1. Hassall's corpuscles are a unique and characteristic feature of:
(A) spleen.
(B) thymus.
(C) lymph nodes.
(D) bone marrow.
(E) tonsils.

2. Lymphatic nodules are found in:
(A) cortex of lymph nodes
(B) tonsils
(C) spleen
(D) respiratory and gastrointestinal mucosa.
(E) all of the above

3. Which of the following statements concerning epithelial reticular cells of the thymus is FALSE ?
(A) They are supporting cells.
(B) They are not located in the thymic medulla.
(C) They have long processes.
(D) They assist in forming the blood-thymus barrier.

4. Department of Histology and Embryology
Digestive System
Department of Histology and Embryology
Yu Hongwei

5. 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 small intestine.

6. Digestive System
oral cavity, esophagus, stomach, small and large intestines, rectum, and anus.
Digestive tract:
small gland: fundis gland, small intestinal gland
large gland: salivary gland, pancreas, liver
Digestive glands:

7. Digestive System Figure 14.1 Slide 14.1
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

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

9. A.Mucosa 1.Epithelium: is highly variable.
contains connective tissue that is rich capillaries and lymphatic tissues.
2.Lamina propria:
3.Muscularis mucosae:
is a thin layer smooth muscle fibers

10. B.Submucosa C.Muscularis D.Adventitia
dense connective tissue, many blood , lymph vessels , glands
C.Muscularis
smooth muscle fibers
D.Adventitia

11. Gastrointestinal (GI) Tract Wall
Figure 14.2
Slide 14.2A
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.

13. Digestive System Function
Mechanical processing and movement: chewing, mixing
Secretion: fluid, digestive enzymes and hormones, bile, acid, alkali, mucus
Digestion: breaking down food to smallest absorbable units
Absorption: through mucosa, into blood or lymph vessels
Elimination: undigested material eliminated
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
Slide 14.3

14.  Tongue 1.Layers 2.Papillae 3.Taste bud Skeletal muscle fibers
Stratified squamous epithelium
Lamina propria, Connective tissue
Circumvallate papillae
Filiform papillae
Fungiform papillae
Foliate papillae
3.Taste bud

15. 2.Papillae Circumvallate papillae Filiform papillae Fungiform papillae
Foliate papillae

16. 3.Taste bud
Figure. showing the taste cells and the taste pore. The drawing also illustrates several cell types (basal, taste, and supporting) and afferent nerve fibers that, upon stimulation, will transmit the sensory information to the central gustatory neurons.

17. Taste bud
These are clustered in taste buds. Each taste bud has a pore that opens out to the surface of the tongue enabling molecules and ions taken into the mouth.

18. There are five primary taste sensations: salty sour sweet bitter
Taste bud
There are five primary taste sensations:
salty
sour
sweet
bitter
Umami is the response to salts of glutamic acid,a flavor enhancer used in many processed meats and cheeses.

19. Taste bud

20. Ⅰ.Salivary glands
Minor salivary glands
Major salivary glands
Parotid, submandibular and sublingual glands

21. Source: parotid, submandibular, sublingual salivary glands
Functions
Produce saliva, to wet and lubricate the oral cavity and initiate the digestion of carbohydrates and lipids, and protective functions
Saliva
Source: parotid, submandibular, sublingual salivary glands
Composition: mucin, salivary amylase, bicarbonate, lysozyme

22. 1. General structure

23. myoepithelial cells
they are contractile epithelial cells, they are located between the secretory cells and the basement membrane.  
Each myoepithelial cell has long cytoplasmic processes which wrap around a secretory unit.  Hence, contraction of the myoepithelial processes can squeeze secretory product from the secretory unit into its duct.

25. Serous acini

26. Mucous acini

27. Mixed acini

28. 2. Type-specific structure
Parotid glands
Contain only serous acini.
Submandibular glands
Serous demilunes are numerous.
Have mucous acini associated with serous demilunes.
Sublingual glands
Are composed almost exclusively of mucous acini.

30. Parotid glands

31. Submandibular glands

32. Sublingual glands

33. Duct system Intercalated ducts Striated ducts Excretory ducts
lined by a low cuboidal epithelium, many contain myoepithelial cells.
Striated ducts
lined by columnar cells. They have prominent basal surface invaginations associated with many mitochondria.
Excretory ducts
Lined simple cuboidal, Are the larger ducts that empty into the oral cavity.

