GI histology Flashcards
what organs are found within alimentary canal?
esophagus, stomach, large and small intestine
types of muscle of alimentary canal
- esophagus = only one with striated muscle
- rest of organs = smooth muscle
types of tissue in alimentary canal
- oral cavity and esophagus = non-keratinized stratified squamous epith.
- rest of organs = simple columnar
what is found within the submucosa?
Meissner’s plexus (nerves and ganglion)
-also blood vessels
what is found within the muscularis externa?
Auerbach’s (myenteric) plexus (nerves and ganglion)
serosa vs adventitia
- serosa = mesothelium + connective tissue - found in distal portion of esophagus
- adventitia = only connective tissue - found w/I most of esophagus
what does the muscularis mucosae layer in esophagus contain?
longitudinally oriented bundles
types of glands in esophagus
- mucosal glands (esophageal cardiac glands)
- only in terminal esophagus - submucosal glands (esophageal glands proper)
- entire esophagus
- tubuloalveolar glands
what types of muscle are in muscularis externa of esophagus?
- upper portion = skeletal muscle
- middle 1/3 portion = skeletal and smooth muscle
- lower portion = smooth muscle
Barrett’s esophagus
metaplasia of esophageal epith.
- transition from non-keratinized Strat. squamous epith. to simple columnar epith.
- caused by gastroesophageal reflux
- precursor for adenocarcinoma
stomach functions
- store food = chyme formation, expandable, rugae
- food digestion = secrete HCl, pepsin, lipase
- regulate GI through gherlin and gastric secretions
pepsin
breakdown proteins
lipase
breakdown TAGs
HCl
- destroy bacteria
- breakdown protein
- convert pepsinogen to pepsin
endocrine cells role in GI regulation
secrete gherlin and gastrin to increase gastric acid secretions
where are the glands of the stomach located?
mucosa layer
-cardiac, fundic, and pyloric glands
3 layers of muscularis externa of stomach?
- inner oblique
- middle circular
- outer longitudinal
what cells are found in the gastric mucosa?
surface mucous cell - secretes insoluble mucous –> forms the lining of the stomach protecting cells from HCl (contact can lead to gastric ulcers)
where are the gastric glands located?
lamina propria
- cardiac, fundic, pyloric glands
- also contain lymphoid tissue and have leukocytes to prevent infection if infiltration occurs
fundic glands
parts: isthmus (apical), neck (principle piece), and base (next to muscularis mucosa)
- parietal, gastric chief, mucous neck, progenitor, and enteroendocrine cells
parietal cell
- secrete HCl and intrinsic factor for vit. B12 absorption
- largest & contain a lot of mitochondria (eosin - red color)
- active cell = intracellular canicullu w/ microvilli for HCl and intrinsic factor production
- resting cell = tubulovesicular system for storage
deficiency of parietal cells (ex. chronic gastritis)
no intrinsic factor –> no absorption of vit. B12 –> no Hb synthesis –> pernicious anemia
gastric ulcers
- destroy epithelial barrier by HCl release
- if untreated, can penetrate deeper into stomach causing peritonitis
gastric chief cells
- secrete pepsinogen (convert pepsinogen to pepsin)
- secrete gastric lipase (breakdown TAGs)
- pepsin = breakdown protein
- many RER for protein synthesis (hematoxylin-blue color)
mucous neck cell
- secrete soluble mucous
- heterochromatic nucleus with “frothy” cytoplasm
- no staining of eosin or hematoxylin
enteroendocrine cell aka G cell
- secrete gastrin = increase gastric acid
- secrete gherlin = increase appetite/hunger
- both released into lamina propria to enter bloodstream
- contain microvilli and secretory granules
progenitor cell
stem cells
- become surface mucous cells or other gland cells
- shorter life span for surface mucous cells –> exposed to acid and chyme and need to regenerated more
cardiac gland
- around esophageal orifice
- secrete mucous for gastric reflux protection
- shorter gastric pit
- no parietal/chief cells
pyloric gland
- pyloric antrum
- secrete mucous for gastric reflux protection
- longer gastric pits
- darker than cardiac
- no parietal/chief cells
carcinoma of stomach
surface epithelial cells
-intestinal metaplasia - contain many goblet cells
adenocarcinoma of stomach
glandular epithelium
-ring shaped cells
stages of stomach cancers
- early
- penetrate submucosa and good prognosis - late
- penetrate to muscularis externa and bad prognosis
functions of the small intestine
- digestion (main)
- absorption
- synthesis and secretion (digestive enzymes)
- antimicrobial
- regulate GI function (enteroendocrine cells)
layers of the small intestine
- mucosa
- submucosa
- muscularis externa
- serosa/adventitia
what makes up the plicae circularis?
mucosa and submucosa
- found in the distal duodenum and proximal jejunum
- permanent fold
what makes up the villi?
mucosa only
- evaginations of mucosa containing surface epith.
