What Are Lymph Nodes?
Lymph nodes are small (about 1-2 centimeters around or the size of a couple of AAA batteries side by side) oval or kidney-shaped structures that are a part of your immune system. They're part of your lymphatic system, which, along with your spleen, tonsils, and adenoids, help you fight off illness and infections. They also filter germs, cancer cells, and wastes out of your lymphatic fluid.
You might be able to feel some of your lymph nodes as bumps in your neck, armpits, or groin, but usually only if you have an infection you're fighting off. Usually, you don't feel them or even know they are there.
How many lymph nodes are in the human body?
The number of lymph nodes varies from person to person. Adults generally have about 600-800 lymph nodes. Most are spread out, but some are in groups in a few major places, like your neck, armpits, chest, belly, and groin.
Lymph Nodes Function
Your lymph system is a key part of your immune system. It's made up of your lymph vessels and lymph nodes. Your lymph vessels connect all your lymph nodes and draw up a clear fluid called lymph from around your cells. Your lymph fluid carries waste (like what's left of a cell after it dies) that has been removed from your cells and trapped bacteria and viruses to your lymph nodes before it flows back into your bloodstream.
The main function of your lymph nodes is to filter these foreign materials out of your lymph fluid. Lymph fluid would build up and cause swelling in your body if it wasn't filtered and drained. Lymph nodes also contain immune cells (white blood cells) that help fight infections and invaders by attacking and killing them.
Bacteria and viruses have proteins on their surface called antigens, which your immune system uses to recognize them as foreign invaders so they know to kill them. By filtering germs out of your lymph fluid, your lymph nodes concentrate them into a space (kind of like immune system school) where your white blood cells can learn about the bacteria and viruses you have come into contact with.
The white blood cells that are in your lymph nodes include:
- Lymphocytes.
- Macrophages (pronounced ma-kroh-fayjes), which surround and kill germs, recycle your dead cells, and act as helpers to your other immune system cells.
- Dendritic (pronounced den-drih-tik) cells, which take the antigens from dead germs and show them to your lymphocytes so they learn to recognize them.
The main white blood cells in your lymph nodes are lymphocytes, which come in two types:
B-lymphocytes (B-cells)
B-cells have proteins on their surface that attach to antigens on the surface of the germ. Then they make specific antibodies to those antigens. Antibodies are protein tags that they attach to germs to let other white blood cells know they need to be killed off.
T-lymphocytes (T-cells)
T-cells have a couple of jobs. Some are called cytotoxic (killer) T cells. These recognize and attach to antigens on the germs and kill them. Other T-cells called helper and suppressor T-cells make proteins (like antibodies) that help other immune system cells do their job or they tell your body to make other kinds of immune cells to help fight the infection.
Lymph Nodes Location
You have lymph nodes spread throughout your body, except in your brain and spinal cord. Some are just under your skin (superficial lymph nodes) in your neck, armpits, and groin and others are deep in your chest and belly. Each node filters the fluid from the vessels that lead into it.
Your superficial lymph nodes drain the lymph from your head, scalp, face, arms, and legs and are located in your:
- Neck (cervical)
- Armpits (axillary)
- Groin (inguinal)
Your deep lymph nodes are in your belly and chest and they drain the lymph from around your lungs and your digestive organs. These deep lymph nodes are also called:
- Mesenteric. These are lymph nodes in your mesentery, the membrane that connects your bowel to the tissue wall around your belly.
- Retroperitoneal. These are lymph nodes around your kidneys and the major blood vessels that connect your lower body to your heart.
- Mediastinal. These are lymph nodes around your trachea (windpipe), esophagus, heart, lungs, and the large blood vessels that lead to your heart. Some of these are supraclavicular, which means they are above your collarbones. These overlap with some of the superficial cervical lymph nodes.
Swollen Lymph Nodes
Your lymph nodes usually swell because your body is fighting off an infection. It's a sign that more lymphocytes are in action than usual, trying to kill off germs.
You may notice swelling most often in the nodes in your neck and under your chin. When you've got a cold or the flu and go see your doctor, they often feel around your neck and under your jawbone to check if those nodes are swollen or tender. Infections in your upper respiratory system often cause the lymph nodes in your neck to swell.
Sometimes medicines like phenytoin (taken for seizures), or drugs that prevent malaria can cause swollen lymph nodes, too.
What does a swollen lymph node feel like?
Swollen lymph nodes are generally soft, or spongy, and they're bigger than normal (which is about as big around as a couple of peas or a bean). They may feel like they slip or move around under your skin. They may also feel tender or painful when you press on them or move that area. For instance, a swollen lymph node under your jaw might hurt when you chew food.
How to check for swollen lymph nodes
To check for swollen lymph nodes use your fingertips in a gentle, circular motion to feel for lumps and tender areas under your skin on both sides of your body. Check your neck, in front of and behind your ears, above your collarbones, all around your armpits, and around your groin.
Swollen lymph nodes and infections
Any infection can make your lymph nodes swell, including:
- Viral infections, such as rhinovirus (colds), the influenza virus (the flu), sexually transmitted infections (herpes and HIV), or COVID-19
- Bacterial infections, such as an ear infection (usually caused by Streptococcus pneumoniae or Haemophilus influenzae), tuberculosis, or an abscessed tooth
Usually, your swollen lymph nodes are close to where your infection is. So, if you have a viral, upper respiratory infection, you'll get swollen lymph nodes in your neck. Or, if you get herpes, you may have swollen inguinal lymph nodes in your groin. Sometimes, people have swollen lymph nodes all over their body. In that case, it may be because you have an autoimmune condition, such as rheumatoid arthritis, or a generalized infection, like mononucleosis.
Swollen lymph nodes and vaccines
Rarely, a vaccine can cause swollen lymph nodes on the same side as you got the shot.
Swollen lymph nodes and cancer
If your lymph nodes feel hard, don't move around under your skin, and they are getting big very fast, it can be a sign of cancer. If this is the case, go see your doctor to get checked out.
Takeaways
Your lymph nodes are an important part of your immune system. They filter materials out of your lymph fluid to help keep you healthy. Talk to your doctor if you notice swollen or tender lymph nodes because this could be a sign of an illness or an infection.