Question

1.)

A. Explain the ANATOMICAL similarities and differences for each of the 4 basic layers of the wall of the esophagus vs stomach.

B. Why are the functions of layers 1, 3 and 4 different in the esophagus vs stomach.

Answer 1

Layers of GI tissue

The GI tract is composed of four layers. Each layer has different tissues and functions. From the inside out they are called: mucosa, submucosa, muscularis, and serosa.

The mucosa is the innermost layer, and functions in absorption and secretion. It is composed of epithelium cells and a thin connective tissue.

The most variation is seen in the epithelium tissue layer of the mucosa.

· In the esophagus, the epithelium is stratified, squamous, and non-keratinizing, for protective purposes.

· In the stomach. the epithelium is simple columnar, and is organized into gastric pits and glands to deal with secretion.

Anatomy of the Stomach

The stomach is a J-shaped organ in the upper belly (abdomen). It’s part of the digestive system. It’s between the end of the food pipe (esophagus) and the start of the first part of the small bowel (duodenum).

The stomach is much like a bag with a lining. The stomach is made of these 5 layers:

· Mucosa. This is the first and innermost layer or lining. It contains the glands that release digestive juices. These are called hydrochloric acid and pepsin. This is where most stomach cancers start.

· Submucosa. This second layer supports the mucosa. It is made up of connective tissue that contains larger blood and lymph vessels, nerve cells and fibres.

· Muscularis. The third layer is made of thick muscles. They help to mix food with the digestive juices.

· Subserosa. This layer contains supporting tissues for the serosa.

· Serosa. the fibrous membrane that covers the outside of the stomach .This is the last and outermost layer. It’s the lining that wraps around the stomach to confine it.

layer of esophageal wall

The esophageal wall contains four layers:

• mucosa—surface epithelium, lamina propria, and glands
• submucosa—connective tissue, blood vessels, and glands
• muscularis (middle layer)
  • upper third, striated muscle
  • middle third, striated and smooth
  • lower third, smooth muscle
• tunica adventitia—connective tissue that merges with connective tissue of surrounding structures