- lamina propria is the core
microvilli
the cells on the villi
-very small and look like brush border
role of plicae circularis, villi, and microvilli?
increase surface area for better absorption
- lacteals absorb lipids packages in chylomicrons
- vascular loops absorb carbs and AAs
crypt of lieberkuhn
invaginations of epithelium that forms a gland
-contain paneth and progenitor cells
celiac disease
gluten enteropathy
- hypersensitivity to gluten
- atrophy of villi (complete or incomplete loss)
- steatorrhea (fatty feces) –> no villi or lacteals to absorb lipids
what type of epithelium is the alimentary canal?
simple columnar epith. containing microvilli
-except esophagus
enterocyte functions (most prominent)
- microvilli to increase surface area for absorption
- tight junctions for barrier against bacteria and immune cells
- digestion of carbs/proteins by vascular loops in lamina propria (enzymes in glycocalyx)
- digestion of lipids
- transcytosis of IgA
how are lipids digested by enterocytes?
lipid breakdown in lumen –> resynthesis of triglycerides in SER –> form protein coat (chylomicrons) –> transport via lacteals to lymphatic vessels
how is IgA transcytosed in enterocytes?
plasma cells make IgA –> bind to receptors on enterocytes and endocytosed –> released into lumen for bacterial and mucosal protection
Goblet Cell
unicellular mucous glands
- mainly in large/small intestine
- do not stain with H&E –> frothy, white areas
- heterochromatic (nonactive) nucleus
M cell
antigen presenting cells
-microfolds capture antigen and transport it from lumen to lymphoid follicle for antibodies to made against it
what is a lymphoid follicle?
area of clusters of immune cells
-contain lymphocytes, neutrophils, or macrophages
enteroendocrine cells
GI function regulation
- produce hormones gastrin and gherlin
- aka APUD cells
intraepithelial lymphocytes
mucosal immunity
- bone marrow derived
- T lymphocytes
paneth cells
eosinophilic granules contain antibacterial enzymes to protect the crypt from bacterial growth
- base of the crypt
- bright red staining cytoplasm
progenitor cells
stem cells of epith. and gland (crypt)
- found in crypt
- mitotic cells
lamina propria of small intestine
connective tissue that contains leukocytes - GALT
- diffuse = lymphocytes and Macs
- scattered = duodenum and jejunum
- peyer’s patch = aggregated lymphoid follicles in ileum
lymphoma (maltoma)
thickening of lamina propria due to infiltration of lymphocytes
- from MALT
- cancer of small intestine
blood supply in small intestine
vascular plexus in submucosa extends as vascular loops into villi
-collect nutrients
lymphatics of small intestine
fats packaged as chylomicrons transported by lacteals to enter lymphatics in submucosa
Brunner’s glands
mucous glands - produce alkaline fluid to neutralize gastric acid
- found within submucosa
- only in duodenum
what is found in submucosa of small intestine?
- messiener plexus
- brunner’s glands
- vascular plexus
what is found in the muscularis externa layer of small intestine?
- inner circular layer
- outer longitudinal layer
- Auerbach’s plexus
what contains mostly adventitia?
duodenum
-distal duodenum, ileum, and jejunum contains serosa (mesothelium + connective tissue)
where are submucosal (Brunner’s) glands located?
duodenum
where are Peter’s patches and most goblet cells found?
ileum
regions of large intestine
- cecum
- colon
- rectum
- anus
function of large intestine
- reabsorption - electrolytes and water
- eliminate waste
mucosa of large intestine
- no paneth cells in crypts of lieberkuhn - only progenitor
- no villi
- many goblet cells
muscularis externa of large intestine
- inner circular layer
- outer longitudinal layer - forms thick bands of tiniae coli
serosa of large intestine
contain omental appendices - fat projections
adenocarcinoma
most common large intestine cancer
- arise in patients with adenomatous polyps or ulcerative colitis
- treat with total resection
regional differences in large intestine
- colon - largest, contains tiniae coli
- vermiform appendix - aggregated lymphoid nodules
- rectum - transverse rectal folds
what are the 4 layers of the GI tract?
