Transport in Animals PDF

## Transport in Animals ### Lymphatic System * The lymphatic system is a network of vessels that carry a fluid called lymph around the body. * Throughout the lymphatic system are clumps of tissue called lymph nodes that contain lymphocytes. * Lymphocytes fight pathogens. * **Key Facts:**...

## Transport in Animals ### Lymphatic System * The lymphatic system is a network of vessels that carry a fluid called lymph around the body. * Throughout the lymphatic system are clumps of tissue called lymph nodes that contain lymphocytes. * Lymphocytes fight pathogens. * **Key Facts:** * The fluid carried by the lymphatic system is called lymph. * The lymphatic system returns lymph to the blood. * Lymph contains lymphocytes. * New white blood cells called lymphocytes are made in lymph nodes. These cells defend the body against pathogens. * The lymphatic duct collects lymph. * The spleen produces white blood cells called lymphocytes that fight germs. * All the body's cells are surrounded by a fluid that seeps from tissues and blood capillaries. * The lymphatic system collects this fluid and returns it to the bloodstream. * As the fluid travels through the lymphatic system, it is filtered by lymph nodes, where lymphocytes screen it for pathogens and attack any they find. * **Movement of Lymph:** * There is no pump to force the lymph around the body. * Instead, lymph vessels contain valves to keep the fluid flowing in one direction. * Muscles around the vessels help when they contract. ### The Lungs * The lungs are part of the respiratory system. * They play an important role in the exchange of gases: * Oxygen from the air enters the bloodstream when you breathe in. * Waste carbon dioxide leaves the bloodstream when you breathe out. * **Key Facts:** * Air mostly enters through the nose and passes through the trachea, bronchi, and bronchioles before reaching the alveoli. * Gas exchange takes place in the alveoli. * Gas exchange surfaces are areas where oxygen enters the bloodstream and carbon dioxide leaves the bloodstream. * **The Respiratory System:** * Inhaled air enters the trachea (windpipe), which is split into two tubes called bronchi. * Inside the two sponge-like lungs, these tubes divide into smaller tubes called bronchioles. * Tough bands of cartilage surround the trachea, stopping it from collapsing when air is breathed out. * The intercostal muscles are located between the ribs. They contract and relax when you breathe. * The diaphragm is a large sheet of muscle that contracts and pulls flat when you breathe in and relaxes and springs upward when you breathe out. ### Gas Exchange * All living organisms have gas exchange surfaces, such as in the lungs, where gases enter and leave the blood. * At the end of each bronchiole are tiny air sacs called alveoli (singular alveolus). * This is where gas exchange takes place: * Oxygen moves from the alveoli into the blood, and carbon dioxide moves from the blood into the alveoli. * Both gases move by diffusion. * The capillary and alveolus both have very thin walls to maximize diffusion. ### Gas Exchange in Fish * In a fish, the gills are the gas exchange surfaces. * Gills are made up of lots of gill filaments. This increases the surface area for gas exchange by diffusion. * Just as the countless alveoli in the lungs increase the gas exchange area for a human. ### Breathing * When you breathe in, oxygen-rich air enters your lungs so the oxygen can enter your bloodstream. * When you breathe out, the air contains less oxygen but more waste carbon dioxide that has entered the air from the bloodstream. * **Key Facts:** * Breathing in is called inhalation (or inspiration); breathing out is called exhalation (or expiration). * The ribs, intercostal muscles, and diaphragm control your breathing. * Air enters and leaves the lungs because of changes in pressure and volume. * Sticky mucus traps dust and particles. * Ciliated cells lining the airways sweep away dust and microorganisms trapped in the mucus. * **Breathing in and Out:** * Breathing is controlled by a set of muscles that work together to make the volume of the chest (thorax) cavity increase and decrease. * This in turn makes air move in and out. * **Inhalation (breathing in):** * The outer set of muscles between the ribs (external intercostal muscles) contract. This makes the ribs move upward and outward. * At the same time, the muscles of the diaphragm contract. This flattens and pulls the dome-shaped diaphragm down. * The volume of the chest cavity increases. This causes pressure inside the chest cavity to fall below the pressure outside the lungs. As a result, air is drawn into the lungs. * **Exhalation (breathing out):** * The inner set of muscles between the ribs (internal intercostal muscles) contract, causing the rib cage to move downward. * The muscles of the diaphragm relax, letting it move back up. * The volume of the chest cavity decreases. This causes pressure inside the chest cavity to rise above the pressure outside the lungs. Air is now forced out of the lungs. * **Cilia and Mucus:** * When you breathe in, hairs inside the nose trap dust particles and microorganisms. * The trachea and bronchi are also lined with cells that have microscopic hairlike structures called cilia and cells that release mucus. * Together, these help prevent dust particles and microorganisms from getting into the lungs. ### Effects of Exercise on Breathing * During exercise, a person breathes more rapidly and more deeply. * This allows more oxygen to be taken into the body, and more carbon dioxide to be removed. * The extra oxygen is used to meet the increased respiration demands in the muscle cells. * **Key Facts:** * During exercise, a person's breathing rate and depth of breathing increases. * Extra oxygen is required for contracting muscle cells to respire more rapidly. * Breathing rate can be measured by counting the number of breaths in one minute. * **Changes to Depth and Rate of Breathing:** * For a person at rest, the volume of air that moves in and out of the lungs is around 500 cm³. * The graph below shows how this changes during exercise. * Not only does the volume breathed in and out (the depth of breathing) increase, but the rate of breathing increases. * Breathing gets faster as more breaths happen each minute. * **Measuring Breathing Rate:** * A person's breathing rate (also known as the respiratory rate) can be measured by counting the number of breaths taken in one minute. * The typical resting respiratory rate for a healthy adult is between 12 and 18 breaths per minute.