What Is the Hilum of the Lung?

The hilum is what connects your lungs to their supporting structures and where pulmonary vessels enter and exit your lungs.

The hilum — or root — functions much like a plant root, securing each lung in place and providing a channel for energy to pass through.

Each hilum is in a flat area at the center of each lung, toward your spine or the back of your lungs (medial surface). The hilum is located between your fifth and seventh thoracic vertebrae in your spine.

The hilum is visible as a triangular section at the inner midpoint of each lung. It is the space where vessels and nerves pass from your bronchus to your lungs. The hilum keeps your lungs anchored in place.

The hilum itself is triangular-shaped and surrounded by a pleura — a strong but delicate sac-like membrane.

The pleura help your lungs expand and contract with each breath and contain pleural fluid that lubricates this movement.

The inner edge of the hilum acts as a channel where a number of structures pass into your lungs. These include your:

• bronchi
• pulmonary veins
• pulmonary arteries
• phrenic nerves
• lymphatic vessels
• nodes
• bronchial arteries

There is some variation between the left and right hilum, just as there is a difference in the number of lobes in each lung.

The left hilum houses just one bronchus, while the right hilum contains two. This is similar to the way your lungs are divided, with your left lung divided into two lobes and your right lung divided into three.

Aside from anchoring your lungs in the thoracic cavity and providing a passageway for vessels, the hilum serves no other critical function.

The hilum is as susceptible to disease as any other tissue in your body. Masses caused by conditions like cancer can be particularly concerning.

Masses or obstructions in the hilum can place pressure on the vital vessels and nerves to your lungs. This can impair your body’s ability to oxygenate your blood.

Some common disorders that affect the hilum include:

• Sarcoidosis. Sarcoidosis is an inflammatory condition that causes atypical cells to form in various organs, like the hilar tissue in your lung.
• Hilar masses or tumors. Lung cancers or lymphomas can cause tumors or masses to form in the hilar tissue.
• Asymmetrical hila. Asymmetrical hila is when the hila are not the same size or shape. Tuberculosis is a common cause of hilar asymmetry.
• Infection. There are a number of bacterial or fungal infections can affect the hilum.
• Lymphadenopathy. Lymphadenopathy is when your lymph nodes in the hilum become larger due to inflammation, infection, cancer, or other conditions.
• Pulmonary artery or venous hypertension. Increased pressure in your pulmonary vessels (pulmonary hypertension) can impair proper blood flow and oxygenation. High pressures in these vessels are often caused by heart failure or chronic pulmonary obstructive disorder (COPD).

The hilum can also present certain surgical challenges. While your vessels and nerves that pass through the hilum are typically arranged in the same order, some variation has been noted.

Being able to tell the difference between your pulmonary vessels and your phrenic nerve is crucial during surgical procedures. Variation in the order of these vessels can thus make surgery even more difficult.

For example, if there is a mass or other condition affecting the hilar tissue, it may need to be surgically removed, or resected. Resection can be a successful treatment for treating small-cell lung cancers, according to a 2018 research review.

Symptoms of disease within the hilum can be difficult to differentiate from other conditions that affect your lungs.

Like many pulmonary diseases, conditions that affect the hilum may cause symptoms such as:

• dry cough
• shortness of breath
• wheezing
• pain in the center of your chest

In most cases, illnesses that affect the hilum are diagnosed when you go to the doctor with breathing problems or chest pain.

A doctor will typically use imaging studies to find out what’s causing your symptoms. Examples of these studies include:

• chest X-rays
• CT scans
• MRI scans

Samples of lung tissue can also be tested with more invasive methods like a bronchoscopy, if needed.

Your lungs are constantly expanding and contracting, so they have to remain elastic to work well.

Lung tissues also need to be kept clear of obstructions or blockages that can be caused by pollutants like cigarette smoke.

Tissue that is blocked or damaged — especially in your alveoli — lose the ability to exchange gases. When this happens, your lungs cannot supply oxygenated blood to your body.

Here are some tips to help keep your lungs healthy and working properly:

• Try to quit smoking.
• If possible, avoid areas with high air pollution or exposure to airborne chemicals.
• Try to keep up on vaccinations to avoid illnesses like pneumonia and influenza.
• Exercise regularly.
• Use indoor air filters.
• Practice deep breathing exercises to maintain lung elasticity.

The hilum is the part of your lung that keeps it anchored and acts as a passageway for critical vessels and nerves.

You can help prevent conditions that may damage the hilum by taking steps to protect your lungs.

Talk with a doctor or healthcare professional about any new or worsening symptoms you notice in your lungs or chest.