Multicellular Organisms Sub-Topic 2.7 Animal Transport & Exchange Systems On completion of this sub-topic I will be able to state that: Rings of cartilage keep the main airways open Oxygen and carbon dioxide are exchanged through the walls of the alveoli (air sacs) Alveoli have a large surface area, thin walls and a good blood supply for more efficient diffusion of gases Mucus in the airways traps dirt and microorganisms and cilia moves this up and out of the lungs Food is moved along the digestive system by peristalsis Villi in the small intestine have a large surface area, thin walls and a good blood supply to aid absorption of glucose and amino acids The lacteals absorb fatty acids and glycerol (the products of fat digestion) Duncanrig Secondary School 2017 Page 1 of 15
Respiratory System Lungs The lungs are where the gases oxygen and carbon dioxide are exchanged between the blood and the air. We obtain oxygen and get rid of carbon dioxide during breathing. The air we breathe in is called inhaled air. The air we breathe out is called exhaled air. The differences between inhaled and exhaled air are shown in the table below. Gas % in inhaled air % in exhaled air Oxygen 21 16 Carbon dioxide 0.04 4 Nitrogen 79 79 Activity 2 Collect: Air composition kit (see diagram below) Mouthpiece 1. Fill each test tube up to the mark with indicator. 2. Gently breathe in and out through the mouthpiece until the indicator in one of the tubes changes colour. Indicator colours Red normal air Yellow normal air plus CO2 Purple normal air less CO2 Use the information about the indicator to help you describe the differences in the CO2 content of exhaled air and inhaled air. Duncanrig Secondary School 2017 Page 2 of 15
Activity 3 Collect: 2 gas jars length of plastic tubing candle stopclock Plastic tube 1. Collect a sample of the air in the room (inhaled air) in a gas jar with a lid on. 2. Collect a sample of exhaled air in a gas jar as shown in the diagram opposite. Put a lid over it and remove it from the water. 3. Test both samples of air by upturning the gas jars over a lighted candle. 4. Record how long the candle burns for. Write a conclusion below for your experiment: From Activities 2 and 3 summarise the differences between inhaled and exhaled air. Duncanrig Secondary School 2017 Page 3 of 15
How does air get into the lungs? Air moves in and out of our lungs as they inflate and deflate. During inhalation (breathing in), the dome shaped diaphragm contracts (moves down) and the rib cage moves up and out. Muscles between the ribcage called intercostal muscles contract to bring about this movement. Both of these movements increase the volume of the chest cavity and therefore decrease the internal pressure. The pressure outside is then greater than inside and the air rushes in. During exhalation (breathing out) the reverse occurs. Rib cage expands as intercostal muscles contract Air inhaled Rib cage gets smaller as intercostal muscles relax Air Exhaled Lung Diaphragm Inhalation Diaphragm contracts (moves down) Exhalation Diaphragm relaxes (moves up) Duncanrig Secondary School 2017 Page 4 of 15
Activity 4 Collect: Tape measure 1. Breathe in as much air as you can and measure round your chest. 2. Now breathe out as much as you can and measure your chest again. 3. Record this information in the table below. Breathing Movement Inhalation Exhalation Size of Chest (cm) Demonstration 2 It is possible to use a model to show what happens when we breathe. Your teacher will now show you the Model Thorax and demonstrate what happens when we breathe. Glass tube Bell jar Balloons Rubber sheet What movement also occurs in breathing, but is not shown by this model? Duncanrig Secondary School 2017 Page 5 of 15
The Structure of the Lungs Use class resources to label the following diagram. The trachea and bronchi are surrounded by rings of cartilage to keep the airways open. Inhaled air (high in O2, low in CO2) passes down the trachea, bronchi, bronchioles and finally reaches the tiny air sacs called alveoli (singularalveolus). Exhaled air (low in O2, high in CO2) passes out of the lungs in the reverse direction. Duncanrig Secondary School 2017 Page 6 of 15
The Alveoli O2 from the air in the alveolus dissolves in the layer of fluid lining each alveolus diffuses rapidly into the blood through the single celled walls of the alveolus and blood capillary. CO2 diffuses out of the blood and into the air in the alveolus. Bronchiole Deoxygenated blood Oxygenated blood O2 CO2 Single celled wall of alveolus Layer of fluid Single celled wall of capillary Duncanrig Secondary School 2017 Page 7 of 15
Efficiency of Gas Exchange Surface The internal structure of the lungs provide many features which make them efficient at gas exchange. Feature Provided by Advantage Large surface area Many alveoli. Large capillary network. Large volumes of gases can be exchanged. Good blood supply Large capillary network. Blood has a continual O2 uptake and CO2 removal. Very thin walls Single celled wall of alveolus and capillary. Reduces the distance which gases have to diffuse making it faster. Moist surfaces Fluid lining the alveoli. O2 can dissolve before it can diffuse through cells. Duncanrig Secondary School 2017 Page 8 of 15
