What is the difference between digestive system and alimentary canal

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What are the names of the tissue layers of the stomach? What are dimensions of the small intestine? What are reasons to explain why the small intestine Where does the process of digestion begin? Are nutrients absorbed from the large intestine? In contrast, accessory organs are responsible for the chemical digestion of food by secreting enzymes. Some of them include the salivary glands, the gallbladder, liver, and pancreas.

What is the Gastrointestinal Tract — Correspondence 3. The alimentary canal is one of the two organ systems of the digestive system, the other being the accessory organs. The other names for alimentary canal include gastrointestinal tract GIT , digestive tract, digestive tract, gut, etc. Moreover, the main functions of the alimentary canal include digesting food, absorbing nutrients, and eliminating waste. Generally, it is 25 feet long.

The organs of the alimentary canal include the mouth, pharynx, esophagus , stomach, small and large intestines , and the anus. Figure 1: Digestive System. Furthermore, the mouth is the opening of the alimentary canal.

It is also important for the intake of food. Hormones secreted by several endocrine glands, as well as endocrine cells of the pancreas, the stomach, and the small intestine, contribute to the control of digestion and nutrient metabolism.

In turn, the digestive system provides the nutrients to fuel endocrine function. Table 1 gives a quick glimpse at how these other systems contribute to the functioning of the digestive system.

The easiest way to understand the digestive system is to divide its organs into two main categories. The first group is the organs that make up the alimentary canal. Accessory digestive organs comprise the second group and are critical for orchestrating the breakdown of food and the assimilation of its nutrients into the body. Accessory digestive organs, despite their name, are critical to the function of the digestive system.

The main function of the organs of the alimentary canal is to nourish the body. This tube begins at the mouth and terminates at the anus. Between those two points, the canal is modified as the pharynx, esophagus, stomach, and small and large intestines to fit the functional needs of the body. Both the mouth and anus are open to the external environment; thus, food and wastes within the alimentary canal are technically considered to be outside the body. Each accessory digestive organ aids in the breakdown of food.

Within the mouth, the teeth and tongue begin mechanical digestion, whereas the salivary glands begin chemical digestion. Once food products enter the small intestine, the gallbladder, liver, and pancreas release secretions—such as bile and enzymes—essential for digestion to continue. Together, these are called accessory organs because they sprout from the lining cells of the developing gut mucosa and augment its function; indeed, you could not live without their vital contributions, and many significant diseases result from their malfunction.

Even after development is complete, they maintain a connection to the gut by way of ducts. Throughout its length, the alimentary tract is composed of the same four tissue layers; the details of their structural arrangements vary to fit their specific functions.

Starting from the lumen and moving outwards, these layers are the mucosa, submucosa, muscularis, and serosa, which is continuous with the mesentery. Figure 2. The wall of the alimentary canal has four basic tissue layers: the mucosa, submucosa, muscularis, and serosa.

The mucosa is referred to as a mucous membrane, because mucus production is a characteristic feature of gut epithelium. The membrane consists of epithelium, which is in direct contact with ingested food, and the lamina propria, a layer of connective tissue analogous to the dermis.

In addition, the mucosa has a thin, smooth muscle layer, called the muscularis mucosa not to be confused with the muscularis layer, described below. As its name implies, the submucosa lies immediately beneath the mucosa. A broad layer of dense connective tissue, it connects the overlying mucosa to the underlying muscularis. It includes blood and lymphatic vessels which transport absorbed nutrients , and a scattering of submucosal glands that release digestive secretions.

Additionally, it serves as a conduit for a dense branching network of nerves, the submucosal plexus, which functions as described below. The third layer of the alimentary canal is the muscalaris also called the muscularis externa. The muscularis in the small intestine is made up of a double layer of smooth muscle: an inner circular layer and an outer longitudinal layer.

The contractions of these layers promote mechanical digestion, expose more of the food to digestive chemicals, and move the food along the canal. In the most proximal and distal regions of the alimentary canal, including the mouth, pharynx, anterior part of the esophagus, and external anal sphincter, the muscularis is made up of skeletal muscle, which gives you voluntary control over swallowing and defecation.

The basic two-layer structure found in the small intestine is modified in the organs proximal and distal to it. The stomach is equipped for its churning function by the addition of a third layer, the oblique muscle. While the colon has two layers like the small intestine, its longitudinal layer is segregated into three narrow parallel bands, the tenia coli, which make it look like a series of pouches rather than a simple tube.

The serosa is the portion of the alimentary canal superficial to the muscularis. Present only in the region of the alimentary canal within the abdominal cavity, it consists of a layer of visceral peritoneum overlying a layer of loose connective tissue. Instead of serosa, the mouth, pharynx, and esophagus have a dense sheath of collagen fibers called the adventitia. These tissues serve to hold the alimentary canal in place near the ventral surface of the vertebral column.