Digestive System Flashcards
1
Q
What is alimentary canal?
A
the digestive tract (from mouth to butt)
2
Q
Digestive system=
A
oral cavity + alimentary canal
3
Q
Layers of digestive tube from inside to outside
A
Mucosa (epithelium, lamina propria, muscularis mucosa)
Submucosa
Muscularis
Adventitia/Serosa
4
Q
What’s the difference between adventitia and serosa?
A
INTRAperitoneal organs=serosa= visceral peritoneum=mesothelium
RETROperitoneal organs=adventitia=loose CT
5
Q
Parts of Mucosa
A
Epithelium, lamina propria, muscularis mucosa
6
Q
Epithelium of digestive tract has the following….where are we?
a) folds
b) villi
c) peyer’s patches
A
a) folds= esophageal
b) villi= small intestine
c) peyer’s patches= illeum (lymphoid nodule aggregates)
7
Q
Where would you find
a) Peyer’s patches
b) Aurebach’s plexus
c) Meissner’s plexus
d) Brunner’s gland
A
a) in epithelium (of illeum)
b) between two layers of muscle (all)
c) submucosa (all over)
d) submucosa (of duodenum)
8
Q
A. Esophageal Mucosa–layers and contents
B. Esophageal submucosa
C. Muscularis externa
A
A. MUCOSA LAYER
1. epithelium=stratified squamous NON keratinized
2. Lamina propria= esophageal cardiac glands
3. Muscularis mucosa= single longitudinal layer of SMOOTH muscle
B. SUBMUCOSA= Esophageal glands proper
C. MUSCULARIS (from superior-inferior)
striated muscle–>smooth and striated–>smooth
9
Q
Esophagus muscularis layers
A
Outer layer has fibers running in longitudinal direction, inner layer has fibers running around tube in circular direction. these fibers change from striated–>smooth muscle fibers as you move inferiorly in the esophagus
10
Q
Esophageal glands- location, secretion, abundance
A
- Esophageal cardiac glands= in lamina propria: mucous
- Esophageal glands proper= in submucosa: mostly mucous secretions but also serous secretions (include lysozymes. MORE ABUNDANT*
11
Q
What are lysozymes (how do they work), where are they secreted (x3)
A
Antibacterial defense mechanism that cleaves peptidoglycan in bacterial cell wall.
Secreted by 1) salivary glands, 2) esophageal glands proper (found in submucosa of esophagus), and 3) paneth cells.
12
Q
Function of esophagus, how?
A
moves food from mouth to the stomach via action of muscularis externa (peristalsis)
13
Q
Esophageal sphincters-
- made from what layer?
- Function
- types, function
A
- Muscularis externa
- Keep food from coming back up
- Upper= pharyngoesophagea l=initiates swallowing
Lower= gastroesophageal= keeps stomach acid from coming up
14
Q
GERD
A
Caused by persistent acid reflux (failure of LES- lower esophageal sphincter)
15
Q
Consequences of constant GERD
A
ulceration and dysphagia. Esophagus can become fibrotic and constrict.
16
Q
Barrett’s Esophagus
- demographic
- abnormality–consequence of abnormality?
A
More common in males (X3). The lower esophagus makes simple columnar epithelium (intestinal) instead of stratified squamous (esophageal) –>more susceptible to acid from stomach= risk factor for esophageal adenocarcinoma
17
Q
Hiatal Hernia
- cause
- consequence of?
A
- esophageal hiatus in diaphragm doesn’t close during development
- reflux esophagitis and ulceration –>dysphagia and feeling of lump in the throat
18
Q
Gastric pits
A
Invaginations from epithelium to lamina propria leading into gastric glands. Deepest in pylorus and shallowest in cardia.
(deeper you go in the stomach, deeper the pits)
19
Q
Stomach function
A
acidifies food to make chyme
makes digestive enzymes and hormones
Chyme characteristic affects the emptying rate of the stomach
20
Q
Rugae
A
longitudinal folds in stomach mucosa AND submucosa that disappear when the tummy is distended
21
Q
Parts of stomach?
A
Cardia, fundus, body, pyloric antrum, pylorus
22
Q
REVIEW: Lump in the throat feeling can be caused by?
