The document summarizes the histology of the digestive tract mucosa, submucosa, muscularis, and serosa. It describes the epithelium and specialized structures of the esophagus, stomach, small intestine, large intestine, and anus. The esophagus contains non-keratinized stratified squamous epithelium. The stomach contains simple columnar epithelium that invaginates into gastric pits and glands. The small intestine contains simple columnar epithelium with plicae circulares and villi containing crypts of Lieberkuhn. The large intestine contains simple columnar epithelium organized in intestinal glands.

1. Digestive System
Continuation
(Digestive Tract)

2. Histology of the Mucosa
Organ Epithelium
Mouth Nonkeratinized Stratified Squamous
Pharynx Nonkeratinized Stratified Squamous
Esophagus Nonkeratinized Stratified Squamous
Stomach Simple Columnar
Small Intestine Simple Columnar
Large Intestine Simple Columnar
Anus Nonkeratinized Stratified Squamous

3. Histology of the Mucosa
Organ Folds of the epithelium
Esophagus none
Stomach L: Rugae, S: gastric pits
Small Intestine
L: Plicae circulares, Villi S: Crypts
of Lieberkuhn, microvilli
Large Intestine L: Haustra S: Intestinal glands

4. Histology of the Submucosa
Organ Specialized structures
Esophagus Esophageal gland
Stomach None
Duodenum Brunner’s glands
Ileum Peyer’s Patches
Large Intestine None

5. Histology of the Muscularis
Organ Smooth muscle layers
Esophagus 2, circular and longitudinal
Stomach 3, oblique, circular, and longitudinal
Small Intestine 2, circular and longitudinal
Large Intestine 2, circular and longitudinal

6. Histology of the Serosa
Organ Serosa
Esophagus
Adventitia due to the fact that the
esophagus is not in a cavity
Stomach Visceral Peritoneum
Small Intestine Visceral Peritoneum
Large Intestine Visceral Peritoneum
Anus Adventitia

7. Esophagus
• A muscular tube whose function is
to transport foodstuffs from the
mouth to the stomach (peristalsis)
and to prevent the retrograde flow
of gastric contents (esophageal
sphincter).
• Peristalsis - controlled by reflexes
and ANS

8. 3 Regions:
• Proximal end - only striated
(skeletal) muscle cells.
• Middle portion - mixture of striated
& smooth muscle cells
• Distal end - only smooth muscle
cells that close to the stomach,
form the lower esophageal
sphincter (LES).

9. Clinical
Significance:
GERD – gastroesophageal reflux
disease
• Due to weakened LES; reflux of
gastric contents to the esophagus.
• Excessive gastric distention
– Fatty meals, smoking, and beverages
such as tea and coffee (with high
xanthine content) also cause relaxed
LES.)

10. • Mucosa: Non-keratinized stratified squamous
epithelium.
• Submucosa: Esophageal glands (mucus-
secreting) facilitates the transport of foodstuffs
and protects the mucosa.
• Lamina propria: Cardiac glands – near
junction between esophagus and stomach
(mucus-secreting)

11. Esophagus , l.s.

12. Esophagus

13. Esophageal Gland
• Mucous secreting
• Similar to salivary glands
• Aid lubrication of bolus
• Most prominent in the
upper and lower thirds
of the esophagus

14. Esophagus

15. • Tunica muscularis (muscularis externa)
• Tunica serosa – covers esophageal
portion in peritoneal cavity
• Tunica adventitia – covers the rest of the
upper esophagus that blends into the
surrounding tissue.

16. STOMACH
• Bean-shaped hollow muscular organ of
the gastro-intestinal tract involved in the
second phase of digestion
• It has four anatomical parts: cardia,
fundus, corpus (body) and pylorus
• It has three histological distinct parts: (1)
cardia, (2) the fundus and the body have
the same histological properties (3)
pylorus

18. Epithelium
• Simple columnar epithelium
invaginates into the lamina propria,
thereby it makes gastric pits
Gastric pits (Foveolae)
empties into branched tubular
glands (cardiac, gastric, and
pyloric) characteristic of each
region of the stomach.

