GI Flashcards
general layers
- mucosa with epithelium>lamina propria>muscularis mucosae
- submucosa
- muscularis externa
- adeventitia or serosa
mucosa layer
- epithelium: rests on basal lamina aka innermost layer
- lamina propria: has CT + glands + lymphatics + blood vessels
- muscularis mucosa: outermost of mucosa, has inner circular + outer longitudinal layer
submucosa layer
has CT + lymphatics + blood vessels + glands (if in duodenum or esophagus)
submucosal nerve plexus
glands pathological if in other places
muscularis externa layer
has inner circular + outer longitudinal (like muscularis of mucosa)
myenteric nerve plexus
controls peristalsis
serosa/adventitia layer
serosa = CT + simple squamous epi @ intraperiotneal organs (if has mesentary then has serosa)
adventitia = CT @retroperitoneal
enteric nervous system
- myenteric plexus @ b/t layers of muscularis externa, regulates peristalsis
- submucosal plexus = reg glandular secretion + blood flow + muscularis mucosae
- visceral afferents monitor chemistry/mechanical stimulation
both plexuses have autonomics (symp + para) and visceral afferent fibers
esophagus function
transport masticated food to stomach so epithelial lining must resist abrasion
esophagus muscle types
upper 1/3 = 100% striated muscle in externa, somatic/voluntary for swallowing
lower 1/3 = 100% smooth muscle
middle 1/3 = mix of both
esophagus layers
- mucosa= nonker SSE + LP w/cardiac glands + muscularis w/ longitudinal only
- submucosa = esophageal glands (mucus + pepsinogen + lysozyme)
- muscularis externa = striated > smooth
- adventitia = thoracic region
- serosa = abdominal region
gastroesophageal junction
transition in function from transportation/propulsion to digestion
mucosa goes from protective > secretory
Z line = visible transition marker
barrett’s esophagus
clinical correlate
simple squamous > metaplastic columnar epi w/ goblet cells from stomach that migrated up
from chronic gastric secretions i.e GERD or frequent vomiting
inc risk of adenocardcinoma
stomach functions
- temporarily store food
- secrete gastric juice
- form chyme via chemical digestion
stomach structure
cardiac + fundus + pylorus
rugae = longitid folds for distension, submucosa extends into mucosa layer
-mucosa has simple columnar that make pits that open into glands
some regions have muscularis externa
gastric pit
@ fundus
simple columnar epi
-surface mucous cells secrete bicarbonate rich protective mucus
gastric glands
@fundus
1. isthmus w/regenerative stem cells
2. neck w/ nucous neck cells + parietal cells (HCl + gastric intrinsic factor)
3. base w/ chief cells (pepsinogen)
4. enteroendocrine cells > hormones
cardiac glands
@cardiac portion of stomach
has shallow pits + coiled glands + surface mucous cells
pyloric glands
@pyloric region
deep pits + mucous neck cells that secrete lysozyme
gastroduodenal junction
mucosa transition from secretory > absorptive
pyloric sphincter (thickened circular layer of muscularis externa)
duodenal glands aka brunner’s @submucosa secrete bicarbonate to neutralize chyme
achalasia
clinical correlate
dysfunction of mysenteric plexus prevents relaxation of lower esophageal sphincter
nothing can enter stomach so have to eat moist food
hirschsprung disease
congenital megacolon, absence of enteric nervous system in a portion of bowel (from failure of neural crest cells to migrate)
= absence of peristalsis in affected area so feces backs up
small intestine modifications
- plicae circulares (mucosa + sub)
- villi (epi + lamina propria)
- microvilli (surface epi)
to inc surface area
small intestine submucosa
@ duodenum has dueodenal/Brunner glands to secrete bicarb mucus to neutralize acidic chyme
small intestine layer histology
mucosa = villi present + simple columnar epi + intestinal glands in LP
submucosa= lacks glands
muscularis externa = typical, 2 layers
serosa = @most except parts of duo (adventitia)
typical mucosa
small intestine
simple columnar for absorption and striated border
-goblet cells inc in freq distally (small>large intestine)
lamina propria = extends into villi, has lacteals (lymphatic capillaries) + intestinal glands (open b/t villi)
muscularis: unremarkable
intestinal sprue
disorder of small intestine, disruption of mucosa = malabsorption
weight loss, diarrhea, anemia, vitamin deficiences
i.e celiac disease = inflamm response triggered by gluten
intestinal sprue biopsy
-atrophied villus
-disordered epithelial cells w/ micovilli atrophy
-inflamm of LP
-intestinal gland hyperplasia
intestinal glands
