Chapter: 02. The Human Body
The Human Body: An Amazing Machine
Our body is an incredible machine that can perform many different functions. It helps us understand the world around us and respond to it. Our body even has the ability to repair itself! Because it’s so important, we must take good care of our bodies.
We use our five sense organs—eyes, ears, nose, tongue, and skin—to see and understand the world. Besides these sense organs, our body has many other organs that work together in groups called organ systems. While sense organs help us interact with our surroundings, organ systems perform various internal functions.
Body Organization: From Cells to Systems
All the organs in our body are made up of tiny building blocks called cells. A cell is the smallest unit of our body.
Cells: There are millions of cells in our body. Cells have different types depending on the type of organ they form. Tissues: Similar cells join together to form tissues. Organs: Tissues then join to form an organ. Organ System: A group of organs that work together to do a particular job forms an organ system. Organism: All these organ systems work together to make it possible for the human body to walk, play, learn, watch, grow, and do many other activities. All these organ systems together form an organism. Examples of organ systems in the human body include the respiratory system, skeletal system, muscular system, digestive system, circulatory system, and excretory system.
Internal Organs
Our body is made up of bones and muscles, which are covered by the skin. Bones are hard, while muscles are soft.
Bones
Number of Bones: An adult human body has a total of 206 bones. A newborn baby has about 305 bones; as they grow, some bones fuse together, reducing the total count. Skeleton: Bones form a framework called the skeleton. The skeleton gives shape and support to our body. Without it, we wouldn’t be able to stand straight or walk. The skeleton also protects the soft, inner parts of our body. For example, the skull covers and protects the soft brain, and the ribs protect the heart and lungs. Joints: The place where two or more bones meet is called a joint. We bend with the help of these joints. There are about 360 joints in our body. Interesting Fact: Earthworms have no bones at all! Muscles
Function: Muscles help the bones to move. Quantity: There are more than 600 muscles in our body. Size: Some muscles are big (like those in our legs and arms), while others are small (like the muscles in our eyes). Brain
Location: The brain is located inside the head and is protected by the skull. It gathers all the information from our surroundings and decides how to respond. It sends and receives messages to and from different parts of the body, giving them instructions.
Heart
Nature: The heart is a hollow muscular organ, meaning it’s a muscle. Location: It is located in the chest cavity. Function: It pumps blood through tiny tubes called blood vessels to different parts of our body. Kidneys
Quantity: We have two kidneys. Function: They remove waste from the blood and produce urine. Urine Pathway: The ureters carry the urine from the kidneys to the bladder. This urine is stored in the urinary bladder before being passed out of the body. Important Information: Urine is a waste product of our body. Ingesting a lot of chemicals can harm the kidneys. Stomach and Intestines
The food we eat provides us energy. But before it provides energy, food needs to be further broken down and absorbed by the body. This process of breaking down food and absorbing it is known as digestion. The organs that help the food break down form the digestive system.
Mouth: We chew food in our mouth. Food Pipe: Food then travels down the food pipe. Stomach: The food pipe leads to the J-shaped bag called the stomach. In the stomach, the food is churned properly and mixed with digestive juices. Small Intestine: The food then moves to the small intestine. Here, the food is further digested by intestinal juices. The nutrients from the digested food are absorbed by the blood. Large Intestine: The undigested food goes to the large intestine. Here, the extra water present in the food is absorbed. Anus: The undigested food is sent out through the anus in the form of faeces. Respiratory System
We breathe in air to live. We take in air through our nose. The air then travels down the windpipe into the lungs. After the air reaches the lungs, we need to breathe out.
Components: The nose, windpipe, and lungs together form the respiratory system. Inhaled Air: The air that we take in is rich in oxygen and is known as inhaled air. Exhaled Air: The air that we breathe out is rich in carbon dioxide and is known as exhaled air. Breathing: The process of taking in oxygen and giving out carbon dioxide is called breathing. Inhalation: Breathing in is called inhalation. Exhalation: Breathing out is called exhalation. How Lungs Work
The lungs are two sponge-like, cone-shaped structures that fill most of the chest cavity. Their essential function is to provide oxygen from inhaled air to the bloodstream and to exhale carbon dioxide. Below the lungs is a muscle called the diaphragm.
