GI Histology Flashcards
2 less known functions of GI:
Secretion and Protection
5 main functions of GI?
Digestion Absorption Secretion Movement Protection
4 common structural features of GIT? and 2 ‘other’ features
mucosa
Submucosa
Muscularis externa
serosa/adventitia
Neurons
Immune cells
Which GIT structural layer is most diverse in cells?
mucosa
What are the 3 layers within the GIT Mucosa?
Epithelium
Lamina Propria
muscularis mucosae
How often are mucosal epithelium renewed? How?
every 5-6 days via local stem cells
Types of mucosal epithelium cells are usually?
columnar (enterocytes)
stratified squamous
endocrine
What is contained in the lamina propria of GIT mucosa? 4 things.
CT
nerves
small blood vessels
immune cells
What is the muscularis mucosae do?
thin layer of muscle marks the mucosal layer boundary, used for mixing
What kind of cells are usually barrier and found in esophagus/anal canal?
stratified squamous
What kind of cells are usually secretory in GIT? where predominantly?
stomach, gastric glands
large intestine: tubular glands
What kind of cells are usually absorptive? where?
small intestine. columnar epithelium
What’s the purpose of the submucosa connective tissue?
strength and elasticity
describe the submucosa connective tissue
dense, irregular
Can you see small ganglia in the submucosa usually?
Hard to see without special stains
Are there glands and immune cells, blood vessels in submucosa?
yes.
Which is stronger: muscularis externa? muscularis mucosae?
muscularis externa
how many layers usually for muscularis externa?
2
what are the two layers of muscularis externa? what do they do?
inner circumferential (narrowing) outer longitudinal (sqeezing)
what and where are the ganglia called within the muscularis externa?
myenteric ganglia found between inner and outer layer
What does GI serosa do? what kind of cells? why?
secretes fluid
simple squamous
allows organ movement
is there adventitia along the entire GIT? where? purpose?
Nope. in parts of esophagus and rectum
CT to join with surrounding structures
ENS is part of which system?
autonomic nervous system
What does ENS regulate?
Absorption secretion
smooth muscle activity
What does myenteric ganglia regulate?
smooth muscle activity
What does submucous ganglia regulate?
absorption, secretion
What kind of nerves are found in the ENS ganglia?
sensory
motor
interneurons
swallowing reflex does what?
propulsion of bolus
what kind of epithelium in esophagus?
non-keratinised squamous
two muscle types in esophagus? where? how controlled?
Top: striated (voluntary)
Bottom: Smooth (involuntary)
What kind of change between esophagus and stomach?
abrupt functional change in epithelium: squamous to glands
describe the 3rd external muscle of the stomach:
oblique layer, varies
4 kinds of cells you can find in a gastric gland? What do they secrete?
Mucous cells
Parietal cells (HCl)
Chief (pepsinogen)
Enteroendocrine (gastrin Hormone)
Small intestine absorbs ___% of digestion products?
85%
Are there immune cells in the small intestine?
yes
Name the surface area increasing structures of the small intestine:
plica circulares
villi
microvilli
What are the spaces between villi called? purpose?
crypt of Lieberkuhn
secrete fluid and mucus
Why have muscularis mucosae in the small intestine?
moves villi to improve mixing of contents
where does the lamina propria of the small intestine go?
CT extends into core of each villus
What is found in the lamina propria of the small intestine?
muscularis mucosae
blood, lymph vessels
immune cells
What are the clear cells seen on the villi?
goblet cells
What are Paneth cells for? where are they?
secrete antimicrobial peptides
found deep in glands
THE distinctive histological feature of the duodenum?
Brunner’s Glands
Describe Brunner’s Glands, where and purpose?
Highly Coiled
in Submucosa
release alkaline mucus to protect
How are the plica circulares and the villi in the duodenum?
low plica circulares
long villi
What are Peyer’s patches? where are they found?
ileum
aggregates of lymphoid follicles
Describe the villi and amount of goblet cells in the ileum
short villi
lots of goblet cells
describe Muscularis externa in large intestine.