35. A.Mucosa B.Submucosa C.Muscularis D.Adventitia ESOPHAGUS 1.Epithelium:
2.Lamina propria:
3.Muscularis mucosae:
B.Submucosa
dense CT
(Esophageal submucosal glands, blood)
The upper one third
Skeletal muscle
C.Muscularis
The middle third
Intermix
The distal third
Smooth muscle
D.Adventitia

37. Esophageal mucosa
Esophageal submucosal glands

39. Gastroesophageal Reflux Disease
Reflux of gastric contents into esophagus
Result of Transient LES relaxations

40. Mucosa Submucosa Muscularis Adventitia
Ⅰ. Stomach
1.Epithelium:
Mucosa
2.Lamina propria:
Glands, lymphoid tissue
3.Muscularis mucosae:
Smooth muscle
Submucosa
DCT
Muscularis
Three layers
Adventitia

41. Regions of the stomach and their histological structure.

42. C. Glands 1.Surface mucous cells 2.Mucous neck cells 3. Chief cells
Glands are present throughout the fundus and corpus.
pit
1.Surface mucous cells
2.Mucous neck cells
glands
3. Chief cells
4.Parietal cells
5. Stem cells
6.Endocrine cells

44. 1. Surface mucous cells
a. They form a simple columnar epithelium that covers the gastric mucosa.
b. They secrete a continuous mucous layer that prevents the proteinase solutions in the stomach.

45. 2.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.

46. 3. 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

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

48. 5.Stem cells Found in the isthmus and neck regions.
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.

49. 6. Endocrine cells
a. In the neck and base of gastric glands

50. Stomach Function
Functions: food storage, digestion, regulation of delivery.
Gastric juice:
--Hydrochloric acid: breaks down large of food
Intrinsic factor; made by cells making acid,
Mucus: protects stomach lining from acid
Pepsinogen: with acid, breakdown the protein
Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc.
Slide 14.9B

51. pernicious anaemia.
Vitamin B12's primary functions are in the formation of RBC and the maintenence of a nervous system.
Absorption of B12 requires the secretion of intrinsic factor.
Certain people are unable to produce intrinsic factor.

52. What prevents the proteolytic enzymes and
low pH from damaging the stomach?
A thick coat of bicarbonate containing mucus coats the stomach wall.
Mucosal epithelial cells are joined by tight junctions
Damaged epithelial cells are shed & quickly replaced.

54. Ⅱ. 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.

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

57. B. Mucosa
1. The epithelium of intestine villi
2. Intestinal glands (intestinal crypts)
3. Five types of cells in intestinal mucosal epithelium
Absorptive cells
Goblet cells
Paneth’s cells
Endocrine cells
Microfold cells

61. a. Absorptive cells (Enterocytes)
Tall columnar
an oval N in the basal of the cell
striated border at the apex
microvilli
Increasing the area
Absorption

62. absorptive cell
The function of the columnar absorptive cell is the absorption of water, minerals, amino acids and simple sugars.    

63. Absorption of Proteins and Carbohydrates
Figure 14.13
Slide 14.14A

64. Absorption of Fats
Figure 14.14
Slide 14.14B

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

66. The Paneth cells
occur in small groups at the base of the intestinal crypt.
These have both phagocytic and secretory properties
They secrete lysozyme (which dissolves the cell wall of bacteria) and secretory IgA.

68. Peyer‘s patches Peyer‘s patch
Appears as a dome shape area lack of villi.
the covering epithelium consist of M cells.
villi
Peyer‘s patch

69. M cells (microfold cells)
are specialized epithelial cells overlying the lymphoid follicles of Peyer‘s patches.
M cells can endocytose antigens and transport them to the underlying macrophages and lymphoid cells. Which then migrate to other compartments of lymphoid system (nodes).

70. 1. intestinal villi Absorptive cells epithelium Goblet cells
Blood capillary
Smooth muscle
Lamina propria
Lymphatic capillary
Lymphocytes
Plasma cells
macrophages

71. 2. Intestine glands (intestine crypts)
Absorptive cells
Goblet cells
Paneth’s cells
epithelium
Enteroendocrine cells
Stem cells

72. Small Intestine Functions:
Digestion: neutralize acid from stomach, add digestive enzymes and bile, break proteins, carbohydrates and lipids to absorbable materials
Absorption: 95% of food absorbed here
Slide 14.10B

73. Location: in submucosa of duodenum.
BRUNNER GLANDS
Location: in submucosa of duodenum.
Function: protection the proximal small intestine by neutralizing the acid-containing chyme.

74. Ⅲ. Large intestine
The mucous membrane does differ from that of the small intestine in several aspects:
    1. There are no villi.     2. The intestinal crypts are larger, more numerous and more densely packed.     3. One-fourth of the epithelial cells are goblet cells. Thus the large intestine is well lubricated             4. There are no Paneth cells.

75. Large intestine

76. Appendix

77. Appendicitis
It is thought that the opening from the appendix into the cecum becomes blocked.
The lymphatic tissue in the Appendix may swell and block the Appendix.
Bacteria which normally are found within the appendix then begin to invade the wall of the Appendix.

78. Homework Describe the structure of the stomach fundus gland.
Describe the cell type of the small intestine.