19. Lamina Propria
• loose connective tissue, which may contain
many lymphocytes
• all the gastric glands are located in this lamina
Muscularis mucosae
• well-developed, usually is composed of two
sublayers
• of smooth muscle cells

20. stomach

21. Structure of gastric glands

22. Branched tubular gastric glands
• cardiac -, fundic- and pyloric glands
• in the three histological portions of the stomach
the glands display somewhat different
morphology; their products are also different
Parts of a gastric gland:
– 1. Isthmus – small canal (opening)
– 2. Neck - passageway
– 3. Base – glandular area

23. The three functional regions of the stomach. The regions have different
luminal secretions and patterns of smooth muscle activity indicative of their
unique functions in response to food.

24. A. Representation of the structure of the gastric mucosa showing a section
through the wall of the stomach.
B. Detail of the structure of gastric glands and cell types in the mucosa

25. Cell types in the stomach
Glandular Epithelium:
• Simple columnar cells
• Chief cells
• Parietal cells
• Enteroendocrine cells
– G cells
– D cells

26. Columnar cells
• All columnar cells - secrete an alkaline mucus
consists primarily of water (95%), lipids, and
glycoproteins, which, in combination, form a
hydrophobic protective gel.
• Surface epithelial cells – secretes bicarbonate
into the mucous gel.
• Mucous gel - pH 1 at the gastric luminal surface
- pH 7 at the epithelial cell surface
- the mucus firmly adherent to the epithelial
surface is very effective in protection, while
the superficial luminal mucous layer is more
soluble, partially digested by pepsin and mixed
with the luminal contents.

27. Chief cells (or zymogenic cells)
• Chief cells (or zymogenic cells)
– most numerous cells; location: body of the
gastric glands
– produce pepsinogen (precursor of pepsin,
proteolytic enzyme); pH optimum of pepsin =
about 2 (break down collagen)

29. Parietal cells (or oxyntic cells)
– most frequent (in neck of the glands,
reaching the lumen of the gland) situated
deeper, between and below chief cells, in
lower parts of the gland.
– secrete the hydrochloric acid of the gastric
juice. Aside from activating the pepsinogen
the hydrochloric acid also effectively
sterilizes the contents of the stomach.
– secrete intrinsic factor, which is necessary
for the resorption of vitamin B12.

30. Clinical Significance
• Pernicious Anemia – Vit.B12 Deficiency
• This condition may result from a destruction of
the gastric mucosa by e.g. autoimmune
gastritis or the resection of large parts of the
lower ileum, which is the main site of vitamin
B12 absorption, or of the stomach.
• Vitamin B12 - cofactor of enzymes which
synthesize tetrahydrofolic acid, which is
needed for the synthesis of DNA components.
An impairment of DNA synthesis will affect
rapidly dividing cell populations, among them
the hematopoietic cells of the bone marrow
(pernicious anemia).

31. • Helicobacter pylori - so far only one type of
bacteria has found which can live happily in the
stomach - Unfortunately, they are involved in
the pathogenesis of gastritis and gastric ulcers.

32. Enteroendocrine cells
• scattered, usually solitary, throughout the
epithelium of the gastrointestinal tract
• G cells - most frequent in the middle third of
the glands; stimulate secretion of acid and
pepsinogen; stimulated by nervous input, the
distension of the stomach or secretagogues.
• D cells - mainly in glands of the pyloric antrum;
inhibit G cells and thereby acid production;
stimulated by acid in the lumen of the stomach
and duodenum.

33. • Enteroendocrine cells
(apex: microvilli)
• The best characterized
endocrine cells in the
gastric mucosa are
gastrin-producing cells
(G cells) and
somatostatin-producing
cells (D cells).

