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Digestive System: Tourist Guide (Enzymes (Amylase, produced in the mouth.…
Digestive System: Tourist Guide
Major Digestive Organs
Esophagus
Stomach
Pharynx
Small Intestine
Mouth
Large Intestine
The Accessory Organs
Liver
Gallbladder
Pancreas
Pathway of food through GI tract
Once you start chewing and breaking the food down into pieces small enough to be digested, other mechanisms come into play. More saliva is produced. It contains substances including enzymes that begin the process of breaking down food into a form your body can absorb and use. Chew your food more -- it also helps with your digestion.
The act of swallowing takes place in the pharynx partly as a reflex and partly under voluntary control. The tongue and soft palate -- the soft part of the roof of the mouth -- push food into the pharynx, which closes off the trachea.
The food then enters the esophagus. The esophagus is a muscular tube extending from the pharynx and behind the trachea to the stomach. Food is pushed through the esophagus and into the stomach by means of a series of contractions called peristalsis. Just before the opening to the stomach is an important ring-shaped muscle called the lower esophageal sphincter (LES).
The stomach is a sac-like organ with strong muscular walls. In addition to holding food, it serves as the mixer and grinder of food. The stomach secretes acid and powerful enzymes that continue the process of breaking the food down and changing it to a consistency of liquid or paste. From there, food moves to the small intestine. Between meals, the non-liquefiable remnants are released from the stomach and ushered through the rest of the intestines to be eliminated.
The small intestine is the 'work horse' of digestion, as this is where most nutrients are absorbed. Peristalsis is also at work in this organ, moving food through and mixing it up with the digestive secretions from the pancreas and liver, including bile.While food is in the small intestine, nutrients are absorbed through the walls and into the bloodstream. What's leftover (the waste) moves into the large intestine (large bowel or colon).
The large intestine is a highly specialized organ that is responsible for processing waste so that defecation (excretion of waste) is easy and convenient. Stool, or waste left over from the digestive process, passes through the colon by means of peristalsis, first in a liquid state and ultimately in solid form. As stool passes through the colon, any remaining water is absorbed. Stool is stored in the sigmoid (S-shaped) colon until a "mass movement" empties it into the rectum, usually once or twice a day.
Enzymes
Amylase, produced in the mouth. It helps break down large starch molecules into smaller sugar molecules.
Pepsin, produced in the stomach. Pepsin helps break down proteins into amino acids.
Trypsin, produced in the pancreas. Trypsin also breaks down proteins.
Pancreatic lipase, produced in the pancreas. It is used to break apart fats.
Deoxyribonuclease and ribonuclease, produced in the pancreas. They are enzymes that break bonds in nucleic acids like DNA and RNA.
Bile salts are bile acids that help to break down fat. Bile acids are made in the liver. When you eat a meal, bile is secreted into the intestine, where it breaks down the fats.
Gastrin, which signals the secretion of gastric acid.
Cholecystokinin, which signals the secretion of pancreatic enzymes.
Secretin, which signals secretion of water and bicarbonate from the pancreas.
Ghrelin, which signals when you are hungry.
Gastric inhibitory polypeptide, which stops or decreases gastric secretion. It also causes the release of insulin in response to high blood glucose levels.
Location of Absorption
The small intestine is the part of the gastrointestinal tract between the stomach and the large intestine where much of the digestion of food takes place.
Brush border enzymes take over from there. The most important brush border enzymes are dextrinase and glucoamylase that further break down oligosaccharides. Other brush border enzymes are maltase, sucrase, and lactase.
The primary function of the small intestine is the absorption of nutrients and minerals found in food.Glucose, amino acids, fats, and vitamins are absorbed in the small intestine via the action of hormones and electrolytes.
