y Digestive
term System
( ans
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Answer:
Explanation:
What Is the Digestive System?
Food is our fuel, and its nutrients give our bodies' cells the energy and substances they need to work. But before food can do that, it must be digested into small pieces the body can absorb and use.
The first step in the digestive process happens before we even taste food. Just by smelling that homemade apple pie or thinking about how delicious that ripe tomato is going to be, you start salivating — and the digestive process begins in preparation for that first bite.
Almost all animals have a tube-type digestive system in which food:
enters the mouth
passes through a long tube
exits the body as feces (poop) through the anus
Along the way, food is broken down into tiny molecules so that the body can absorb nutrients it needs:
Protein must be broken down into amino acids.
Starches break down into simple sugars.
Fats break down into into fatty acids and glycerol.
The waste parts of food that the body can't use are what leave the body as feces.
How Does Digestion Work?
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 (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 (FAIR-inks). The pharynx is a passageway for food and air. A soft flap of tissue called the epiglottis (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 (ih-SAH-fuh-gus). Waves of muscle contractions called peristalsis (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 (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.
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