89 Fun Facts About Lymphatic System

The lymphatic system is considered part of which other body system?

Immune. The vessels that drain leaked fluid back to the blood double as highways for infection-fighting white cells, and the nodes along the route act as checkpoints where invaders are trapped.

Like veins, lymph vessels are fitted along their length with which structures?

Valves. They keep lymph flowing one way, and they sit so close together that lymph vessels look like strings of beads.

Lymph originates from which fluid that leaks out of blood into the tissues?

Interstitial fluid bathes every cell, and lymph is the very same liquid under a new name: it only becomes lymph at the moment it slips inside a lymph capillary.

Which of these vitamins travels from the gut in the lymph, with dietary fat, rather than straight into the blood?

Vitamin D. Like vitamins A, E and K it dissolves in fat, so it hitches a ride with digested fat into the gut's lymph vessels instead of going straight into the bloodstream.

About how much leaked fluid does the lymphatic system return to the bloodstream each day?

3 litres. Around 20 litres of fluid seep out of the blood capillaries every day; the capillaries take 17 straight back, and the lymphatic system has to collect the rest.

Lymph is described as very similar to which component of blood?

Plasma. Lymph begins as the liquid part of blood seeping out through the capillary walls, and because the red cells are too big to follow, it runs clear and colourless instead of red.

Where in the adult body do all lymphocytes begin life?

The bone marrow. Every lymphocyte starts there as a stem cell, but only B cells stay to grow up: future T cells leave early and finish their training in the thymus.

Which clusters of lymphoid tissue in the wall of the small intestine are named after a 17th-century Swiss anatomist?

Peyer's patches. Their surface is studded with M cells, which grab samples of whatever is passing through the gut and hand them to the lymphocytes waiting underneath.

What does the acronym MALT stand for?

Mucosa-associated lymphoid tissue guards the moist linings where germs most often get in, such as the airways and the gut. Unlike a lymph node it has no capsule: just loose clusters of lymphocytes under the surface.

The large left lymphatic duct draining most of the body is known by what name?

Thoracic. The body's lymph drainage is lopsided: this single duct serves both legs, the abdomen and the whole left side, while its partner handles only the right arm and the right side of the head and chest.

The lymph ducts empty into which veins to return lymph to the bloodstream?

Subclavian. The two lymph ducts join these veins at the base of the neck, one on each side; if the fluid never made it back to the blood there, the body's tissues would swell with it.

With no central pump, what mainly moves lymph through the human body?

Muscle contractions. Lymph is squeezed along from outside by the body's ordinary movements, breathing included, and from inside by muscle in the walls of the larger vessels themselves.

Which epidemic disease is named from the Greek word for groin, after the swollen lymph nodes it causes there?

Bubonic plague. Bacteria from a flea bite travel along the lymph vessels to the nearest node and multiply there until it balloons into a painful swelling called a bubo.

Where in the lymphatic system do deep pits, called crypts, deliberately trap germs so the body can learn to fight them?

The tonsils. The pits are no design flaw: they invite germs in on purpose, giving a child's defences an early look at common infections at the very spot where food and air enter the body.

Which extra primary lymphoid organ, absent in mammals, do birds have?

Bursa of Fabricius. B cells were first worked out in birds, where they mature in this small sac off the gut, and the B in their name has stood for bursa ever since.

Developing T cells undergo positive selection in which part of the thymus?

The cortex. Here each young T cell is tested on whether it can recognise the body's own identity tags at all; only then does it move inward to the medulla for the opposite test, of whether it reacts to them too strongly.

During which life stage does the thymus begin to atrophy and fill with fatty tissue?

Adolescence. The thymus does most of its work in childhood; from puberty it slowly shrinks and turns to fat, which is thought to be why the body makes fewer new T cells as it ages.

Where in the body is the thymus located?

Lower neck and upper chest. The thymus sits just behind the breastbone, in front of the heart, and it is where T cells mature, which is how they came by the T in their name.

Which infection, spread in saliva and common in teenagers, typically brings swollen lymph nodes in the neck?