The Lining of Trachea and Bronchi Mucus lines the air sacs, to allow the gases to dissolve so that they can diffuse easier. Mucus also lines the trachea and bronchi this sticky mucus traps any dust and micro-organisms which are breathed in. The cells that line the air tubes (trachea and bronchi) are covered in tiny hairlike structures called cilia. The cilia move back and forth to sweep the mucus upwards towards the throat. This helps to remove the dust and micro-organisms trapped by the mucus (the mucus is usually swallowed). Cilia Mucus Columnar epithelium Goblet cells Basal cells Duncanrig Secondary School 2017 Page 9 of 15
Digestive System Food needs to be digested so that the large insoluble food molecules are broken down into small soluble ones. These can dissolve and be absorbed through the walls of the small intestine into the blood. The human gut is sometimes called the alimentary canal. It is a tube approximately 5 metres long, running from the mouth to the anus. Part of the tube is coiled up in order to fit into the body. The following diagram illustrates the alimentary canal and associated organs. Use class resources to label the following diagram. Duncanrig Secondary School 2017 Page 10 of 15
Complete the following table that summarises what each part of the alimentary canal does: Part of Alimentary Canal Function (job) Mouth Salivary Glands Oesophagus Stomach Small Intestine Large Intestine Rectum Anus Duncanrig Secondary School 2017 Page 11 of 15
Complete the following table that summarises what each organ does that is associated with the alimentary canal: Associated Organ Function (job) Liver Pancreas Gall Bladder Digestion begins in the mouth. Teeth mechanically break down large insoluble food molecules into manageable-sized pieces and mixed with a fluid called saliva. One function of the saliva is to soften the food and make it easier to swallow. Food then passes down a tube called the oesophagus into the stomach. The walls of the oesophagus contain muscles which move food along the oesophagus towards the stomach. This muscular activity is called peristalsis. Duncanrig Secondary School 2017 Page 12 of 15
The following diagram shows the mechanism of peristalsis. Contraction of muscle behind food Food Activity 5 Collect: rubber tubing washing up liquid marble 1. Rinse the tube with some washing up liquid to lubricate it. Try to get the marble through the tubing. 2. Discuss with your teacher what you needed to do to get the marble to move. 3. Watch the video Feeding. Describe the action of peristalsis in the space provided below: Duncanrig Secondary School 2017 Page 13 of 15
Small Intestine When food leaves the stomach and passes into the small intestine, digestion is completed by the action of a number of enzymes. The soluble molecules produced by digestion then pass across the small intestine wall and enter the bloodstream. The structure of the small intestine allows maximum absorption in the following ways The small intestine is long. The inner lining is folded. The inner lining has many finger like projections called villi Each of these features increases the surface area available for the absorption of soluble food molecules. The Villus Thin wall Blood capillary Lacteal The thin wall is only one cell thick. This allows dissolved molecules to pass through quickly and easily. The blood capillaries ensure a good blood supply is present to receive absorbed molecules. Glucose, amino acids, vitamins and minerals all pass into the blood. The lacteal receives fatty acids and glycerol produced by the digestion of fats. Duncanrig Secondary School 2017 Page 14 of 15
Activity 6 Collect: test tube rack iodine solution spotting tile clinistix stop clock 2 droppers boiling tube goggles visking tubing starch/glucose mixture water 1. Tie a knot in one end of the visking tubing and fill with the starch/glucose mixture, unitl the tubing is approximately ¾ s full. 2. Knot the other end of the visking tubing. visking tubing (gut wall) starch/glucose solution (food) 3. Wash the visking tubing bag under the tap and dry off with a paper towel. 4. Place it in a boiling tube and cover the visking tubing bag with water from the tap. 5. Immediately remove two samples of water from the boiling tube using a clean dropper and put each sample on to a separate dimple on the spotting tile. Test one sample for the presence of starch using iodine solution and the other sample for glucose using clinistix. Take a note of your results in your jotter. 6. Leave for 15 minutes and repeat step 5. ** NOTE : Iodine solution turns black when starch is added. If it does not turn black, then starch is not present. Clinistix turn a purple colour at the tip when glucose is present. If glucose is not present, there is no colour change. Describe what has happened to the starch and glucose in your experiment. Duncanrig Secondary School 2017 Page 15 of 15