消化系统-英文版ppt课件.ppt

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1、1精品The digestive system is responsible for breaking down food,absorbing nutrients from the food,and ridding the body of waste products from the food.It is roughly nine meters long and begins at the mouth and ends at the anus.2精品The digestive system consists of the:the alimentary tract mouth,pharynx,

2、esophagus,stomach,small and large intestines,rectum and anus the accessory organs salivary glands,liver,gall bladder and pancreas 3精品The mouth,or oral cavity,is the first part of the digestive tract.It is adapted to receive food by ingestion,break it into small particles by mastication,and mix it wi

3、th saliva.The lips,cheeks,and palate form the boundaries.The oral cavity contains the teeth and tongue and receives the secretions from the salivary glands.Kids have 20 teeth,but by the time they are fully grown,they should have 32 teeth(some people do have less!).The esophagus is the second step to

4、 digestion and closely follows the oral cavity once swallowing has initiated.the Alimentary Tract4精品The stomach is divided into the fundic,cardiac,body,and pyloric regions.The stomach has three layers of muscle:an outer longitudinal layer,a middle circular layer,and an inner oblique layer.The inner

5、lining consists of four layers:the serosa,the muscularis,the submucosa,and the mucosa.The mucosa is densely packed with gastric glands,which contain cells that produce digestive enzymes,hydrochloric acid,and mucus.The stomach is a multi-functional organ,it stores food,breaks it down and then empties

6、 it into the small intestine.5精品The small intestine consists of three sections.duodenum,jejunum and ileum which attaches to the first portion of the large intestine.Functiondigestion,and absorption.The small intestine finishes the process of digestion,absorbs the nutrients,and passes the residue on

7、to the large intestine.The liver,gallbladder,and pancreas are accessory organs of the digestive system that are closely associated with the small intestine.6精品The large intestine is made up of three portions:the ascending,transverse and descending colon.It is the portion of the digestive system most

8、 responsible for absorption of water from the indigestible residue of food.The ileocecal valve of the ileum(small intestine)passes material into the large intestine at the cecum.Material passes through the ascending,transverse,descending and sigmoid portions of the colon,and finally into the rectum.

9、From the rectum and anus,the waste is expelled from the body.7精品Three pairs of major salivary glands(parotid,submandibular,and sublingual glands)Saliva contains water,mucus and enzyme amylase.Functions It has a cleaning action on the teeth.It moistens and lubricates food during mastication and swall

10、owing.It dissolves certain molecules so that food can be tasted.It begins the chemical digestion of starches through the action of amylase,which breaks down polysaccharides into disaccharides.the Accessory Organs 8精品Liver is the largest gland in the body.On the surface,the liver is divided into two

11、major lobes and two smaller lobes.It overlies and almost completely covers the stomach.Functions secretion synthesis of bile salts synthesis of plasma protein storage detoxification excretion carbohydrate metabolism lipid metabolism protein metabolism filtering 9精品The gallbladder is a pear-shaped sa

12、c that is attached to the visceral surface of the liver by the cystic duct.The principal function of the gallbladder is to serve as a storage reservoir for bile.Bile salts act as emulsifying agents in the digestion and absorption of fats.It is secreted from the intestine and specifically the duodenu

13、m.10精品The pancreas is located in the back of the abdomen,behind the stomach.The pancreas makes pancreatic juices and hormones,including insulin.Pancreatic juices,also called enzymes,help digest food in the small intestine.Insulin controls the amount of sugar in the blood.Both enzymes and hormones are needed to keep the body working right.11精品12精品