2. • To overview the histology of the Alimentary System
from mouth to anus
• Name the most common changes in
histology causing pathology in different
areas of the GI tract
Outcomes
Use the man in
the top corner of
each slide to help
orientate yourself
Please use the
navigation pane
on the left of the
slides to help you
move around the
pages
3. The structure of the GI tract conforms to a general structure from the
oesophagus to the anus. It is essentially a muscular tube lined by a mucous
membrane, with a few minor variations along the way. There are four distinct
functional layers : mucosa, submucosa, muscularis propria and adventitia.
• Mucosa- made up of 3 components – epithelium, supporting lamina propria,
and a thin smooth muscle layer called the muscularis mucosae, which
produces local movement and folding of the mucosa.
• Submucosa- The layer of loose collagenous supporting tissue supports the
mucosa and contains the larger blood vessels, lymphatics and nerves
• Muscularis propria- the muscular wall consists of smooth muscle which is
usually arranged in an inner circular layer and longitudinal layer. In the
stomach there is also an inner oblique layer of muscle. The action of the
different layers at right angles is for peristaltic contraction
• Adventitia- the outer layer of loose supporting tissue which conducts the
major vessels, nerves and variable adipose tissue. Within the peritoneal
cavity, the adventitia is referred to as the Serosa and is lined by a simple
squamous epithelium (Mesothelium). Elsewhere the adventitia layer merges
with the retroperitoneal tissues
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract overview
QUIZ
The Basics
4. The mouth (or oral cavity) contains the tongue, teeth and cheeks. The
epithelium of the mucosa lining the cheeks and tongue is able to resist
wear and tear involved in chewing foods, and in most regions it is a
stratified, squamous (non-keratinised) epithelium. This epithelial surface
is moistened by secretions from small serous and mucus glands within the
submucosal layer and from the salivary glands.
Saliva is produced by three pairs of salivary glands, the parotid,
submandibular and sublingual glands. Two types of cells are found within
the salivary glands, these are serous cells and mucous cells.
The Mouth
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract
overview
QUIZ
The parotid gland consists
almost exclusively of serous
cells, the sublingual glands
consist mostly of mucous
secretory cells and
submandibular has both
**Acini means a cluster of cells
5. The tongue is covered by a stratified non-keratinized, squamous
epithelium, which on the under surface is similar to the epithelium of the
mouth. The upper surface is studded by prominent projections many of
which are due to aggregations of lymphocytes deep in the epithelium . In
addition, three distinct types of projections, known as papillae are also
seen:
TheTongue
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract
overview
QUIZ
Filiform papillae: these are numerous on the upper
surface and are in parallel rows which converge
towards the midline. Their surface is covered by
keratinised stratified squamous epithelium. (small
and sharp a)
Fungiform papillae: These are covered by stratfied
(non-keratinised) squamous epithelium.
Specialised clusters of sensory cells (taste buds) are
present in the epithelium covering this type of
papilla (slightly larger b)
Circumvallate papillae: there are 8-12 of these
visible to the eye just towards the posterior aspect
of the tongue. They are also covered by stratified
(non-keratinised) squamous epithelium which
contain taste buds.
6. The oesophagus is a muscular tube through which food passes from the
pharynx to the stomach. During swallowing food passes from the
mouth through the pharynx into the oesophagus and travels via
peristalsis to the stomach.
The mucosa of the oesophagus is covered in stratified non-squamous
epithelium and serves a protective effect due to the high volume transit
of food, saliva and mucus.
The submucosa contains mucous-
secreating glands to help lubricate the
transit of food to the stomach
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract
overview
QUIZ
The Oesophagus
7. This is an abnormal change (metaplasia) in the cells epithelium in the inferior
part of the oesphagus
The normal squamous epithelium is replaced with metaplastic columnar
epithelium
There is a strong association with oesophageal adenocarcinoma. The
associated risk of oesophageal cancer is about 0.5%.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract
overview
QUIZ
Barratt’s Oesophagus
Metaplastic
columnar
epithelium
(Left)
Normal oesphagusBarrett’s (red patches) Normal
Squamous
epithelium
(right)
8. The dilated portion of the GI tract. It is described using 4 regions: the
cardiac region, fundus, body and pylorus. When the stomach is in its non-
distended state it has longitudinal folds in the mucosa called rugae
The The stomach has 3 layers of smooth
muscle orientated on 3 different planes
The inner one is oblique, the middle is
circular and the outer is longitudinal to
help squeeze chyme and mix with the
stomach secretions.
