3rd Grade ICSE

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02. The Human Body

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Last edited 37 days ago by Learn LoopHQ.

Chapter: 02. The Human Body

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Explain how the human body is organized, starting from the smallest building block.

The human body is organized hierarchically, beginning with the smallest units called cells. Similar cells group together to form tissues, which then combine to create organs, each with a specific function. Multiple organs working in coordination form an organ system, such as the digestive or respiratory system. Finally, all the different organ systems work together seamlessly to form a complete and functional organism, enabling complex activities like walking, learning, and growing.

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Describe the structure and main functions of the skeletal system.

The skeletal system is formed by bones, creating a framework called the skeleton. An adult human body has 206 bones, while newborns have about 305 that later fuse. This skeleton provides essential shape and support, allowing us to stand straight and move. Additionally, it acts as a protective shield for delicate internal organs, such as the skull safeguarding the brain and the ribs protecting the heart and lungs. Joints, where two or more bones meet, enable bending and flexibility, with around 360 joints present in our body.

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Explain the primary functions of the brain and the heart in the human body.

The brain, located inside the head and protected by the skull, is the body’s control center. It helps us think, gathers information from our surroundings, and decides how to respond. Crucially, it sends and receives messages to and from different body parts, giving them precise instructions for all activities. The heart, a hollow muscular organ situated in the chest cavity, is responsible for pumping blood. It circulates blood through a network of tiny tubes called blood vessels to every part of our body, ensuring that oxygen and nutrients are delivered where needed.

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Detail the journey and digestion of food through the stomach and intestines.

The journey of food begins when it is chewed in the mouth and then travels down the food pipe. It reaches the J-shaped stomach, where it is thoroughly churned and mixed with digestive juices to break it down further. From the stomach, the partially digested food moves into the small intestine, where it undergoes additional digestion by intestinal juices, and crucially, nutrients are absorbed into the bloodstream. Finally, the undigested food passes into the large intestine, where excess water is absorbed. The remaining waste is then eliminated from the body through the anus as faeces.

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Detail the process of breathing, including the roles of the nose, windpipe, lungs, and diaphragm.

Breathing is the process of taking in oxygen and giving out carbon dioxide, involving the nose, windpipe, and lungs. Air first enters through the nose, then travels down the windpipe to reach the lungs. The lungs are two sponge-like structures responsible for providing oxygen to the bloodstream and exhaling carbon dioxide. Below the lungs lies the diaphragm, a crucial muscle. During inhalation, the diaphragm contracts and moves downwards, increasing the chest cavity’s size and drawing air into the lungs. Conversely, during exhalation, the diaphragm moves upwards, decreasing the chest cavity’s size and pushing air out.

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What are the main causes and effects of air pollution?

Air pollution occurs when harmful substances like gases, dust, fumes, or odour are introduced into the atmosphere, making the air detrimental to living beings. The main causes include industrial emissions from factories, smoke released from burning garbage and crackers, and dangerous gases found in car exhaust fumes. The effects of air pollution are severe and widespread. It can make people sick, cause breathing difficulties, and lead to serious conditions like lung cancer, various respiratory diseases, and heart problems, even triggering asthmatic attacks. Furthermore, certain types of air pollution can damage the protective ozone layer in the atmosphere.

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