A
Hiatal hernia
23
Q
Gastric Mucosa: Epithelium
A
Epithelium- simple columnar SURFACE LINING CELLS (mucous)
24
Q
Cells found in gastric pit and gastric gland
A
- surface lining (pit),
- regenerative (isthmus of gland),
- mucous neck (neck of gland),
- oxyntic=parietal (upper half),
- zymogenic=chief (base of gland–in fundus only)
- enteroendocrine cells (base of gland0
25
Gastric mucosa: lamina propria
| What are the contents (x7) and purpose?
Lamina propria is loose CT with:
- smooth muscle fibers
- lymphocytes
- plasma cells
- mast cells
- enterochromaffin-like cells
- fibroblasts
- highly vascularized (fenestrated capillaries receive bicarb from parietal cells)
* *provides support for gastric pits and gastric glands,
26
Gastric mucosa: muscularis mucosa
2 LAYERS (sometimes 3)
1. poorly defined circular layer (inner)
2. longitudinal layer of SM (outer)
3. SOMETIMES- outermost circular layer
27
Gastric submucosa
| type of tissue, contents?
Dense irregular COLLAGENOUS CT with fibroblasts, mast cells, lymphoid elements, and meissner's plexus (PNS)
28
Gastric muscularis layer- parts?
| -which one makes the pyloric sphincter?
3 LAYERS (inner to outer)
1. incomplete inner oblique layer
2. middle circular THICK=PYLORIC SPHINCTER
3. Outer longitudinal layer
29
Gastric muscularis layer--function?
mixing gastric contents, emptying stomach.
| Rate of emptying affected by chyme characteristics
30
Protein vs sugar vs fat with gastric emptying?
Protein is slowest, sugar is fastest, fat is in between.
31
Does stomach have serosa or adventitia?
SEROSA (intraperitoneal)
32
Glands of the fundus
1. same as glands in ___ of stomach
2. shape--be specific-what's the pit like?
3. cell types
1. Body
2. Shallow gastric pit leading to simple tubular glands with isthmus, neck and base.
3. surface lining cells, parietal cells, chief cells, mucous neck cells, enteroendocrine cells, and regenerative cells
33
What is primary source of gastric juices?
Fundus- this way the food gets early exposure (not sure if this is true, but good way to remember it)
34
Surface lining cells
1. type
2. location
3. function
4. life span
1. simple columnar
2. found in epithelium of stomach
3. secrete THICK VISCOUS mucous with high HCO3. Also has mucinogen granules (secrete mucin) on apical side of surface cells.
4. 3-5 days
35
What secretes bicarbonate? What is the function of bicarb?
Secreted by surface lining cells of the stomach to protect the epithelium from the acid.
36
Compare Cardia, fundus and pylorus
```
Cardia= tubular glands with COILED end. Secrete mucous
Fundus= shallow pits with simple tubular glands. Secrete gastric juices
Pylorus= deep pits with branched glands- mucus and gastrin secreting.
```
37
1. Where are parietal cells found?
2. G-cells?
3. chief cells?
1. mainly fundus, some pylorus
(parietal->party= FUNdus, PYlorus --pies are at some parties)
2. Pylorus and duodenum (g-cells are type of enteroendocrine cell)
3. Fundus
38
Compare muscularis MUCOSA of stomach and esophagus
Esophagus- single longitudinal layer (SM)
| Stomach- 2 layers- inner circular, outer longitudinal (SM), and sometimes outer circular layer
39
Compare muscularis of stomach and esophagus
Esophagus- 2 layers- circular and longitudinal that changes from striated to smooth muscle as you move down
Stomach- 3 layers-incomplete oblique, thick circular, outer longitudinal. -all SM
40
Lesson we just learned about layers of stomach vs esophagus
Stomach one-ups esophagus in number of layers (muscularis mucosa and muscularis) .
41
Mucous Neck cells
1. Location
2. Characteristics
3. Function & activation
4. Life span?
1. in NECK of gastric glands
2. short microvilli, apical mucous granules, prominent golgi, shorter columnar cells
* *necks are kinda short--everything in it is short
3. Secrete SOLUBLE mucous, VAGAL activation
4. Might be able to divide
42
What has apical mucinogen granules?
| What has apical mucous granules?
