The Sternum Is Anterior To The Vertebral Column

The Sternum is Anterior to the Vertebral Column: A Deep Dive into Human Anatomy

Understanding the spatial relationships between different anatomical structures is crucial for comprehending human anatomy and physiology. One fundamental relationship is the anterior position of the sternum relative to the vertebral column. This article will explore this relationship in detail, delving into the anatomy of both structures, their functional interconnections, and the clinical implications of understanding their relative positions.

Understanding Anatomical Terminology: Anterior vs. Posterior

Before diving into the specifics of the sternum and vertebral column, let's clarify the directional terms used in anatomy. Anterior refers to the front of the body, while posterior refers to the back. Therefore, stating that the sternum is anterior to the vertebral column means the sternum is situated in front of the vertebral column. Other relevant terms include:

• Superior: Towards the head
• Inferior: Towards the feet
• Medial: Towards the midline of the body
• Lateral: Away from the midline of the body

The Sternum: The Body's Central Supporting Structure

The sternum, commonly known as the breastbone, is a flat, elongated bone located in the anterior thoracic cage. It's a crucial component of the skeletal framework, providing attachment points for ribs and muscles. The sternum is composed of three parts:

1. Manubrium: The Superior Section

The manubrium is the superior, most broad part of the sternum. Its superior border articulates with the clavicles (collarbones), forming the sternoclavicular joints. The manubrium also articulates with the first two pairs of ribs. It's a significant landmark in many clinical procedures.

2. Body (Gladiolus): The Central Section

The body, or gladiolus, is the longest part of the sternum, forming the main portion of the breastbone. It articulates with the costal cartilages of ribs 2 through 7. The body's size and shape can vary between individuals.

3. Xiphoid Process: The Inferior Section

The xiphoid process is the smallest and most inferior part of the sternum. It's cartilaginous in young individuals and ossifies (turns to bone) with age. It serves as an attachment point for some abdominal muscles. The xiphoid process is particularly important in certain surgical procedures.

The Vertebral Column: The Body's Central Axis

The vertebral column, also known as the spine, is the central axis of the body. It's a complex structure composed of 33 vertebrae:

• 7 Cervical Vertebrae (Neck): These are the smallest and most mobile vertebrae, allowing for a wide range of neck movements. The first two, the atlas (C1) and axis (C2), have unique structures that facilitate head rotation.

• 12 Thoracic Vertebrae (Chest): These vertebrae are larger and less mobile than the cervical vertebrae, articulating with the ribs to form the thoracic cage. They are characterized by the presence of costal facets (surfaces) for rib articulation. Understanding the relationship between the thoracic vertebrae and the ribs is crucial to understanding the posterior aspect of the rib cage's connection to the axial skeleton.

• 5 Lumbar Vertebrae (Lower Back): These are the largest and strongest vertebrae, supporting the weight of the upper body. They are designed for weight-bearing and limited movement.

• 5 Sacral Vertebrae (Sacrum): These vertebrae are fused together to form the sacrum, a triangular bone that forms the posterior wall of the pelvis.

• 4 Coccygeal Vertebrae (Coccyx): These are small, fused vertebrae forming the tailbone.

The vertebral column provides support for the body, protects the spinal cord, and facilitates movement. Its curvature is essential for maintaining balance and shock absorption.

The Relationship: Sternum Anterior to Vertebral Column

The crucial point emphasized by the title "The Sternum is Anterior to the Vertebral Column" is the clear spatial relationship between these two structures. The sternum lies entirely in front of the vertebral column. This anterior positioning is fundamental to the protection of vital organs. The thoracic cage, formed by the ribs, sternum, and thoracic vertebrae, creates a protective shell around the heart, lungs, and major blood vessels. The sternum's anterior position contributes to the robust structural integrity of the thoracic cage, providing a strong shield against external forces.

This anterior placement is also significant in clinical contexts. For example, during chest compressions in cardiopulmonary resuscitation (CPR), the pressure applied to the sternum is transmitted to the heart, which lies posterior to the sternum. The effectiveness of CPR hinges on this precise anatomical relationship.

Functional Interconnections: Rib Cage and Respiration

The sternum and vertebral column are intimately interconnected through the ribs and their associated costal cartilages. These structures form the rib cage, a vital component of the respiratory system. The ribs articulate posteriorly with the thoracic vertebrae and anteriorly with the sternum (or costal cartilages that attach to the sternum). This arrangement allows for the expansion and contraction of the chest during breathing:

• Inhalation: The diaphragm contracts, moving downwards. Simultaneously, the intercostal muscles (muscles between the ribs) contract, elevating the ribs. This action increases the volume of the thoracic cavity, drawing air into the lungs. The sternum moves slightly anteriorly during this process.

• Exhalation: The diaphragm relaxes, moving upwards. The intercostal muscles relax, lowering the ribs. This decreases the volume of the thoracic cavity, expelling air from the lungs. The sternum returns to its resting position.

The sternum's anterior position plays a pivotal role in the mechanics of breathing, facilitating the efficient expansion and contraction of the chest during respiration.

Clinical Significance: Sternum and Vertebral Column Injuries

Understanding the relationship between the sternum and vertebral column is essential in diagnosing and treating various injuries:

1. Sternum Fractures:

Sternum fractures are often caused by blunt trauma to the chest, such as a car accident or a fall. These fractures can range from simple cracks to severe breaks. They are frequently accompanied by injuries to adjacent structures, like the ribs, lungs, or heart. Accurate diagnosis and timely treatment are crucial to prevent complications.

2. Rib Fractures:

Rib fractures are common chest injuries that often involve the articulation points between the ribs and both the sternum and the vertebrae. Rib fractures can be painful and can compromise respiratory function. Understanding the biomechanics of the rib cage helps in assessing the severity of the injury and planning appropriate treatment.

3. Spinal Injuries:

Spinal injuries, including fractures and dislocations, can impact the overall integrity of the rib cage and affect the respiratory function. The close relationship between the vertebral column and the sternum and ribs can increase the risk of associated thoracic cage damage.

4. Cardiac Surgery:

The anterior location of the sternum makes it readily accessible for cardiac surgery. Sternotomy, the surgical procedure involving splitting the sternum, provides surgeons with direct access to the heart and other thoracic structures.

5. Other Clinical Conditions:

Other conditions impacting the sternum and/or vertebral column, such as pectus excavatum (a condition causing an inward indentation of the chest) or scoliosis (a sideways curvature of the spine), can alter the normal anterior positioning of the sternum and the relationship to the vertebral column.

Conclusion: The Importance of Anatomical Relationships

The statement "The sternum is anterior to the vertebral column" is not just a simple anatomical fact; it's a fundamental principle that underpins our understanding of the human body. This anterior position is crucial for the protection of vital organs, the mechanics of respiration, and numerous clinical procedures. A comprehensive understanding of this anatomical relationship is vital for healthcare professionals, students of anatomy, and anyone seeking a deeper understanding of the human body's intricate structure and function. The intricate interplay between these two essential skeletal structures highlights the body's remarkable design and efficiency. By appreciating the complexities of this relationship, we can further our comprehension of human physiology and the diagnosis and treatment of numerous medical conditions.