During inhalation, the diaphragm contracts and moves downwards, creating more space in the chest cavity, which allows air to enter the lungs. During exhalation, the diaphragm moves upwards, reducing the space, which pushes air out of the lungs. This movement changes the size of the chest cavity. This mechanism can be understood by imagining a sealed bottle with a balloon inside attached to a straw. When you pull down a flexible sheet covering the bottom of the bottle (like the diaphragm), the balloon inside inflates because air rushes in through the straw. When you release the sheet, the balloon deflates as air is pushed out.
Deep Breathing
Deep breathing is a simple breathing exercise that helps in the complete exchange of gases in your lungs. It is done by contracting the diaphragm effectively. In this type of breathing, the air enters the lungs fully, and the belly expands.
Inhale through your nose for about 3 to 4 seconds. While doing this, push out your abdomen (belly will expand, and lungs will expand completely). Hold your breath for 3 to 4 seconds. Then exhale for about 3 to 4 seconds through your mouth. The lungs will contract completely when the air is exhaled. Health Benefits: Pranayam, a set of breathing exercises in yoga, helps in maintaining lung health.
Air Pollution
We all know we need food, air, and water to survive. We cannot live without air for even a few minutes, which shows how important clean air is.
What is Air Pollution?
Air pollution occurs when unwanted and harmful gases, dust particles, fumes, or odour are introduced into the atmosphere in a way that makes the air harmful for humans, animals, and plants.
Causes of Air Pollution
Air pollution is caused by various human activities:
Factories and industries release smoke and other harmful gases. Smoke is released when garbage is burnt and when crackers are burst. Fumes from car exhausts contain dangerous gases. Effects of Air Pollution
Air pollution can make people sick. Polluted air makes breathing difficult and can cause lung cancer and many respiratory and heart diseases. It can even trigger an asthmatic attack (a respiratory infection). Some types of air pollution can damage the ozone layer present in the atmosphere, which protects us from harmful sun rays. Solution Highlight: Electric vehicles run on electricity and produce no smoke, making them better for our environment. Key Terms
Cells: The smallest building blocks in our body. Bones: The hard parts of our body that form the skeleton. Muscles: The soft parts of our body that cover the bones and help them move. Skeleton: The framework of bones that gives shape and support to our body. Joint: The place where two or more bones meet. Digestion: The process by which food is converted into substances that can be absorbed into the body. Breathing: The process of taking in oxygen and giving out carbon dioxide. Inhalation: Breathing in. Exhalation: Breathing out. Air pollution: Pollution of the atmosphere as a result of different human activities. Chapter Summary
The human body is a complex and amazing machine. It is organized in levels, starting from the smallest units called cells, which form tissues, then organs, then organ systems, and finally, a complete organism. Our body uses five sense organs (eyes, ears, nose, tongue, skin) to understand the world.
Internally, essential organs like bones and muscles provide structure and movement. Bones form the hard skeleton, protecting vital organs and allowing us to stand and move. Muscles, which are soft, work with bones to create motion. Other crucial internal organs include the brain (for thinking and control), the heart (for pumping blood), kidneys (for waste removal), and the stomach and intestines (for digesting food and absorbing nutrients).
The respiratory system, comprising the nose, windpipe, and lungs, enables us to breathe. Breathing involves inhalation (taking in oxygen) and exhalation (giving out carbon dioxide), with the diaphragm playing a key role in lung expansion and contraction. Deep breathing exercises can enhance lung health.
However, the air we breathe can be harmed by human activities leading to air pollution from industrial smoke, burning garbage, and car exhausts. Air pollution has serious health consequences, affecting breathing and causing various diseases, and can also damage the ozone layer. Understanding these systems and threats helps us appreciate our body and the environment.
Self Study
