Tag: human respiratory system

The diaphragm separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity and performs an important function in respiration. As, the diaphragm contracts, the volume of the thoracic cavity increases and air is drawn into the lungs.  It is a dome-shaped sheet of muscle that is inserted into the lower ribs. 

• Some amount of air remains behind in the various parts of the respiratory tract.
• The air in the trachea and bronchi (where no diffusion occurs) is called dead space air.
• The air remaining in the alveoli or air sacs in alveolar air. The maximum volume of air that can be exchanged in one breath in and out is called the vital capacity. It is about 5000ml. 
  
  

Tidal Volume (TV) is the amount of volume of air that can be inspired / expired normally.

A person who is born and lives at sea level will develop a slightly smaller lung capacity than a person who spends their life at a high altitude. This is because the partial pressure of oxygen is lower at higher altitude which, as a result means that oxygen less readily diffuses into the bloodstream. In response to higher altitude, the body's diffusing capacity increases in order to process more air. 

The total lung capacity of the adult male is six liters. Tidal volume is the volume of air inhaled in a single, normal breath. Inspiratory capacity is the amount of air taken in during a deep breath, while residual volume is the amount of air left in the lungs after forceful respiration.

• The lungs are the primary organs of the respiratory system in humans and many other animals. Human lung size is determined by genetics, gender, and height. 
• Different animals exhibit different lung capacities based on their activities. For example, cheetahs have evolved a much higher lung capacity than humans in order to provide oxygen to all the muscles in the body, allowing them to run very fast. 
• Elephants also have a high lung capacity due to their large body and their need to take up oxygen in accordance with their body size. Hence, elephants and cheetahs have higher lung capacities than humans. 
  

During one breath in and out, the volume of gas exchanged is called the tidal volume. It is about 450ml during quiet breathing. The volume of air that can be drawn in after normal inspiration is about 1500 ml and is called as the inspiratory reserve volume (IRV) or complemental air.