Layers:
1. Mucosa: This is the innermost layer and is directly exposed to the food. It consists of:
* Epithelium: A single layer of columnar epithelial cells that are responsible for secreting mucus and gastric juices.
* Lamina propria: A layer of connective tissue containing blood vessels, nerves, and glands.
* Muscularis mucosae: A thin layer of smooth muscle that helps move the mucosa.
2. Submucosa: A layer of connective tissue containing blood vessels, nerves, and lymph vessels.
3. Muscularis propria: A layer of smooth muscle that contracts to churn the food and move it along the digestive tract. This layer has three distinct sub-layers:
* Oblique layer: Innermost layer, running diagonally.
* Circular layer: Middle layer, running in a circular pattern.
* Longitudinal layer: Outermost layer, running lengthwise.
4. Serosa: The outermost layer, composed of a thin layer of epithelial cells and connective tissue.
Specialized Features:
* Gastric pits: These are invaginations of the mucosa that lead to gastric glands.
* Gastric glands: These glands are responsible for secreting gastric juice, which contains:
* Hydrochloric acid (HCl): This strong acid breaks down food and kills bacteria.
* Pepsinogen: An inactive enzyme that is converted to pepsin in the presence of HCl. Pepsin breaks down proteins.
* Mucus: This protective layer lubricates the stomach and prevents it from digesting itself.
* Rugae: The mucosa is folded into ridges called rugae, which increase the surface area of the stomach.
Function:
The lining of the pig stomach plays a vital role in digestion. It:
* Mechanically breaks down food: The muscularis propria churns and mixes the food.
* Chemically breaks down food: Gastric juice digests proteins and kills bacteria.
* Protects the stomach: Mucus prevents the stomach from digesting itself.
Interesting facts:
* The lining of the pig stomach is highly acidic, with a pH of 1-3.
* The stomach can hold about 1 gallon of food.
* The pig stomach is similar to the human stomach in its structure and function.
Understanding the lining of the pig stomach is essential for understanding the digestive process and for studying animal physiology.