12.4.2 Human Gas Exchange System

Question 1

human gas exchange system

Answer 1

• Gas exchange (also referred to as respiration) involves the uptake of oxygen from the air and the release of carbon dioxide.
• Breathing through the nose serves to warm and moisten the air as it enters the lungs.
• The trachea, covered with cartilaginous rings, serves as a passageway for air into the lungs. The trachea branches into two bronchi, which further branch into smaller tubes called bronchioles, and end as air sacs called alveoli.
• The alveoli are covered in capillaries and serve as the site for transferring oxygen to the blood.
• Mammals’ lungs operate as a negative pressure system.

Question 2

air enters

Answer 2

• Air enters the nasal cavity during inhalation where it is
  warmed and moistened. Mucus in the nasal cavity aids in moistening air and acting as a trap for microbes, dust, and other small particles.
• The air flows through the trachea, which leads to the lungs. The trachea is a tube that is lined with cartilaginous rings, which keep it open. The epiglottis is a flap of tissue that prevents food from entering the trachea. When swallowing, the trachea moves up and is covered by the epiglottis.

Question 3

alveoli

Answer 3

• Air branches from the trachea into two bronchi. Bronchi branch repeatedly into smaller bronchioles, which end as air sacs called alveoli.
• The alveoli are the site of gas exchange. Several
  characteristics that make them ideal for this purpose include:
  1. They are as thin as one cell layer, allowing
  for gasses to pass through.
  2. They are near a blood supply. Each alveolus
  is covered in capillaries to aid in
  oxygen transfer.
  3. They are moist. Gases diffuse more readily
  across moist surfaces.
  4. They are near a transport system. Oxygenated
  blood at the alveoli will be delivered to the rest
  of the body.

Question 4

negative pressure

Answer 4

• The lungs of mammals ventilate by a negative pressure system. During inhalation, muscles of the diaphragm and rib cage contract and move down to expand the lungs. As lungs expand, air is pulled into the lungs. During exhalation, rib muscles and the diaphragm relax and move up, which makes the lung cavity smaller, forcing air out.

Question 5

The trachea is held open during rapid, vigorous breathing by:

Answer 5

• rings of cartilage.

Question 6

All of these are important characteristics of alveoli except:

Answer 6

• cartilaginous walls

Question 7

The nose plays several roles in respiration. Which of the following is not one of them?

Answer 7

• gas exchange

Question 8

What is the major benefit of having alveoli for gas exchange, rather than a smooth lung surface?

Answer 8

• increased surface area for gas exchange

Question 9

Place the following in order by decreasing size (diameter): bronchioles, bronchi, trachea.

Answer 9

• trachea, bronchi, bronchioles

Question 10

Mammals’ lungs operate as a __________ with the pressure differential caused primarily by contraction of the __________.

Answer 10

• negative pressure system, diaphragm

Question 11

Which of the following structures acts as a trapdoor to prevent swallowed food from entering the lungs?

Answer 11

• epiglottis

Question 12

Stroke patients with poor swallowing reflexes are often at risk of aspiration pneumonia. How does proper swallowing protect healthy individuals from this risk?

Answer 12

• During swallowing, the trachea moves up and is covered by the epiglottis to prevent food and liquids from entering the lungs.