Mononucleosis. Saliva is how it earned the nickname 'the kissing disease', and the 'glands' behind its British name, glandular fever, are those same swollen lymph nodes.

Which part of the spleen synthesises antibodies and houses its lymphocytes?

The white pulp, named for looking paler than the tissue around it, wraps the spleen's small arteries like a lymph node built into the bloodstream. The red pulp around it does the filtering of worn-out blood cells.

A 2009 mouse study found the spleen holds a reserve army of which white blood cells?

Monocytes. More of them wait in the spleen than circulate in the blood, and when the heart is damaged they pour out together, travel to the injury and help it heal.

Which of these animals has dedicated "lymph hearts" that beat to pump lymph into its veins?

Frogs. Amphibians and reptiles have small beating lymph hearts spaced along their lymph vessels to push the fluid on, but mammals, people included, have none at all.

How does the spleen release its reserve of red cells during acute blood loss?

It contracts. The same squeeze happens when you hold your breath: the spleen shrinks and pushes extra red cells into the blood, a trick humans share with diving seals.

The spleen breaks down haemoglobin from old red cells into which reusable building blocks?

Amino acids. They are sent off to help build brand-new red cells, and the iron at the heart of each haemoglobin molecule is saved and reused as well.

Roughly how many lymph nodes does the human body contain?

Several hundred. Textbooks cannot agree on the exact figure, with counts running from about 450 to about 800, but you can feel a few of them for yourself in the neck, armpit and groin when they swell.

What is the indentation on one side of a lymph node, which gives it its bean shape, called?

The hilum. It is the node's only way out: lymph arrives through several vessels around the rim but leaves by this one notch, where the node's blood vessels also pass in and out.

Vessels that carry lymph into a lymph node are described by which adjective?

Afferent. Several of these vessels feed each node around its outer curve, so lymph trickles in from many directions at once but is funnelled out again through just one.

In which part of a lymph node does the selection of B cells take place?

Germinal centre. It forms only once an invader has been spotted: B cells multiply there at speed and shuffle their antibody genes, and the ones whose antibodies grip the invader best are the ones kept.

Lymphocytes enter lymph nodes through what specialised blood vessels in the paracortex?

High endothelial venules. The name describes their lining: the cells are tall and plump instead of flat, which lets lymphocytes squeeze straight out of the bloodstream and into the node.

Which gut organ has a colon-like lining that is heavily infiltrated with lymphocytes?

The appendix. Its lining is crowded with lymphocytes that sample whatever the gut sends past, and when its narrow opening gets blocked, the reaction they set off can turn into appendicitis.

Tertiary lymphoid organs form in peripheral tissues under what condition?

At sites of chronic inflammation. These makeshift lymph nodes spring up wherever trouble will not go away, from stubborn infections to rejected transplants, and inside a tumour they are often a hopeful sign for the patient.

In 2015, researchers described working lymphatic vessels lining which structures around the brain?

The dural sinuses. Until then textbooks taught that the brain and spinal cord had no lymph vessels at all; these ones had hidden in the tough membrane that wraps the brain.

Which cells control the "glymphatic" channels that carry waste out of the brain?

Glial cells. The system's name blends glia with lymphatic, because it does for the brain what lymph vessels do elsewhere: fluid sweeps along channels beside the blood vessels and carries waste away.

Unlike blood capillaries, which link arteries to veins, lymph capillaries begin in the tissues as what kind of vessel?

Blind-ended. A lymph capillary starts as a closed tip, like the finger of a glove, whose overlapping wall cells part under pressure to let tissue fluid seep in and then press shut behind it.

Lymphatic filariasis, a worm infection that damages the lymph vessels, is spread by the bite of which insects?

Mosquitoes. The larvae they pass on grow into adult worms that nest inside the lymph vessels for up to eight years, doing hidden damage to the drainage they live in.

The thymus develops as an outgrowth of which embryonic structure?

The third pharyngeal pouch. The same pair of pouches in the embryo's throat also gives rise to parathyroid glands, so the school for T cells and the body's calcium regulators begin life side by side.

