The word “lingula” is a term used in human anatomy to describe a small, tongue-shaped projection found in several different locations throughout the body. Derived directly from the Latin word meaning “little tongue,” the name is a general descriptor for any anatomical structure with this specific physical appearance. While the term is applied to features on both bone and soft tissue, the most commonly referenced structure is a part of the respiratory system. Understanding the location of the lingula requires clarifying which specific structure is being discussed, as its function and clinical importance vary significantly.
The Lingula of the Left Lung: Primary Location and Structure
The most recognized lingula is a distinct projection of the superior lobe of the left lung, serving as the anatomical counterpart to the middle lobe of the right lung. It is situated on the anterior surface of the left lung, below the cardiac notch, the indentation accommodating the heart. This tongue-like extension curves forward, partially wrapping around the pericardium. The lingula is delineated by the oblique fissure above it, which separates the upper and lower lobes of the left lung. It is further divided into two distinct bronchopulmonary segments—the superior and inferior lingular segments—each receiving its own air supply through dedicated tertiary bronchi.
The lingula’s appearance is highly characteristic, extending downward toward the diaphragm and the ribs surrounding the lower chest wall. Its unique shape and position are a direct result of the heart occupying a large portion of the left side of the thoracic cavity. The tongue-like projection maximizes the available space for lung tissue while fitting snugly around the heart’s curvature.
Functions and Clinical Significance in the Lung
The primary function of the pulmonary lingula is to facilitate the exchange of oxygen and carbon dioxide between the air and the bloodstream. Air travels through the superior lobar bronchus and into the lingular segments, where it eventually reaches millions of tiny air sacs called alveoli. Gas exchange occurs across the thin alveolar membranes, ensuring the body receives the necessary oxygen.
The lingula holds specific clinical relevance due to its anatomical position and the characteristics of its airway. It is particularly susceptible to conditions like atelectasis and certain types of pneumonia. The relatively narrow and elongated nature of the lingular bronchus makes it prone to obstruction from inflammation, mucus, or edema.
When the lingula experiences consolidation or collapse, it often creates a visible sign on X-rays due to its close proximity to the heart border. This radiographic observation, called the silhouette sign, helps clinicians localize the disease to this specific area of the left lung. From a surgical perspective, the lingula is treated as a separate unit. In cases of localized disease like cancer or severe bronchiectasis, a specific procedure called a lingulectomy can be performed to remove only the affected segments.
Other Anatomical Structures Named Lingula
Beyond the lung, the term “lingula” describes two other structures located within the bones of the head.
Lingula of the Mandible
The Lingula of the Mandible is a small, sharp projection of bone found on the inner, or medial, surface of the lower jawbone. It is located directly adjacent to the mandibular foramen, the opening through which the inferior alveolar nerve and blood vessels enter the jaw. This bony projection serves as the attachment point for the sphenomandibular ligament, which connects the mandible to the base of the skull. Clinically, the mandibular lingula is a landmark for dental professionals when administering a mandibular nerve block, an injection used to anesthetize the lower teeth and jaw.
Lingula of the Sphenoid Bone
A third structure is the Lingula of the Sphenoid Bone, located at the base of the skull. This small, bony ridge is found along the lateral margin of the carotid sulcus, a shallow groove on the sphenoid bone. The ridge is situated in the angle where the body of the sphenoid bone meets its greater wing. The lingula helps to define the pathway of the internal carotid artery as it passes through the skull, separating it from surrounding structures in the middle cranial fossa.