The Digestive System. Digestive System. ∞ a group of organs working together to convert food into energy and basic nutrients to feed the entire body .
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∞ a group of organs working together to convert food into energy and basic nutrients to feed the entire body.
∞ made up of the digestive tract—a series of hollow organs joined in a long, twisting tube from the mouth to the anus—and other organs that help the body break down and absorb food.
∞ contains a layer of smooth muscle that helps break down food and move it along the tract.
∞ From the word digestio which means from, dis means apart and gerere is to carry
Steroids the animal needs
Proteins the animal needs
Other lipids the animal needs
Microminerals- known as trace minerals, animals need these in very small amounts
Vitamins- the general term for a number of chemically unrelated , organic substances that occur in many foods in small amounts and are necessary for normal metabolic functioning
tiny food particles are taken into the body wall cells by endocytosis,
digestive enzyme in the vacuole then break the small particles into constituent molecules
the enzymatic breakdown of larger pieces of food into constituent molecules, in special organ or cavity and then can take part in energy metabolism
Incomplete digestive tract is a tract that has one opening for entrance and exit.
Complete digestive tract is a tract with the development of the anus for exit of wastes.
Platyhelminthes(planarian) has also incomplete digestive tract.
The ingestion of planarian occur in pharynx, sticks it out of its mouth and sucks in food.
Nematodes have a complete digestive tract, it has mouth pharynx and anus.
Mouth ( Oral Cavity)
∞ Food begins its journey through the digestive system in the mouth.
∞ Inside the mouth are many accessory organs that aid in the digestion of food—the tongue, teeth, and salivary glands. Teeth chop food into small pieces, which are moistened by saliva before the tongue and other muscles push the food into the pharynx.
∞ a funnel-shaped tube connected to the posterior end of the mouth.
∞ responsible for the passing of masses of chewed food from the mouth to the esophagus.
∞ plays an important role in the respiratory system, as air from the nasal cavity passes through the pharynx on its way to the larynx and eventually the lungs.
∞ it contains a flap of tissue known as the epiglottis that acts as a switch to route food to the esophagus and air to the larynx.
∞ a muscular tube connecting the pharynx to the stomach that is part of the upper gastrointestinal tract.
∞ carries swallowed masses of chewed food along its length.
*At the inferior end of the esophagus is a muscular ring called the lower esophageal sphincter or cardiac sphincter. The function of this sphincter is to close of the end of the esophagus and trap food in the stomach.
∞ a muscular sac, located on the left side of the abdominal cavity, just inferior to the diaphragm.
∞the stomach is about the size of their two fists placed next to each other.
∞ acts as a storage tank for food so that the body has time to digest large meals properly.
∞ contains hydrochloric acid and digestive enzymes that continue the digestion of food that began in the mouth.
Structures associated with the
∞ a long, thin tube about 1 inch in diameter and about 10 feet long that is part of the lower gastrointestinal tract.
∞ located just inferior to the stomach and takes up most of the space in the abdominal cavity.
∞ coiled like a hose and the inside surface is full of many ridges and folds.
*These folds are used to maximize the digestion of food and absorption of nutrients. By the time food leaves the small intestine, around 90% of all nutrients have been extracted from the food that entered it.
∞ a roughly triangular accessory organ of the digestive system located to the right of the stomach, just inferior to the diaphragm and superior to the small intestine.
∞ weighs about 3 pounds
∞ the second largest organ in the body.
∞ the main function of the liver in digestion is the production of bile and its secretion into the small intestine.
∞ a large gland located just inferior and posterior to the stomach.
∞ It is about 6 inches long and shaped like short, lumpy snake with its “head” connected to the duodenum and its “tail” pointing to the left wall of the abdominal cavity.
∞ secretes digestive enzymes into the small intestine to complete the chemical digestion of foods.
∞ a small, pear-shaped organ located posterior to the liver.
∞ used to store and recycle excess bile from the small intestine so that it can be reused for the digestion of subsequent meals.
Large Intestine (Colon)
∞ a long, thick tube about 2 ½ inches in diameter and about 5 feet long.
∞ located just inferior to the stomach and wraps around the superior and lateral border of the small intestine.
∞ absorbs water and contains many symbiotic bacteria that aid in the breaking down of wastes to extract some small amounts of nutrients.
∞ Feces in the large intestine exit the body through the anal canal.
Terms that must
be familiar with:
Chyme – semi fluid mixture of food with stomach secretions.
Hydrochloric acid – has a pH of 2.0 in the stomach; a gastric gland that kills bacteria and converts pepsinogen to pepsin.
Pepsin – a gastric gland that digest proteins.
Mucus – mucous cell that protects stomach lining
Intrinsic factor – a gastric gland that binds to B12 and aids in its absorption
The digestive system is responsible for taking whole foods and turning them into energy and nutrients to allow the body to function, grow, and repair itself.
The six primary processes of the digestive system include:
∞ Ingestion of food – eating
∞ Peristalsis – the involuntary, sequential muscular contractions that move ingested nutrients along the digestive track
∞ Segmentation – mixing the contents in the digestive tract
∞ Secretion – the release of hormones, enzymes and specific ions and chemicals that take part in digestion
∞ Digestion – the conversion of large nutrient particles or molecules into small particles or molecules
∞ Absorption – the passage of usable nutrient molecules from the small intestine into the bloodstream and lymphatic system for the final passage to body cells