Digestive System - Ingestion, Digestion In The Stomach, Gastric Juice, Alexis St. Martin's Stomach
food tube glands consists
The digestive system is a group of organs responsible for the conversion of food into absorbable chemicals which are then used to provide energy for growth and repair. The digestive system is also known by a number of other names, including the gut, the digestive tube, the alimentary canal, the gastrointestinal (GI) tract, the intestinal tract, and the intestinal tube. The digestive system consists of the mouth, esophagus, stomach, and small and large intestines, along with several glands, such as the salivary glands, liver, gall bladder, and pancreas. These glands secrete digestive juices containing enzymes that break down the food chemically into smaller, more absorbable molecules. In addition to providing the body with the nutrients and energy it needs to function, the digestive system also separates and disposes of waste products ingested with the food.
Food is moved through the alimentary canal by a wavelike muscular motion known as peristalsis, which consists of the alternate contraction and relaxation of the smooth muscles lining the tract. In this way, food is passed through the gut in much the same manner as toothpaste is squeezed from a tube. Churning is another type of movement that takes place in the stomach and small intestine, which mixes the food so that the digestive enzymes can break down the food molecules.
Food in the human diet consists of carbohydrates, proteins, fats, vitamins, and minerals. The remainder of the food is fiber and water. The majority of minerals and vitamins pass through to the bloodstream without the need for further digestive changes, but other nutrient molecules must be broken down to simpler substances before they can be absorbed and used.
Additional Topics
Food taken into the mouth is first prepared for digestion in a two step process known as mastication. In the first stage, the teeth tear and break down food into smaller pieces. In the second stage, the tongue rolls these pieces into balls (boluses). Sensory receptors on the tongue (taste buds) detect taste sensations of sweet, salt, bitter, and sour, or cause the rejection of bad-testing food. Th…
There are several mechanisms responsible for the secretion of gastric juice in the stomach. The stomach begins its production of gastric juice while the food is still in the mouth. Nerves from the cheeks and tongue are stimulated and send messages to the brain. The brain in turn sends messages to nerves in the stomach wall, stimulating the secretion of gastric juice before the arrival of the food.…
An understanding of the complex mechanisms of gastric juice secretion began with an American army doctor, William Beaumont (1785-1853). He was able to directly observe the process of digestion in the stomach from the wound of a soldier named Alexis St. Martin. In 1822, Beaumont treated the soldier for an accidental gunshot wound. This wound left a large hole in the left side of St. Martin's…
While digestion continues in the small intestine, it also becomes a major site for the process of absorption, that is, the passage of digested food into the bloodstream, and its transport to the rest of the body. The small intestine is a long, narrow tube, about 20 ft (6 m) long, running from the stomach to the large intestine.
The digestive process. Illustration by Hans & Cassidy. Co…
The large intestine, or colon, is wider and heavier then the small intestine, but much shorter—only about 4 ft (1.2 m) long. It rises up on one side of the body (the ascending colon), crosses over to the other side (the transverse colon), descends (the descending colon), forms an s-shape (the sigmoid colon), reaches the rectum, and anus, from which the waste products of digestion (feces or …
The liver is the largest organ in the body and plays a number of vital roles, including metabolizing the breakdown products of digestion, and detoxifying substances that are harmful to the body. The liver also provides a quick source of energy when the need arises and it produces new proteins. Along with the regulation of stored fats, the liver also stores vitamins, minerals, and sugars. The liver…
The gallbladder lies under the liver and is connected by various ducts to the liver and the duodenum. The gall-bladder is a small hollow organ resembling a money pouch. Its main function is to store bile until it is concentrated enough to be used by the small intestine. The gall bladder can store about 2 oz (57 g) of bile. Bile consists of bile salts, bile acids, and bile pigments. In addition, bi…
When food reaches the small intestine, the pancreas secretes pancreatic juices. When there is no food in the small intestine, the pancreas does not secrete its juices. The economy of this process puzzled researchers who wondered what the mechanism for this control might be. In 1902, William Bayliss and Ernest Starling, two British physiologists, conducted experiments to find the answer. They reaso…
Several disorders of the esophagus are esophagitis, esophageal spasm, and esophageal cancer. Esophagitis (heartburn) is an inflammation of the esophagus usually caused by the reflux of gastric acids into the esophagus and is treated with (alkalis) antacid. Esophageal spasm is also caused by acid reflux and is sometimes treated with nitroglycerine placed under the tongue. Esophageal cancer can be c…
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User Comments
11 months ago
HAJII
digestive system
2 months ago
what are the digetive juices
5 months ago
i have a gaster ach