science lesson 2 class 3 with help of an activity, explain how do we inhale and exhale air
Answers
Answer:
Take
Explanation:
We have two lungs (right and left) contained in the thoracic cavity (chest). Surrounding the lungs are ribs, which not only protect them from damage but also serve as anchors for the intercostal muscles. Beneath the lungs is a very large dome-shaped muscle, the diaphragm. All these muscles are attached to the lungs by the parietal and visceral membranes (also called parietal and visceral pleura).
The parietal membrane is attached to the muscles and the visceral membrane is attached to the lungs. The liquid between these two membranes, pleural fluid, sticks them together just as panes of glass become stuck together when wet.
As the visceral membrane covers, and is part of, the lungs and is stuck by pleural fluid to the parietal membrane, when the muscles in the thorax move, the lungs move with them. If air gets between the membranes, they become unstuck and, although the muscles can still contract and relax, they are no longer attached to the lung – as a result, the lung collapses. This abnormal collection of air in the pleural space is called a pneumothorax. If the pleural fluid liquid becomes infected, the person develops pleurisy.
When the intercostal muscles contract, they move up and away from the thoracic cavity. When the diaphragm contracts, it moves down towards the abdomen. This movement of the muscles causes the lungs to expand and fill with air, like a bellows (inhalation). Conversely, when the muscles relax, the thoracic cavity gets smaller, the volume of the lungs decreases, and air is expelled (exhalation).
Activity:
Materials List
Each group needs:
2-liter empty plastic bottle with cap
2 plastic drinking straws; available inexpensively at restaurant supply stores or donated by fast-food chains; do not use the flexible drinking straws
2 9-inch balloons
1 larger balloon; for example, for a punch ball
2 rubber bands
Procedure
Before the Activity
Gather materials and make copies of the Lung Worksheet.
In each of the 2-liter bottle caps, drill 2 holes that are just big enough for a drinking straw to fit through. Tip: Make sure to drill the holes far enough apart that the holes do not become one big hole!
Using a pair of scissors, cut off the bottom of each 2-liter bottle.
Peel off the labels, if any, on the 2-liter bottles.
Tell students that the 2-liter bottle represents the human chest cavity.
Stick two drinking straws through the two holes in the bottle cap.
Place one 9-inch balloon on the end of each straw and secure them with rubber bands,straws represent the bronchi and the balloons represent the lungs.
Stick the balloon ends of the straws through the bottle opening and tightly screw on the lid.
Stretch out the larger balloon and place it over the open bottom of the bottle. larger balloon represents the diaphragm. Now they have a finished model of the lungs!
Pull the diaphragm (balloon) down (that is, away from the lungs) in order to inflate the lungs. (Note: This makes the chest cavity larger and decreases the pressure.)
Push the diaphragm (balloon) in (towards the lungs) in order to deflate the lungs. (Note: This makes the chest cavity smaller and increases the pressure.)
bronchi: Two large tubes connected to the trachea that carry air to and from the lungs.
diaphragm: A shelf of muscle extending across the bottom of the rib cage.
lungs: Spongy, saclike respiratory organs that occupy the chest cavity, along with the heart. They provide oxygen to the blood and remove carbon dioxide from it.