aka crypts of lieberkuhn
+has paneth cells @ base to secrete antibiotic agents and maintain intestinal flora
+goblet cells
+enteroendocrine (DNES) cells for hormones
+stem cells
paneth only in small intest
jejunum features
lacks distinct distinguishing features
plicae circulare well developed
narrow villi
ileum features
has peyer’s patches aka aggregated lymphoid nodules that extend from LP to submucosa
-M cells transport antigens + immune response
fewer plicae circulares and shorter villi (vs jejunum)
large intestine histology layers
- mucosa = lack villi, irreg microvilli, straight intestinal glands, more goblet cells
- muscularis externa= complete inner layer + reduced outer layer (3 teniae coli)
-appendix and rectum have 2 uniform layers - serosa = intraperitoneal portions (transverse, sigmoid)
- adventia= retroperitoneal portions (asc/dec)
vermiform appendix
has abundant lymphoid nodules in LP and submucosa, but not form big patches like in ileum
-2 uniform layers of muscularis externa
-epi typical of lg intestine
appendicitis
imflammation of appendix
blockage = buildup mucus, inc pressure, rupture
infection of mucosa = inflamm and ulceration
rectum
has transverse rectal folds from inner layer of externa
+ temporary longitudinal folds @mucosa and sub for distension
2 layers of muscularis externa have no tenia coli
anal canal
transtions
transition from:
-simple columnar to simple cuboidal to stratified squamous
-autonomic to somatic inn
-muscle transition
anal canal features
anal columns mark anorectal junction
anal sinuses has mucous glands
anal valves compress sinuses
pectinate line
intersphincteric line b/t internal and external (nonkeratinized SSE above to pectinate, keratinized SSE below aka skin)
major salivary glands
- parotid= biggest, serous only
- submandibular = mostly serous + some mucous
- sublingual = mostly mucous + some serous
salivary gland function
secrete saliva
-digestion, gustation, lubrication, antibacterial
has proteins + enzymes + ions (protect teeth) + mucins
exocrine pancreas
histology
acinar cells (pyramidal shape) with zymogen granules to contain inactive digestive enzymes
intercalated duct of centroacinar cells that project into acini + ductal cells that secrete waater and bicarb
liver structure
glisson’s capsules = CT capsule covered by liver mesothelium (simple squamous)
hepatic lobules = hepatocytes + sinusoids (spaces b/t hepatocytes) + central vein
ways to organize liver
- classic lobule = hexagonal
- portal lobule = triangular
- hepatic acinus= quadrangular
classic lobule
central vein @center + portal canal @corners
traces flow of blood thru liver so 75% from portal vein + 25% from hepatic artery
1. blood from portal cein and hepatic artery anastomose =sinusoids
2. thru sinusoid for processing by hepatocytes
3. flow into central vein
4. hepatic veins
5. IVC
portal lobule
bile duct/portal canal @center + central veins @corners
traces bile production (oppo of blood flow)
1. syn by hepatocytes into bile canaliculi
2. flow to bile duct in portal canal
hepatic acinus
short axis = opposting portal canals
long axis = opposing central veins
describes blood perfusion/metabolic activity
-zone 1 = more oxy/nut/toxins + less co2/waste, first to regen
-zone 3 = less oxy/nut/toxins + more co2/waste, first to die
portal canal
has portal triad (portal vein + bile duct + hepatic artery)
+CT/lymphatic vessel
+periportal space/space of mall b/t hepatocytes and portal canal
sinusoids
formed by anastomosis of hepatic artery and portal vein in canal
-lining cells = endothelial, line sinusoids, simple squamous, discontinous
-kupffer cell = macrophage, part of lining
-perisinusoidal space = exchange b/t blood plasma and hepatocytes (hepatocytes microvilli)
-stellate cells for lipid and vitamin A storage
hepatocytes
organelles
25% have 2 nuclei
+ RER
+ SER
+ golgi apparatus
+ mitochondria
hepatocytes function
- syn bile
- lipid metabolism/storage
- carb metabolism/storage
- protein metabolism
- vit A, K, D, B12 storage
- detox drugs
- degrade hormones
- immune response
- jaundice (acc unconj bilirubin in blood, obstructive, hemolytic)
biliary tract
bile flow
- bile canaliculi (b/t hepatocytes)
- canal of hering (simple cuboidal lined w/ cholangiocytes)
- intrahepatic bile ductules (cuboidal)
- interlobular bile ducts (@w/i portal canal, cuboidal)
- hepatic duct (simple columnar)
- gallbladder
gallbladder
histology
- mucosa = simple columnar epi with microvilli and LP
- no muscularis mucosae or submucosa
- disorganized externa
- adventitia and serosa
