The parts of the human digestive system Science Unit: Human Digestive System Outcome I can describe parts of the digestive system and how they are adapted to digest food. Keywords digestion digestive system gland adaptation fibre Keywords Digestion is the process of breaking down food into substances that can be absorbed into the blood. The digestive system is a collection of organs that break down food. A gland is a tissue or an organ that produces chemicals. An adaptation is a feature that helps an organism to function and survive. Fibre bulks up food so it can be moved through the digestive system more easily. Lesson outline The parts of the human digestive system The human digestive system Adaptations of the organs, glands and tissues Undigested food The human digestive system Food is our source of energy. Food also gives us the materials needed for growth and repair. The food we eat must be broken down into nutrients before it can be used for energy, growth and repair. This process is called digestion. Explanation The human digestive system Check Which student gives the most accurate description of what we need food for? Food gives us energy so we can grow. Food has to be digested to get the goodness out. Laura Food allows us to live. Andeep a b Izzy c The human digestive system The digestive system is a group of organs that digest our food. Explanation mouth Food moves through the digestive system from the mouth to small intestine the anus in the anus following order: oesophagus stomach large intestine rectum The human digestive system Check Starting with the first, sort these parts of the digestive system into digestion order. a large intestine mouth 3 oesophagus b c stomach small intestine 1 2 stomach small intestine anus large intestine rectum Task A The human digestive system 1) Label the diagram to show the main organs of the digestive system. mouth small intestine anus rectum stomach large intestine oesophagus Practice Task A The human digestive system 1) Label the diagram to show the main organs of the digestive system. Feedback mouth oesophagus small intestine anus stomach large intestine rectum Task A The human digestive system 2) Starting with the mouth, complete the flowchart to show the correct order that food moves through the organs. Practice mouth Task A The human digestive system 2) Starting with the mouth, complete the flowchart to show the correct order that food moves through the organs. Feedback mouth oesophagus stomach small intestine large intestine rectum anus Lesson outline The parts of the human digestive system The human digestive system Adaptations of the organs, glands and tissues Undigested food Adaptations of the organs, glands and tissues The digestive system is made up of specialised tissues, organs and glands. ● A tissue is a group of one type of cell. ● An organ is a group of specialised tissues. ● A gland is a tissue or an organ which produces chemicals. They secrete (release) these chemicals into the digestive system. Salivary glands in the mouth secrete saliva Explanation Adaptations of the organs, glands and tissues In biology, an adaptation is a feature that helps an organism to function and survive. Each organ in the digestive system is adapted to digest our food. Explanation Adaptations of the organs, glands and tissues Explanation The mouth has several adaptations: ● the teeth cut and chew food into smaller pieces. teeth ● the tongue rolls and mixes the food in the mouth. ● the salivary glands produce chemicals and add water to the food. tongue salivary glands Adaptations of the organs, glands and tissues After food is swallowed, it moves down the oesophagus. The oesophagus has rings of muscle which contract behind the bolus of food. This pushes food down to the stomach. This process is called peristalsis. oesophagus muscle contractions bolus of food Explanation Adaptations of the organs, glands and tissues Which of these describe the function of the salivary glands? a Produce chemicals for digestion b Roll and mix food in the mouth c Add water to food Check Adaptations of the organs, glands and tissues The stomach is a bag which receives recently swallowed food. It produces hydrochloric acid which enables food to be digested and kills pathogens. Explanation Adaptations of the organs, glands and tissues The small intestine is a long, narrow tube which slows down the passage of food. This ensures that food is fully digested. Nutrients are absorbed into the blood. small intestine Explanation Adaptations of the organs, glands and tissues The inside surface of the small intestine has many tiny structures called villi. Explanation villi Nutrients from digested food are absorbed into the blood through the villi. The nutrients are transported in the blood to all the living cells of the body. The inside of the small intestine Adaptations of the organs, glands and tissues The pancreas is an organ. It is also a gland. It secretes (releases) chemicals into the small intestine which break down food into nutrients. Food does not pass through the pancreas. pancreas Explanation Adaptations of the organs, glands and tissues The liver is another organ which is also a gland. It secretes a liquid called bile into the small intestine. Bile breaks down fat and