Power point of cardiovascular system

? Lecture Objectives
By the end of this lecture, students are expected to:
1. List and describe the layers of the GIT.
2. Outline the histological features of the three layers of submucosa.
3. Compare the local function and histological features of Meissner and Auerbech plexuses.
4. Outline the different types of epithelium within oral cavity and link this difference to functional adaptation.
5. Summarize the functional and histological structure of submucosal gland.
6. Relate the functional to histological feature of the of layer muscularis externa of the esophagus in a process of swallowing.
7. Outline the structural and functional adaptations of the gastroesophageal glands
8. Outline the difference in histological features of outer layer of esophagus along its course.
Digestive Tract: Introduction
The digestive system consists of the digestive tract; oral cavity, esophagus, stomach, small , large intestines, rectum, and anus and its associated glands; salivary glands, liver, gallbladder and pancreas. Its function is to obtain the molecules necessary for the maintenance, growth, and energy needs of the body from ingested food.

Large molecules such as proteins, fats, complex carbohydrates, and nucleic acids are broken down into small molecules that are easily absorbed through the lining of the digestive tract, mostly in the small intestine. Water, vitamins, and minerals are also absorbed from ingested food. In addition, the inner layer of the digestive tract is a protective barrier between the content of the tract s lumen and the internal milieu of the body.

The first step in the complex process known as digestion occurs in the mouth, where food is moistened by saliva and ground by the teeth into smaller pieces; saliva also initiates the digestion of carbohydrates. Digestion continues in the stomach and small intestine, where the food transformed into its basic components (e.g, amino acids, monosaccharaides, free fatty acids, monoglycerides) is absorbed. Water absorption occurs in the large intestine, causing the undigested contents to become semisolid.

General Structure of the digestive
Based on its histological organization, the wall of the digestive tract can be divided into four tunics (Fig.1).

1. Mucosa is the innermost layer of the digestive wall. It includes epithelium, lamina propria, and muscularis mucosae.

a. The epithelium consists of simple columnar epithelium lining most of the tract and stratified squamous epithelium lining the two ends, the esophagus and anal canal.

b. The lamina propria is a loose connective tissue that contains abundant ground substance, many fibers, and numerous connective tissue cells such as fibroblasts,