What is a lung ?

About a lung

The right lung is made of three. Each is compared to a leaf and is named an upper lobe, and middle and a lower lobe. The left lung is made of two. An upper lobe and a lower lobe.  Weight is presumed to be 300-350 g of each right and left. It is surmised that the rate of the volume of a right lung and a left lung is about 5:4.

In a standing position, there is much quantity in which the way swells in the lower part (portion which touched the belly) than the upper part (direction near a head). Look at the anime. Moreover, as shown in a lower figure, if we are standing, the blood in a lung has gathered to the lower one mostly by gravity.  As work of a lung is making oxygen in air melt into blood, or sticking oxygen to the hemoglobin in red corpuscles. That the lung in the direction of the bottom with much blood swells greatly, much oxygen will adhere to blood easily. It is structure profitable to us.

Air vesicle (The place which oxygen in the air solves into blood, adheres to red corpuscles, or the carbon dioxide in blood leaves outside of the body).
It is said that the number of newborn air vesicles is about 45 million pieces. At an adult, it seems to be 2-300 million pieces.  Well, when will it become the number of grown-up air vesicles?
It is when we become 8-12 years old. An air vesicle continues increasing until it becomes a sixth grader in an elementary school. Let's watch growth of a lung carefully while we are schoolchildren.