The document provides an overview of the histology of the gastrointestinal tract. It describes the five main phases of GIT function and the major organs that make up the digestive system, including the oral cavity, esophagus, stomach, small and large intestines, rectum, and anus. For each organ, it discusses the epithelial lining, layers (mucosa, submucosa, muscularis externa), and cell types (e.g. gastric glands in stomach). It also describes the tongue papillae, esophagus layers, stomach regions and glands, and small intestine function. In summary, it provides a detailed histological analysis of the gastrointestinal tract.

1. GASTO-INTESTINAL
TRACT HISTOLOGY
NICK FEDHA

3. Introduction
GIT function-break down food for absorption into the
body
The process occurs in five main phases;
1. ingestion,
2. fragmentation,
3. digestion, (Food enzyme molecules)
4. absorption
5. elimination of waste products

4.  The digestive system consists of the digestive tract:
 oral cavity (lip and tongue)
 Esophagus
 Stomach
 small
 large intestines
 Rectum
 anus
 and its associated glands:
 Salivary glands
 Liver
 Pancreas.

5. The tongue
• A mass of striated muscle
covered by a mucous
membrane whose structure
varies according to the region.
• The mucous membrane is
smooth on the lower (ventral)
surface but has papillae on
the dorsal part.
• The surface of the tongue has
two types of small lymphoid
aggregations, lymphoid
nodules and the lingual
tonsils, the lymphoid nodules
aggregate around
invaginations (crypts).

6. Histological components
Epithelium - What type of epithelium covers the tongue?
Keratinised stratified squamous epithelium.
- On which surface of the tongue is the epithelium most
keratinised and why?
On the dorsal surface.
There is most contact on this surface.
 Fat (adipose tissue)
 Salivary glands
 Blood vessels and nerves
 Skeletal (striated) muscle- seen in longitudinal, oblique and
transverse orientations.
 Papillae.

7. Skeletal muscle and adipose tissue
adipocytes
B : LS section
A : TS section

8. Blood vessels and nerves
N
N
A
A
V
nerve
artery
vein

9. Papillae
Filiform Papillae
 Filiform papillae have an elongated conical shape; they
are quite numerous and are present over the entire surface
of the tongue. Their epithelium, has no taste buds, but is
keratinized.
Fungiform Papillae
 Fungiform papillae resemble mushrooms in that they have
a narrow stalk and a smooth-surfaced, dilated upper part.
These papillae, which contain scattered taste buds on their
upper surfaces, are irregularly interspersed among the
filiform papillae.

10. Foliate Papillae
 Foliate papillae are poorly developed in humans.
They consist of two or more parallel ridges and
furrows on the dorso-lateral surface of the tongue
and contain many taste buds.
Circumvallate Papillae
 Circumvallate papillae are 7–12 extremely large
circular papillae whose flattened surfaces extend
above the other papillae. They are distributed in the
posterior portion of the tongue.

11. Identify the main papilla in this section.
Circumvallate (vallate) papilla (arrowed).
Decide whether : glands : Yes
taste buds : Yes
lymphatic tissue : Yes
can be associated with this papilla

12. Identify the main papillae in this section.
Foliate papillae form a series of parallel folds.

13. Decide whether : glands : Yes
taste buds : Yes
lymphatic tissue : Some (seen here labelled L)
can be associated with this papilla.
L : Some lymphocytes

14. Identify the main papillae in this section.
Filiform papillae (arrowed).
Decide whether : glands : No
taste buds : No
lymphatic tissue : No
can be associated with these papillae.

15. Salivary glands

16. Taste buds

17. Lymphatic tissue : found deeper into the papillae.

18. ESOPHAGUS
 It is a muscular tube whose function is to transport
foodstuffs from the mouth to the stomach and to prevent
the retrograde flow of gastric contents.
 Transport is achieved by peristaltic contractions and
relaxation of the esophageal sphincters (upper and
lower), usually controlled by reflexes and by the
autonomic nervous system.
 In humans the esophagus is covered by nonkeratinized
stratified squamous epithelium

19. Name the four layers:
1: mucosa. 2: submucosa. 3: tunica muscularis.
4: serosa or adventitia.

20. How is the tunica muscularis (skeletal subdivided further?
Tunica muscularis consists of :
1. outer longitudinal muscle layer.
2. inner circular muscle layer.