The stomach has 2 distinct histological areas – the body and fundus making
up one and the pylorus and cardia making up the other
The pylorus and cardia have mostly mucous cells
to protect the entrance and exits of the stomach.
The pylorus also secretes endocrine hormones
The body and the fundus have more of the gastric
cells which secrete the exocrine hormones and
other chemicals
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract
overview
QUIZ
The Stomach
9. This gastric gland area occupies roughly the proximal 80% of the stomach.
The major exocrine secretions are all derived for this area.
The gastric glands project downwards and are composed of
pareital cells which secrete HCl and intrinsic factor and the
peptic (chief) cells which secrete pepsinogen.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract overview
QUIZ
The Body and Fundus of the Stomach
Gastric
gland
area
Columnar mucous cells
Lamina Propria
Parietal
cells –
larger than
chief cells
Chief cells –
pyramidal
in shape
Oblique angle through the
cells within the Gastric glands
Cross-section of the Stomach
Gastric pitsGastric glands occupy
the entire thickness of
the mucosa
10. The gastric glands within the antrum and pyloric area consist of
endocrine cells, which secrete gastrin and somatostatin
The pyloric glands are more branched and coiled (see pic below)
compared to glands of the body and fundus. Gastric pits occupy almost
50% of the thickness of pyloric mucosa.
Scattered among the pyloric mucous cells are neuroendocrine
cells that secrete somatostatin and gastrin (G cells).
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract overview
QUIZ
The Pylorus of the Stomach
Pyloric
gland
area
An antibody has been used
to highlight gastrin within
cells at the base of the
convoluted gastric pits.The
same pattern can be seen
with somatostatin.
In the pylorus the gastric pits and more
branched and coiled than those in the
fundus and body of the stomach
11. Helicobacter pylori is a gram-negative bacteria which can inhabit various areas
of the stomach, particularly the antrum. It causes chronic low-level
inflammation of the stomach lining causing indigestion and is strongly liked to
the development of gastric and duodenal ulcers and adenocarcinomas.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
Helicobacter Pylori
The arrows here show H. pylori
in situ with their curved,
coccoid morphologic features
Gastric adenocarcinoma in
situ caused by H. Pylori
Chronic gastric ulceration –
there is erosion of the
mucosa and the muscularis
propria
12. The small intestine has 3 parts to it – the duodenum, jejunum and ileum.
The wall of the small intestine conforms to a generalised structural plan
of the GI tract though there are features which characterise each part.
The epithelium of the mucosal lining of the small intestine contains:
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
The Small Intestine - Cells
Cells What do they do? Picture
Columnar
epithelial cells
Specialised for absorption of small molecules
Goblet cells Make and secrete mucous which helps protect the
luminal surface
Paneth cells Make, store and secrete lysozyme
Neuroendocrine
cells
Secrete molecules which affect the function of
others
Too numerous for one
picture!
Lymphocytes Immune cells may be found between epithelial cells Too numerous!
13. There are also several structures of the small intestine that facilitate their
function:
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
The Small Intestine - Functions
Structure/
feature
What it does Picture
Transverse
folds (plicae
circulares)
These are visible in the duodenum, jejunum and
first half of the ileum to the naked eye. These
folds are formed of mucosa and submocosa
Villi These are present throughout the small
intestine and are microscopic finger-like
structures which project from the mucosa into
the lumen. They are covered by columnar
epithelial absorptive cells and goblet cells and
have a core of connective tissue, supporting
blood cells and lymphatic vessels. Some
smooth muscle cells help villi waft between
chyle aiding absorption
Microvilli These are small folds in the apical membrane of
the columnar epithelial cells of the villi. They
are revealed by a light microscope as a ‘brush
border’
Intestinal
glands
(crypts of
Lieberkühn)
These are tubes which dip into the mucosa as
far as the muscularis mucosae. As well as
columnar epithelial and goblet cells, Paneth
cells, neuroendocrine cells and stem cells are
present
14. The duodenum is located in the retroperitoneum, the duodenal mucosa
has numerous elongated villi, between the bases of which are shorter
crypts.
In the distal duodenum, the height of the villi is about 4x the length of the
crypts.