3 bundles called taeniae coli
3 regions of large intestine?
colon
rectum
anal canal
immune cells in large intestine?
yes
area with most goblet cells in colon
rectum
anal canal?
rectum
Large intestine mucosa have villi?
Nope
describe glands of Large intestine mucosa, what kind of cells?
straight tubular
columnar epithelium
More goblet cells in large or small intestine?
large intestine
Describe rectum to anal mucosa transitional zone.
abrupt again
glandular to squamous stratified
what is the largest solid gland in the body?
liver
6 primary functions of liver
glucose regulation (glycogen) lipid metabolism (cholesterol) absorption of fats into bile protein synthesis storage of iron/vitamins detoxification
liver is 80% what?
hepatocytes
what are sinusoids?
specialized liver capillaries
what kind of CT in liver?
reticular fibres of Type 1 and III collagen
what do the following the hepatocyte do?
the rough ER/golgi
smooth ER
Rough: protein synthesis
Smooth: fat/steroid metabolism
how many nuclei and mitochondria in hepatocytes?
two nuclei
many mitochondria
lifespan of a hepatocyte?
150 days
if liver has extensive damage, how is the regeneration?
not same lobular structure, more fibrous
can live regenerate from damage from alcohol/hepatitis?
if severe, then no
how are hepatocytes organized in the liver?
in lobules around blood vessels
what are the 2 blood supplies to the liver?
arterial
hepatic portal system:75%
what is the portal ‘triad’. 4 things.
hepatic artery
hepatic portal vein
bile duct
lymphatics
what kind of cells are the bile duct epithelium made of? vs. arterial epithelium?
columnar
squamous
smooth muscle in the central veins of the liver?
not much
what converge on the central vein in the liver? then where does it go?
sinusoids to hepatic vein > IVC
what give rise to sinusoids?
vein and artery
blood in sinusoids flow where in relation to the lobule?
towards the middle of lobule
what kind of blood is in sinusoids?
mixture
20% oxygenated
80% deoxygenated
describe the sinusoids’ size?
larger than normal capillaries
special features of sinusoids?
discontinuous lining
gaps between hepatocytes
microvilli
kupfer cells
what are kupfer cells?
macrophages on inner walls of sinusoids
what is the gap between endothelium and adjacent hepatocyte in sinusoids called?
space of Disse
what is the space of Disse for?
easier to transfer certain nutrients
3 models of hepatocyte organization. they are? what are each of their foci?
- Classic centres around central vein. Focus: BLOOD flow
- Portal. Veins in periphery. focus on BILE.
- Acinar. Focus: physiological oxygenation.
what is the surfactant produced in the liver called?
bile salts
where is bile synthesized from?
cholesterol
what are the bile collection channels called?
canaliculi
what is the direction of flow for bile?
outwards to be collected in bile duct within triad
focus of acinar lobule model?
physiological: O2 saturation/metabolic function
portal lobule model focus?
bile flow
what lobule model focuses on blood flow?
classic lobule model
what does the gall bladder do to the bile?
remove water and salts to concentrate it
what controls release of bile into duodenum?
sphincter of Oddi
what does classic lobule model focus on?
Blood Flow
Bile flow focus model of lobules called?
Portal lobule model
what lobule model focuses on physiological [O2] and metabolic function?
Acinar Model
What hormone controls bile secretion?
CCK from fat stim
what kind of cells in gall bladder epithelium?
simple columnar
what is the exocrine function of the pancreas?
create proenzymes/bicarbonate to be released into duodenum
2 areas of pancreatic exocrine cells are? colours on H&E?
basal: purple
Lumenal: pink
What does the basal and lumenal region of pancreatic exocrine cells each do?
basal: rough ER - protein synthesis
lumenal: zymogen granules
which part of the pancreatic exocrine cells faces inward towards the central duct?
lumenal side
what is a acini?
balls of cells with a central duct
what % of pancreas is endocrine?
1-2% of total pancreas volume
about how many islets of langerhans are in the pancreas?
around 1 million
what do islets of langerhans make?
insulin
glucagon
how is the vascular supply to the islets of langerhans?
rich