Problem 99 - Objective Biology for NEET

Question

Ribs attached to sternum are (a) First seven pairs (b) All ten ribs (c) First ten rib pairs (d) First five rib pairs

Step-by-Step Solution

Answer

(a) First seven pairs

Step 1: Understanding the rib structure

In human anatomy, most people have 12 pairs of ribs. The ribs are categorized based on their attachments. True ribs refer to the first seven pairs that attach directly to the sternum via costal cartilage. False ribs (8th, 9th, and 10th pairs) indirectly attach to the sternum via costal cartilage. The last two pairs, known as floating ribs, do not attach to the sternum.

Step 2: Matching the understanding with choices

From the understanding of rib attachments, it can be concluded that the first seven pairs of ribs, also known as true ribs, directly attach to the sternum. Match this understanding with the given multiple choices.

Step 3: Choosing the correct answer

Upon checking, the choice (a) 'First seven pairs' matches the understanding, thus, this is the correct answer.

Key Concepts

True Ribs

True ribs are an essential part of the human rib cage. They are the first seven pairs of ribs in the ribcage structure. These ribs have a direct connection to the sternum, or breastbone, which is crucial for providing structural support to the front of the ribcage.
Unlike other ribs, true ribs connect to the sternum through costal cartilage, a flexible tissue. This direct connection allows the true ribs to better protect the heart and lungs.

• The true ribs form a cage that is pivotal for respiration.
• They contribute to the overall flexibility and stability of the chest cavity.

Understanding true ribs helps in comprehending the structure and function of the rib cage.

Sternum

The sternum, commonly known as the breastbone, is a flat bone located at the center of the chest. It serves as an anchor for the rib cage. Functionally, the sternum protects vital organs such as the heart and lungs by forming the front shield of the rib cage.
The sternum consists of three parts: the manubrium, the body, and the xiphoid process. Together, they create a strong yet slightly flexible support system:

• The manubrium is the uppermost section where the clavicles and first ribs attach.
• The body of the sternum is the largest part that connects to rib pairs two through seven.
• The xiphoid process is a small cartilaginous projection at the bottom of the sternum.

Knowing the sternum's structure assists in understanding how it functions like a central component of the rib cage.

Costal Cartilage

Costal cartilage is the cartilage that connects the front ends of the ribs to the sternum. This cartilage is vital for rib cage mobility and elasticity.
Costal cartilage has several important roles:

• It allows the rib cage to expand and contract with breathing, providing the necessary flexibility to protect internal organs without sacrificing stability.
• It joins the true ribs firmly to the sternum, ensuring the integrity of the rib cage is maintained.

Costal cartilage plays a crucial role, acting as a cushion that helps absorb shocks and impacts, protecting internal organs further.

Floating Ribs

Floating ribs are the last two pairs of ribs in the human rib cage, numbered eleven and twelve. These ribs have a distinct structure compared to the others: they do not attach to the sternum at all. Instead, they terminate in the muscles of the abdominal wall.
Key characteristics of floating ribs include:

• They provide protection for the kidneys, related to their position in the lower back.
• Due to their lack of sternum attachment, they offer greater freedom of movement.

Despite being termed "floating," these ribs are securely held in place by muscles and ligaments, contributing to the overall flexibility and efficacy of the rib cage.