Compendium Review Chapter 8

The gastrointestinal tract is where all the tubes are located for the organs of the digestive system. Some molecules are too big so they can’t get across the plasma membrane. The purpose is to break down these macromolecules to their unit molecules. Mainly sugars, amino acids, fatty acids and glycerol, can cross plasma membranes. Our food also has water salts, vitamins, and minerals that helps our body function normally.

These functions are necessary to our digestive process:

Ingestion: happens when the growth lets food in and can have something to do with our diet. That’s why learning good nutrition is highly important.

Digestive: mechanical or chemical mechanical is when food is divided into pieces that might be used by the digestion enzymes. Chewing our food good before swallowing it helps with digestion. A chemical process begins in the mouth and isn’t complete until food reaches the small intestine.

Absorption: when unit molecules are produced by digestion and cross the wall of the GI tract then enter the cells that are lining the tract. After that the nutrients enter the blood to be delivered to the cells.

Elimination: molecules that can’t be digested have to be eliminated. It is removed from the anus in the form of feces which is defecation.

The four layers of the digestive tract

First layer of the wall is called the mucosa also known as the mucous membrane. It produces mucus which protects the walls from the digestive enzymes. In the mouth, stomach and small intestine mucosa has glands that secrete or receive digestive enzymes.. Divertulosis is a portion of mucous that has pushed through and formed layers so pouches can be created.

Second layer the GI wall is called the sub mucosa. This layer contains loose connective tissue that contains blood vessels, lymphatic vessel, and nerves. All these vessels will carry the nutrients that were absorbed by the mucosa.

Third layer is the muscular which contains two layers of smooth muscle. Inner layer encircles the tract. The outer layer lies in the same way as the tract. When these muscles contract it accounts for movements of digestion of food from the esophagus to the anus.

Fourth layer of the tract is serosa. The secrete contains a serous fluid that is a part of the peritoneum, which is the inner lining of the abdominal cavity.

First part of digestive tract
The first couple parts of the digestive tract are the mouth, pharynx, and the esophagus.

Mouth: Mechanical digestion occurs when the teeth chew food into little pieces in order to swallow them. The first two years of life we have 20 smaller teeth also known as our baby teeth. Then we eventually get 32 adult teeth. In addition to the 32 teeth you also might gain a third pair of molars or also called wisdom teeth. These don’t always come through so then they might have to be removed. Each tooth has two main divisions a crown and a root.

Crown: layer of enamel with a hard outer covering of calcium, dentin a thick layer of bone like material, an inner pulp that contains nerves and blood vessels.

Root: dentin and pulp found in the root.
The pharynx and the esophagus
Mouth and nasal passages lead to a cavity which is the pharynx. Food passage and air passage cross the pharynx because the trachea is an anterior to the esophagus.

Esophagus: a long narrow tube that takes our food to the stomach.
The stomach and small intestine

The stomach: is a thick J shaped wall that is the left side beneath the diaphragm. The stomach stores food and.initiates the digestion of protein and controls the movement of chime into the small intestines. The stomach normally empties in 2-6 hours. When food leaves it is a think, soupy liquid which is called chime. That liquid then enters the small intestine in small amounts.

Small intestine: is small in diameter but big in length. It is about 18 feet long and contains enzymes to digest different types of foods. These foods are primarily carbohydrates, proteins and fats. The wall of the small intestine absorbs molecules namely sugars, amino acids, fatty acids and glycerol, that are products of the digestive process. Nutrients are absorbed into the vessels of a villus which contains blood capillaries and small lymphatic capillary. Vessels carry fluid to the cardiovascular system then sugars, amino acids enter blood capillaries of villus. Glycerol and fatty acids enter the epithelial cells of villus and with each cell are joined packaged as lipoprotein droplets called chylomicreins which enter a lacteal. After nutrients are absorbed they are the taken to the cells of the body by the bloodstream.
Three accessory organs and regulation of secretions

Pancreas: fish shaped spongy, grayish pink organ that goes across the back of the abdomen which is behind the stomach. It is also an endocrine gland that secretes the hormone in insulin into the blood. This works when blood glucose levels rise but the pancreas produces a lot of insulin so that the level comes down.
The liver is the largest major metabolic gland in our bodies and is mainly in the upper right sections of the abdominal cavity under the diaphragm. It contains about 100,000 lobuis that are structural and functional units. Liver is a storage unit and it removes iron and vitamins A,D,E,K and B 12 from the blood and stores theandm.

The liver produces glucose in order for food to get broken down.
The large intestine has the cecum, the colon, the rectum and the anal canal. Functions of the large intestine are to absorb water that is really valuable for use. It prevents the body from dehydration and absorbs vitamins that are produced by bacteria.

Classes of nutrients
Carbohydrates: products such as refined grains
Proteins: vegetables, seeds and nuts also grains supply us with amino acids
Lipids: oils containing fatty acids
Corn and sunflower oil are high in polyunsaturated fatty acids