surrounds fat so that it can be suspended in water. Food does not pass through the liver. Explanation Adaptations of the organs, glands and tissues Food does not pass through some organs in the digestive system. Which organ does food not pass through? a Stomach b Small intestine c Pancreas d Oesophagus Check Task B Adaptations of the organs, glands and tissues 1) Draw lines to match the adaptation to the organ. Teeth Mouth Peristalsis Oesophagus Salivary glands Practice Task B Adaptations of the organs, glands and tissues 1) Draw lines to match the adaptation to the organ. Teeth Mouth Peristalsis Oesophagus Salivary glands Feedback Task B Adaptations of the organs, glands and tissues 2) Draw lines between each column of boxes to make three sentences about digestion. The first line has been drawn for you. The pancreas secretes chemicals into the blood The liver absorbs nutrients to break down fat The small intestine secretes bile to digest food Practice Task B Adaptations of the organs, glands and tissues 2) Draw lines between each column of boxes to make three sentences about digestion. The first line has been drawn for you. The pancreas secretes chemicals into the blood The liver absorbs nutrients to break down fat The small intestine secretes bile to digest food Feedback Lesson outline The parts of the human digestive system The human digestive system Adaptations of the organs, glands and tissues Undigested food Undigested food Explanation The large intestine receives all the parts of the food that cannot be digested and absorbed by the small intestine. large intestine This includes fibre which is important in our diet because it helps food to move through the digestive system. from small intestine The unabsorbed waste will be passed out of the body as faeces. faeces Undigested food As waste moves through the large intestine, water is absorbed into the blood. Explanation water water Finally, the faeces is stored in the rectum. faeces rectum water Undigested food Explanation When we are ready to defecate, the faeces is pushed through the anus. The anus is a ring of muscle which controls the exit of faeces and gases. faeces rectum anus Undigested food The function of the large intestine is to absorb… a fibre. b food. c water. Check Undigested food Check True or false? Fibre is absorbed in the digestive system. T True F False Justify your answer a Fibre helps food move through the digestive system but cannot be absorbed. b Fibre provides energy for growth and repair. Task C Undigested food Practice 1) Complete the sentences to describe what happens to undigested food. Use words from the list. rectum faeces nutrients fat peristalsis large intestine emulsifier fibre anus __________ bulks up food so that it can be moved through the digestive system by the process of _________. It is not digested but forms __________ which are passed out of the body via the __________. It is stored in the __________ until you are ready to defecate. Undigested food Check 1) Complete the sentences to describe what happens to undigested food. Use words from the list. rectum faeces nutrients peristalsis fibre large intestine anus fat Fibre emulsifier __________ bulks up food so thatperistalsis. it can be moved through the digestive system by the process of _________. faeces anus. It is not digested but forms __________ which are passed out of the body via the __________. rectum It is stored in the __________ until you are ready to defecate. Task C Undigested food 2) This meal contains nutrients, water and fibre. Describe the journey of this meal through the digestive system. Include information about: ● the parts of the digestive system involved in digesting this food ● what will happen to the different parts of the meal after digestion Practice Task C Undigested food This meal contains nutrients, water and fibre. Describe the journey of this meal through the digestive system. Your answer may have included: The organs of the digestive system, listed in order. The roles of the liver and pancreas in digestion. The role of peristalsis in moving food through the digestive system. Nutrients from the food are absorbed into the blood through the villi in the small intestine. ● Water from the food is absorbed into the blood through the wall of the large intestine. ● Fibre from the food is not absorbed and is passed out of the body as faeces. ● ● ● ● Feedback Summary The parts of the human digestive system ● The digestive system breaks down food into nutrients that can be absorbed into the blood. mouth oesophagus stomach ● This process is called digestion. ● Each part of the digestive system is adapted to digest food. ● Food passes from the mouth, down the oesophagus to the stomach. ● Most digestion occurs in the small intestines. small intestine Summary The parts of the human digestive system ● The pancreas and the liver are organs with glands which secrete chemicals to digest food. ● Nutrients are then absorbed into the blood. ● Waste products, including fibre, continue into the large intestine and form faeces. ● Faeces are stored in the rectum and passed out of the body via the anus. liver pancreas small intestine rectum large intestine anus © Oak National Academy 2023. 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