Question

How many ribs are present in human beings?
(a) 6 pairs
(b) 9 pairs
(c) 15 pairs
(d) 12 pairs

Answer 1

Hint: The rib cage is a bony and cartilaginous structure that surrounds the thoracic cavity and supports the shoulder girdle to form the core part. Ribs are long curved bones which form the rib cage, part of the axial skeleton. Human ribs are flat bones that form part of the rib cage to help to protect internal organs. At the front of the body, most of the ribs are joined by the costal cartilage to the sternum. The ribs are classified into true ribs, false ribs, floating ribs, etc.

Complete step by step answer:
A typical human rib cage consists of 24 ribs in 12 pairs. The skeletal system of humans consists of a framework of bones and few cartilages. In humans, the system consists of 206 bones and a few cartilages. They are classified into axial and appendicular skeletons. The skull, vertebral column, sternum, and ribs constitute the axial skeleton. Bones of limbs along with their girdles constitute the appendicular skeleton. Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. It has two articulation surfaces on its dorsal end and is hence called bicephalic. First, seven pairs of ribs are called true ribs. Dorsally they are attached to thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage. The 8^th, 9^th, and 10^th pairs of ribs do not articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called false ribs. The last two pairs of ribs are not connected ventrally and are therefore called floating ribs. Thoracic vertebrae, ribs, and sternum together form the rib cage. Ribs are described based on their location and connection with the sternum. The space between the ribs is known as intercostal spaces; they contain intercostal muscles and neurovascular bundles containing nerves, arteries, and veins.
So, the correct answer is ‘12 pairs’.

Additional Information:
- Axial skeleton consists of 80 bones distributed along the main axis of the body. The skull, vertebral column, sternum, and ribs constitute the axial skeleton.
- Skull composed of two sets of bones cranial and facial, that totals to 22 bones.
- A vertical column is formed by 26 serially arranged units called vertebrae.
- Bones of limbs along with their girdles constitute the appendicular skeleton. Each limb is made of 30 bones.

Note:
- Rib cage has a major function in the respiratory system. It protects the heart, lungs, and diaphragm.
- Each rib consists of a head, neck, and shaft. The expansion of the rib cage in males is generally caused by the effects of testosterone during puberty.
- Thus, males generally have broad shoulders and expanded chests, allowing them to inhale more air to supply their muscles with oxygen. Variations in the number of ribs occur. 1 in 200- 500 people have an additional cervical rib, and there is a female predominance.