21. How is the mucosal layer subdivided further?
The mucosal layer consists of :
1. epithelium.
2. lamina propria.
3. lamina muscularis.
epithelium
lamina propria
lamina muscularis

22. NOTE:
 In the submucosa are
groups of small mucus-
secreting glands, the
esophageal glands,
whose secretion facilitates
the transport of foodstuffs
and protects the mucosa.
 In the lamina propria of
the region near the
stomach are groups of
glands, the esophageal
cardiac glands, that also
secrete mucus.

23. Gastro-oesophageal junction
What is the most obvious change at this junction?
Epithelium changes from stratified squamous
nonkeratinized in the oesophagus to simple columnar
in the stomach.
Glands from few or no mucous glands in oesophagus
to gastric glands in stomach.
Thickening of tunica muscularis in the stomach
(cardiac sphincter muscle).

24. Lumen of stomach
Lumen of oesophagus
Stratified squamous
nonkeratinized
Simple columnar

25. gastric glands
columnar epithelium
stratified squamous
epithelium

26. Stomach

27.  Food starts to be digested and absorbed in the stomach,
although absorption is mostly limited to water, alcohol
and some drugs.
 The stomach is an expandable, muscular bag, and it keeps
swallowed food inside it by contracting the muscular
pyloric sphincter.
 Food can stay in the stomach for 2 hours or more.
 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.

28.  Gastric juice is secreted by gastric mucosal glands, and
contains hydrochloric acid, mucus, and proteolytic
enzymes pepsin (which breaks down proteins), and
lipase (which breaks down fats).
 When the stomach is empty, and not distended, the lining
is thrown up into folds called rugae.
 After eating, these folds flatten, and the stomach is able to
distend greatly.

29. The stomach has three anatomical regions:
1. cardiac, which contains mucous secreting glands (called
cardiac glands) and is closest to the oesophagus.
2. fundus, the body or largest part of the stomach which
contain the gastric (fundic) glands.
3. pyloric, which secretes mucus, and the hormone gastrin.

30. Layers of the stomach.
 Mucosa
 Submucosa
 Muscularis externa
 Serosa

31.  The mucosa is made up of:
 Epethelium (simple columnar).
 Full of gastric glands and pits.
 Laminar propria (loose connective tissue).
• The lamina propria, located just below the epithelium, is
rich in macrophages and lymphoid cells(lymphocytes),
some of which actively produce antibodies mainly IgA
against viral & bacterial invasion.
• viral and bacterial invasion.
 Prominent layer of smooth muscle - the muscularis
mucosae (contraction of this muscle helps to expel the
contents of the gastric glands).

33. Identify: Epithelium
Gastric pits
Lumen
Lymphocytes

35. Pyloric region of glandular stomach
Identify : deep gastric pits
coiled glands in lamina propria opening into gastric pits
lamina muscularis
Gastric pits
Coiled glands
Lamina muscularis

36. Gastric pits and glands
opening of gastric pit to stomach
Tubular glands

37.  The submucosa is composed of dense connective tissue
containing blood and lymph vessels; it is infiltrated by
lymphoid cells, macrophages, and mast cells.
 The muscularis externa layer has three layers of
muscle. An innner oblique layer , a middle circular and
an external longitudinal layer. The contraction of these
muscle layers help to break up the food mechanically.
 The stomach is covered by a thin serosa.

38. N/B:
Gastric Glands in the fundus (body) of the stomach
The epithelium of the mucosa of the fundus and body of
the stomach forms invaginations called gastric pits. The
lamina propria contains gastric glands, which open into
the bases of the gastric pits. These glands are responsible
for the synthesis and secretion of the gastric juice.
The lining epithelium of the stomach, and gastric pits is
entirely made up of mucous columnar cells. These cells
produce a thick coating of mucus, that protects the gastric
mucosa from acid and enzymes in the lumen. Even so, these
cells have to be replaced after 4-6 days.

39. Small Intestine
 Site of terminal food digestion, nutrient absorption,
and endocrine secretion.
 The processes of digestion are completed here.
 is relatively long—approximately 5 m—and consists of
three segments: the duodenum, jejunum, and ileum.

41. Colon
Tunica muscularis
Submucosa
Lymphatic nodule
Mucosa
Lumen

43. Columnar epithelial cells with the brush border (arrowhead)
interspersed with mucus-secreting goblet cells.

44. DUODENUM