Histology & Anatomy of Digestive and Immune Systems University of
Sydney
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Important info
Definitions/key words
Week 1: Histology of the digestive system
Revise and Epithelial tissue
describe the basic - Lines inside/outside of surfaces
tissue types in the - Protection, secretion, absorption functions
body Connective tissue
- Cells (fibroblasts) + extracellular matrix (collagen and elastic fibres)
- Loose, dense CT
- E.g bone, tendon, blood, cartilage
Muscle tissue
- Smooth, skeletal, cardiac
Neural tissue
- Nerves + glial cells
,Describe the four Mucosa
distinct layers - Epithelial cells (simple columnar cells in stomach, small intestine and colon, stratified
(from the lumen squamous in oesophagus)
outwards) that - Secretes mucous (from mucous cells in stomach or goblet cells in small, large
make up this tube. intestine)
Identify these - Lamina propria – loose CT containing vessels, sometimes glands, and immune cells
layers on - Muscularis mucosa (thin smooth muscle layer)
histological images.
Submucosa
- Dense irregular CT containing glands, lymph nodes, vessels, Meissner’s nerve plexus
Muscularis externa
- 2 (or 3 layers in stomach) of smooth muscle
- Inner circular smooth muscle (that wraps around gastrointestinal tube)
- Outer longitudinal smooth muscle (that runs up and down tube)
- Smooth muscle layers separated by Auerbach’s/myenteric nerve plexus
Serosa/Adventitia
- Both contain either loose/dense CT
- Serosa – simple squamous epithelium (mesothelium) that lines organs suspended in
body, secreting protein liquid acting as lubricant
- Adventitia – no epithelium, directly continuous and attached to the next structure (e.g
adventitia connects oesophagus and trachea)
,What are the Chief cells
different cell types - Located deep (at the bottom) of gastric glands in stomach
found along the - Produce pepsinogen (protein) which is activated into pepsin (by HCl) and breaks down
length of the GIT? proteins
How are some of
these cells
organised into
glands in different
regions of the GIT?
Identify these cells
and glands on
histological images.
Parietal cells
- Located within the gastric glands of the stomach
- Large, triangular shaped cells (orange staining with large, centred nucleus – like fried
egg)
- Secretes HCl for digestion of proteins
Enterochromaffin cells
- Small cells within gastric glands in stomach, helping regulate gastric function
- Secretions released into bloodstream (not lumen)
- Secrete gastrin, which then stimulates parietal cells to release more HCl
Surface mucous neck cells
- Mucous secreting epithelial cells lining the surface and top of gastric pits in the
stomach
Mucous neck cells
- Mucous secreting epithelial cells located in the neck and deep into gastric glands in
stomach
- Stem cells that differentiate into surface or other cells (parietal, chief)
Goblet cells
- Only in small and large intestine
- More goblet cells in large intestine
Paneth cells
- Produce antimicrobial peptides, for immune defence
- Located at the base of intestinal glands
- Located in small intestine
Enterocyte cells
- Simple columnar epithelial cells lining small intestine (not found in stomach)
- Contain microvilli for absorption
- Located in small and large intestine
, How does the inner Oesophagus
“mucosa” layer of - Stratified squamous epithelial layer – protective role against irritants, pathogens
the GIT change entering GIT
from the
oesophagus, to the Stomach
stomach, small - Simple columnar epithelium – absorption, secretion role
intestine, large - Mucosa and submucosa layers fold forming rugae, allowing for stretch and distention
intestine and anal when food enters stomach (rugae are different to villi in that they don’t increase SA,
canal? How do instead accommodate expansion of stomach)
these changes
reflect the various
underlying
functions occurring
in the different
regions of the GIT
tube?
- Mucosa layer contains gastric pits and gastric glands (within lamina propria)
- Gastric glands contain parietal cells, chief cells, mucous neck cells, enteroendocrine
cells (G cells, enterochromaffin cells)
Small intestine
- Simple columnar epithelium (enterocyte cells) and some goblet cells
- Plicae circularis (permanent folds in mucous membrane), villi (finger-like projections
from plicae circularis) and microvilli all increase SA for absorption
- Intestinal gland extends deep to the base of the epithelium
- Submucosa layer of duodenum contains distinctive Brunners glands
- Ileum contains NO glands in submucosa but has large, prominent lymphatic nodules -
> Peyer’s patches
Duodenum containing Brunners glands (lek), Ileum containing lymphatic nodules (right)
Large intestine
- Simple columnar enterocyte epithelial cells