Week 2 - Chapter 2 Flashcards
1
Q
Main structures of the digestive tract (top to bottom)
A
Oral cavity (Pharynx) Esophagus Stomach Small intestine Large intestine
2
Q
Upper GI tract =
A
oral cavity, esophagus
3
Q
Lower GI tract =
A
stomach, intestines
4
Q
Digestive tract accessory organs
A
pancreas, liver, gallbladder
5
Q
4 layers of lumen of digestive tract (inner to outer)
A
mucosa, submucosa, muscularis externa, serosa (adventitia)
6
Q
Mucosa - 3 sublayers
A
epithelium, lamina propria (lymphoid tissue), muscularis mucosa (smooth muscle)
7
Q
Mucosa - epithelium contains
A
contains endocrine and exocrine cells
8
Q
Submucosa - 3 sublayers
A
connective tissue, lymphoid tissue, submucosal plexus
9
Q
Submucosa generally gives the lumen
A
flexibility
10
Q
Muscularis externa - 3 components
A
circular/longitudinal smooth muscle, myenteric plexus
11
Q
Serosa/adventitia
A
connective tissue, visceral peritoneum
12
Q
3 salivary glands
A
Above tongue - parotid
Below tongue - submandibular, sublingual
13
Q
Oral cavity moves food through ___ to ___ by ____
A
through pharynx to esophagus by swallowing
14
Q
Bolus =
A
in esophagus, = food + salivary juices
15
Q
3 stages of swallowing
A
voluntary, pharyngeal, esophageal
16
Q
Peristalsis
A
wave-like motion from muscle fibers contracting and relaxing
17
Q
Gastroesophageal sphincter
A
between esophagus and stomach, aka lower esophageal sphincter
18
Q
GERD aggravated by
A
smoking, chocolate, high-fat foods, alcohol, and carminatives (peppermint/spearmint) promote relaxation of the esophageal sphincter and increase the likelihood of acid reflux
19
Q
4 main regions of the stomach
A
Cardia - top
Fundus
Body - main
Antrum or distal pyloric region - bottom with pyloric sphincter
20
Q
Food in the stomach =
A
chyme, = food + gastric juices
21
Q
Rugae in stomach (folds) purpose
A
increase SA
22
Q
Stomach is ______ but small intestine is ______
A
Stomach - acidic
Small intestine - alkaline
23
Q
Stomach pH approx
A
2
24
Q
Barrier between stomach and small intestine
A
pyloric sphincter
25
Gastric (stomach) glands (3)
cardiac, oxyntic, pyloric
26
Cells in gastric glands (4)
Neck (mucus)
Parietal (oxyntic)
Chief (peptic or zymogenic)
Enteroendocrine
27
Neck (mucus) cells
secrete bicarbonate and mucus
28
Parietal (oxyntic)
secrete HCl and intrinsic factor
29
Chief (peptic/zymogenic) cells
secrete enzymes that break down proteins (pepsinogens)
30
Enteroendocrine cells
produce hormones like gastrin that stimulates other cells to secrete
31
Gastric juice components
HCl, enzymes (pepsin, amylase, lipase), mucus, intrinsic factor
32
HCl function in stomach (4)
Converts pepsinogen to pepsin
Denatures proteins
Releases nutrients from organic complexes
Acts as bacteriocide
33
Enzymes in stomach mostly
pepsin - mostly protein digestion occurs in the stomach
34
Pepsin is an
endopeptidase; hydrolyzes interior peptide bones within proteins; optimal activity at about 3.5 pH
35
alpha amylase in stomach
originates from salivary glands; retains some activity until inactivated by low pH of gastric juice
36
Gastric lipase
made by chief cells
37
Mucus in stomach stimulated by
prostaglandins and nitric oxide
38
Intrinsic factor is necessary to
absorb B12
39
What's absorbed in the stomach
water, alcohol, a few drugs and a few minerals
40
HCl important for _____, IF important for ______
HCl - iron
| IF - B12
41
HCl release stimulated by
gastrin, acetylcholine (NT released by neurons in myenteric plexus), histamine
42
Zollinger-Ellison syndrome
