Breathing and Exchange of Gases – Human Lungs

A set of question-and-answer flashcards covering thoracic anatomy, pleura, lung lobes and surfaces, alveolar structure, and gas-exchange details.

What organs serve as the main respiratory organs in humans and where are they situated?

A pair of lungs located in the thoracic chamber on either side of the heart.

Which structures form the boundaries of the thoracic chamber dorsally, ventrally, laterally, and inferiorly?

Dorsally: vertebral column; Ventrally: sternum; Laterally: ribs; Inferiorly: dome-shaped diaphragm.

What is the double-walled sac surrounding each lung called, and what fluid does it contain?

Pleura; it contains pleural fluid.

What is the function of pleural fluid?

It reduces friction on the lung surface during breathing movements.

Which pleural membrane is in close contact with the thoracic wall and which with the lung surface?

Outer pleural membrane contacts the thoracic lining; inner pleural membrane contacts the lung surface.

Which lung is smaller and why?

The left lung is smaller because it has a cardiac notch to accommodate the heart.

Name the three external surfaces of each lung.

Costal, diaphragmatic, and mediastinal surfaces.

What structures pass through the groove (hilum) on the mediastinal surface of the lung?

Bronchi, pulmonary arteries, pulmonary veins, pulmonary nerves, and lymph vessels.

How many lobes are present in the right and left lungs, respectively?

Right lung: three lobes (superior, middle, inferior); Left lung: two lobes (superior, inferior).

What are alveoli?

Tiny sac-like structures in the lungs that serve as the real respiratory (gas-exchange) surface.

Approximately how many alveoli are present in an adult human lung?

About 300 to 400 million alveoli.

What is the estimated total alveolar surface area available for gas exchange?

Roughly 140 square metres.

How does the alveolar surface area compare with the total human skin surface area?

Alveolar area (~140 m²) far exceeds skin area (~1.6 m²).

Which blood vessels supply and drain the alveolar capillaries?

Branches of the pulmonary artery supply blood; pulmonary veins return oxygenated blood.

By which process are respiratory gases exchanged between alveolar air and blood?

Diffusion across the alveolar wall.