Chemical digestion breaks down different nutrients, such as proteins, carbohydrates, and fats, into even smaller parts:. Some people may lack certain enzymes used in chemical digestion. Chemical digestion begins in your mouth. As you chew, your salivary glands release saliva into your mouth. The saliva contains digestive enzymes that start off the process of chemical digestion. In your stomach , unique chief cells secrete digestive enzymes.
One is pepsin, which breaks down proteins. Another is gastric lipase, which breaks down triglycerides. In your stomach, your body absorbs fat-soluble substances, such as aspirin and alcohol. The small intestine is a major site for chemical digestion and absorption of key food components, such as amino acids, peptides, and glucose for energy. There are lots of enzymes released in the small intestine and from the nearby pancreas for digestion.
These include lactase to digest lactose and sucrase to digest sucrose, or sugar. It also absorbs vitamins, minerals, and water. Chemical digestion is a vital part of the digestive process.
While mechanical digestion involves physical movements, such as chewing and muscle contractions, chemical digestion uses enzymes to break down food. But how does your body process it? You have 3 major pairs of salivary glands:. Your upper digestive tract and your esophagus also contain smaller clusters of salivary glands.
Saliva contains special enzymes that help digest the starches in your food. An enzyme called amylase breaks down starches complex carbohydrates into sugars, which your body can more easily absorb.
Saliva also contains an enzyme called lingual lipase, which breaks down fats. This can make it difficult for you to chew and swallow food. Stress or dehydration can cause occasional xerostomia. Certain medicines or more serious conditions such as diabetes and Sjogren syndrome can also cause it.
To reduce the symptoms of dry mouth, drink plenty of water, take sips of water while eating, and don't have caffeinated or alcoholic beverages. These can make dry mouth worse. When your saliva begins to break down your food, the taste buds on your tongue and on the roof of your mouth sense how the food tastes.
Taste buds contain gustatory cells, which send taste signals to the brain. Chemical digestion is facilitated by the churning action of the stomach. Contraction and relaxation of smooth muscles mixes the stomach contents about every 20 minutes.
The partially-digested food and gastric juice mixture is called chyme. Chyme passes from the stomach to the small intestine. Further protein digestion takes place in the small intestine. Gastric emptying occurs within two to six hours after a meal. Only a small amount of chyme is released into the small intestine at a time. The movement of chyme from the stomach into the small intestine is regulated by the pyloric sphincter.
Learning Objectives Describe the parts of the digestive system from the oral cavity through the stomach. Key Points Mechanical and chemical digestion begin in the mouth with the chewing of food and the release of saliva, which starts carbohydrate digestion. The epiglottis covers the trachea so the bolus ball of chewed food does not go down into the trachea or lungs, but rather into the esophagus. The tongue positions the bolus for swallowing and then peristalsis pushes the bolus down the esophagus into the stomach.
In the stomach, acids and enzymes are secreted to break down food into its nutrient components. The churning of the stomach helps to mix the digestive juices with the food, turning it into a substance called chyme. The digestive system is made up of the alimentary canal also called the digestive tract and other organs, such as the liver and pancreas. The alimentary canal is the long tube of organs — including the esophagus, stomach, and intestines — that runs from the mouth to the anus.
An adult's digestive tract is about 30 feet about 9 meters long. Digestion begins in the mouth, well before food reaches the stomach. When we see, smell, taste, or even imagine a tasty meal, our salivary glands in front of the ear, under the tongue, and near the lower jaw begin making saliva spit. As the teeth tear and chop the food, spit moistens it for easy swallowing.
A digestive enzyme in saliva called amylase pronounced: AH-meh-lace starts to break down some of the carbohydrates starches and sugars in the food even before it leaves the mouth.
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.
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