- mucosa (epith., lamina prop., muscularis mucosa)
- submucosa (blood & lymph vessels, meissner plexus)
- muscularis (aka muscularis externa) - Auerbach nerve plexus b/w inner circular & outer longitudinal muscle
- serosa (mesothelium + connective tissue)
what 2 nerve plexuses comprise the enteric nervous system?
- Meissner plexus (in submucosa)
- Auerbach plexus (in muscularis externa)
Auerbach’s plexus
b/w the smooth muscle layers of muscularis externa
-controls peristalsis
Hirschsprung disease (congenital aganglionic megacolon)
dilation and hypertrophy of the colon due to reduced or loss of ganglion in myenteric plexus of gut and rectum
-loss of peristalsis contractions (gut motility)
oral cavity wall structure
- mucosa (epithelium contains keratinized & non-keratinized epith., lamina propria, no muscularis mucosa)
- submucosa (salivary glands, Meissner plexus)
- muscularis externa (skeletal muscle, Auerbach’s plexus
- no serosa or adventitia
function of Meissner (submucosa) plexus
- motility of the mucosa and submucosa
- secretory activity
lips
- vermilion zone - red/pinkish color from dermal papillae containing capillaries
- contains minor salivary glands
cold sores
contagious blisters on outside of mouth
-caused by HSV type 1 (reside in trigeminal ganglion in dormant state)
canker sores (aphthous ulcers)
sores inside the mouth
-may be due to virus, autoimmune, or allergic rxn
tongue
- intrinsic muscle - alter shape
- extrinsic muscles - move tongue
- terminal groove (sulcus) divides tongue into lingual tonsil (post.) & mucosal projections (ant.)
- foramen cecum - thyroid origin
leukoplakia
cancer of oral region
-white patch or plague
where does the majority of cancers of oral cavity arise from?
stratified squamous epith. –> squamous cell carcinoma
-ulcers, malignant keratinocytes
purpose of lingual papillae
gustation via taste buds
- taste buds scattered everyone (not constricted to papillae)
- taste buds contain supportive cells & basal (stem) cells
- salty, sour, bitter, sweet, savory
filiform papillae
- most numerous
- entire surface of tongue
- scrape food off surface (sand paper)
- NO taste buds
Fungiform papillae
- “mushroom”
- most numerous at apex and sids
- has taste buds
foliate papillae
- posterolateral folds
- has taste buds
circumvallate (vallate) papillae
- anterior to terminal groove
- taste buds down sides
- surrounded by moat like trenches where serous salivary (von Ebner) glands drain into
function of von Ebner glands
- flush food particles away from vallate papillae
- contain lipase to prevent formation of film that would hinder gustation
4 types of teeth
- incisors - cutting, one root
- canines - grasping and tearing, one root
- premolars - crushing, two roots
- molars - crushing, 3 roots
3 calcified mineral substances of tooth
- dentin - bulk of tooth
- enamel - covers crown
- cementum - covers root
enamel
overlies dentin of crown
- hardest substance in body (Ca2++ hydroxyappetite)
- studied by decalcification & ground sections
- ameloblasts make enamel
- cannot repair enamel
- acidic pH –> dental carries
dentin
bulk of tooth
- 2nd hardest substance in body (Ca2++ hydroxyappetite)
- odontoblasts make dentin
- viable for life
- can be repaired
cementum
outer layer of root of tooth (over dentin)
- anchors periodontal lig. to roots of tooth
- made by cementoblasts
- viable for life
pulp of tooth
consists of blood vessels, nerves, fibroblasts
-center of tooth
4 regions
1. odontoblastic layer - overlies pulp layer & under dentin layer
2. cell free zone
3. cell rich zone
4. core
periodontal ligament
attaches to cementum and alveolar bone
- holds tooth in place
- shock absorber
- sharpes fibers (type 1 collagen fibers)
gingiva
bound to periosteum of jaw bone
- junctional epith. - attaches gingiva to enamel
- gingival sulcus - site for periodontal disease
how can food lodged in teeth cause damage?
bacterial flora secrete organic acids to dissolve food –> can dissolve Ca2++ hydroxyappetite causing tooth decay
-fluoride makes enamel more resistant to bacteria by decreasing the acids (Fluoroapatite crystals instead of hydroxyapatite crystals)
what happens if you don’t brush or floss teeth?
