Tag: gas exchange in humans

• The process of breathing ) is divided into two distinct phases, inspiration and expiration occur simultaneously.
  
• Inspiration can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure,
•  Inspiration is initiated by the contraction of a diaphragm which increases the volume of the thoracic chamber in the anteroposterior axis. The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorsoventral axis.
• The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intrapulmonary pressure to less than the atmospheric pressure which forces the air from outside to move into the lungs. Hence, When the pressure of air within the lungs is less than the atmospheric pressure, air will not flow out of the lungs.
  

• Carbon dioxide is the waste gas that is produced when carbon is combined with oxygen as part of the body's energy-making processes.
• The lungs and respiratory system allow oxygen in the air to be taken into the body, it also helps the body to get rid of carbon dioxide in the air breathed out.
• When the blood from the heart flows through the capillaries and collects oxygen from the alveoli. At the same time, carbon dioxide passes out of the capillaries and into the alveoli. These blood brings oxygen to the body cells and takes away their carbon dioxide.  Hence, the circulatory system and respiratory system eliminates carbon dioxide from the body.

The digestive system includes alimentary canal and associated glands to carry out the digestion of food and release the energy stored in these food substances. The primary function of the respiratory system is to allow atmospheric oxygen from the air to enter the blood and carbon dioxide from the blood to exit into the air. The endocrine system includes endocrine glands and maintains the homeostasis of the body through hormonal actions. Nervous system serves in the reception of sensory input followed by their integration in the brain and spinal cord and generation of motor output to produce the response. Thus, the correct answer is B.

The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs. The bronchus divides into smaller branches known as segmental bronchi, which divide again into bronchioles, and then again into terminal bronchioles. 

Bronchi are tubes that branch off from the trachea into each lung. Bronchioles are smaller tubes that branch off from each bronchus. There are only two bronchi compared with the hundreds of bronchioles.

The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs, in which branches no longer contain cartilage or glands in their submucosa.  The diameter of the bronchioles is often said to be less than 1 mm, though this value can actually range from 0.3 mm to 5 mm.

The cartilage rings in the trachea prevent the trachea from collapsing during the absence of air and also protect it. These cartilaginous rings are C-shaped.

(d) Some snakes have only one bronchus and the right lung. in mammalian lungs each alveolar duct ends in a passage, called atrium, which leads into a number of rounded alveolar sacs. Each alveolar sac is studded with a large number of air sacs or alveoli. Alveoli are the sites of respiration.