AP Biology : Understanding Alveoli

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding Alveoli

What is cell type forms the lining of the alveoli?

Possible Answers:

Respiratory

Apical

Epithelial

Basal

Endothelial

Correct answer:

Epithelial

Explanation:

The alveoli are lined with a single layer of squamous epithelial cells, which allow for easy diffusion of vital gases. Basal and apical cells refer to cells located at the bottom and top of structures, respectively. Endothelial cells line the circulatory system and blood vessels. There is no formal class of cells known as "respiratory cells."

Example Question #12 : Animal Biology

The alveoli of the human lungs cluster together in alveolar sacs. These clusters are commonly said to resemble clusters of grapes, as the nearly spherical alveoli appear to bud away from "stems" (alveolar ducts). Which response best explains the alveoli's spherical shape?

Possible Answers:

The epithelial cells of the alveoli have a natural tendency to form spherical shapes; the alveoli's shape is a result of this tendency and is somewhat of a biological accident

The alveoli lie immediately adjacent to the capillaries around the lungs; the alveoli's spherical shape is nothing more than the result of the capillaries' generally round shape

Some extracellular matrix (ECM) material helps connect the alveoli to the capillaries; the presence of this material causes the alveoli to "pucker" into approximately spherical shapes

Alveoli's spherical shape gives them the maximal amount of surface area possible for their volume; this large surface area allows for highly efficient gas exchange between the blood and the air in the lungs

Correct answer:

Alveoli's spherical shape gives them the maximal amount of surface area possible for their volume; this large surface area allows for highly efficient gas exchange between the blood and the air in the lungs

Explanation:

The spherical or grape-like shape of the alveoli allows for maximum contact between the alveoli and the capillaries that surround them. The alveoli are filled with air that has been taken into the lungs from the environment, so a high surface area allows for maximum contact between air from the environment and capillaries. Oxygen rapidly diffuses through the exceptionally thin alveolar walls to the capillaries, which carry hemoglobin-containing blood cells that bind to the oxygen and shuttle it around the body. Blood cells also release carbon dioxide into the alveoli and lungs, which is why this process is called gas exchange. 

Capillaries are considerably smaller than alveoli; they surround the alveoli like a mesh, and are certainly not the cause of the alveoli's shape. Furthermore, though the cells of the alveoli do secrete extracellular matrix material, the cells affect the structure of the extracellular matrix, rather than the other way around. The shape of the alveoli is crucial to their function in gas exchange and cannot be considered an "accident," or the unexpected result of the shapes of other biological structures. 

Example Question #13 : Animal Biology

What type of epithelial tissue surrounds the alveoli?

Possible Answers:

Stratified squamous epithelium

Simple cuboidal epithelium

Simple columnar epithelium

Simple squamous epithelium

Correct answer:

Simple squamous epithelium

Explanation:

Alveoli are the site of gas exchange in the lungs. Because rapid diffusion of gases is necessary between the capillaries and the alveoli, a very thin epithelial layer is needed. As a result, alveoli use simple squamous epithelium so that gases can easily diffuses to and from the bloodstream.

Example Question #2 : Respiratory Anatomy

Which of the following structures is found within the lungs and helps facilitate gas exchange?

Possible Answers:

Bronchi

Trachea

Alveoli

Microvilli

Secretory vesicles

Correct answer:

Alveoli

Explanation:

Alveoli are at the end of the respiratory pathway in humans, and act as a site of gas exchange (carbon dioxide and oxygen).

The path of air through the respiratory tract is: trachea, bronchi, bronchioles, alveoli. It is important to note that no gas exchange takes place in the bronchi, but does in the bronchioles, which are passageways that branch off from the main bronchi and eventually lead to alveolar ducts.

Micorvilli are found int he small intestine and act to increase the surface area in order to increase nutrient absorption. Secretory vesicles are used to transport proteins, hormones, and other molecules from a cell into the extracellular space.

Example Question #1 : Respiratory System

The function of an alveolus is most evident in the basic anatomy of which type of alveolar cell?

Possible Answers:

The very thin type 1 alveolar cells

The cuboidal or round type 2 alveolar cells

The phagocytic alveolar macrophages

Clara cells

Correct answer:

The very thin type 1 alveolar cells

Explanation:

The vast majority of the surface area of an alveolus is made up of type 1 alveolar cells, which are squamous (flat), thin epithelial cells that allow rapid gas exchange between the air inside the alveoli and blood in the surrounding capillaries. The healthy adult human has millions of alveoli in his/her lungs, providing a huge total surface area across which gas can diffuse, letting oxygen into the bloodstream and carbon dioxide out.

Example Question #1 : Understanding Alveoli

Which of these describes the gas exchange that occurs in the alveoli?

Possible Answers:

The process of bringing air into the lungs

Exchange of oxygen and hydrogen between the blood vessels and the alveoli

Exchange of carbon dioxide and oxygen between the blood vessels and the alveoli 

Exchange of molecules across the pulmonary cell surfaces

The process of cleansing the air inhaled through the bronchi

Correct answer:

Exchange of carbon dioxide and oxygen between the blood vessels and the alveoli 

Explanation:

Diffusion is the spontaneous process by which substances move from areas of high to low concentration. During diffusion in alveoli, the high levels of  that are in the blood vessels surrounding the alveoli causes it to diffuse out of the blood vessels and into the alveoli where there are low levels of  (atmospheric air is about  ). In the same way, high levels of oxygen in the alveoli diffuses into the area of low oxygen concentration within the blood vessels. 

Example Question #2 : Understanding Alveoli

Which best describes the structure of the alveoli?

Possible Answers:

A thin layer of epithelial cells separated from endothelial cells in capillaries by interstitial fluid

A thick layer of epithelial cells separated from endothelial cells in capillaries by interstitial fluid

A thick layer of epithelial cells directly connected to endothelial cells in capillaries

Tiny sacks that fill up with blood to facilitate the exchange of oxygen and nutrients

A thin layer of epithelial cells directly connected to endothelial cells in capillaries

Correct answer:

A thin layer of epithelial cells directly connected to endothelial cells in capillaries

Explanation:

The alveoli's structure maximizes the efficient transfer of gas from air to the capillaries and vice versa. Therefore the contact point between air and the capillaries needs to be as thin as possible so gas has only a short distance to diffuse. Alveoli are therefore made up of a thin layer of epithelial cells that are in direct contact with endothelial cells in the capillaries.

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