III - The pharynx :
The pharynx represents a transition space between the oral cavity and the respiratory and digestive system . It contains the tonsils
IV - Esophagous :
Is a muscular tube whose function is to transport food stuffs from the mouth to the stomach ,the layers that constitute the wall from the lumen to outward are :
• Mucosa , consists of :
1) Epithelium , nonkeratinized stratified squamous ep. T.
2) Lamina propria, thin layer
3) Muscularis mucosa , longitudinal smooth muscle
• Submucosa , is composed of connective tissue with groups of small mucus – secreting glands, the esophageal glands.
• Muscularis externa ,composed of two well defined muscle layers , the inner is circular and the outer is longitudinal. The muscularis externa of the esophagus is highly variable in different species ,in humans , the upper third of esophagus consists of striated skeletal muscle ,the middle third , a mixture of both smooth and skeletal muscle can be seen and in the lower third only smooth muscle is found .
• Adventitia , consists of loose connective tissue .
V-Stomach :
Is an expanded part of the digestive tube that lie under the diaphragum , is divided into :
Cardiac is the superior region , fundic is the body form , and the pyloric, which is the inferior region of the stomach . The stomach wall exhibit four general layers :
• Mucosa
The gastric mucosa consists of a surface epithelium that invaginates to varying extents in to the lamina propria, forming gastric pits . Emptying in to gastric pits are branched, tubular glands ( cardiac, gastric , and pyloric ) characteristic of each region of the stomach .
The lamina propria of the stomach is composed of loose connective tissue interspersed with smooth muscle and lymphoid cells. Separating the mucosa from the underlying submucosa is a layer of smooth muscle ,the muscularis mucosa , this layer is composed of an outer group of longitudinal fibers and circular fibers closer to the lumen .
• Submucosa
Consists of connective tissue with numerous lymph vessels, capillaries, and another contents.
• Muscularis externa
Consists of three layers of smooth muscle in different arrangements(directions) ,the internal is oblique ,the middle is circular, and the external is longitudinal layer.
• Serosa
Is thin and covered by mesothelium.
VI-Small intestine
Is relatively long permitting prolonged contact between food and digestive enzymes .It consists of 3 segments : duodenum, jejunum, and ileum.
• Mucosa :- The small intestine presents folds like finger, known as villi , that change their morphology and decrease in height from the duodenum to the ileum . Villi are elevations of epithelially covered lamina propria .
1-Epithelium, the simple columnar epithelium consists of goblet cells
2-Lamina propria, composed of loose connective tissue ,houses glands, known as the crypts of Lieberkuhn ,that extend to the muscularis mucosae
3-muscularis mucosae , consists of an inner circular and an outer longitudinal layer of smooth muscle .
• Submucosa :- display spiral fold , plicae circulars .
• Muscularis externa , is composed of the usual inner circular and outer longitudinal layers of smooth muscle, with Auerbach, s plexus.
• Serosa :- composed of connective tissue covered with mesothelium.
1- Duodenum:
Has the same layers above ,but it has a characteristic features :-
-Submucosa ,with the mucous duodenal (Bruner,s ) glands.
-Covered with serosa and adventitia.
2- Ileum
Has a lamina propria , with abundant of lymphatic nodules, are known as (Peyer , s patches) .