- biofilm known as plaque
- plaque can calcify forming calculus - covering for bacteria to grow causing gingivitis
- progressive gingivitis –> attack periodontal lig. –> periodontitis
what are the 2 components of salivary glands?
- ducts - deliver saliva to oral cavity
- secretory cells - tell you whether acinus contains serous, mucous, or both
roles - moisten mucous membrane and food, digestion, germicidal protection
lobes –> lobules
what are found w/I the lobules of salivary glands?
adenomeres - secretory units of glands that contain acini cells (serous or mucous)
-both types of acini dump into intercalated ducts
how do you identify serous acini?
- round nuclei
- stain dark
- protein secreting, accumulation of RER and ribosomes
how do you identify mucous acini?
- flattened nuclei
- stain light
- GAG secretion
2 types of intralobular ducts
- intercalated ducts - continuous w/ acini, simple squamous
2. intralobular - striated, infoldings that allow products to enter, cuboidal
interlobular (excretory) ducts
excretory ducts that enter oral cavity
- larger than intralobular ducts
- columnar to strat. columnar
parotid gland
- largest salivary
- SEROUS acini - stain dark, round nucleus
- opens into vestibule of oral cavity
submandibular gland
- make up most of saliva
- both serous and mucous acini (mostly serous)
- dark and light stains
- opens into lingual frenulum
- some mucous acini surrounded by cap cells (serous demilune) that secrete serous fluid
sublingual gland
- smallest salivary gland
- mainly MUCOUS acini - light stain, flat nuclei
xerostomia
dry mouth
-caused by decreased production of saliva
causes
-medications, cancer therapy (radiation), Sjogren’s, nerve damage
effects
-cracks in tongue, breakdown teeth, oral infections, gingivitis
hepatocytes
major cell of liver - endocrine and exocrine functions
- bile production (digest fat)
- hormone & protein synthesis (high RER & Golgi)
- metabolic functions
- detoxification via SER
lobules of the liver
- contain capillaries called sinusoids
- hexagon shape
- portal triad and lymph vessels on outside
- central vein in center
what is found w/I the portal triad?
- hepatic portal vein
- hepatic artery
- bile duct
where does the blood supply travel in liver lobule?
from periphery to the central vein
-dual blood supply by portal triad
where does lymph and bile travel in liver lobule?
from center to periphery
function of RER in hepatocytes
protein synthesis
-basophilic staining
function of SER in hepatocytes
- enzymes for detoxification and for conjugating bilirubin to glucuronate
- formation of bile
- put bile components into bile canaliculi to enter bile ducts in periphery
metabolic functions of hepatocytes
storage of glucose, fat, and iron
function of peroxisomes of hepatocytes
oxidation of fats and breakdown of hydrogen peroxide
the celiac trunk
supplies the foregut
-gives rise to common hepatic, left & right gastric, and splenic artery
what are the 2 sources of blood supply to the liver?
- hepatic artery proper (supplies the O2)
- hepatic portal vein (supplies the nutrients)
- found in portal spaces
- branches –> hepatic arteriole & hepatic portal venule
blood drainage of the liver
central vein –> 3 hepatic veins (right, middle, and left) –> IVC –> right atrium
portal spaces
periphery of the lobules
- contain portal triad
1. hepatic arteriole (lot of smooth muscle, round)
2. portal venule ( large, irregular lumen)
3. bile ductule (simple cuboidal epith.)
what are sinusoids?
