Digestive System

the digestive system feeding and nutrition:-

feeding is the process of introducing foodstffs into the body.nutrition is the transformation of food so it can be utilized by the body.the energy obtained from food is necessary for development,growth,and activity.the digestive and respiratory systems are responsible for providing us with

nutrients. the digestive system supplies water and fundamental chemical element obtained from food (such as potassium,sodium, chlorine,iron,calcium,vitamins,pro teins,fats and carbhydrates).the respiratory system provides us with oxygen.the circulatory system carries nutrients and oxygen to all the body cells.

metabolism:-metabolism is

the chemical process that occurs when nutrients are broken down to release useful energy.

why we need organic food:-carbohydrates,fats,and

protins are the three main groups of organic foodstuffs.carbohydrates are sweet and starchy foodstuffs such as sugar,fruits,rice, potatoes,bread,and pasta.these foods supply the body with the basic energy it needs.they are also known as sugars because the most simple carbohydrate is glucose.during the digestion process,all the carbohydrates we ingest are broken down into the simplest mulecles and stored

in the liver and muscles.fats,such as oil,pork,and dried fruts are also energyproducing foods. they have the same chemical composition as carbohydrates(carbon,oxygen,an d hydrogen) but whereas a gram of sugar provides 4 calries (energy in the from of heat),a gram of fat provides 9 calories.fats are therefore a concentrated source of energy. proteins are the most important elements of nutrition.they are found in meat,fish,eggs, and

cheese. wheras cabohydrates and fats have a similar chemical construction,proteins are large molecules composed of combinations of amino acids.amino acids are also responsible for muscular contraction, and they act as ctalysts.

how digestion begins:-as

food passes throgh the digestive system,it is broken down into simple substances that our bodies are able to use.the digestive process starts in the mouth and is set in motion by

the teeth,the tongue,and saliva.the sharp-edged teeth chop and tear the food,while have flatter surfaces,grind it up.this is the process of mastication,or chewing.the tongue is the most muscular organ in the body.it can carry out any kind of movement and it pushes the food and places it between our teeth.the 1 to 2 quarts (about 1to2 liters) of saliva secreted daily by the salivary glands helps to dissolve the food and make it easier to swallow.while the saliva

lubricates the food,the enzymes it contains start to act on the starch.

swallowing:- swallowing is a

totally mechanical process that consists of a series of movements which propel the bolus toward the stomach.first,the tongue rises up toward the palate,causing the food to slide backward.at the same time,the palate rises and closes the nasal cavity,preventing the food from entering the nose.once in the pharynx,the food could take

either of two routes,the larynx or the esophagus.the epiglottis,which is located in the pharynx, operates like a valve at the movement of swallowing in response to a command from the brain.this has the effect of blocking the larynx and preventing solids or liquids from passing through the trachea into the lungs.with the epiglottis closed,the bolus enters the esophagus and moves down to the stomach,propelled by the force of gravity and peristaltic movements.

the stomach:-the stomch is

made of three layers.an external layer envelopes it. a middle layer consists of muscles that mix the foodstuffs by meams of perisaltic movements.an internal layer arranged in numerous folds contains the glands that secrete gastric juices.the gastric juices are responsible for the chemical phase.the prime function of the gastric juices,which are composed of water,hydrochloric acid and enzymes,is the transformation of the proteins into amino acids,through the

action of an enzyme called pepsin.

the small intestine:-this

section of the digestive tract,which we call the small intestins,is more than 20 feet long.it is divided into three parts: the duodenum,the jejunum,and the ileum.the main features of the small intestine are the villi contains an atterial capillary and a lymoh vessel.there are some 5 million intestinal villi.the chyme is neutralized as it moves through the small intestine because of

secretions taking place all the way along,plus the metabolizing action of the pancreatic secretions and the bile.

absorption:- the waste

products that have been nither digested nor absorbed make up the feces,which pass through the ileocecal valve into the large intestine.the large intestine is made up of the cecum,the colon,and the rectum.

the liver:-the liver is the

largest gland in the human body,weighing more than 3 pound (1 kg).because of its many

functions,the liver is as vital as the heart.it is as vital as the heart.it is located in the right abdominal cavity,just below the diaphragm,and has four lobes.the cell of the liver are called hepatocytes,and they are grouped to from the hepatic lobules.every lobule is,in itself,a small liver functions.the liver contains some 80,000 hepatic lobules. the liver carries out the function of cleanssing the blood of its waste products (dead blood cells) and controls and stores foodstuffs in the from of

gulcose and vitamins.

the pancreas:-

the pancreas is an elongated and fairly narrow gland located just behind the duodenum,in the upper center of the abdomen,below the stomach. the liver works party as a gland to produce bile,but also has other functions.the pancreas is a true gland.it has two structures:the langerhans islets,which are responsible for proucing insulin;an other glandular cells,similar to the salivary glans,which produce pancreatic secretions.

digestive glands:-

there are two type of glands salivary glands and parotid glands.there are millions of tubular glands in the mucous membrane of the stomach that are connected to the gastric cavity through orifices visible on its suface.among the intestinal villi,there are tubular glands that secrete gastric juices which are very rich in mucous and certain enzymes,and will take part in the final phase of the digestion of food.

waste matter:-metabolism

is the sum total of the chemical processes that occur druing the digestive process.it consists of a constructive process called anabolism and a process of destuction and excretion called catabolism. 1 the lungs contribute to the emlimination of excess carbon dioxide and water. 2 the skin has a multitude of tiny opening, called pores,through which it breathes.each pore has a very fine conduit that is the duct of a

sweat gland,through which sweat leaves the body. 3 the formation of feces facilitates the excretion of the waste matter from food digestion as well as from the breakdown of the hemoglobin of the old red blood cells. but it is the kidneys that really carry out the work of excretion.

presented by:-mrs shashi kiran

science mistress from govt. model. senior. sec. school. pheel khana patiala