Chapters :
  • Human Body – 01

Human Body – 01

If we were to “break apart” the human body at the microscopic level, then the cell would constitute the most basic unit of life. The average adult has somewhere between 30 – 40 trillion cells  and an estimated 242 billion new cells are produced every day. When a select group of cells with similar functions come together, it forms a tissue. Tissues  cumulate into organs, organ systems and eventually, an individual organism.

Cells -> Tissues -> Organs -> Organ System -> Organism


The human body exhibits a variety of movements from walking, bending and crawling to running, jumping and climbing. The framework that enables us to do all these activities is the skeleton. Humans have as much as 300 bones at birth. However, the bones start to fuse with age. At adulthood, the total number of bones is reduced to 206. Human Anatomy is the scientific study of form and shapes of human beings: The skeleton also protects several vital organs such as the heart, lungs and the liver. Bones are attached to other bones through ligaments, a fibrous connective tissue. Joints are points at which two bones meet. They enable a range of movements like rotation, abduction, adduction, protraction, retraction and more. Based on flexibility and mobility, joints can be further classified into movable joints and immovable joints. Movable joints are flexible while immovable joints (also called fixed joints) are non-flexible since the bones are fused. MUSCLES Muscles are specialized tissues which assist the bones in locomotion. Muscles are attached to the bones through tendons. Movement of limbs happens due to the contraction and relaxation of the corresponding muscles present in that region. Joints help in the flexibility of bones, but a bone cannot be bent or stretched until a muscle acts on it. In other words, the muscles attached to that bone pulls it to the direction of movement. Furthermore, most movement involves muscles that work as a pair. For example, when we bend our arm, muscles in that region contract, become shorter and stiffer and pull the bones to the direction of movement. For relaxation (stretching), muscles in the opposite direction have to pull the bones towards it. List of Human Body Parts
    • Human body parts comprise a head, neck and four limbs that are connected to a torso.
  • Giving the body its shape is the skeleton, which is composed of cartilage and bone.
  • Human body internal parts such as the Lungs, Heart, And Brain, are enclosed within the skeletal system and are housed within the different internal body cavities.
  • The spinal cord connects the brain with the rest of the body.

There are different cavities in the human body that house various organ systems.
  1. The cranial cavity is the space within the skull, it protects    the brain and other parts of the central    nervous system.
  2. The lungs are protected in the pleural cavity.
  3. The abdominal cavity houses the intestines, liver and spleen.
Humans have evolved separately from other animals, but since we share a distant common ancestor, we mostly have a body plan that is similar to other organisms, with just the muscles and bones in different proportions. For example, we might assume giraffes have more vertebrae in its neck than humans. No, despite being incredibly tall, giraffes have the same number of vertebrae, i.e., they also have seven vertebrae in their neck. One of the most prominent characteristic features is the ability to use our hands, especially for tasks that require dexterity, such as writing, opening a bottle of water, opening a doorknob, etc. This is the result of humans having ancestors that began walking on their hind limbs rather than using all four limbs. Most of our anatomical insight was gained through the dissection of corpses (cadavers), and for a long time, it was the only way we could gain anatomical knowledge about the human body. It was a rather grotesque affair, but it made up the bulk of medical literature for centuries. These days, technological innovation has made it possible to explore human anatomy at a microscopic level. Even to this day, scientists are newly discovering organs that were previously overlooked or have been mistakenly identified as other existing tissues. In 2018, scientists had discovered a new, body-wide organ called the Interstitium that exists right under the skin. 


It is referred to the physical, mechanical, and biochemical function of humans. This connects health, medicine, and science in a way that studies how the human body acquaints itself to physical activity, stress, and diseases. The person who is trained to study human physiology is called a physiologist.  CLAUDE BERNARD is referred to as the father of Physiology for his exemplary research.


The list of human body parts vary as the standard definition of an organ is still up for debate. However, there are an estimated 79 organs identified to date. We also possess organs that have “lost” their function throughout our evolution. Such organs are called Vestigial Organs. Some of these organs work together and form systems that are specialized to perform a specific function or a set of functions. Collectively, these are known as Organ Systems. And out of these 79 organs, five are crucial for survival, and any damage to these five organs might result in termination of life. These five crucial human body parts are the Brain, Heart, Liver, Lungs and Kidneys.
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