usually caused by a tumor, extremely high levels of gastrin into the blood (-->hypergastrinemia) --> formation of multiple ulcers
43
Peptic ulcers result when
normal defense and repair systems that protect the GI tract are disrupted
44
Most common cause of peptic ulcers
H. pylori
45
Can disrupt barriers and --> peptic ulcers
aspririn, alcohol, and NSAIDs
46
Migrating motility complex/myoelectric complex
sweeps out the GI contents and prevents bacterial overgrowth in the intestine
47
Gastric emptying following a meal usually take between
2 to 6 hours
48
Zooming in on small intestine
folds of kerkring --> villi/crypts of lieberkuhn --> microvilli
49
_________ in the small intestine is where nutrients are absorbed
capillary network in the villi
50
Each cell within a villus has
a brush border with microvilli
51
Microvilli
hair-like extensions of the cells' plasma membranes
52
Crypts of lieberkuhn
cells in the crypts will migrate up to eventually become absorptive cells in the tips of the villus
53
Enterocyte (small intestine cell) turnover occurs every
3-5 days
54
Factors that increase intestinal secretions and motility (4)
1) VIP (vasoactive intestinal polypeptide) in myenteric plexus
2) Neuropeptide substance P
3) Motilin
4) CCK
55
Factors that decrease secretions and motility in the small intestine (3)
1) Peptide YY
2) Secretin
3) Glucagon-like peptides
56
Hormone definition
act at a distant location; can be protein or not
57
3 ways nutrients cross cell membrane to be absorbed
simple diffusion, facilitated diffusion, active transport
58
2 ways nutrients are absorbed that depends on a concentration gradient
Simple and facilitated diffusion
59
Simple diffusion
water and small lipids cross into intestinal cells freely
60
Facilitated diffusion
water-soluble nutrients (etc.) diffuse using a transporter protein
61
Active transport
Some nutrients (like glucose and AA) move against a concentration gradient using ATP
62
Immune cells and tissues are found throughout the GI tract but especially high concentrations in the
small intestine
63
Immune system protection of the GI tract (2 types of tissue)
Mucosa-associated lymphoid tissue (MALT)
| Gut-associated lymphoid tissue (GALT) - non-mucosal layer
64
Pancreas is located
right below stomach
65
2 types of active cells in the pancreas
1) ductless endocrine
| 2) acinar exocrine
66
Pancreatic ductless endocrine cells secrete
hormones (insulin, glucagon etc.) into the blood
67
Pancreatic acinar exocrine cells secrete
digestive enzymes (produce pancreatic juice)
68
Pancreatic juice contains
bicarbonate, electrolytes, digestive enzymes
69
Pancreatic juice bicarbonate purpose
neutralizes the acidic chyme
70
Secretions from the pancreas go into the
small intestine
71
3 parts of small intestine
duodenum (1st), jejunum (longest), ileum (last)
72
Islets of langerhans
ductless endocrine portion of pancreas that secretes hormones
73
Pancreatic enzymes work on
fat and carb mostly
74
Factors that promote pancreatic secretion
Secretin, CCK, neuropeptide substance P, VIP
75
Liver consists of
2 lobes made of lobules
76
Owing to the alkaline pH of bile, the conjugated bile acids combine with _______ to form bile salts
sodium, potassium, or calcium
77
Bile is made in the
liver
78
Bile is composed of
bile acids, salts, cholesterol, phospholipids, and bile pigments (bilirubin and biliverdin) in an alkaline solution
79
About 90% of the bile acids and salts secreted into the duodenum are
reabsorbed in the ileum
80
Bile goes to
small intestine
81
Cholecystokinin (CCK) is secreted by ___ and does what?