Mucinogen granules=surface lining cells
Mucous granules= mucous neck cells
**mucinogen is a long word= surface lining cells are LONGER columnar cells than mucous neck cells.
43
What secretes soluble mucous? what secretes the thick viscous mucous?
```
Soluble= neck cells
viscous= surface cells
```
44
Oxyntic cells (AKA?)
1. Shape
2. Staining (what stains opposite?)
3. Location
4. Function
5. Characteristics
= parietal cells (Oxy at parties, duhh!)
1. pyramidal
2. pink in H&E vs purple chief cells
3. upper half of gastric glands (neck/isthmus area?)
4. Secrete HCL and gastric intrinsic factor
5. lots of mitochondria (=pink staining), tubulovesicular system, intracellular canniliculi with microvilli
45
Resting vs active parietal (oxyntic) cell
| **what constitutes active?
Resting: complex tubulovesicular system
Active: proliferation of intracellular canaliculi and microvilli--secretion of HCl
46
Gastric intrinsic factor
glycoprotein needed for vit B12 to be absorbed in small intestine
47
What stimulates HCl secretion?
acetylcholine and gastrin (APUD cells of pylorus) which causes structural change in the parietal cell to increase intracellular canaliculi (lined by microvilli)
48
Zymogenic Cells (AKA?)
1. shape
2. location
3. staining (why?)
4. Characteristics
5. Function
Chief cells
1. pyramidal shaped
2. base of FUNDIC gland
3. basophilic-lots of rER
4. lots of rER (basal location), supranuclear golgi, zymogen secretory granules (apical)
5. Secrete pepsinogen, renin precursors, lipase precursors
49
Enteroendocrine cells (AKA-why is this a faulty AKA)
APUD=amine precursor uptake and decarboxylation
Pyloric APUD induce HCl secretion (with gastrin and acetylcholine)
Faulty because not all enteroendocrine cells take up amine precursors
50
Enteroendocrine cells
1. Location
2. DNES?
3. Function?
- ->specific ex?
1. Found in base of gastric gland
2. diffuse neuroendocrine cells=population of cells that enteroendocrine cells belong to
3. secrete hormones specific to cell--each cell only secretes one type of hormone--over 12 types of cells
- ->pyloric cells secrete gastrin and acetylcholine to induce HCl secretion
51
Gastric Juices--
1. REVIEW- main source is?
2. Contents
3. Function
1. Fundus of stomach
2. water, HCl, pepsin, lipase, renin, electrolytes. pH2
3. Changes pepsinogen-->pepsin (hydrolysis of proteins)
52
HCl formation
1. Secretion stimulation by?
2. Location of production?
3. byproduct
4. How is it eliminated?
**extra info
1. Acetylcholine and gastrin (from APUD cells=enteroendocrine cells)
2. HCl production in parietal cells
3. HCO3 by product
4. HCO3 into fenestrated epithelium of capillaries in lamina propria
CO2 + H20 --> H2CO3 (CARBONIC ANHYDRASE NEEDED)
H2CO3-->H + HCO3
H+ exits into lumen, HCO3 into blood (in exchange for Cl-)
53
2 Factors that affect pH of mucous blanket in stomach
HCl secretion from parietal cells
HCO3 secretion from surface cells. Surface cells get HCO3 diffusion from capillaries in lamina propria (HCO3 is from parietal cells-->lamina propia) AND they make HCO3, i think....
54
Blood pH
bicarbonate from parietal cells. Only some of it diffuses into the mucous, the rest stays in the blood
55
Acid secretion enhanced by? Where is this "enhancer" made?
Histamine-- it binds histamine H2 receptors which increases the effects of acetylcholine and gastrin on parietal cell
Histamine produced in enterochromaffin-like cells in lamina propria
56
G-Cells
Type of enteroendocrine cells (these are in the base of gastric gland) that make gastrin. Gastrin stimulates HCl secretion by
1) stimulating histamine secretion which in turn increases effects of gastrin and Ach.
