The digestive system breaks down food and absorbs nutrients, which the body then uses for cell development and repair. The human digestive system and nutrition are concerned with an organism’s food consumption and energy use. This is an important mechanism that allows living organisms to acquire energy from a variety of sources. Before the nutrients in the food we consume are used to produce energy, many refinements go through. Digestion is the term for this operation. For this operation, humans and other species have specific organs and structures.

Below are the main components of the digestive system: 

• Mouth
• Teeth
• Tongue
• Oesophagus
• Stomach
• Liver
• Pancreas
• Gastrointestinal tract
• Small and large intestines
• Rectum

The biochemical method of inhaling and exhaling gases between the cells and the air is known as breathing. Breathing entails respiratory organs, including the windpipe, lungs, and nose. 

In contrast, respiration is a chemical reaction that occurs within the organism. The air we breathe carries oxygen to our lungs and then to our cells, where it aids in the breakdown of glucose, resulting in the production of electricity. The cells use this energy to carry out their various tasks.

The intensity of the air we breathe in and out of our lungs differs. But, as the air pressure drops, the alveolar spaces expand, and air reaches the lungs (inhalation), and when the pressure of the alveoli inside the lungs exceeds the ambient pressure, the air is blown out of the lungs (exhalation). The amplitude of the pressure differential determines the airflow volume.

The heart pumps blood into the circulatory system, made up of a network of lungs, nerves, and capillaries. The primary function is to provide the body with vital foods, minerals, and hormones. On the other hand, the circulatory system is in charge of gathering metabolic waste and chemicals from the cells and tissues, either filtered or removed from the body.

The human circulatory system comprises four major organs, each with its purpose and function. The organs of the circulatory system that are important include: 

• Heart
• Blood (technically, blood is considered a tissue and not an organ)
• Blood Vessels
• Lymphatic system

The ABO mechanism distinguishes four major blood groups: 

• Blood group  A – has A antigens on red blood cells and anti-B antibodies in the plasma 
• Blood group  B – has B antigens and anti-A antibodies in the plasma 
• Blood group O – has no antigens, yet all anti-A and anti-B antibodies in the plasma blood 
• Blood group AB – has both A and B antigens but no antibodies

Below are the essential characteristics of the human circulatory system: 

• Blood, heart, blood vessels, and lymph make up the human circulatory system. 
• Blood is circulated in the human circulatory system in two chains (double circulation): one for oxygenated blood and the other for deoxygenated blood. 
• There are four chambers in the human heart: two ventricles and two auricles. 
• A body-wide network of blood vessels makes up the human circulatory system. Atherosclerosis affects arteries, nerves, and capillaries. 
• Blood arteries’ primary role is to distribute oxygenated blood and nutrients across the body. It’s also in charge of gathering metabolic wastes for expulsion from the body. 
• The duration of the circulatory system is not physically shown in most diagrams. If a human’s lungs, muscles, and capillaries were spread out end to end, they would cover a complete distance of 1,00,000 kilometres (or roughly eight times the diameter of the Earth).

The human body’s blood flow is unusual, and it’s also powerful. Double circulation refers to the fact that blood circulates twice across the heart. Some species, such as fish, have single circulation, in which blood just makes one circle across the whole body. 

The greatest benefit of double circulation is that oxygenated blood is supplied to all tissues of the body at all times and is not combined with deoxygenated blood.

In this chapter, we learned about the different systems of the human body. We learned about the Function Of Each Organ, the process of every system and the blood groups.

1. What are the different components of the human body?
   A bony skeleton and muscles make up the human body. The brain, trunk, and limbs are the three primary components of the body.
2. What are the human body’s five main organs?
   Humans have five vital organs that function to survive. The brain, heart, kidneys, liver, and lungs are among these organs.
3. What is the body’s tiniest organ?
   The gland of the pineal.
4. What is the body’s hardest-working organ?
   The heart. This muscle, the body’s hardest-working organ, is essential to any cell in the body.
5. Is blood considered an organ?
   Blood is a tissue as well as a solvent. It’s called tissue because it’s made up of identical specialised cells that perform specific functions. The blood is fluid, and these cells are trapped in a liquid matrix (plasma).