Gas Exchange in Humans (B11.1)

Which process takes place at the alveoli?

• Digestion

• Gas exchange

• Photosynthesis

• Respiration

Answer explanation

Gas exchange occurs at the alveoli, where oxygen is absorbed into the blood and carbon dioxide is released from the blood. This process is essential for respiration, but the specific function at the alveoli is gas exchange.

True or False? Alveoli are surrounded by several layers of cells.

• Only during exercise

• False

• Depends on the species

• True

Answer explanation

Alveoli are tiny air sacs in the lungs and are surrounded by a single layer of cells called the alveolar epithelium, not several layers. Therefore, the statement is false.

What are the features of alveoli that make them an efficient exchange surface?

• Thick walls

• Large total surface area

• No ventilation

• Low blood supply

Answer explanation

The large total surface area of alveoli allows for more efficient gas exchange, maximizing the contact between air and blood. Thick walls, no ventilation, and low blood supply would hinder this process.

How is a steep concentration gradient for both oxygen and carbon dioxide maintained in the alveoli?

• High humidity

• Good ventilation and blood supply

• Low surface area

• Thick alveolar walls

Answer explanation

Good ventilation and blood supply ensure a constant exchange of gases in the alveoli, maintaining steep concentration gradients for oxygen and carbon dioxide, which is essential for efficient gas exchange.

Why is a large surface area important for gas exchange within the lungs?

• Increases blood pressure

• Prevents infection

• Allows faster diffusion

• Reduces oxygen levels

Answer explanation

A large surface area in the lungs allows for faster diffusion of gases, such as oxygen and carbon dioxide, between the air and blood. This efficiency is crucial for effective gas exchange, supporting respiration.

What is the function of the trachea?

• Stores oxygen

• Produces mucus

• Filters blood

• Connects the nose and mouth to the lungs

Answer explanation

The trachea, or windpipe, serves as the airway that connects the nose and mouth to the lungs, allowing air to flow in and out during breathing. This makes 'connects the nose and mouth to the lungs' the correct function.

Describe the alveoli.

• Fluid-filled cavities

• Solid tissues

• Tiny air sacs surrounded by capillaries

• Large muscular structures

Answer explanation

The alveoli are tiny air sacs in the lungs where gas exchange occurs. They are surrounded by capillaries, allowing oxygen to enter the blood and carbon dioxide to be expelled, making this choice the correct description.

What is inspired air?

• Air drawn into the body

• Air expelled from the body

• Air in the stomach

• Air in the bloodstream

Answer explanation

Inspired air refers to air drawn into the body during inhalation. This is essential for respiration, as it provides oxygen needed for cellular processes.

True or False? Expired air is air breathed out from the body.

• False

• Only during sleep

• Only during exercise

• True

Answer explanation

True. Expired air is indeed the air that is breathed out from the body after oxygen has been used by the lungs and tissues, making the statement correct.

How does the oxygen content of inspired and expired air differ?

• Inspired air has higher oxygen concentration

• Expired air has higher oxygen concentration

• Both have the same oxygen concentration

• Oxygen is absent in expired air

Answer explanation

Inspired air has a higher oxygen concentration (about 21%) compared to expired air, which contains less oxygen (around 16%) due to the body's consumption of oxygen during respiration.