Digestive System - Upper Flashcards
1
Q
contents of digestive system
A
oral cavity and alimentary canal:
- esophagus
- stomach
- small and large intestines
- extrinsic glands
2
Q
describe digestive tract and name the 4 layers
A
layered hollow tube:
- mucosa
- submucosa
- muscularis externa
- serosa (where continuous w/ mesentery) or adventitia (where fixed to wall of cavity)
3
Q
function of digestive system
A
secrete enzymes and hormones that function in digestive process
4
Q
epithelium of esophagus
A
stratified squamous nonkeratinized epithelium
5
Q
glands of esophagus
A
- esophageal cardiac glands
- esophageal glands proper
6
Q
esophageal cardiac gland secretion
A
mucus-secreting
7
Q
esophageal cardiac gland location
A
in lamina propria, at top and bottom of esophagus (mainly top), but not super abundant
8
Q
what are esophageal cardiac glands similar to?
A
cardiac glands in stomach
9
Q
esophageal glands proper secretion
A
primarily mucus secreting, but also some serous cells that secrete lysozyme
10
Q
esophageal glands proper location
A
in submucosa
11
Q
muscularis mucosae
A
single longitudinal layer of smooth muscle
12
Q
how does the muscularis externa change as you move proximal to distal in the esophagus?
A
- upper third = striated, skeletal muscle
- middle third = outer layer of smooth muscle, inner layer of skeletal muscle
- lower third = smooth muscle
13
Q
function of esophagus
A
conveys food (bolus) from pharynx to stomach by the peristaltic activity of the muscularis externa
14
Q
what are the two sphincters in the muscularis externa?
A
- upper = pharyngoesophageal
- lower = gastroesophageal
15
Q
overall function of the two sphincters of esophagus
A
ensures bolus transported in one direction only - toward stomach
16
Q
function of the upper esophageal sphincter (UES)
A
initiates swallowing
17
Q
function of the lower esophageal sphincter (LES)
A
prevents acid reflux from stomach into esophagus
18
Q
GERD and cause
A
gastroesophageal reflux disease - caused by persistent acid reflux
19
Q
what can acid reflux from stomach into esophagus lead to?
A
ulceration and dysphagia - ultimately can lead to fibrosis and stricture of the lower esophagus
20
Q
Barrett’s esophagus
A
- abnormal growth growth of intestinal-type cells (simple columnar) in the lower esophagus
- more easily injured by stomach acid
21
Q
what is Barrett’s esophagus a risk factor for?
A
adenocarcinoma of esophagus
22
Q
what sex does Barrett’s esophagus present in more?
A
3x more incidence in males
23
Q
hiatal hernia
A
portion of stomach that can move into thoracic cavity
24
Q
what causes hiatal hernia?
A
if esophageal hiatus in diaphragm does not close entirely during development
25
what can result from hiatal hernia?
reflux esophagitis and ulceration - difficulty swallowing and a feeling of a lump in the throat
26
function of the stomach
acidifies and converts food into viscous fluid called chyme
27
what does the stomach produce?
digestive enzymes and hormones
28
rugae
longitudinal folds of the mucosa and submucosa that disappear in distended stomach
29
describe gastric pits in the different parts of the stomach
deepest in pylorus and shallowest in cardia
30
what are gastric pits?
entrance to gastric glands
31
regions of stomach
- cardia
- fundus
- body
- pylorus
32
cardia
- tubular glands with coiled end
| - mucus secreting
33
fundus
- simple tubular glands
- shallow gastric gland pits
- abundant parietal and chief cells
34
what section of stomach is the primary contributor to gastric juice?
fundus
35
body of stomach
similar to fundus
36
pylorus
- deep gastric pits
- branched glands
- primarily mucus secreting
- occasional parietal cell
- gastrin secreting G cells
37
lining of gastric mucosa
mucus-producing simple columnar surface lining cells (NOT goblet cells)
38
lamina propria of gastric mucosa
loose CT containing:
- smooth muscle cells
- lymphocytes
- plasma cells
- mast cells
- fibroblasts
39
what type of glands does the gastric mucosa contain?
