Rib cage
Anatomy
The human rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the pectoral girdle, forming a core portion of the human skeleton. A typical human rib cage consists of 24 ribs, the sternum, costal cartilages, and the 12 thoracic vertebrae. It, along with the skin and associated fascia and muscles, makes up the thoracic wall and provides attachments for the muscles of the neck, thorax, upper abdomen, and back.
Structure
Ribs
The human rib cage is made up of 12 paired rib bones; each are symmetrically paired on a right and left side. Of all 24 ribs, the first seven pairs are connected to the sternum and known as "true ribs", while the remaining five pairs are known as "false ribs". The false ribs include the 8th, 9th and 10th pairs, which are connected to the sternum by shared cartilaginous extensions, and the 11th and 12th pairs, also known as "floating ribs", which are not connected to the sternum or other ribs.
Sternum
The sternum, or breastbone, is a long, flat bone located in the center of the thorax, connected to the 12 ribs via cartilage. It consists of three parts: the manubrium, the body, and the xiphoid process. The manubrium is the upper part of the sternum, while the body, or corpus sterni, is the longest part of the sternum, and the xiphoid process is the lower, pointed end.
Costal Cartilages
Costal cartilages are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension.
Functions
The rib cage has several important functions:
1. Protection: It encloses and protects the heart and lungs. 2. Support: It provides a strong framework onto which the muscles of the shoulder girdle, chest, upper abdomen and back can attach. 3. Respiration: The ribs have a vital role in respiration. During inspiration, the muscles of respiration, including the diaphragm and intercostal muscles, contract, causing the rib cage to expand and the volume of the thoracic cavity to increase. This reduces the pressure within the thoracic cavity, drawing air into the lungs.
Clinical Significance
The rib cage is not immune to pathological conditions. These include fractures, which are usually caused by trauma and can lead to serious complications such as pneumothorax, hemothorax, or damage to internal organs. Costochondritis is an inflammation of the costal cartilages and can cause chest pain. Flail chest is a serious condition that occurs when a segment of the rib cage breaks due to trauma and becomes detached from the rest of the chest wall.