to bilirubin?
converts it to uribilinogens and stercobilinogens
110
how is intestinal gas formed in the large intestine?
bacteria feeds on indigestible carbohydrates
111
true or false, an important function of bacteria in the colon is the production of vitamins?
true
112
what are three vitamins produced by bacteria in the colon?
vitamin k, biotin, vitamin b5
113
what is the function of vitamin K?
required by the liver for synthesizing four clotting factors including prothrombin
114
what is the function of biotin?
important in glucose metabolism
115
what is the function of vitamin B5?
required in manufacture of steroid hormones and some neurotransmitters
116
what is a major cancer found in colon?
colorectal cancer
117
what is the exocrine function of the pancreas?
production of enzymes
118
what cells secrete enzymes in the pancreas?
acinar cells
119
how are secretions of acinar cells controlled?
controlled by hormones of the duodenum (secretin and CCK)
120
what are the 4 pancreatic enzymes?
1. pancreatic alpha-amylase
2. pancreatic lipase
3. nucleases
4. proteolytic enzymes
121
what are the two types of proteolytic enzymes?
proteases and peptidases
122
what do proteases break down?
large protein complexes
123
what do peptidases break down?
small peptide into amino acids
124
what system is responsible for the secretion of bile?
heptatic bile duct system
125
what is responsible for the production and secretion of bile?
the liver
126
where does the liver secrete bile through?
bile canaliculi
127
where does the liver secrete bile to?
gallbladder
128
what shape is the gallbladder?
hollow, pear shaped sac
129
what is the function of the gallbladder?
stores and concentrates bile and releases bile into duodenum
130
what is the stimuli for the release of bile into the duodenum?
cholecystokinin
131
are dietary lipids water soluble?
no
132
what does mechanical processing in the stomach break fat into?
large lipid droplets
133
is pancreatic lipase lipid soluble? what are the implications?
no, they only act at the surface of lipid droplets
134
what do lipid salts do to large fat droplets?
coat them and cause emulsification, breakdown of droplets which increases surface area and create tiny emulsion droplets
135
what segment of the GI tract does Crohn's disease influence?
any part of the GI tract from the mouth to anus. Mainly affects the ileum
136
what segment of the GI tract does ulcerative colitis influence?
large intestine and the rectumq
137
what is an abscess?
infected fluid collection in a tissue cavity
138
what is bowel obstruction?
scarred, thickened and narrowed bowel amy block flow of contents though the lumen
139
what are fissures?
tears in the anus lining that cause pan and bleeding
140
what are fistula?
abnormal tunnels that form between 2 structures of the body which are caused by inflammation
141
what is a perforated bowel?
chronic inflammation that can weaken the intestinal wall and cause a hole to develop
142
what are strictures?
narrowing of the intestine caused by chronic inflammation
143
what are ulcers?
chronic inflammation that leads to open sores anywhere in the GI tract from mouth to anus
144
what happens when the mucosal barrier is damaged by Crohns or UC?
unrestricted flux pathways open up
145
what are three proteins that are used to link adjacent cells together to maintain gut health and barrier integrity?
tight junctions
adherens junctions
desmosomes
146
in C and UC, what happens to the tight junction proteins?
inflammation impacts the tight junction proteins to increase permeability and compromise the tight junctions. Unrestricted pathway dominates
147
how does IBD impact the skin?
leaky gut barriers, ulcers, mouth ulcers, increased skin infections
148
how does IBD impact the pulmonary system?
bronchiectasis, bronchitis, bronchiolitis
149
how does IBD impact the renal system?
- terminal ileal involvement decreases the ability of the SI to absorb fat so fat binds calcium so there is less calcium to bind oxalate which is then excreted by kidney
- diarrhea from IBD flare increases risk or uric acid stones. get dehydration and concentrated urine
150
how does IBD impact bones?
vitamin D deficiency, calcium malabsorption, bone loss (osteopenia and osteoporosis), use of steroids increases bone lossq
151
how does IBD impact hemoglobin?
anemia from blood loss in stool
anemia from chronic inflammation (hepcidin increase)
anemia from lack of appetite
anemia from deficit in other nutrients (folate/B12)
may get autoimmune hemolytic anemia
thromboembolism
152
how does IBD impact malnutrition?
common in those with Crohns. small intestine is where most nutrients are absorbed. the colon is important in water uptake, malnutrition is less common in those with UC
153
what hormones would increase in response to blood loss from ulcerations in the stomach?
EPO and ERFE
154
what substances secreted by gastric cells may be compromised?
parietal cells - HCL and intrinsic factor
chief cells - pepsinogen
enteroendocrine cells: gastrin/somatostatin/ghrelin
mucus neck cells: mucus and bicarbonate
155
true or false, skeletal muscle cells are elongated and have multiple nuclei?
true
156
do skeletal muscles have striations?
yes
157
true or false, cardiac muscle tissue has visible striation and single/binucleate central nucleus?
true
158
what movement is skeletal muscle responsible for?
voluntary
159
what movement is cardiac tissue responsible for?
involuntary
160
what is a distinct feature of cardiac muscle tissue?
intercalated discs
161
what shape are smooth muscle cells?
spindle shaped
162
do smooth muscle cells have single or multiple nuclei?
single central nucleus
163
do smooth muscle cells have striations?
no
164
what is the comparison between the contraction time and energy cost of smooth muscle compared to skeletal muscle?
takes 30 times longer to contract but at less then 1% the energy cost
165
what is different about the type of myosin in smooth muscle?
heads along the whole lenth; actin filament radiate from dense bodies and ends overlap a myosin filament midway between the dense bodies
166
true or false, smooth muscle have sarcomeres and t-tubules?
false, no sarcomers or T-tubules
167
true of false, smooth muscle have no Z discs and instead have intermediate filaments attached to dense bodies
true
168
how does smooth muscle filaments align when they contract?
align diagonally so twists when contract
169
what does smooth muscle have instead of troponin?
calmodulin
170
true or false, smooth muscle lacks neuromuscular junctions?
true
171
what are the bulbous swellings on innervating nerves of smooth muscle called?
varicosities
172
what do varicosities release? and where do they release it?
neurotransmitters into wide synaptic clefs called diffuse junctions
173
what are the pouch-like infoldings that sequester ECF containing high conc of Ca ions?
caveolae
174
where does Ca enter from to start contraction?
enters from ECF and from sarcoplasmic reticulum
175
what does Ca bind to?
calmodulin
176
what does the calmodulin-Ca complex do?
it activates myosin light chain kinase (phosphorylating enzyme)
177
what does the myosin light chain kinase do?
it phosphorylates the myosin light chain which can now bind to the actin filament
178
what splits phosphate from myosin light chain?
myosin phosphatase
179
what is the key determinant in the time to relaxation?
the amount of myosin phosphatatse?
180
how does Ca get back into ECF or SR?
actively pumped by a slow-acting Ca pump
181
what are three reasons why smooth muscle contraction is slower?
- greater distance Ca must diffuse from ECF into cell
- rate at which action potentials are propagated between smooth muscle cells
- slower rate of cross-bridge formation between actin and myosin
