Organ of the alimentary canal Essay

Organ of the alimentary canal Essay.

Food enters the digestive tract through the mouth. The labia (lips) protect its anterior opening, the cheeks form its lateral walls, the hard palate forms its anterior roof, and the soft palate forms its posterior roof. The space between the lips and cheeks externally and the teeth and gums internally is the vestibule. The area contained by the oral cavity is the oral cavity proper. The tongue occupies the floor of the mouth and has many bony attachments. As food enters the mouth, it is mixed with saliva and masticated (chewed).

This is where the breaking down of food begins.


From the mouth, food passes posteriorly into the pharynx, which is the common path for food, fluids, and air. The pharynx is divided into three sections: the nasopharynx (air from the nose passes here), the oropharynx (food and air from the mouth passes here), and the laryngopharynx (air going to the lungs passes here).The walls of the pharynx contain two skeletal muscle layers.

The cells of the inner layer run longitudinally; those of the outer layer (the constrictor muscles) run around the wall in a circular fashion. Alternating contractions of these muscle layers propells food through the pharynx into the esophagus below. This propelling mechanism is called peristalsis.


The esophagus runs from the pharynx through the diaphram to the stomach. The esophagus conducts food to the stomach by peristalsis. Begining with the esophagus, the walls of the GI tract have a basic pattern that reflects their common functions. Because the tissue arrangement in the alimentary canal walls is modified along its length to serve special functions, here are the basic wall functions for reference.

The walls of the alimentary canal organs from the esophagus to the large intestine have four characteristic layers:

1- The mucosa is the innermost layer. Its a moist membrane that lines the cavity or lumen of the organ. It consists primarily of a surface epithelium, plus small amounts of connective tissue, and a scanty smooth muscle layer. 2- The submucosa is just beneath the mucosa. It is a soft connective tissue layer containing blood vessels, nerve endings, and lymphatic vessels. 3- The mascularis externa is muscle layer made up of a circular inner layer and a longitudinal outer layer of smooth muscle cells. 4- The serosa is the outermost layer of the wall. It consists of a single layer of flat serous fluid-producing cells, the visceral peitoneum. All layers of the alimentary canal wall except the mucosa contain a nerve plexus, and intrinsic network of nerve fibers that is actually part of the autonomic nervous system.

These plexuses help to regulate the mobility of the GI tract organs Stomach

The stomach is a muscular, hollow, dilated part of the digestion system which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects (mid-gut), and molluscs. It is involved in the second phase of digestion, following mastication (chewing). The stomach is located between the esophagus and the small intestine. It secretes protein-digesting enzymes and strong acids to aid in food digestion, (sent to it via oesophageal peristalsis) through smooth muscular contortions (called segmentation) before sending partially digested food (chyme) to the small intestines.

The small intestine (or small bowel) is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms “gastrointestinal tract” and “large intestine” are often used to describe the entireintestine. This article is primarily about the human gut, though the information about its processes is directly applicable to most placental mammals. The primary function of the small intestine is the absorption of nutrients and minerals found in food. [2] (A major exception to this is cows; for information about digestion in cows and other similar mammals, see ruminants.)

large intestine The large intestine (or large bowel) is the last part of the digestive system invertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass useless waste material from the body.[1] This article is primarily about the human gut, though the information about its processes are directly applicable to most mammals. The large intestine consists of the cecum, colon, rectum and anal canal.[1][2][3][4] It starts in the right iliac region of the pelvis, just at or below the right waist, where it is joined to the bottom end of the small intestine. From here it continues up the abdomen, then across the width of the abdominal cavity, and then it turns down, continuing to its endpoint at the anus. The large intestine is about 4.9 feet (1.5 m) long, which is about one-fifth of the whole length of the intestinal canal.

Rectum and Anus The rectum provides temporary storage for feces before they are expelled. As the rectal walls expand due to collecting feces, stretch receptors in the rectal walls stimulate the desire to defecate. Peristaltic waves then push the feces out of the rectum. The anus controls the expulsion of the feces. The flow of feces through the anus is controlled by the anal sphincter muscle. The internal and external sphincter muscles relax, allowing the feces to be passed by muscles and pulling the anus up over the exiting feces.

The accessory organs of digestion include the salivary glands, pancreas, liver, and gallbladder. As stated earlier, during the digestive process, the accessory organs produce secretions that assist the organs of the alimentary canal.

Salivary Glands

The salivary glands are located in the mouth (fig. 1-53). Within the salivary glands are two types of secretory cells, serous cells and mucous cells. The serous cells produce a watery fluid that contains a digestive juice called amylase. Amylase splits starch and glycerol into complex sugars. The mucous cells secrete a thick, sticky liquid called mucus. Mucus binds food particles together and acts to lubricate during swallowing. The fluids produced by the serous and mucous cells combine to form saliva. Approximately 1 liter of saliva is secreted daily.

