As peristalsis continues, the waste products of the digestive process move into the large intestine. Large intestine. Waste products from the digestive process include undigested parts of food, fluid, and older cells from the lining of your GI tract.
The large intestine absorbs water and changes the waste from liquid into stool. Peristalsis helps move the stool into your rectum. The lower end of your large intestine, the rectum, stores stool until it pushes stool out of your anus during a bowel movement.
Watch this video to see how food moves through your GI tract. As food moves through your GI tract, your digestive organs break the food into smaller parts using:. The digestive process starts in your mouth when you chew. Your salivary glands make saliva , a digestive juice, which moistens food so it moves more easily through your esophagus into your stomach.
Saliva also has an enzyme that begins to break down starches in your food. After you swallow, peristalsis pushes the food down your esophagus into your stomach. Glands in your stomach lining make stomach acid and enzymes that break down food. Muscles of your stomach mix the food with these digestive juices. Your pancreas makes a digestive juice that has enzymes that break down carbohydrates, fats, and proteins. The pancreas delivers the digestive juice to the small intestine through small tubes called ducts.
Your liver makes a digestive juice called bile that helps digest fats and some vitamins. Bile ducts carry bile from your liver to your gallbladder for storage, or to the small intestine for use. Your gallbladder stores bile between meals. When you eat, your gallbladder squeezes bile through the bile ducts into your small intestine.
Your small intestine makes digestive juice, which mixes with bile and pancreatic juice to complete the breakdown of proteins, carbohydrates, and fats. Bacteria in your small intestine make some of the enzymes you need to digest carbohydrates. Your small intestine moves water from your bloodstream into your GI tract to help break down food. Your small intestine also absorbs water with other nutrients.
In your large intestine, more water moves from your GI tract into your bloodstream. Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues.
An enzyme in the juice of the stomach starts the digestion of swallowed protein. Further digestion of the protein is completed in the small intestine. Here, several enzymes from the pancreatic juice and the lining of the intestine carry out the breakdown of huge protein molecules into small molecules called amino acid. These small molecules can be absorbed from the hollow of the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells.
Fat molecules are a rich source of energy for the body. The first step in digestion of a fat such as butter is to dissolve it into the water content of the intestinal cavity. The bile acids produced by the liver act as natural detergents to dissolve fat in water and allow the enzymes to break the large fat molecules into smaller molecules, some of which are fatty acids and cholesterol.
The bile acids combine with the fatty acids and cholesterol and help these molecules to move into the cells of the mucosa. In these cells, the small molecules are formed back into large molecules, most of which pass into vessels called lymphatics near the intestine. These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body. The large, hollow organs of the digestive system contain muscle that enables their walls to move.
The movement of organ walls can propel food and liquid and also can mix the contents within each organ. Typical movement of the esophagus, stomach, and intestine is called peristalsis. The action of peristalsis looks like an ocean wave moving through the muscle. The muscle of the organ produces a narrowing and then propels the narrowed portion slowly down the length of the organ.
These waves of narrowing push the food and fluid in front of them through each hollow organ. Most of the material absorbed from the cavity of the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands. Swallowing, done by muscle movements in the tongue and mouth, moves the food into the throat, or pharynx pronounced: FAIR-inks. The pharynx is a passageway for food and air. A soft flap of tissue called the epiglottis pronounced: ep-ih-GLAH-tus closes over the windpipe when we swallow to prevent choking.
From the throat, food travels down a muscular tube in the chest called the esophagus pronounced: ih-SAH-fuh-gus. Waves of muscle contractions called peristalsis pronounced: per-uh-STALL-sus force food down through the esophagus to the stomach. A person normally isn't aware of the movements of the esophagus, stomach, and intestine that take place as food passes through the digestive tract.
At the end of the esophagus, a muscular ring or valve called a sphincter pronounced: SFINK-ter allows food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the esophagus. The stomach muscles churn and mix the food with digestive juices that have acids and enzymes, breaking it into much smaller, digestible pieces. An acidic environment is needed for the digestion that takes place in the stomach.
By the time food is ready to leave the stomach, it has been processed into a thick liquid called chyme pronounced: kime. A walnut-sized muscular valve at the outlet of the stomach called the pylorus pronounced: pie-LOR-us keeps chyme in the stomach until it reaches the right consistency to pass into the small intestine. Chyme is then squirted down into the small intestine, where digestion of food continues so the body can absorb the nutrients into the bloodstream.
The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi pronounced: VIH-lie. The lining of the small intestine is covered in tiny microvilli. These are microscopic, finger-like protrusions which give the lining of the small intestine a massive surface area for absorption of nutrients to occur across.
The microvilli give the inside of the intestine the look and feel of velvet. Each microvillus contains a minute blood capillary. When nutrients are absorbed into a microvillus, they enter its blood capillary. This is how nutrients from your food enter your blood.
By the time food leaves your small intestine all the nutrients in your food will have entered your bloodstream. All that remains is indigestible food which is passed from your small intestine to your large intestine for further processing. Home Explore the BBC.
0コメント