Topic 4: Digestion and Nutrition

Transcription

1 Topic 4: Digestion and Nutrition THE CONTENTS OF FOOD Food contains nutrients: Nutrients include: Nutrients must be small enough to enter our cells. If they are too large they must be digested first. o Digestion is the process of breaking down complex molecules into simpler substances o Once food is digested, nutrients will diffuse from our digestive system into our blood o The circulatory system carries them to our cells (circulatory and digestive systems work together) Nutrients Digested Digested Digested Diffuse directly into the blood stream Diffuse into blood stream 1

2 Food also contains roughage fiber and cellulose from fruits and vegetables that we can t digest. o Roughage is not absorbed into our blood but is eliminated from the body o Prevents us from becoming constipated. DIGESTION Purpose: food particles are broken down into molecules small enough to diffuse into our blood o are needed (written on top of arrow) The human digestive system Know diagram (also in review book page 47) The mouth (oral cavity) 1. Food is ingested (taken in) 2. Chewing breaks down food into smaller pieces 3. Chemical digestion of AMYLASE: an enzyme in saliva that breaks down starch into sugar The esophagus Tube that extends from the mouth to the stomach PERISTALSIS: Muscle contractions that move food down the esophagus The is a small flap of tissue that prevents food from going down the trachea 2

3 The stomach mechanical digestion muscle contractions move food around, breaking it apart 3. chemical digestion of gastric juice contains HCl (hydrochloric acid) which kills bacteria in food also contains the enzyme which breaks down proteins into amino acids The small intestine long tube where 1. Chemical digestion physically breaks down fats and oils into droplets (called emulsification) Allows chemical digestion to occur faster the enzyme then breaks down lipids (fats) into fatty acids and glycerol digestion of starches and proteins CONTINUES 2. absorption of nutrients into the blood the small intestine is lined with They are fingerlike projections that the nutrients are then carried by the circulatory system to our cells The large intestine NO DIGESTION OCCURS HERE Receives undigested food and water from the small intestine 1. prevents the body from becoming dehydrated 2. absorb vitamins bacteria that live in large intestine produce vitamins B and K 3. Elimination (egestion) Removal of undigested material (feces) out the anus 3

4 The liver Digestive 1. : used to break down fats into smaller molecules 2. Stores glucose as the starch glycogen. When energy is needed the glycogen is broken down into glucose The glucose will enter the circulatory system and travel to cells for cellular respiration The gall bladder 1. It is secreted into the small intestine when needed. The pancreas secretes pancreatic juice into the 1. Neutralizes the acidic food from the stomach, making it slightly basic 2. Contains the enzymes: a) amylase: breaks down carbs b) trysin: breaks down proteins c) lipase: breaks down fats Appendix Small pouch located off the large intestine Vestigial structure: no longer serves any purpose Summary of Digestion Substance Where digestion begins Enzyme Carbohydrates (starch) Proteins Lipids When things go wrong with the digestive system 1. Ulcers A thick layer of mucus protects the stomach from the acid When that layer breaks down, enzymes will begin to digest the stomach wall. This digested portion is called an ulcer The acid coming into contact with the ulcer makes them very painful Causes: bacterial infection. Treatable with antibiotics 4

5 2. Constipation the large intestine absorbs too much water Feces will remain in the large intestine for a long period of time It is believed that this could be a cause of colon cancer Eating a lot of roughage (diet high in fiber) prevents constipation 3. Diarrhea The large intestine does not absorb enough water Causes: virus Can lead to dehydration 4. gall stones accumulation of hardened cholesterol/calcium in the gall bladder 5. Appendicitis Appendix becomes infected and swollen PRACTICE REGENTS PROBLEMS 1) In the human body, hydrochloric acid is responsible for the low ph of the contents of the A) stomach B) kidney C) lungs D) liver Questions 2 and 3 refer to the following: The diagram below represents the digestive system of a student who has eaten a sandwich consisting of two slices of bread, chicken, lettuce, and mayonnaise. 2) Which organ produces a substance that would be used in the emulsification of the lipids in the mayonnaise? A) 4 B) 2 C) 1 D) 7 5

6 3) In which organs would chemical digestion of the chicken take place? A) 1 and 3 B) 1 and 7 C) 3 and 5 D) 2 and 6 4) An accumulation of hardened cholesterol deposits is associated with the development of A) gallstones B) appendicitis C) constipation D) gout 5) Which structures secrete chemicals utilized for the completion of digestion within the small intestine? A) liver and pancreas B) gallbladder and pharynx C) glomerulus and villi D) esophagus and alveoli 6