2) Gastrin also increases HCl production directly (increase number of K/H pumps)
57
Drug(s) affecting acid secretion--mechanism(s) and name(s)
Cimetidine INHIBITS H2 receptors (histamine) preventing histamine dependent HCl secretion=INHIBITION
Omeprazole binds H/K dep ATPase to INACTIVATE acid secretion. = INACTIVATION
58
HCl production mechanism
| this is probably way more info than we need for this class
```
EXTRACELLULAR
1. Hydrogen Ion formation and Cl in Cell:
H2O + CO2= HCO3 + H
(carbonic anhydrase)
HCO3 traded for Cl- (basal side of cell--from capillaries in lamina propria)
2. Export out of cell into canaliculi
a) H+ via H+/K+ ATPase
b) Cl and K+ diffuse out
3. combine in canaliculi=HCl
```
59
Gastrin-types-location
G17=pyloric gastrin, smaller
G34=duodenal, larger
Gastrin indirectly stimulates HCl by increasing histamine secretion from ECL cells (enterochromaffin-like)
**also increases number of K/H ATPase pumps in membrane
DIRECT AND INDIRECT STIMULATION OF HCL PDT
60
D-Cells
1. Location
2. Secretion
3. Function
* 4. what activates D-cells?
*=bonus info
1. In duodenum and pylorus
2. Somatostatin
3. INHIBITS GASTRIN= INDIRECT HCl inhibition
* *EXTRA: Inhibition of: secretin, histamine, decreased rate of gastric emptying, inhibition of endocrine and exocrine pancreas)
4. Ach and H+
61
S-Cells
1. location (specific)
2. secretion
3. Function of secretion
4. Another function
1. duodenum (Crypts)
2. release secretin when pH <4.5.
3. Secretin stimulates watery pancreatic HCO3 secretion
4. Secretin stimulates chief cells to release pepsinogen
62
Gastric inhibitory peptide
1. Function.
* 2. Activation from
* 3. cells that release this
1. DIRECT inhibition of HCl secretion, stimulation of insulin release. Also enhances epithelial cell division.
2. Glucose in duodenum/jejunum
3. K-Cells in brunners glands of duodenal submucosa. Also released by enteroendocrine cells in duodenum and jejunum...
63
Urogastrone
1. secretion from?
2. Function (x3)
AKA gastric inhibitory peptide.
1. secreted from Brunner's glands (from submucosa of duodenum) AND from enteroendocrine cells in duodenum and jejunum.
2. inhibits parietal and chief cells = DIRECT INHIBITION OF HCl. Increase epithelial cell division. Stimulates insulin release.
64
CCK
* 1. produced by?
2. Activated by
3. Function
4. Levels
1. I-cells in mucosal epithelium of duodenum and jejunum
2. Chyme
3. Stimulates bile secretion (contraction of gallbladder, relaxation of sphincter), stimulates acinar cells of PANCREAS to release digestive enzymes
4. Levels go down as chyme is digested-->less activation
65
Gastritis
Inflammation of gastric mucosa in middle aged and older people. Etiology is unknown. Inflammation can be superficial or all the way (if all the way then mucosal atrophy)
66
Zollinger Ellison syndrome
gastrin secreting tumors that cause hyperplasia and hypertrophy of fundus. High acid secretion can cause ulcers and diarrhea
67
Ulcers
1. location (most common)
2. Cause
3. Treatments
1. Usually in cardiac and pyloric part of duodenum.
2. too much HCl secretion, nervous irritation, reduced vascular supply, reduced mucus secretion, NSAIDs, h pylori
3. antibiotics, stress management, decreased (alcohol, NSAID's and cigarette usage), antacids
68
H Pylori- phases
1. Active= Make ammonia with urease = increased pH
2. Stationary= attach to fucose-containing receptors on mucus cells in pyloris. Release protease to kill SURFACE CELLS
3. Colonization= bacteria detach and replicate in mucos blanket
69
3 Functions of Small intestine
hormone secretion, digestion, and absorption
70
Duodenum
1. mucosa
2. submucosa
3. Muscularis
4. Adventitia/Serosa
1. Short broad villi, plicae circulares (distal 1/2)
2. Fibroelastic CT-contains brunner's glands, plicae circulares (distal 1/2)
3. inner circular, outer longitudinal
4. Incomplete serosa, mostly adventitia
71
Jejunum
1. Mucosa
2. Submucosa
3. Muscularis
4. Adventitia/serosa
1. long finger-like villi, lots of paneth cells in crypts, well developed lacteals, plicae circulares
2. Fibroelastic CT. Plica circulares
3. inner circular, outer longitudinal
4. serosa
72
Illeum
1. Mucosa
2. Submucosa
3. Muscularis
4. Adventitia/serosa
1. short finger-like villi, paneth cells, plicae circulares (proximal 1/2)
2. Fibroelastic CT-plica circulares (prox .5); Peyer's patches (extending from lamina propria)
3. inner circular, outer longitudinal
4. serosa
73
Villus core
lamina propria with plasma cells, lymphocytes, fibroblasts, mast cells, smooth muscle cells, capillaries and single lacteal
74
Increased intestinal SA by (3X)