34. Stomach: Pyloric-duodenal junction

36. Small Intestines

37. Small intestine

38. Villus
Enterocytes – tall columnar cells; the main
absorptive cells.

39. Crypts of Lieberkühn
• Simple tubular glands
• in between intestinal villi e
• extends through the lamina propria down to the
muscularis mucosae.
• secretes "intestinal juice" (about 2 liter/day),
closely resembles ECF, which is rapidly
reabsorbed.
• The intestinal juice enzymes are
enteropeptidase (or enterokinase), which
activates the pancreatic enzyme trypsin, and
small amounts of amylase.

40. Crypts of Lieberkuhn

41. Cell proliferation
Small intestine mucosa – instestinal gland

42. Secretory cells of Intestinal Gland
• Goblet cells – produce mucin for the
lubrication of the intestinal contents and
protection of the epithelium.
• Paneth cells – located at the bottom of
the crypts;
• produce antimicrobial peptides known as
defensins (lysozyme), which provide the
first line of defense against any disease
producing microbes. involved in the
control of infections (maintains normal
flora)

43. Other cells in the intestinal gland
• Enteroendocrine cells – produce
locally acting hormones which
regulate gastrointestinal motility
and secretion.
• Enterocytes – tall columnar cells;
the main absorptive cells.
• Mitotic cells – stem cells; divide
continuously to replenish all of the
above four cells.

44. • Lamina propria: similar to the
lamina propria of the stomach;
– with larger lymph nodules (Peyer’s
patches)
• Muscularis mucosae: 2 muscle
layers and extends into the
intestinal villi, where the smooth
muscle cells form a longitudinal
bundle in the center of the villi.

45. Duodenum
• Submucosa – (+) glands only in the
(Brunner's glands).
• Brunner’s gland – Secretion: mucous
and slightly alkaline due to bicarbonate
ions (pH 7-8).
• The amount of bicarbonate is however too
low to neutralize the acidic contents of the
duodenal lumen. Instead, the secretion of
Brunner's glands protects the duodenal
mucosa - similar to the mucus which
protects the gastric mucosa.

46. • Submucosal glands – Brunner’s gland

47. Jejunum
• Plicae circulares (lined with long
intestinal villi)
• Surface epithelium: (+) simple
columnar with goblet cells, intestinal
crypts, muscularis mucosae,
submucosa and muscularis externa.
• Intestinal Crypts - fairly short and
narrow.
• Do not have Peyer’s patch

48. • Plicae circularis

49. Jejunum

50. ILEUM
ILEUM
• Tall villi
• Thin submucosa
• Tunica serosa –
well-defined
(mesothelium)

51. Ileum – with Peyer’s patch
• Accumulations of lymphocytes are
common in the mucosa of the GIT, and
they occur frequently in the small
intestine to facilitates their function in
the immune-defense of the body
against possible pathogens in the
lumen of the intestine.

52. Ileum

53. Colon (Large Intestine/Bowel)
• Constitutes the terminal part
of the digestive system.
• 3 main sections: cecum
(including the appendix),
colon, and rectum (with the
anal canal)
• Primary function:
Reabsorption of water and
inorganic salts.
• Mucus - the only important
secretion (lubricant for
transport of the intestinal
contents)

54. Large Intestine:
• Mucosa
– Surface is relatively smooth
– No plicae circulares or intestinal villi.
– Crypts of Lieberkühn are present and usually
longer and straighter than those of the small
intestine
– Goblet cells account for more of the
epithelial cells than in the small intestine.
• Lamina propria
– very little; squeezed between the intestinal
glands.
• Muscularis mucosae
– forms 2 smooth muscle layers

56. • Submucosa: considerable amounts of fat
• Muscularis externa: Different from the
small intestine.
Inner circular layer of muscle - forms the
usual sheath around the large intestine
Outer longitudinal layer - forms Tenia
coli (3 flattened muscles)
• Tunica Adventitia (serosa): Forms
Appendices epiploicae (small pouches
filled with fatty tissue) along the large
bowel.

57. • Thank you for taking this journey of the human
body …TISSUE LEVEL !
• MS. O. HARA