What are the lymph vessels in the small intestine that absorb fats called?

Lacteals. Most digested nutrients are carried straight off in the blood, but fats take this slower back road instead, travelling through the lymph before they ever reach the bloodstream.

What name is given to the fat-enriched lymph that comes from the small intestine?

Chyle. Tiny globules of fat turn the normally clear lymph a milky white, most of all in the hours after a fatty meal.

What term describes cancer cells spreading between body parts, often via the lymphatics?

Metastasis. Stray cancer cells often lodge first in the nearest lymph nodes, which is why surgeons remove and test those nodes to judge how far a tumour has spread.

What is the medical term for one or more enlarged lymph nodes?

Lymphadenopathy. Alarming as a lump in the neck can feel, it is usually a good sign: the nodes nearest an infection swell because they are busy fighting it.

Extreme lymphedema, in which the skin of a swollen limb thickens and hardens, is known as what?

Elephantiasis. The name comes from limbs so swollen that their thick, rough skin looks like an elephant's, and the usual cause is a parasitic worm infection that blocks the lymph vessels.

Which named cell is the microscopic hallmark of Hodgkin lymphoma?

Reed–Sternberg. These giant abnormal lymphocytes, often with more than one nucleus, are what a pathologist hunts for in a lymph node biopsy: finding them is how the disease is confirmed.

Hodgkin lymphoma has traditionally been staged with a system named after which US city?

Ann Arbor. An international committee of specialists met in the Michigan university town in 1971 to agree the four stages, and the newer Lugano system used today is still built on their work.

Which ancient Greek physician described the lymph nodes as early as the 5th century BC?

Hippocrates. Writings under his name list the 'glands' of the armpit, groin and neck, the very places doctors still feel for swollen nodes, some two thousand years before the vessels linking them were mapped as a system.

In 1622, Gaspare Aselli identified the intestinal lymph vessels while dissecting which animal?

Dogs. The animal had been well fed shortly before, so the fat-filled vessels in its gut stood out as fine white cords oozing a creamy fluid, and he went on to compare fed and unfed animals to be sure.

In 1651 Jean Pecquet overturned the old belief that fatty lymph from the gut drains into which organ?

The liver. Since Galen, doctors had taught that the liver turned digested food into blood; Pecquet followed the milky fluid to a small reservoir and up a long duct into the veins instead.

Olaus Rudbeck announced his lymphatic discoveries at the court of which monarch?

Christina of Sweden. Rudbeck was barely in his twenties when he showed the queen his dissections in 1652, but he was slow to publish, and a rival anatomist got his own account into print first.

Which anatomist is credited with coining the name 'lymphatic vessels'?

Thomas Bartholin. The Danish anatomist chose the name to set these vessels, with their clear contents, apart from the milky white ones already known in the gut.

The word "lymph" comes from the Latin lympha, which meant what?

Water. To the Romans lympha was clear spring water and the goddess who watched over it, and its y and ph are thought to have crept in under the pull of the Greek word nymph.

The words 'vaccine' and 'vaccination' come from the Latin word for which farm animal?

Cow is the root: the first vaccine used cowpox, which its pioneer named variolae vaccinae, Latin for 'smallpox of the cow'. The mild infection protected people against the far deadlier smallpox.

Élie Metchnikoff saw how cells engulf invaders after pushing citrus thorns into the larvae of which sea creature?

Starfish larvae showed him unusual cells gathering around each thorn. That 1882 experiment in Messina led to a share of the Nobel Prize in 1908.

Pigment from which form of body art can migrate through lymph vessels and collect in nearby lymph nodes?

Tattoos shed part of their pigment into the lymph nodes, where it can show up on a mammogram and be mistaken for a sign of cancer.

A scratch from which household pet can spread Bartonella henselae, leaving swollen lymph nodes near the wound?

Cat-scratch disease is carried by cats that show no symptoms themselves, and kittens are the likeliest to pass it on. Flea control is the main way to prevent it.

Calf or lamb thymus, and sometimes pancreas, is served on restaurant menus under which culinary name?

