Test: Respiratory Organs & Human Respiratory System

• The respiratory or gas-exchange surface consists of millions of small sacs, or alveoli, lined by a simple squamous epithelium.
• This epithelium is exceedingly thin to facilitate the diffusion of oxygen and CO₂. 
• The alveolar walls also contain cuboidal surfactant-secreting cells.
  

• In animal cells process of aerobic respiration is carried out in mitochondria. The mammalian red blood cells (RBC) lack nucleus, mitochondria and all other major cell organelles as well.
• Hence, RBCs cannot metabolize glucose aerobically and depend on anaerobic respiration for their energy needs.

• The pharynx opens into the larynx by a slit-like aperture called the glottis, which is covered by a cartilaginous flap called the epiglottis.
• The epiglottis closes the glottis to prevent the entry of food particles during swallowing.
  

A book lung is a type of respiration organ used for atmospheric gas exchange that is found in many arachnids, such as scorpions and spiders.

• The respiratory system helps in the regulation of blood pH, gaseous exchange and also contain receptors of smell, produces vocal sound and filter inspired air.
• While the cardiovascular system protects against blood loss by the formation of blood clots.

• Earthworms respire only through the moist skin which is permeable to gases and Leeches also breathe through the skin.
• Frogs don't respire always through the skin whereas Fishes respire through gills.

• The volume of air remaining in the lungs even after a forcible expiration is called residual volume.
• This residual volume prevents the lungs from collapsing.

• The narrow tubes found inside the lungs are called bronchioles. 
• When we breathe, air travels from the nose or mouth, and goes down the trachea and reaches the part called the carina.
• From here the tube branches into two, creating two bronchi that lead to the left and right lung each.
• From there onwards, the bronchi split into smaller and smaller bronchioles until it terminates in the alveoli where gas exchange occurs. 

• The pleural membranes are two layers of the serous membrane which enclose and protect the lung.
• The superficial layer is called the parietal pleura and lines the wall of the thoracic cavity.
• The deep layer is called the visceral pleura and covers the lungs themselves.

The trachea serves as a passage for air, moistens and warms it while it passes into the lungs, and protects the respiratory surface from an accumulation of foreign particles.