Problem 118 - Objective Biology for NEET

Question

Mark the correct statement from the following: (a) Tracheal rings are of hyaline cartilage. (b) Dorsal side of thoracic chamber is formed by sternum. (c) Expiration occurs when there is negative pressure in lungs. (d) All the above

Step-by-Step Solution

Answer

The correct statement is (a) Tracheal rings are of hyaline cartilage.

Step 1: Evaluate Statement (a)

The statement 'Tracheal rings are of hyaline cartilage' is referring to the type of cartilage that composes the tracheal rings. The trachea, also known as the windpipe, is the tube that connects the pharynx and larynx to the lungs. It is supported by semi-circular, C-shaped rings of hyaline cartilage, which give it structure, making this statement true.

Step 2: Evaluate Statement (b)

The statement 'Dorsal side of thoracic chamber is formed by sternum' suggests that the sternum, or breastbone, forms the dorsal, or back side, of the thoracic, or chest cavity. This, however, is not anatomically correct. The sternum forms the ventral (front) aspect of the chest cavity, while the vertebrae form the dorsal side. Consequently, this statement is false.

Step 3: Evaluate Statement (c)

The third statement 'Expiration occurs when there is negative pressure in lungs' mentions a condition for the process of exhalation. However, during expiration, internal pressure in the lungs becomes higher than atmospheric pressure, leading air to move out of the lungs. This makes the statement false.

Key Concepts

Tracheal Cartilage

The trachea, or windpipe, is essential in our respiratory system. It acts as a pathway for air to travel to and from the lungs. To maintain its structure and prevent collapse, the trachea is supported by a series of C-shaped tracheal cartilage rings. These rings are made of hyaline cartilage, a type of cartilage known for its strength and flexibility. The open part of the C-shaped rings faces backward towards the esophagus. This design allows the esophagus to expand when swallowing. Understanding the role and composition of tracheal cartilage helps appreciate its support and protection functions for the trachea.

• Provides rigidity and support to the trachea
• Makes sure the trachea remains open despite changes in pressure during breathing
• Composed of hyaline cartilage, known for durability

Without these tracheal rings, the trachea could collapse, leading to severe breathing difficulties. Thus, the hyaline cartilage is crucial to maintaining an open airway.

Thoracic Structure

Our thoracic, or chest structure, houses vital organs, including the heart and lungs. The thoracic cavity is encapsulated by the rib cage, spine, and sternum. Contrary to some misconceptions, the sternum, also known as the breastbone, is located at the front (ventral side), not the back (dorsal side) of the thoracic chamber.

• The sternum provides an attachment point for the ribs and helps protect the heart and lungs.
• The dorsal side of the thoracic chamber is actually formed by the vertebral column.
• Ribs connect at the back to the spine and at the front to the sternum through costal cartilage.

This structure supports and encloses the thoracic cavity, playing a crucial role in safeguarding our internal organs.

Expiration Process

Breathing involves both inspiration (inhaling) and expiration (exhaling). The expiration process is when air is expelled from the lungs, and it occurs when the pressure inside the lungs exceeds the atmospheric pressure outside. This happens primarily because the respiratory muscles relax.

• The diaphragm moves upwards, and the rib cage moves downwards and inwards.
• Volume of the thoracic cavity decreases, raising pressure in the lungs.
• Air moves out of the lungs to equalize pressure.

Understanding that expiration is a passive process of pressure changes helps visualize how delicate and efficient our respiratory system really is. It's like letting air out of a balloon when pressure is applied. Remember, during expiration, pressure in the lungs becomes greater than the air pressure outside, which is why air flows out.