The layer of the alimentary canal where goblet cells are present is the Mucosa layer.

Goblet cells are specialized columnar epithelial cells that secrete mucus. They are found in various parts of the body, including the respiratory tract, reproductive tract, and digestive tract. In the alimentary canal, goblet cells are present in the mucosa layer.

Layers of the alimentary canal:
The alimentary canal is the long tubular structure that extends from the mouth to the anus. It is composed of four main layers, which are:

1. Serosa:
- The outermost layer of the alimentary canal.
- Composed of connective tissue and a layer of simple squamous epithelium.
- It provides protection and support to the digestive organs.

2. Muscularis:
- The layer of smooth muscle that surrounds the other layers of the alimentary canal.
- Responsible for the movements of the digestive tract, such as peristalsis.
- It consists of two layers of smooth muscle, an inner circular layer, and an outer longitudinal layer.

3. Submucosa:
- A layer of connective tissue that lies beneath the mucosa.
- Contains blood vessels, lymphatic vessels, and nerves.
- It provides support and nourishment to the mucosa.

Mucosa:
- The innermost layer of the alimentary canal.
- Composed of three layers: epithelium, lamina propria, and muscularis mucosae.
- The epithelium is made up of various types of cells, including goblet cells.
- Goblet cells are scattered among the columnar epithelial cells in the mucosa.
- They secrete mucus, which helps to lubricate and protect the lining of the digestive tract.

Functions of goblet cells:
1. Secretion of mucus: Goblet cells are responsible for the production and secretion of mucus in the digestive tract. Mucus helps to protect the lining of the digestive tract from mechanical damage, acid, and enzymes.

2. Lubrication: The mucus secreted by goblet cells helps to lubricate the passage of food through the digestive tract, making it easier for food to move along.

3. Protection: The mucus produced by goblet cells forms a protective barrier that helps to prevent the epithelial cells in the mucosa from coming into direct contact with potentially harmful substances.

Summary:
Goblet cells, which secrete mucus, are present in the mucosa layer of the alimentary canal. They play a crucial role in protecting and lubricating the digestive tract.