THE ALIMENTARY CANAL
The alimentary canal, or the digestive tract as it is most commonly known, is 9 meters from the oesophagus to the anus. Digestion begins at the mouth, where food is chewed and mixed with saliva, which adds moisture and contains the enzyme amylase that begins to break down starches. The tongue moulds the food into a ball mass, known as the bolus.
In the small intestines is where most of the digestion occurs because different enzymes, released by the pancreas and by glands in the intestinal wall, affect each food molecule in the chyme. At the end of this laborious process, each complex molecule has been broken down into its simple states. For example, carbohydrates are broken down into simple sugars, the protein into amino acids, and the fats into glycerol and fatty acids. As chime reaches the end of the ileum, it must then pass through a valve into the Cecum (the first section of the colon) this Ileocecal valve is normally closed, but opens as chime reaches it. (Any water from a colonic does not go back through this valve into the small intestine is the valve is functioning properly.
Nutrients are absorbed into the blood stream through five million finger-like projections and folds called villi, which line the walls.
Large intestines (colon)
1.2 – 1.5 meters length. 6.35 centimetres round. Substances that cannot be broken down by the body pass through the large intestine, or the colon, where the last of the water, ions, and salts are reabsorbed,
The remaining solid material, called faeces, exits through the anus. Thus, the alimentary canal is a passageway for food to be transported, absorbed, and released.
Pockets
A smooth, mucous membrane lines the villi-free walls of the colon. A small amount of alkaline mucus is secreted from glands in the wall, protecting the delicate lining from too much acidity or abrasive waste matter. The colon has many pouches or pockets, called haustras, which contain layers of muscle that allow the colon to expand whenever necessary to accommodate varying amounts of solid matter. These muscles regularly make rhythmic contractions and relaxations called peristalsis, which slowly mix and move the bowel content along.
THE LARGE INTESTINE “ COLON ”
The vermiform appendix ( appendixes )
is a blind ended tube connected to the Cecum. It develops embryologically from the cecum. In adults, the appendix averages 10 cm in length but can range from 2-20 cm. The diameter of the appendix is usually less than 7-8 mm. While the base of the appendix is at a fairly constant location, the location of the tip of the appendix can vary from being retrocaecal to being in the pelvis to being extraperitoneal . In most people, the appendix is located at the lower right quadrant of the abdomen. In people with situs inversus , the appendix may be located in the lower left side.
Cecum
The Cecum is a approximately 6.35 centimeter blind end pouch that forms the first part of the colon .
Ascending colon
This section is wider near the Cecum and narrows as it approaches a 90º bend called the hepatic (liver) flexure. Chime must move slowly uphill against gravity, and then make a sharp turn. If eliminations are sluggish, the ascending colon can become very distended and congested.
Transverse colon
This is the largest and most movable section of the colon. It makes another 90º bend on the persons left side, called the splenic (spleen) flexure. It will sag or prolapse from the weight of solid matter remaining in the colon too long.
Descending colon
The colon then descends 12 – 15 centimeters before connecting to the sigmoid section
Sigmoid colon
This is the narrowest part of the colon and is approximately 40.6 centimeter long. It is shaped like an “S” to prevent solid waste matter from emptying to quickly into the rectum.
Rectum
This is the final part of the colon. It is approximately 30.5 centimeter long
Anus
The Anus is the external sphincter that closes off the rectum from the outside of the body. It is a ring of muscles. It can easily stretch to about 2.5 centimetres diameter.
