Tag: respiratory system in humans

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.

Alveoli are tiny, balloon-like structures that significantly increase the total surface area of the lungs, facilitating efficient gas exchange between air and blood.

Humans use a diaphragm and rib cage muscles for ventilation (negative pressure breathing), whereas frogs use a buccal pump mechanism and lack a diaphragm.

From the larynx, air moves into lower respiratory tract, starting with the trachea and down to the intersection that branches to form the right and left primary (main) bronchi. Each of these bronchi branch into secondary (lobar) bronchi that branch into tertiary (segmental) bronchi that branch into smaller narrow tube airways called bronchioles that eventually connect with tiny specialized structures called alveoli that function in gas exchange.

Ventilation in mammals is achieved by changing the volume of the thoracic cavity, which is controlled by the contraction and relaxation of the diaphragm and the intercostal muscles.