1. Plicae circulares (distal half of duodenum to proximal half of ileum)
2. villi
3. microvilli
TOTAL OF 400-600X increase
75
Plicae circulares
1. What are they?
2. location
1. permanent spiral folds in mucosa and submucosa
| 2. Distal .5 duodenum, jejunum, proximal .5 ileum
76
Major ways of differentiating 3 parts of small intestine (histologically)
Duodenum- brunner's glands
Jejunum- nothing special
Ileum- peyer's patches
77
Peyer's patches
- thickening of lamina propria and extending into submucosa
- lymphoid follicles
- Dendritic cells associate with peyer's patches
78
Crypts of Lieberkuhn
1. shape, location, etc.
2. Cell types
1. SIMPLE TUBULAR glands that extend from middle of villus to base of epithelium (near muscularis mucosa)
2. goblet cells, columnar cells, enteroendocrine cells, regenerative cells and paneth cells (paneth only in jej & ileum)
79
Regenerative cells in stomach vs. small intestine
In stomach can turn into any of the epithelial cell types, top half of gland.
In the small intestine can only become enterocyte or goblet cell and located in bottom half of crypt.
80
Cells of the intestinal epithelium
Goblet cells, absorptive cells=enterocytes, paneth cells, M-cells, dendritic cells, enteroendocrine cells.
81
Microvilli
1. Location
2. Core
1. On apical surface of enterocytes (striated border?)
2. Actin filaments linked with fimbrin and villin. Actin is anchored to plasma membrane by myosin I and calmodulin. Actin bundle has rootlet on base. Rootlets are attached to each other by intestinal form of spectrin. Rootlets attach to intermediate filaments (that contain cytokeratin)
82
Terminal web
intermediate filaments + spectrin
83
Autonomics of small intestine
Meissner's plexus- submucosal
| Auerbach's plexus- between SM layers of muscularis externus
84
Goblet Cells
1. Characteristics
2. Produce
3. Location
1. UNIcellular glands, granules on apical surface
2. Mucinogen (dif than stomach), becomes mucous after release
3. interspersed between enterocytes in villi. Increase as you move from duodenum-->ileum
85
Enterocytes
1. Characteristics
2. Lifespan
3. Junctions?
1. tall columnar cells with microvilli covered by glycocalyx
2. 5-6 days, divide in crypt and move up villus
3. Zonula occludens (tight junction), zonula adherens (belt junction), lateral plications
86
M-Cells
1. Characteristics
2. Location
3. Function
1. Apical: Microfold instead of microvilli; Basal: intraepithelial pocket with a B-cells
2. Ileal epithelium on top of lymphoid nodules (also in appendix)
3. Antigen uptake, processing and transport to lymphocytes and macrophages
87
Intraepithelial pocket
Formed by basolateral part of M-cell. Contains B-cells (intraepithelial lymphocytes)
88
Antigen Processing
Processed in vesicles containing cathepsin E (protease). After processing they are transcytosed to B -cells.
89
What can extend through enterocytes tight junctions?
Dendritic cell processes
90
Dendritic Cells
1. Association
2. Function
1. Associated with lymphoid follicular epithelium in Peyer's patches.
2. Extend processes across basal lamina and between enterocyte tight junction. Part of process may be exposed to lumen of intestine.
91
Paneth Cells
1. Characteristics (staining?)
2. Location?
3. Function- how is it accomplished?
4. Life span
1. Large eosinophilic apical secretory granules
2. bottom of crypts of lieburkuhn (small intestine-->appendix)
3. Protect regenerative cells by production and secretion of lysozymes and TNF alpha. Also secreting cryptidins.
4. 20 days (LONGEST)
92
Are paneth cells found in the large intestine?
