1. Department of Histology and Embryology
Digestive System
Department of Histology and Embryology
Zhang Xi-Mei

2. What is the Digestion?
Digestion is the process by which food and drink are broken down into their smallest parts so that the body can use them to build and nourish cells and to provide energy.
Digestion begins in the mouth when we chew and swallow, and is completed in the large intestine.

3. Digestive System Digestive tract: Digestive glands:
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

4. Digestive Tract Ⅰ.GENERAL STRUCTURE OF THE DIGESTIVE TRACT Epithelium
Mucosa
Lamina propria
Muscularis mucosae
Submucosa
Muscularis
Adventitia

5. A.Mucosa 1.Epithelium: is highly variable.
contains loose connective tissue that is rich capillaries, lymphatic tissues, and glands.
2.Lamina propria:
3.Muscularis mucosae:
smooth muscle fibers.

6. B.Submucosa C.Muscularis D.Adventitia
dense connective tissue, many blood , lymph vessels.
C.Muscularis
smooth muscle fibers
D.Adventitia
Serosa or fibrosa.

8. ESOPHAGUS A.Mucosa B.Submucosa C.Muscularis D.Adventitia
1.Epithelium:nonkeratinized stratified squamous epithelium.
A.Mucosa
2.Lamina propria: esophageal cardiac glands.
3.Muscularis mucosae: longitudinal smooth muscles.
dense CT
Esophageal glands, mucus-secreting.
B.Submucosa
The upper one third
Skeletal muscle
C.Muscularis
The middle one third
Intermix
The distal one third
Smooth muscle
D.Adventitia
Fibrosa.

10. Esophageal mucosa
Esophageal glands

12. STOMACH Mucosa Submucosa Muscularis Adventitia 1.Epithelium:
simple columnar epihelium
surface mucous cells, form gastric pits.
1.Epithelium:
Mucosa
2.Lamina propria:
Glands, lymphoid tissue.
3.Muscularis mucosae:
Smooth muscle.
Submucosa
Dense connective tissue.
Oblique
Circular
longitudinal
Muscularis
Three layers smooth muscles:
Adventitia
Serosa.

13. Surface mucous cells
a. They form a simple columnar epithelium that covers the gastric mucosa.
b. They secrete a continuous mucous layer that protects stomach lining from acid.

14. Regions of the stomach and their histological structure

15. Glands 1.Mucous neck cells 2.Chief cells 3.Parietal cells 4.Stem cells
Glands are present throughout the fundus and body, branched, tubular gastric glands.
pit
1.Mucous neck cells
glands
2.Chief cells
3.Parietal cells
4.Stem cells
5.Enteroendocrine cells

16. Parietal cells
Chief cells
Enteroendocrine cells

17. Mucous neck cells
a. They are present between parietal cells in the necks of gastric glands.
b. They can secrete mucous. They are difficult to distinguish from chief cells in plain H&E stained section.

18. Chief cells
a. In the lower region of tubular glands, and have the characteristics of protein-synthesizing cells.
b. The granules in their cytoplasm contain the inactive enzyme pepsinogen.
pepsinogen
pepsin H+
Chief cell
Parietal cell
Diagram of a chief cell

19. Parietal cells
a. Rounded or pyramidal cells, intensely eosinophilic cytoplasm.
Resting---tubulovesicles---few microvilli.
Activity---canaliculus---more microvilli.
b. Parietal cells secrete HCl and Intrinsic factor.
Diagram of a parietal cell

20. Enteroendocrine cells
Stem cells
a. Found in neck regions.
b.These cells have a high rate of mitosis: some of them move upward to replace the pit and surface mucous cells, other cells migrate more deeply into the glands and differentiate into parietal, chief cells and etc.
Enteroendocrine cells
In base of gastric glands.

21. Small intestine A. Basic anatomy duodenum, jejunum, ileum
Structure of small intestine
Plicae circulares, villi, and microvilli increase the absorptive surface area of small intestine.

23. The Wall of the Small Intestine
Figure 14.9
Slide 14.10A
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

26. Intestinal villi Absorptive cells Epithelium Goblet cells
Blood capillary
Smooth muscle
Lamina propria
Lymphatic vessel
Lymphatic tissue

27. Mucosa 1. The epithelium of intestine villi 2. Intestinal glands
3. Five types of cells in intestinal glands
Absorptive cells
Goblet cells
Paneth’s cells
Endocrine cells
Stem cells

28. 1. Absorptive cells Tall columnar,
an oval nucleus in the basal half of the cell,
striated border at the apex.
Microvilli
Increasing the area
Absorption
The function of the columnar absorptive cell is the absorption of water, minerals, amino acids, simple sugars, and lipid.    

29. 2. Goblet cells Interspersed between the absorptive cells. duodenum
increasing
jejunum
ileum
Goblet cell secretion of mucin .
The mucus lubricates and forms a barrier which protects the mucosal epithelium from potentially noxious intraluminal substances.

30. 3. Paneth’s cells
Occur in small groups at the base of the intestinal glands.
They have both large eosinophilic secretory granules.
They secrete lysozyme.

31. Large intestine
The mucosa does differ from that of the small intestine in several aspects:
    1. There are no villi.     2. The intestinal glands are larger, more numerous and more densely packed.     3. Numerous goblet cells.     4. There are no Paneth’s cells.

32. Appendix Small, narrow, and irregular lumen.
Abundant lymphoid nodules.
Fewer and shorter intestinal glands.

33. Homework Describe the structure of the stomach fundus gland.
Describe the cell type of the small intestine gland.
Describe the structure of intestinal villi.
What prevents the proteolytic enzymes and low pH from damaging the stomach?