gastric glands
40
muscularis mucosae of gastric mucosa
- poorly defined inner circular layer
- outer longitudinal layer of smooth muscle
- occasionally an outermost circular layer
41
contents of gastric mucosa
- epithelium
- lamina propria
- gastric glands
- muscularis mucosae
42
composition of gastric submucosa
- dense irregular collagenous CT
- fibroblasts
- mast cells
- lymphoid elements
- Meissner's plexus
43
composition of gastric muscularis externa
3 layers of smooth muscle:
- incomplete inner oblique
- thick middle circular
- outer longitudinal
44
which layer of gastric muscularis externa forms the pyloric sphincter?
thick middle circular layer
45
function of gastric muscularis externa
mixing gastric contents and stomach emptying
46
what influences rate of stomach emptying?
chyme characteristics:
- viscosity
- pH
- lipid content
- osmolality
- caloric density
47
gastric serosa
covers the external surface of the stomach
48
epithelium of fundus and body region
mucus-secreting surface lining cells
49
parts of gastric glands
isthmus, neck, and base
50
isthmus of gastric glands
connects gland to the base of a gastric pit
51
what types of cells do gastric glands have?
parietal, chief. mucous neck, enteroendocrine
| -also have regenerative cells
52
regenerative cells
replace all other cells in the gland, pit and luminal surface - located primarily in neckand isthmus
53
what do surface-lining simple columnar cells contain?
apically located mucinogen granules
54
what do surface-lining simple columnar cells secrete?
cloudy, thick, viscous mucus with high bicarbonate content (acid protection) - coats surface epithelium (~100 um thick)
55
how often are surface lining cells renewed?
every 3-5 days
56
mucous neck cells location
neck of gastric glands
57
can mucous neck cells divide?
maybe
58
mucous neck cell description
- short microvilli
- apical mucous granules
- prominent golgi
- shorter columnar cell than surface lining cells
59
what do mucous neck cells secrete?
soluble mucous - not as thick as mucus produced by surface lining cells
60
what induces mucous neck cell secretion?
vagal stimulation
61
parietal/oxyntic cells description
- pyramidal-shaped cells in upper half of gastric glands
- eosinophilic w/ H&E
- intracellular tubulovesicular system
- many mitochondria
- secretory intracellular canaliculi
62
function of parietal/oxyntic cells
seecrete HCl and gastric intrinsic factor
63
what is gastric intrinsic factor and why is it needed?
glycoprotein needed for vitamin B12 absorption in small intestine
64
intracellular canaliculi of parietal cells
deep invaginations of the apical plasma membrane lined by microvilli
65
changes to parietal cell when stimulated to secrete HCl
- number of microvilli increase
| - complexity of the tubulovesicular system decreases
66
what stimulates HCl secretion?
ACh and gastrin (APUD cells of pylorus)
67
how is HCl formed by parietal cells?
H+, K+, and Cl- are pumped into canaliculus and then HCl is formed extracellularly
68
what event increases effects of ACh and gastrin on parietal cell secretion?
histamine binding to histamine H2 receptor
69
what cells produce histamine?
enterochromaffin-like cells in lamina propria around gastric glands
70
what drugs inhibit histamine-dependent acid secretion?
anti-acid drugs like cimetidine (1st generation)
71
what drugs inactivate acid secretion?
