Question

Select the incorrect statement from the following: (a) Pleural fluid reduces friction on the lung surface. (b) The anatomical setup of lungs in thorax is such that any change in the volume of the thoracic cavity will be reflected in the lung (pulmonary) cavity. Such an arrangement is essential for breathing, as we cannot directly alter the pulmonary volume. (c) The tracheae, primary, secondary and tertiary bronchi and initial bronchioles are supported by complete cartilaginous rings. (d) During swallowing, the glottis can be covered by a thin elastic cartilaginous flap called epiglottis to prevent the entry of food into the larynx.

Short answer

The incorrect statement is (c): 'The tracheae, primary, secondary and tertiary bronchi and initial bronchioles are supported by complete cartilaginous rings.' This is incorrect because the cartilage in these airways do not form complete rings.

Step-by-step solution

Evaluate Statement a

Pleural fluid does indeed reduce friction on the lung surface. It is found in a thin layer between the lungs and the chest wall, and its primary function is to reduce the friction between these surfaces when the lungs expand and contract during breathing. So, this statement is correct.

Evaluate Statement b

This statement correctly describes the relationship between the thoracic cavity and the lung cavity. Any change in volume in the thoracic cavity will indeed be reflected in the lung cavity. This is because the lungs are housed inside the thoracic cavity and are line with pleura that is connected to the chest wall. Therefore, this statement is also correct.

Evaluate Statement c

Statement c is incorrect. While it's true that the tracheae, primary, secondary and tertiary bronchi and initial bronchioles are supported by cartilage, the cartilage does not form complete rings. Instead the cartilage plates only surround the anterior and lateral aspects of these airways. The posterior part of these airways are composed of smooth muscle fibre and connective tissue. This allows the airways to adjust their diameter and therefore control the flow of air to and from the alveoli.

Evaluate Statement d

The statement d accurately describes the role of the epiglottis. During swallowing, the epiglottis covers the glottis, which is the opening into the windpipe, to prevent food from entering the lungs. Thus, this statement is correct.

Key concepts

Pleural Fluid

Pleural fluid plays a crucial role in our respiratory system. It is a thin layer of liquid found between the layers of pleura, which are membranes lining the lungs and the chest cavity. The primary function of pleural fluid is to reduce friction between these surfaces during the process of breathing.

Pleural fluid allows the lungs to slide smoothly against the chest wall as they expand and contract with each breath. Without it, this movement would cause irritation and pain. Additionally, it helps to maintain optimal pressure within the thoracic cavity, which is essential for effective lung function. By cushioning and lubricating, pleural fluid ensures that our breathing remains efficient and pain-free.

Thoracic Cavity

The thoracic cavity is a vital area of the body, housing the lungs and playing a significant role in our respiratory process. It is enclosed by the ribcage and contains the heart, lungs, and other essential structures.

When it comes to breathing, the thoracic cavity is crucial because any volume change within it directly affects the volume of the lung cavity. This connection is due to the pleura, a thin membrane lining that adheres to both the lung tissue and the chest wall. When the thoracic cavity expands or contracts, the lungs follow suit, allowing air to move in and out efficiently.

Essentials:

• Contains the lungs and heart.
• Changes in its volume influence lung function.
• Covered by the protective ribcage and intercostal muscles.

Epiglottis

The epiglottis is a small yet vital structure in our airway located at the base of the tongue. It acts as a switch between the trachea and esophagus, ensuring that air goes into the lungs and food goes into the stomach.

During swallowing, the epiglottis folds back to cover the glottis, which is the opening to the windpipe. This action prevents food and liquids from entering the lungs, protecting the respiratory tract from potential blockages or infections.

Key Functions:

• Prevents the entry of food into the airways.
• Maintains clear pathways for air to reach the lungs.
• Made of elastic cartilage, allowing it to move easily with each swallow.

Cartilaginous Rings

In the respiratory system, cartilaginous rings play an essential role in keeping air passages open and maintaining the structure of the airway. These rings are not complete; they are most prominent in the trachea and the initial parts of the bronchi.

The structure and support provided by these rings prevent the airway from collapsing, thus ensuring an unobstructed path for air to reach the lungs. The openness of the anterior and lateral aspects, with the posterior made of smooth muscle, allows for some flexibility and control over the airway diameter.

Features:

• Found in the trachea and bronchi.
• Provide sturdy support to prevent airway collapse.
• Facilitate the controlled passage of air through expansion and contraction.