Organs Of The Digestive System

Organs of the Digestive System

6 main organs of the alimentary canal: the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. Accessory glands & organs: salivary glands, pancreas, liver, and gallbladder, (secrete digestive juices into the alimentary canal)

Mouth • Your mouth functions both in ingestion and in the beginning of digestion. • Your teeth and tongue are responsible for mechanical digestion. The various shapes of different types of teeth cut, smash, and grind food into smaller pieces. This makes the food easier to swallow and exposes more surface area to digestive enzymes.

Mechanical (physical) Digestion 1

Teeth

Herbivores Incisors in lower jaw used to cut through grass by biting against a hard pad on the upper jaw. Premolars and molars are flat helping in grinding. Jaws move side by side to help grind vegetation. Carnivores Carnassial teeth and the premolars and molars are used to shear Meat and grind bones. Incisors and canines are used to tear meat. Jaws have strong scissor action because they move up and down. Omnivores Some teeth like herbivores and some teeth like carnivores. Can move jaws from side to side and up and down. Hence can eat a wide range of foods.

Dental decay

Cause of the decay…. • Present in fruits and other foods • Bacteria (spaces between teeth, crevices on tooth surface, edges of the gums) produce acids. • Corrode the enamel and expose the softer dentine.

Fluoride • Mineral Strengthens enamel • Strong enamel will prevent cavity formation • In some places fluoride is added to drinking water toxic kidney stones cancer Toothpaste

Along the Alimentary Canal MOUTH 1

½ LITRESOFSALIVA

3PAIRSOFSALIVARY GLANDS CELLS, DUCTS 99%WATER, MUCIN, AMYLASE

Salivary gland Salivary gland

Salivary gland

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Oesophagus

Next, the bolus enters a long, muscle-encased tube called the oesophagus, which connects the pharynx to the stomach. Food is pushed through the esophagus by a series of muscle contractions called peristalsis. Peristalsis is a radially symmetrical contraction of muscles which propagates in a wave down the muscular tube The muscles contract in a wave-like motion that forces the bolus of food toward the stomach. Food continues to move along the alimentary canal by peristalsis .

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A thick layer of muscle tissue enables the stomach to break up and stir a bolus of food.

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Stomach

Stomach wall is line with glands which produce Hydrochloric acid and pepsin enzyme. Hydrochloric acid breaks apart the cells in food. It also kills many of the bacteria swallowed with food. Acidic conditon helps in activity of pepsin Pepsin, hydrolyzes large protein molecules into smaller polypeptides. Mechanical digestion turns the bolus into an acidic liquid called chyme . Stomach muscles contract, creating a churning motion that stirs the chyme and eventually forces it into the small intestine. At the opposite end of the stomach, a muscular valve called the pyloric sphincter regulates the flow of chyme into the small intestine. It typically takes 2 to 6 hours after a meal for the stomach to empty. Most of the time, the stomach is pinched closed at both ends. The passageway between the esophagus and the stomach opens when peristalsis delivers a bolus. But in some people, the passageway may open at inappropriate times, allowing acidic chyme to flow backward into the esophagus. This creates a burning sensation called heartburn.

Duodenum, liver and pancreas

Duodenum: connects the stomach to the small intestine Two tubes are connected to it One carries bile from gall bladder to mix with the food Other carries enzymes from pancreas to mix with the food Stomach + Liver + Pancreas

SMALL INTESTINE Cells lining the small intestine make enzymes Different nutrient groups are broken into smaller molecules so that they are soluble and pass through the wall of the small intestine and carried from the blood to all the cells of the body

• As an end result of digestion, carbohydrates are hydrolyzed to monosaccharides. Monosaccharides provide your cells with a source of energy. They are also a source of carbon skeletons (chains of carbon atoms) for constructing other organic molecules. • The complete digestion of proteins results in individual amino acids. Your cells use these amino acids to build their own "brand" of proteins. • Hydrolysis of fats by the enzyme lipase (which is secreted by the pancreas) results in fatty acids and glycerol. Your cells use these raw materials to build their own lipids and cell membranes.

FATE OF UNDIGESTED FOOD

Large Intestine • By the time food reaches the end of the small intestine, the nutrients have all been broken down and absorbed. Undigested material passes through another sphincter from the small intestine into the large intestine. • water is absorbed into the body. • Remaining semisolid substances form the faeces stored in rectum

ENZYMES REGION OF PRODUCTION

KIND OF ENZYME

NOTES

SALIVARY GLANDS

CARBOHYDRASE ENZYME CALLED AS AMYLASE

GASTRIC GLANDS PROTEASE

ENZYME IS CALLED PEPSIN

LIVER

BILE

EMULSIFIES FATS

PANCREAS

PROTEASE ENZYMES ENTER CARBOHYDRASE DUODENUM AND LIPASE MIX WITH FOOD AND BILE

INTESTINE

PROTEASE CARBOHYDRASE LIPASE

ILEUM • Long • Inside is covered with villi • Microvilli VILLI: Thin permeable walls Good blood supply (maintains concentration gradient) Lymph vessels (absorb fatty acids)

Assimilation • Liver Vitamins and iron are stored Glucose (insulin and glucagon)- homeostasis Proteins- converted to other form rest broken down in liver and parts are recycled (deamination). amino part- excreted in the form of urea