Pancreas The pancreas is a large, elongated gland lying posteriorly to the stomach (fig. 1-53). As discussed earlier in “The Endocrine System,” the pancreas has two functions: It serves both the endocrine system and the digestive system. The digestive portion of the pancreas produces digestive juices (amylase, proteinase, and lipase) that are secreted through the pancreatic duct to the duodenum. These digestive juices break down carbohydrates (amylase), proteins (proteinase), and fats (lipase) into simpler compounds.

Liver The liver is the largest gland in the body. It is located in the upper abdomen on the right side, just under the diaphragm and superior to the duodenum and pylorus (fig. 1-53).

Of the liver’s many functions, the following are important to remember: · It metabolizes carbohydrates, fats, and proteins preparatory to their use or excretion. · It forms and excretes bile salts and pigment from bilirubin, a waste product of red blood cell destruction. · It stores blood; glycogen; vitamins A, D, and B12; and iron. · It detoxifies the end products of protein digestion and drugs. · It produces antibodies and essential elements of the blood-clotting mechanism.


The gallbladder is a pear-shaped sac, usually stained dark green by the bile it contains. It is located in the hollow underside of the liver (fig. 1-53). Its duct, the cystic duct, joins the hepatic duct from the liver to form the common bile duct, which enters the duodenum. The gallbladder receives bile from the liver and then concentrates and stores it. It secretes bile when the small intestine is stimulated by the entrance of fats.

Organ of the alimentary canal Essay

Erie Canal Essay

Erie Canal Essay.

The Erie Canal was completely built in 1825. Built in New York State, the canal runs from the Hudson River to Lake Erie, which connects the Great Lakes with the Atlantic Ocean. Ultimately, the Canal resulted in a colossal population explosion in Western New York, but perhaps more importantly, it opened regions further to the west for increased settlement. This led to faster transportation routes between the Eastern sea side and the Western interior lands.

This book describes the complicated and fascinating social history of the canal that shrunk time and distance and transformed western New York, brought great wealth to many and opened up the west.

But this progress came at a price and the book explores some of the paradoxes of progress. Carol Sheriff’s book Artificial River: The Erie Canal and the Paradox of Progress explore both the cultural and social impacts that the building of the Erie Canal had on America. Sheriff discusses in great detail the difficulties that resulted in the building of the Canal.

For example, farms were often divided up, businesses were faced with new hardships, and the canal molded nature in a whole new way. While it of course represented progress, the government also took a much greater role than it previously had. For example, as the market expanded, the government took an active role in intervening with economic development. The beginning of the book starts out, “Oysters! Oysters! Beautiful Oysters,” as the headline of a Batavia, New York newspaper stated in 1824.

The achievement of finding Oysters so far from the sea symbolized an extremely notable achievement that had previously seemed impossible. It was a daily reminder to the people living along the Canal that transportation had effectively changed and had re-shaped the lives of millions of everyday Americans. In addition, one of the most interesting facts given by the author is that many people died from drowning during the building of the canal, even though the water was only five feet deep, because very few people during that time period could actually swim.

In addition, a lot of people died in the night for standing on the top of the boat and getting hit by a bridge – giving a new meaning to duck! One of the main themes that the author addressed was the fact that by building the Erie Canal, the population significantly increased in the New York area. However, the Canal brought all sorts of travelers to New York City, as well as Philadelphia and Baltimore, quite possibly the largest and most populous cities at that time. Towns in New York, particularly Rochester, Buffalo, and Schenectady helped contribute a large amount of both wealth and importance to New York.

The Canal helped to increase trade throughout the rest of the nation by opening eastern and overseas markets. In addition, more ethnic communities, such as the Irish, began forming in some of the smaller towns along the routes of the Canal. Irish immigrants made up a huge portion of the labor force involved in the construction, so it was only natural for those working on the Canal to relocate closer to its actual location. The progress and transformation that the Erie Canal brought also brought a new set of challenges for residents and legislators.

The canal split many farms causing great problems to many farmers who wanted bridges to get to their farms, the low bridges were a hazard to canal passengers and traffic. Water diverted for the canal and locks created water shortages though the region. Leaks in the canal caused flooding on some farms and created mosquito infested ponds, which were fertile grounds for malaria epidemics. The author addressed the fact that because so many immigrants traveled on the canal, genealogists have been trying to find passenger manifestos that include complete passenger lists.

However, this has been nearly impossible, as it was not required by law for these ships to include passenger manifestos, thus making it highly unlikely to determine a solid number as to how many traveled via the Canal. However, because of the immense population growth, crime in these areas also increased. For example, Ditch diggers who lived in shantytowns, who drank and cusses, who tore down fences caused consternation among the inhabitants who feared that the county was creating a permanent underclass.

When the digging was done and the diggers gone they were replaces with another underclass, the boat drivers, who drank, cussed, robbed and whored making the areas adjoining the canal crime-ridden. Overall, this was an excellent and very interesting book. Not only was it well-written, it was actually fun to learn about how much the Erie Canal actually changed the lives of everyday Americans. Rarely do history classes, or the History Channel cover such a small topic, yet it truly changed America between the War of 1812 and the Civil War.

Erie Canal Essay