Oesophagus
• Normally esophagus lumen is collapsed with longitudinal mucosal folds. Functionally it is a passage for bolus of food.
• Four layers of gastrointestinal (GI) tract-mucosa, submucosa, muscularis externa, adventitia/serosa.
1. Mucosa
-Epithelium made of non-keratinized stratified squamous epithelium
-Lamina propria---loose connective tissue with blood vessels.
-Muscularis mucosa is two layered-inner longitudinal, outer circular (smooth muscle).
2. Submucosa-loose connective tissue with blood vessels and nerves. Also contains mucus secreting esophageal glands. The secretions from the glands helpin
lubrication of lumen and protect the mucosa.
3. Muscularis externa-inner circular, outer longitudinal layer. Muscle fibers are skeletal muscle proximally, mixed in the middle portion and distally only smooth muscle.
4. Adventitia/serosa---loose connective tissue called adventitia with blood vessels and nerves.
Stomach - Fundus
• Mucosal folds of stomach are called rugae, are temporary.
• It has four layers-mucosa, submucosa, muscularis externa, serosa.
1. Mucosa
-Lining epithelium is simple columnar type. Invagination of surface lining into the lamina propria is called gastric pit which is shallow. Depth of gastric pits is about
one-third of thickness of mucosa.
-Lamina propria filled with simple straight tubular gastrie glands which open into bottom of the pits. -Gastric glands lined by parietal cell, chief cell, mucus neck
-Muscularis mucosa-inner circular and outer longitudinal layer of smooth muscles.
2. Submucosa-loose connective tissue with blood vessels and nerves.
3. Muscularis externa (three layers)-Inner oblique, middle circular, outer longitudinal smooth muscle
4. Serosa - membrane made of a simple squamous epithelium.
• Parietal cells also called oxyntic cells. They secrete gastric acid and intrinsic factor. Cells are large and eosinophilic: present in the upper part of the glands.
•Chlef cells also called rymogen cells. They secrete pepsinogen. They are basophilic, present in the lower part of glands.
• Mucus neck cells--secrete mucus which helps in protection of mucosa.
cells.
Stomach - Pylorus
•It has four layers-mucosa, submucosa, muscularis externa and serosa.
1. Mucosa:
-Lining epithelium is simple columnar type. Shows depressions called gastric pits which are deeper occupying two-third of thickness of mucosa.
-Lamina propria filled with pyloric glands which are colled tubular type, open into base of pits.
-Glands lined by mucous secreting cells, few parietal cells present.
-Muscularis mucosae made of inner circular and outer longitudinal layers.
2. Submucosa-loose connective tissue with numerous blood vessels, lymphatics and nerve fibers.
3. Muscularis externa has three layers-inner oblique, middle circular, outer longitudinal smooth muscle.
4. Serosa-membrane made of a simple squamous epithelium.