Presentation on theme: "Digestive System Department of Histology and Embryology Zhang Xi-Mei."— Presentation transcript:
Digestive System Department of Histology and Embryology Zhang Xi-Mei
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.
Digestive Tract Ⅰ.GENERAL STRUCTURE OF THE DIGESTIVE TRACT Lamina propria Submucosa Muscularis Adventitia Mucosa Epithelium Muscularis mucosae
A.Mucosa 2.Lamina propria: is highly variable. 3.Muscularis mucosae: 1.Epithelium: contains loose connective tissue that is rich capillaries, lymphatic tissues, and glands. smooth muscle fibers.
B.Submucosa dense connective tissue, many blood, lymph vessels. C.Muscularis smooth muscle fibers D.Adventitia Serosa or fibrosa.
ESOPHAGUS A.Mucosa 2.Lamina propria: esophageal cardiac glands. B.Submucosa C.Muscularis D.Adventitia 1.Epithelium:nonkeratinized stratified squamous epithelium. Skeletal muscle dense CT Esophageal glands, mucus-secreting. 3.Muscularis mucosae: longitudinal smooth muscles. The middle one third The distal one third The upper one third Intermix Smooth muscle Fibrosa.
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.
Diagram of a chief cell 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. pepsinogenpepsin H + Chief cell Parietal cell
Diagram of a parietal cell 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.
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. Stem cells a. Found in neck regions. Enteroendocrine cells In base of gastric glands.
Small intestine A. Basic anatomy duodenum, jejunum, ileum Plicae circulares, villi, and microvilli increase the absorptive surface area of small intestine. Plicae circulares, villi, and microvilli increase the absorptive surface area of small intestine. Structure of small intestine
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
1. Absorptive cells Microvilli Absorption Tall columnar, an oval nucleus in the basal half of the cell, striated border at the apex. Increasing the area The function of the columnar absorptive cell is the absorption of water, minerals, amino acids, simple sugars, and lipid.
increasing 2. Goblet cells Interspersed between the absorptive cells. duodenum Goblet cell secretion of mucin. The mucus lubricates and forms a barrier which protects the mucosal epithelium from potentially noxious intraluminal substances. jejunum ileum
Occur in small groups at the base of the intestinal glands. They have both large eosinophilic secretory granules. They secrete lysozyme. 3. Paneth’s cells
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.
Appendix Small, narrow, and irregular lumen. Abundant lymphoid nodules. Fewer and shorter intestinal glands.
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?