NO
93
Cryptidins
antimicrobial peptide. Also called defensins. Secreted in response to bacteria, or food, or ach. Released by paneth cells.
94
Brunner's gland
1. location
2. Shape
3. Function
1. submucosa of duodenum
2. branched tubuloalveolar glands
3. produce alkaline secretion, bicarb ions, and GIP to protect duodenum from acidic chyme
95
Small intestine lamina propria
Found in villus cores and between crypts
| Loose CT with lymphoid cells, fibroblasts, mast cells, SMC, nerve endings, lymphoid nodules and lacteals.
96
GALT
Gut associated lymphoid tissue. Lymphoid nodules in ileum= peyer's patches
97
Colon
1. Function
2. Cell types
1. absorption of water and electrolytes
| 2. simple columnar, no villi! enterocytes, goblet cells, and enteroendocrine (some), regenerative cells
98
Colon lamina propria
Same as small intestine- main features= lymphoid nodules and closely packed crypts
99
Colon submucosa
FIBROELASTIC connective tissue with meissner's plexus
100
Colon Muscularis externa
2 layers- inner circular and outer longitudinal. Longitudinal layers forms TENIA COLI which form HAUSTRA when contracted
101
Auerbachs plexus
between two muscle layers
102
Appendix
1. Characteristics
2. Function
1. Lymphoid organ with lymphoid nodule aggregates
| 2. Site of bacteria pool to repopulate colon after diarrhea.
103
Appendix mucosa
1. Cells
2. lymphoid organ, how?
3. characteristics: villi? crypts?
1. surface columnar, regenerative, paneth cells, enteroendocrine cells, goblet cells.
2. lymphoid nodules + m-cell caps
3. no villi, shallow crypts,
104
Rectum vs Colon?
Rectum has fewer crypts that are deeper
105
Anal Mucosa
Anal columns separated by anal sinuses
106
Transition from rectum to anus
Rectum: Simple columnar-->
Anus: simple/stratified cuboidal-->strat squamous NON keratinized-->stratified squamous keratinized
Before valves= strat squ NK
After valves= strat squ KER
107
Gluten enteropathy
nontropical sprue. Glutens destroy intestinal villi and reduce SA. Treatment= no wheat/rye
108
Idiopathic Steatorrhea
fatty stool due to malabsorption of fat
109
Malabs of Vit K
poor clotting
110
B12 malabsorption
pernicious anemia. B12 absorption is dependent on gastric intrinsic factor production by parietal cells. If they are defective--> low B12 -->pernicious anemia
111
2nd highest cancer death in US
1. what
2. risk factors
3. cause
4. good prognosis if caught before?
1. colorectal cancer
2. high fat diet, low fiber
3. from adenomatous polyps
4. if doesn't extend beyond muscularis mucosa
112
Endothelin issues cause?
Hirschsprung disease
endothelin B or ligand
Endothelin 3
113
RET
rearranged during transfection---neural crest cells dont migrate to enteric NS neurons.
Cause of hirschsprung disease
114
Hemorrhoids
Ruptures of venous plexus veins above (internal) or below (external) anorectal line.
115
Carb breakdown
Brush border with lactase, maltase, and sucrase
116
Protein breakdown (3 steps)
1. Pepsin, trypsin and chymotrypsin break down proteins in lumen
2. Enterokinase and aminopeptidase in microvilli degrade further
3. Cytoplasmic peptidases into AA
117
Lipid breakdown
TAG-->MG + FA by pancreatic lipases (in lumen)= Micelle
118
Fatty acid binding protein
in microvilli, binds micelles and moves them to ER
119
Fatty acid esterification
sER
120
Chylomicron formation
golgi. Fuse with basolateral membrane and enter intercellular space and then lacteals.
121
Motilin
Gastric hormone
Released cyclically during fasting (~90 mins) from cells in upper GI tract. Causes contractions to ensure everything is all cleared out before the next meal.
122
Two hormones released in digestive tract that act on accessory organs (pancreas/gallbladder?)
1. Secretin (increased HCO3 from pancreatic cells and biliary tract)
2. CCK (contraction of gall bladder and increased secretion of pancreatic enzymes)