special capillaries b/w the plates of hepatocytes
- where portal venule and hepatic arteriole drain
- converge at central vein
- fenestrated endothelium - take up nutrients, O2, release hormones
zones of the hepatic lobule
zone 1 - least affected by ischemia (closer to blood supply); oxidative processes, most susceptible to blood borne pathogens
zone 2 - intermediate
zone 3 - most affected by ischemia
space of disse (perisinusoidal space)
b/w the sinusoids and the hepatocytes
-contains lymphatic capillaries that flow towards lymph vessels in portal spaces
bile canaliculi
anastomoses of bile channels –> form bile canals of Hering –> dump into bile ductules in portal space –> right and left hepatic ducts to leave liver
-canal of Hering composed of cholangiocytes (cuboidal)
Kupffer cells
liver macrophages
- found in lumen of sinusoids
- phagocytose foreign matter and breakdown RBCs
Ito (fat storing or hepatic stellate cells)
fibroblasts in space of disse
- lipid droplets that store vit. A and fat
- produce extracellular matrix components
- divide forming myofibroblasts - pathogenesis of fibrosis and portal HTN (no exchange of nutrients due to connective tissue)
classic liver lobule
- hexagon
- ENDOCRINE function (make proteins & hormones)
- portal spaces on edge of lobule
- blood flows to central vein to go to rest of body
portal lobule
- triangle formed by 3 central veins on corners
- EXOCRINE function (make bile)
- portal triad (bile ductule) at the center
- flow of bile from bile canaliculi to bile ductules
hepatic acinus (acinus of Rappaport)
- blood supply carrying nutrients and O2 (which varies) from periphery to central vein
- diamond (2 portal triads & 2 central veins)
- 3 zones
periportal hepatocytes of acinus
zone 1
- nearest portal triad
- get most O2, hormones, and nutrients
- more oxidative metabolism (glycogen & protein synthesis)
zone 3 hepatocytes
- near the central vein
- least amount of O2 and nutrients
- 1st to show ischemic necrosis and fat accumulation
- lipolysis, glycolysis, drug/ETOH detox
cirrhosis
advanced stage of liver disease associated w/ fibrosis
- connective tissue fills perisinusoidal space interfering w/ metabolic exchange w/ sinusoids (no detox or hormone release)
- fibrosis from Ito cells
- scar tissue from trying to heal itself
- caused by alcohol or hepatitis
- fibrosis destroys portal tract to central vein
fatty liver disease
steatosis - accumulation of fat in lipid droplets
- associated with alcoholism or obesity
- may produce non-infectious hepatitis –> steatohepatitis
nonalcoholic fatty liver disease
too much storage of fat (not caused by alcohol)
- obesity or insulin resistance
- can lead to non-alcoholic steatohepatitis (NASH) –> fat accumulation, inflammation (WBCs), and scarring –> can progress to cirrhosis and liver failure
gallbladder
stores, concentrates, and released bile
-bile enters duodenum when there is dietary fat
function of enteroendocrine cells of small intestine
release CCK –> contraction of gallbladder and secretion of pancreatic juice
gallbladder histology
- mucosa - columnar epith., lamina propria, no muscularis mucosa
- branched mucosal folds (appear glandular) –> Rokitansky-Aschoff crypts/sinuses - no submucosa
- muscularis externa (contract & empty GB)
- adventitia and serosa
what is cholelithiasis?
formation of gallstones
- formed by reabsorption of water from bile or from gallbladder not emptying correctly
- excess cholesterol from liver –> cholesterol stones
- excess bilirubin from SER –> pigment stones (black) which cause inflammation
what can gallstones lead to?
biliary obstruction –> lead to chronic cholecystitis
- block flow in cystic duct
- can be acute or chronic cholecystitis
acute cholecystitis
- suddenly; sever pain in abdomen
- obstruction of neck or cystic duct
- most common reason for emergency cholecystectomy
chronic cholecystitis
inflammation that lasts a long time
- gallstones can pass
- periodic attacks when gallstones cause blockage
- damage caused by the repeat attacks causing inflammation –> scarring, wall thickening, parcelain GB)
pancreas
- exocrine functions - make digestive enzymes and bicarb rich buffering fluid by acinar cells
- endocrine functions - make hormones by islets of langerhans
pancreatic acinar cells function
produce digestive enzymes that breakdown nutrients when entering duodenum
- round nuclei and zymogen granules (house proenzymes)
- enzyme release by CCK (main) and ACh
centroacinar cells
secrete a watery, bicarb rich fluid to alkalinize the hydrolytic enzymes of acinar cells
-bicarb secreted when secretin signals (from enteroendocrine cells); also from ACh
pancreatic cancer
usually carcinoma of the duct cells in the head region
- high mortality (asymptomatic until metastasis)
- poorly defined acinar cells and a lot of fibrosis on histo
pancreatitis
inflammation of pancreas - destroy pancreatic acinar cells
- acute - activate proenzymes and digest tissue
- chronic - fibrosis and loss of pancreas function
causes - duct obstruction, acinar cell injury, defective intracellular transport
effects - inflammation, edema, breakdown proteins, fat necrosis, hemorrhage
