Parts of the nervous and circulatory systems also play major roles in the digestive system. The large, hollow organs of the digestive tract contain a layer of muscle that enables their walls to move. The movement of organ walls can propel food and liquid through the system and also can mix the contents within each organ. Food moves from one organ to the next through muscle action called peristalsis. The first major muscle movement occurs when food or liquid is swallowed.
The pancreas secretes trypsin and chymotripsin. The liver and gall bladder secrete bile, used for the emulsification of fats. The second section of the small intestine, the jejunum, is where the majority of food is absorbed into the bloodstream. The last section of the small intestine, the ileum, is where the remainder of nutrients is absorbed. What is not absorbed by the small intestine passes into the large intestine, which includes the colon and rectum.
Peristalsis also is at work in this organ, moving food through and mixing it with digestive secretions from the pancreas and liver. The duodenum is largely responsible for the continuous breaking-down process, with the jejunum and ileum mainly responsible for absorption of nutrients into the bloodstream. Pancreas-The pancreas secretes digestive enzymes into the duodenum, the first segment of the small intestine. These enzymes break down protein, fats, and carbohydrates. The pancreas also makes insulin, secreting it directly into the bloodstream.
The main goal of the digestive system is to break down large macromolecules (proteins, fats and starch), which cannot be absorbed as-is, into smaller molecules (amino acids, fatty acids and glucose) that can be absorbed across the wall of the tract, into the circulatory system for diffusion around the body, and excretion. There are two types of digestion which are mechanical digestion (breaking food into smaller pieces ie. chewing) and chemical digestion (enzymes ie. salivary amylase). Mechanical digestion in the mouth helps begin chemical digestion by mixing the food with enzyme-containing saliva.
Then the esophagus pushes the food to the stomach, and that’s when things really start to happen! The pancreas which are the two organs in the digestive system, make digestive juices and the juices help digest food breaking –down protein, carbohydrates ,and fat. Every 24 hours, the pancreas sends 1 to 2 pints of digestive enzymes through the pancreatic duct into the duodenum. After the pancreas, comes the liver which is used to dissolve fat and break down even more. From the stomach the food travels through the small intestine, which transfers water and nutrients into the blood and then other parts of the body.
The mouth contains the enzyme amylase which breaks down carbohydrate chains. The food then travels to the esophagus, which is a tube that connects the pharynx to the stomach. Wave-like contractions also called peristalsis aid in pushing the food down to the stomach. The stomach produces hydrochloric acid and pepsinogen. The hydrochloric acid helps convert pepsinogen to pepsin which is needed for protein digestion.
BIOH12008 Human Pathophysiology Assessment 1 The small intestine is the organ responsible for the absorption of most nutrients. Digested food passes into the blood vessels and into the wall of the small intestine, this process is call diffusion. The inside wall of the small intestine is called the mucosa, and is lined with columnar epithelial tissue; the mucosa is covered in folds called plicae circulares. The villi in the small intestine are small finger like projections that protrude from the epithelial lining of the intestinal wall. These minuscule projections are approximately 1mm high and play a number of roles in the human body.
The small intestine is the principal site of digestion and absorption. Enzymes from the pancreas, liver, gallbladder, and the small intestine itself combine to break down nutrients so that they can be absorbed. The pancreas supplies enzymes to digest proteins, fats and carbohydrates. The live produces bile required for emulsification of fat, and the gallbladder stores the bile until it is needed. The absorption of nutrients in the small intestine is facilitated by tiny projections called villi, which provide more surface area for absorption.
The lymphatic system is made up of lymphatic vessel and lymphatic organs. The lymphatic system has four main functions; lymphatic capillaries absorb excess tissue fluid and return it to the bloodstream. In the small intestines, lymphatic capillaries called lacteals absorb fats in the form of lipoproteins and transport them to the bloodstream. The lymphatic system also is responsible for the production, maintenance and distribution of lymphocytes. It also helps defend the body against pathogens.
Digestion of carbohydrates begins in the mouth as mentioned earlier with the enzyme amylase which is present in the saliva. This breaks the carbohydrates into their simpler subunits (saccharide forms). In the stomach, the carbohydrates are converted into chyme with the peristaltic action of the stomach. Next, the chyme will pass into the duodenum. At the introduction to the duodenum, alpha amylase is secreted by the pancreas and further breaks down the carbohydrates into primary simple sugars.