L27 - GI tract microanatomy Flashcards
What type of epithelium lines the oesophagus
Stratified squamous non keratinising epithelium
What do the oesophageal glands in the submucosa secrete
An equal amount of serous and mucus
what epithelium lines stomach
simple columnar
shape of gastric glands (stomach)
compound tubular
what do glands of the gastro-oesophageal junction secrete and what is the function of these secretions
mucus
coats stomach with protective layer
how many types of gastric glands
what are their names
3
gastric glands
brunners glands
gland of crypt of lieberkuhn
what are folds in the gastric mucosa called and what is their function
rugae
accumulate different volumes
what do gastric glands of stomach secrete
hcl
mucus
zymogen granules
visual characteristics of parietal cells
rounded
central nucleus
pink (eosinophilic)
what do stomach parietal cells secrete
HCL
intrinsic factor
function of intrinsic factor
aids vitamin b12 absorption
visual characteristics of chief cells
speckled (zymogen granules)
purple (basophilic)
what colour do chief cells stain
what colour do parietal cells stain
purple
pink
what layer are stomach glands in
mucosa
what layer are crypts of L found in
lamina propria (mucosa)
example of specialisation of duodenum epithelial cells and what it does
microvilli to increase SA
what do brunners glands (of duodenum ) secrete
thin alkaline mucus
secretin into crypts
function of the crypts of Lieberkuhn?
- release protective enzymes (paneth cells)
- secrete hormones (enteroendocrine cells)
- cell replacement (stem cells) (MAINLY)
what are folds of mucosa of small intestine called and what is their function
plica circulares
increase SA
why does colon contain many goblet cells
Lubrication to ease passage of semi solid waste material
What is the function of the lymphoid tissue in the colon
inflammatory response
in what regions can glands be sometimes found in submucosa
oesophagus and duodenum
what parts of the tract have no glands in the submucosa
stomach
ilium
jejunum
what are the 5 phases of the GI tract
- ingestion
- fragmentation
- digestion
- absorption
- elimination
name the 4 layers of the GI tract
- mucosa (lumen)
- submucosa
- muscularis externa (/propria)
- adventitia (outer)
what are the 3 layers of the mucosa
- specialised surface epithelium (innermost)
- lamina propria
- muscularis mucosae (outer, in contact with submucosa)
describe the lamina propria
loose connective tissue
contains blood and lymph vessels
contains nerve fibres
contains smooth muscle
what does the epithelium of the mucosa layer rest on?
basal lamina
describe the muscularis mucosae
thin double layer of smooth muscle
what is the muscularis mucosae SM controlled by?
Meissner’s (submucosal) plexus (PNS)
what are the roles of the mucosa epithelium in different parts of the body?
protective - mouth/pharynx/oesophagus/anal canal
secretory - stomach
absorptive - SI
absorptive&protective - LI
describe the structure (and components) of the submucosa
- loose connective tissue
- contains blood vessels
- contains nerves which form the Meissner’s (submucosal) plexus
- contains leukocytes
- contains variable amounts of lipids
-glands in oesophagus
where is the Meissner’s plexus located
submucosa
how is the submucosa of the oesophagus and duodenum different to the rest of the GI tract
can contain glands
describe the structure of the muscularis externa
2 thick SM layers
- inner circular
- outer longitudinal
how does the structure of the muscularis externa differ in the stomach from the rest of GI tract
has 3 layers in the stomach rather than 2
what is found between the two layers of the muscularis externa
(auerbachs) myenteric plexus.
function of the muscularis externa
responsible for peristaltic waves
describe adventitia structure
thin connective tissue continuous with surrounding organs
what epithelium is the adventitia and what is its correct name
simple squamous
mesothelium
function of mesothelium
bounds adventitia to cavity
how does the muscularis externa differ down the oesophagus
starts as skeletal then gradually smooth as initiation of swallowing is voluntary
how does epithelium change from the oesophagus to the stomach
stratified squamous to simple squamous to simple columnar
what are the layers of muscularis externa in the stomach
- oblique layer (inner, in contact with stomach contents)
- circular layer
- outer longitudinal layer
name the 3 regions of the stomach
fundus (food first arrives)
body
antrum
properties of the cardia mucosa
mucous secreting
few glands
properties of the fundus/body mucosa
densely packed glands secreting mucus, gastric juice, acid and enzymes
what is secreted from glands in the fundus
mucus
acid
gastric lipase
properties of the pyloric mucosa
deep gastric pits
mucus secreting glands
endocrine glands secreting gastrin
how are gastric pits formed and what are they connected to
invaginations of the epithelium
glands
what cells types are found in gastric pits and glands?
- surface mucus cells
- mucus neck cells
- stem cells
- endocrine cells
- parietal cells
- chief cells
function of gastric surface mucus cells
secrete mucus and bicarbonate to protect from stomach acid
where are gastric mucous neck cells located and what do they do
upper parts of the gastric glands
secrete mucus
where are gastric stem cells located
neck region of gland
function of gastric endocrine cells in glands
secrete gastrin + somatostatin (hormones)
where in the gastric gland are parietal cells located and what are their function
throughout the gland
- make and secrete HCL
- secrete intrinsic factor
where in gastric glands are chief cells located and what is their function
lower regions secrete zymogens (enzymes) in response to gastrin
what layer of the SI would you find plicae circularis
mainly mucosa sometimes submucosa
what is found on the plicae circularis?
villi which have a brush border or microvilli
what surface epithelium do villi have
simple columnar
what is found within villi
goblet cells
endocrine cells
blood vessels
micrvilli lining
what lines microvilli
glycocalyx coating - wherever there is no cilia
in what layer of the duodenum are brunners glands
submucosa
what cells are found in the crypts of L
stem cells
paneth cells
enteroendocrine cells
where are crypts of L located
between villi
from pyloric mucosa of stomach to colon
where are paneth cells located and what is their function
lower 1/3 of crypt
release protective enzymes to destroy bacteria
how are enteroendocrine cells stimulated and what do their hormones stimulate
by acidic chyme from stomach
enzyme secretion
release of bile from gall bladder
what part of the SI has the tallest villi
jejunum
order of large intestine
caecum appendix ascending colon transverse colon descending colon sigmoid colon rectum anal canal
what is different about the muscularis externa layer of the colon
the outer longitudinal layer has 3 bands called tenia coli for powerful peristalsis of solid faeces
role of the muscularis mucosae in the colon
prevents clogging of glands and helps mucus expulsion
how do the no. of goblet cells increase throughout the GI tract
increase towards rectum
what epithelium in anal canal
stratified squamous
where are peyers patches found
musosa (lumen) of ileum mainly
function of peyers patches
removal of pathogens
what are peyers patches
bulging lymphoid follicles
what is MALT and where is it found
mucus associated lymphoid tissue
in mucosa layer