small intestine, stimulates gallbladder to contract and release bile
82
________ inhibits gallbladder contraction
somatostatin
83
Gallstones form when
bile becomes supersaturated with cholesterol
84
Some medication enhance (cholesterol meds)
fecal excretion of bile to reduce cholesterol
85
After aiding in lipid digestion, the bile constituents are reabsorbed from the ileum and returned to ___ via
the liver via the hepatic portal vein
86
Gallbladder contracts to release bile into the ____ which combines with the ______ to form the _________ which goes to small intestine
Gallbladder contracts to release bile into the cystic duct which combines with the hepatic duct to form the common bile duct which goes to small intestine
87
Carb -->
Protein -->
Fats/lipids -->
Carb --> monosaccharides
Protein --> AA
Fats/lipids --> triglycerides and FAs
88
Mechanism of absorption depends on
solubility (fat vs water), concentration of electrical gradient, size of molecule
89
Unabsorbed molecules continue to
colon (large intestine)
90
Colon contracts to
mix materials
91
Proximal colonic epithelia absorb
Na, Cl, H2O
92
Materials in the colon are
dehydrated
93
Passage of material through the colon takes
12-70 hours
94
Ileocecal sphincter is where
the ileum connects to the large intestine
95
Lots of bacteria in
large intestine
96
Presence of SCFAs from bacteria effectively
lowers pH of colon to effect nutrient absorption
97
SCFAs including butyric acid stimulate...
GI cell proliferation and maintain integrity of intestinal epithelial cells
98
Probiotics are thought to (5)
1) Enhance immunity
2) Prevent colonization by pathogens
3) Lower pH of colon
4) Transform/promote excretion of toxic substances
5) Enhance fecal bulk (may decrease transit time)
99
Myenteric plexus - 2 main functions
peristalsis, motility
100
Submucosal plexus - 2 main functions
secretions, local blood flow
101
Paracrines
have a local action, diffuse through extracellular spaces to target tissue rather than being secreted into the blood
102
Enteric nervous system = nervous system of the GI tract subdivided into 2 networks
myenteric plexus and submucosal plexus
103
NPY in hypothalamus
stimulation --> hunger
104
Ghrelin (hunger regulation)
from stomach, stimulates NPY
105
PYY (hunger regulation)
From large and small intestines, inhibits NPY
106
CCK (hunger regulation)
From small intestine, inhibits NPY
107
Insulin (hunger regulation)
From pancreas, inhibits NPY
108
MCS (melanocortin secreting hormones) in hypothalamus
stimulation --> satiety
109
Leptin (hunger regulation)
From adipose tissue, stimulates MCS
110
PYY prevents
stomach from emptying too quickly
111
Short term appetite regulators
ghrelin, PYY, CCK
112
Long term appetite regulators
Leptin, insulin
113
Human obesity is linked to unresponsiveness to
leptin
114
Leptin inhibits secretion of
appetite stimulants
115
GERD can result in
esophagitis
116
Symptoms of GERD
heartburn, sometimes excessive belching or coughing
117
IBD characterized by
acute, relapsing or chronic inflammation of the GI tract, especially the intestines
118
How does IBD impair nutrient absorption?
Diminishes brush border activity
Reduces transit time
Causes direct damage to enterocytes
119
Symptoms of IBD
diarrhea and steatorrhea
120
General recs for IBD
low fat diet bc fat digestion is impaired
| inc. vit./nutrients/pritein because lost or not well absorbed
121
In Celiac disease, gluten consumption -->
inflammation of small intestine and attack of mucosa by immune cells, villi damaged
122
Chronic pancreatitis can result from
long-term excessive use of alcohol, gallstones, liver disease, viral infections, and certain medications
123
With chronic pancreatiti, pancreas can ultimately fail to
produce sufficient digestive enzymes and juices
124
Chronic pancreatitis symptoms
pain (esp. with eating), nausea, vomiting, diarrhea
125
Chronic pancreatitis diet
needs to be low-fat because not enough pancreatic lipase