At the proximal part of the duodenum, most the entire submucosa is
occupied by Brunner’s glands which secrete alkaline mucins into the
lumen if the small intestine to make the chyle less acidic.
**Brunner’s glands are one of the main features that differentiates
the duodenum from the rest of the small intestine.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
The Duodenum
15. The jejunum starts and the duodenum ends at the ligament of Treitz which
is where the mesentery, which surrounds the jejunum and ileum, starts.
The submucosa and mucosa are thrown up into circumductive arranged
folds called the plicae circulares (a.k.a. valvulae conniventes) – This is found
throughout the small intestine but is particularly numerous in the jejunum
and helps to increase the surface area and therefore absorption from the
jejunum.
Its mucous membrane, is covered in villi which increase absorption. The
epithelial cells which line these villi possess even larger numbers of
microvilli. The transport of nutrients across epithelial cells through the
jejunum and ileum includes the passive transport of sugar fructose and the
active transport of amino acids, small peptides, vitamins, and most glucose.
The villi in the jejunum are much longer than in the duodenum or ileum.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
The Jejunum
Villi increase absorption
Lumen
Plicae circulares
16. Coeliac Disease is a gluten-sensitive enteropathy. It is a malabsorptive
immune disorder which is characterised by lymphocytic enteritis, flat mucosa
(loss of villi) within the small intestine. Diagnosis is from a distal duodenal/
jejunal biopsy and a good response to removal of gluten from the diet, but
will reappear on reintroduction of gluten.
Coeliac disease is caused by a reaction to gliadin, a gluten protein found in
wheat. Upon exposure to gliadin, the enzyme tissue transglutaminase
modifies the protein, and the immune system cross-reacts with the small-
bowel tissue, causing an inflammatory reaction. This leads to a truncating of
the villi lining the small intestine (called villous atrophy). This interferes with
the absorption of nutrients, because the intestinal villi are responsible for
absorption.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
Coeliac Disease
Loss ofVilli
This mucosa is completely flat and devoid
of villi but it’s height is not decreased.
**Also, please note the high numbers of
lymphocytes in the tissue
17. In humans the Ileum is normally about 2-4m in length and its main
function is to absorb bile salts and vitamin B12 as well as any nutrients
that haven’t been absorbed by the jejunum.
The main difference between the ileum and jejunum is the presence of
Peyer’s patches which are unencapsulated lymphoid nodules which
contain large numbers of lymphocytes and other immune cells. They are
found within the lamina propria layer of the mucosa and extend into the
submucosa of the ileum and each patch measures a few centimetres in
length. Within the Peyer’s patches, B lymphocytes predominate the
follicle germinal centres and T lymphocytes are found in the zones
between the follicles.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
The Ileum
18. Crohn’s disease is an inflammatory disease of the intestines, most
commonly effecting the terminal ileum, but it can effect any part of the GI
tract from the mouth to the anus. It is a chronic inflammatory bowel
disease affecting the colon, ileum and other parts of the digestive tract. It
is characterized by skip lesions (diseased areas separated by normal bowel
segments).
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
Crohn’s Disease
Histological evidence of diagnosis
includes: transmural inflammation
(full thickness of the intestinal wall),
fissures and granulomas.
Fissure entering the wall of the intestine
19. The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
The Colon
The principle function of the colon is the recovery of salt and water from
the faeces and propulsion of increasingly solid faeces to the rectum prior
to defecation.
The muscular wall is thick and capable of powerful peristaltic activity.
The muscularis propria of the colon consists of thick inner circular and
longitudinal smooth muscle layers. The longitudinal layer forms 3
separate bands called the tinea coli.
**There are no villi in the colon.
Mucosa with lamina propria and glands/crypts
Circular muscularis propria
Longitudinal muscularis propria
20. The rectum is the final part of the human GI tract which terminates at the
anus. The human rectum is about 12cm long .
The rectal mucosa is the same as the rest of the colon, except it has more
goblet cells which secrete mucus.
The recto-anal junction undergoes an abrupt transition from rectal
mucosa to become stratified squamous epithelium in the anal canal.
