GI histology Flashcards
what are the layers of gut tube?
Mucosa
Epithelium
Lamina Propria
Muscularis mucosae
Submucosa
Muscularis externa
Inner circular
Outer longitudinal
Adventitia /Serosa
what are characteristics of the layers in the oesophagus?
Stratified squamous non-keratinised epithelium
Submucosa shows mucous glands
Muscular layer – upper 1/3 skeletal, middle 1/3 – smooth+ skeletal, lower 1/3 - smooth
what do parietal cells secrete?
HCL
what do chief cells secrete?
pepsinogen
what are characteristics of the layers in the small intestines
Villi
Crypts of Leiberkuhn
Lymphoid aggregations in mucosa - Peyer’s patches
what are characteristics of the layers in ileum?
Villi +
Peyer’s patches
what are characteristics of the layers in the large intestine?
Thick mucosa, crypts, mucous secreting cells. No villi.
what are the glands in the GI?
Salivary glands (in head/neck block)
Pancreas
Liver (very elaborate gland!)
what are Secretory (acinar component) – roundish structure with columnar cells and nuclei at the base
Ducts
characteristics of the pancreas?
Islet of Langerhans – endocrine part – no acini
2 – exocrine part – pancreatic acini
3 – pancreatic duct ( for exocrine part)
what are the regions of the stomach?
cardia
fundus
body
pylorus
functions of the stomach
Food starts to be digested and absorbed in the stomach.
Food is broken down chemically, by gastric juice, and mechanically, by contraction of the three layers of smooth muscle in the muscular externa layer. The broken up food at the end of this process is called chyme.
what are rugae?
folds found on the interior layer of the stomach and aid in breaking down food when the stomach contracts.
what are gastric pits?
are indentations in the stomach epithelium which denote entrances to the tubular shaped gastric glands. The human stomach has several million of these pits which dot the surface of the lining epithelium
what are the three types of gland?
cardiac – secrete mucus;
fundic – secrete HCl and intrinsic factor;
pyloric – secrete gastrin
what are the gastric glands responsible for?
synthesis and secretion of the gastric juice.
what is the lining epithelium of the stomach and gastric pits made up of?
mucus secreting simple columnar epithelium.
where are parietal cells found?
concentrated in the isthmus region, but also found in the base and neck of the glands. These are large pale pink staining cells with a central spherical nucleus thus having a ‘fried egg’ appearance
where are cheif cells found?
found in the bases of gastric glands. They have a stongly basophilic granular cytoplasm, as they have lots of rER for production of peptin, which is secreted (as precursor pepsinogen), and basally located nuclei.
where are endocrine cells found?
cells in the bases of the glands secrete gastrin and other hormone
function of mucous cells
Secrete mucus to protect epithelial cells
from enzymes & acid
histological features of the small intestine
. It has large circular mucosal folds
called plicae circulares
- Projecting from the plicae are
smaller folds called villi, which
are finger like mucosal projections,
about 1mm long. - The lining columnar epithelial cells
have fine projections on their apical
surfaces called microvilli (“brush border”
Between the villi there are crypts, called crypts of Lieberkuhn/intestinal glands, which extend down to the muscularis mucosae. These crypts are short glands
- The lamina propria which underlies the epithelium has a rich vascular and lymphatic network, which absorbs the digestive products.
The lymphatic capillaries are called lacteals, and absorb lipids.
The vascular capillaries are fenestrated to aid absorption.
what do crypts contain?
Paneth cells
Endocrine cells
Stem cells
Intraepithelial lymphocytes
function of paneth cells
they have a defensive function, and stain intensely eosinophilic.
Secrete antimicrobial peptides.
function of endocrine cells
which produce secretin, somatostatin, enteroglucagon and serotonin.
function of stem cells
found at the base of the crypts, which divide continuously to replace enterocytes (every 2-3 days), goblet cells, paneth cells and neuroendocrine cells
where are lymphoid aggregations commonly found?
found in the sub-mucosa of the small intestine, an you can see one here. The larger aggregations of lymphoid tissue are known as Peyer’s Patches.
what does the muscularis externa contain?
contains two layers of smooth muscle, an inner circular and outer longitudinal, for continuous peristaltic activity of the small intestine
comparisons between duodenum and small intestine?
The villi are broader
Peyer’s Patches are less common
One unique feature: Brunner’s glands, which are found in the sub-mucosa.
comparison between jejunum and ileum
The villi of the jejunum are tall and cylindrical, while they are very short and cylindrical/non-existent in the ileum.
Crypts are more extensive in the mucosa of the jejunum, and contain Paneth cells.
Peyer’s Patches found in the submucosa of the ileum, but not the jejunum.
function comparison of small intestine and large intestine
SI
principle site for digestion of food and absorption of the products of digestion
LI
reabsorption of water and elimination of undigested and waste
