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LIFE PROCESSES By :- Shailendra Solanki Class 10 Kendriya Vidyalaya Chittorgarh

Life processes

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Page 1: Life processes

LIFE PROCESSES

By :- Shailendra SolankiClass 10

Kendriya Vidyalaya Chittorgarh

Page 2: Life processes

Human beings are heterotrophic , omnivorous organisms. Carbohydrates , proteins , fats , vitamins and minerals are essential components of human diet.The process of nutrition involves ingestion , digestion , assimilation, absorption and egestion .

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The human digestive system consists of the alimentary canal and secretory glands. It consists of the buccal cavity, oesophagus , stomach , small intestine , large intestine ending in rectum and anus.

The main digestive glands which secrete digestive juices with digestive enzymes are the salivary glands , the liver and the pancreas. The stomach wall and the wall of the small intestine also secrete digestive juices.

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BUCCAL CAVITY :After the food is ingested through mouth, it is crushed, softened and partially digested in the buccal cavity.

The buccal cavity has four types of teeth for crushing the food: Incisors for cutting and biting ,canines for piercing and tearing , premolars and molars for grinding. The teeth cut the food into small pieces and makes it soft for easy swallowing.

The tongue in the buccal cavity mixes saliva with the food and helps in swallowing the food. It also helps in tasting the food.

The buccal cavity has three pairs of salivary glands. The salivary glands secrete saliva through their ducts. The saliva contains water , salts and an enzyme salivary amylase. The salivary amylase splits starch into sugar (maltose). Thus carbohydrates digestion begins in the buccal cavity itself.

Starch------------------salivary amylase--------------- Maltose (sugar)

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OESOPHAGUS: It is a long muscular tube which carry the food from pharynx to the stomach. The wall of the oesophagus is muscular. It pushes the food forward into the stomach by contraction and expansion of it’s muscles. Such movements are called peristaltic movements. These occur all along the alimentary canal.

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STOMACH : The stomach is a large muscular sac present on the left side of the abdomen. The partially digested food reaches into stomach from buccal cavity through pharynx and oesophagus.

The stomach severs following functions: Storage of food Mechanical churning of food Partial digestion: the gastric glands present in the walls of the stomach

secret HCl , protein digesting enzyme and mucous. HCl kills the microbes entering the system along with food, also it creates an acidic medium which facilitates the action of enzyme pepsin. Protein digesting enzyme pepsin breaks down proteins into peptones. Gastric juices also contain gastric lipase which partially break down lipids. Mucous covers the inner lining of the stomach and protects it from corroding action of HCl and pepsin enzyme.

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SMALL INTESTINE: It is the longest part of the alimentary canal. It’s length varies in different animals depending on the type of food they eat . It is longer in herbivores and shorter in carnivores.The small intestine is the site of the complete digestion of carbohydrates, proteins and fats.It receives secretions from liver and pancreas for this purpose through a common duct formed by the union of bile duct and pancreatic duct.The liver secretes the bile juice and it is stored in the gall bladder . The bile helps in breaking the fat molecules into small globules so that it becomes easy for the enzymes to act on them . Also bile makes the acidic food coming from the stomach, alkaline for the pancreatic juices to act.The pancreas secretes pancreatic juice which contain various enzymes . The pancreatic amylase cause break down of starch, pancreatic lipase breaks down lipids and trypsin causes digestion of proteins.The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert the proteins into amino acids , carbohydrates into glucose and fats into fatty acids and glycerol.The digested food is taken up by the walls of the small intestine.

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The digested food is taken up by the walls of the small intestine. The inner lining of the small intestine is has numerous finger like projections called villi which increase the surface area for absorption.The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body , where it is utilised for obtaining energy , building up of new tissues and the repair of the old tissues.

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LARGE INTESTINE : The undigested and unabsorbed food is sent into the large intestine where more villi absorb water from this material . The rest of the material is removed from the body via anus. The exit of this waste material is regulated by anal sphincter.

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Digestive System.wmv