2nd generation drugs - omeprazole - bind to H+, K+-dependent ATPase
72
describe series of reactions mediated by CA that affects blood and mucous pH on surface
- CO2 absorbed from blood or formed in parietal cells (metabolism) combines w/ OH- to form carbonic acid (requires CA)
- carbonic acid -> HCO3- and H+
- HCO3- diffuses out of cell and is picked up by capillaries
73
what happens to the HCO3- once it exits the parietal cells?
enters a fenestrated capillary in lamina propria, w/ blood flowing toward surface epithelium -> diffuses into the mucus blanket to increase the pH
74
chief/zymogenic cells
- pyramidal-shaped cells in lower half of fundic glands
| - basophilic w/ H&E
75
what do chief/zymogenic cells secrete?
- pepsinogen
| - rennin and lipase precursors
76
pepsinogen
precursor of pepsin enzyme
77
chief/zymogenic cell description
- abundant basally located rER
- supranuclear golgi
- apical secretory granules (zymogen)
78
enteroendocrine cells
- DNES = diffuse neuroendocrine cells
| - also called APUD cells = amine precursor uptake and decarboxylation cells
79
do all enteroendocrine cells take up amine precursors?
no
80
number of enteroendocrine cell types
> 12 different cell types that contain small hormone-containing granules
81
how many hormones does any given enteroendocrine cell secrete?
only one hormone
82
where are enteroendocrine cells located?
down near base of crypts
83
what is typical of all cells of the diffuse endocrine system?
numerous small, electron dense granules
84
gastric juices
- water
- HCl
- mucus
- pepsin
- lipase
- rennin
- electrolytes
85
what facilitates activation of pepsinogen to pepsin?
very acidic conditions (pH 2.0) - catalyzes partial hydrolysis of proteins
86
regulation of gastric secretion, in general
affected by neural (vagus n.) and hormonal activity
87
secretin
- released by cells in duodenum when pH < 4.5
- stimulates pancreatic HCO3- and fluid section
- stimulates chief cells to secrete pepsinogen
88
gastrin
- G cells in pylorus and duodenal mucosa
- 2 forms: small G17 in pylorus + large G34 in duodenum
- stimulates HCl secretion
89
somatostatin
- D cells of pylorus and duodenum
- inhibits gastrin release
- indirectly inhibits HCl secretion
90
gastric inhibitory peptide/ urogastrone
- cells in duodenum and jejunum
- directly inhibit HCl secretion
- stimulate insulin release
91
what are the two gastric hormones?
cholescystekinin (CCK) and motilin
92
cholescystekinin
- produced in duodenum and jejunum
| - stimulates gallbladder contraction when fat is in small intestine
93
motilin
-released cyclically (every 90 min) during fasting from cells in upper GI tract
94
gastritis
gastric mucosal inflammation common in middle-aged and older individuals - may be superficial or affect entire thickness, causing mucosal atrophy
95
what causes gastritis
often unknown etiology
96
zollinger-ellison syndrome
patients w/ gastrin secreting tumors have hyperplasia and hypertrophy of fundus + high acid secretion -> stomach ulcers, diarrhea
97
gastric/peptic ulcers
areas of gastric or duodenal mucosa destroyed by gastric secretions
98
where are gastric/peptic ulcers commonly found?
in cardiac and pyloric regions and first part of duodenum
99
causes of gastric/peptic ulcers
- excess HCl secretion
- nervous irritation
- reduced vascular supply
- reduced mucus secretion
- infection (H. pylori)
- NSAIDS
100
treatment of gastric/peptic ulcers
- antibiotics
- stress management
- elimination of alcohol, aspirin/NSAIDS, and cigarette use
- antacids and/or drugs that inhibit gastric secretions
101
how do NSAIDS cause ulcers?
shut down prostaglandin synthesis, which is important in protecting the GI tract
102
phases of H. pylori infection
- active phase
- stationary phase
- colonization phase
103
active phase of H. pylori infection
H. pylori increases gastric pH by producing ammonia via urease
104
stationary phase of H. pylori infection
bacteria attach to fucose containing receptors on surface of mucus cells in pylorus - bacteria releases proteases that kill surface cells
105
colonization phase of H. pylori infection
bacteria detach and replicate in mucus blanket
