Digastive system

Digestive System

The digestive system consists of the digestive tract extended from oral cavity, mouth , esophagus, stomach , small and large intestine, rectum and anus and digestive glands , salivary gland , pancreas , liver , and gallbladder . The digestive tract is a hollow tube composed of four (4) principal layers from the lumen outward :
• Mucosa , consisting of a lining epithelium , an underlying connective tissue called the Lamina propria , and a muscularis mucosae ,composed of smooth muscle
• Submucosa , consisting of dense irregular connective tissue
• Muscularis externa , consisting of two layers of muscle
• Serosa , consisting of a simple squamous epithelium, the mesothelium , and a small amount of underlying connective tissue

Oral cavity
The oral cavity is lined with nonkeratinized stratified squamous epithelium
I- Lip :
In the lips a transition from nonkeratinized to keratinized epithelium can be observed ,the lamina propria has papillae. A submucosa containing diffuse small salivary glands (tubuloacinar labial glands) , and has a core of skeletal muscle, which called Orbicularis oris .