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine overview
GI Tract overview
QUIZ
The Rectum
Simple
columnar
epithelium
with goblet
cells
Stratified
squamous
epithelium
21. Small to Large Intestine - Clarification
Thicker circular
and longitudinal
tunica muscularis
22. Part of the GI
tract
Type of epithelium
Main cell types of
epithelium
Other distinctive features
Mouth and tongue Stratified squamous
Squamous cells
Serous cells
Mucous cells
Tongue has special papillae:
filiform, fungiform and
circumvallate
Oesphagus Stratified squamous Squamous cells Submucosal glands
Body/fundus of
stomach
Glandular columnar –
straight tubular
Surface mucous cells
Neck mucous cells
Parietal cells
Chief (peptic) cells
Lymphoid cells very sparse
No lymphoid aggregates
Pylorus and cardia
of stomach
Glandular columnar –
coiled, branched tubular
Mucous cells
May be occasional parietal cells
Lymphoid cells very sparse
No lymphoid aggregates
Duodenum
Glandular columnar with
villi and crypts of
Lieberkühn
Enterocytes with microvilli
Goblet cells
Paneth cells
Brunner’s glands
Plicae circulares (distal
duodenum)
Jejunum and ileum
Glandular columnar with
villi and crypts of
Lieberkühn
Enterocytes with microvilli
Goblet cells
Paneth cells
Peyer’s patches become more
prominent distally
Plicae circulares
Colon and rectum Glandular – straight crypts
Goblet cells
Absorptive cells
Prominent lymphoid tissue
Comparison of Structure of Parts of the
GITract
23. 1. The lamina propria is part of the submucosa True False
2. The mouth contains Serous cells True False
3. The circumvallate papillae of the tongue have taste buds
True False
4. Filiform papillae are covered in keratinised squamous epithelium
True False
5. The underside of the tongue has the same epithelium as the cheek
True False
6. Squamous epithelium is replaced by columnar epithelium in Barrett’s
oesphagus True False
7. Parietal cells secrete HCl and Intrinsic factor True False
8. Helicobacter pylori is linked to gastric ulceration True False
QUIZ –turn up your sound or click on the
mini-man to go to the page with the answer
**Correct sounds like this **Incorrect sounds like this
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract overview
QUIZ **Questions continued on the next page as well as answers
24. 9. The glands secrete exocrine hormones within the pyloric region of the
stomach True False
10. Squamous epithelial cells are important for absorption within the small
intestine True False
11. Paneth cells store and secrete lysozyme True False
12. Coeliac Disease is caused by an allergy to glucose True False
13. Vitamin B12 is absorbed from the terminal ileum True False
14. Crohn’s disease is characterised by skip lesions True False
15. The rectum contains many goblet cells True False
Answers: 1F, 2T, 3T, 4T, 5T, 6T, 7T, 8T, 9F, 10F, 11T, 12F, 13T, 14T, 15T.
QUIZ –Write your answers down or
turn up your sound!
**Correct sounds like this **Incorrect sounds like this
The Basics
Mouth
Tongue
Oesophagus
Barratt’s
oesophagus
Stomach
Body + fundus
Pylorus
H. Pylori
Small intestine –
cells
Functions
Duodenum
Jejunum
Coeliac Disease
Ileum
Crohn’s Disease
Colon
Rectum
Small + Large
Intestine
overview
GI Tract overview
QUIZ
Answers: Click here!
25. a) Mouth
b) Tongue
c) Oesophagus
d) Stomach - fundus and body
e) Stomach - pylorus
f) Duodenum
g) Jejunum
h) Ileum
i) Colon
j) Rectum and anus
Match up answers 1-8 with the most
common areas they are found
1) Tinea coli
2) Brunner’s glands
3) Serous cells
4) Crohn’s disease
5) Chief cells
6) plicae circulares
7) Fungiform papillae
8) Peyer’s patches
Quiz - EMQ
26. • Wikipaedia is a good basic source of information which can give you a
grounding in the subject (*beware of american spellings!)
• Wheater’s Functional Histology byYoung, Lowe, Stevens and Heath –
full of everything you would ever want to know about histology
• Human Histology by Stevens and Lowe – lots of easy pictures to look at
• Histology: an illustrated colour text by Mitchell and Peel – if you
haven’t discovered this series – go and look now!
• http://www.pathguy.com/ - this guy has way too much time on his hands
but there are a lot of good pics on here
• http://www.pathconsultddx.com/pathCon/home - This is a great website
to type in diseases and look at histological and pathological slides.
Further Reading