Sweetbreads from the thymus come only from young animals, because the gland turns fibrous in older ones.

The first successful kidney transplant, in Boston in 1954, avoided rejection because donor and recipient were what?

Identical twins are genetically the same, so Richard Herrick's body accepted his brother Ronald's kidney with no drugs to suppress rejection.

The disease lupus, whose rash was likened to a bite, takes its name from the Latin for which animal?

Wolf is 'lupus' in Latin, a name given in the 13th century when the rash was thought to resemble a wolf's bite. The disease is better known for a butterfly-shaped rash across the nose and cheeks.

In the ancient theory of the four humours, the spleen was said to produce which fluid, blamed for depression?

Black bile was the spleen's supposed product, and too much of it meant gloom. The word melancholy comes from the Greek for exactly that fluid.

Which English country doctor tested the first smallpox vaccine on his gardener's eight-year-old son, James Phipps?

Edward Jenner is often called the father of immunology, and his work is said to have saved more lives than any other man's.

Which virus is the usual cause of glandular fever, nicknamed the kissing disease because it spreads through saliva?

Epstein–Barr causes about 90% of cases. Patients are told to avoid contact sports for weeks afterwards, because the spleen can swell and, rarely, rupture.

Which chemical, released by mast cells, drives the itching, sneezing and swelling of an allergic reaction?

Histamine pours out when an allergen binds to IgE antibodies sitting on the mast cells. It is also a central mediator of itching.

Which yellowish milk, produced in the first few days after birth, is packed with antibodies that protect a newborn?

Colostrum is vital on farms too: calves denied it almost always die of bacterial infection.

The axillary lymph nodes, which drain most of the lymph from the breast, sit in which part of the body?

Armpit nodes take about 75% of the breast's lymph, which is why surgeons check them when staging breast cancer.

Which part of the brain raises the body's temperature set point to produce a fever during an infection?

Hypothalamus signals reset the body's thermostat upward, so a person shivers and feels cold until the new, higher target is reached.

Which tuberculous swelling of the neck's lymph nodes was known as King's Evil, supposedly cured by a royal touch?

Scrofula sufferers queued to be touched by the kings of France and England. English monarchs then gave each one a gold coin to wear on a ribbon.

Which hormone, injected into the thigh, is the primary treatment for the severe allergic reaction anaphylaxis?

Adrenaline, known in the US as epinephrine, is given as soon as anaphylaxis is suspected. That is why people with a history of it are advised to carry an auto-injector pen.

Which name do surgeons give the first lymph node a tumour is likely to spread to, checked by biopsy?

Sentinel node biopsy uses a tracer to find it. If that node is free of cancer, the patient can be spared the removal of many more.

Alongside fever and unexplained weight loss, which third 'B symptom' do doctors ask about when assessing lymphoma?

Night sweats have to be drenching to count, and any B symptom puts the letter B after the stage number a lymphoma is given.

Louis Pasteur's new vaccine was given to nine-year-old Joseph Meister in 1885 to protect him against which disease?

Rabies vaccine went into the boy 13 times over 11 days after a rabid animal mauled him, and three months later he was in good health.

Which German scientist, who proposed the side-chain theory of how antibodies form, also coined the term 'magic bullet'?

Paul Ehrlich shared a Nobel Prize in 1908 for his work on immunity. His 'magic bullet' idea survives in modern drugs built to deliver poison only to cancer cells.

Emil von Behring won the first Nobel Prize in Medicine for a serum therapy against which childhood killer?

Diphtheria was such a major cause of child death that the serum, drawn from the blood of immunised horses, earned him the nickname 'saviour of children'.

HIV cripples the body's defences mainly by infecting and depleting which type of white blood cell?

Helper T cells, also called CD4 cells, direct much of the body's defence. When their numbers fall below a critical level, ordinary infections turn dangerous and AIDS develops.

The whitish-yellow pus of an infected wound is made up mostly of which dead white blood cells?

Neutrophils rush to an infection and die there in huge numbers. A green tinge in pus comes from myeloperoxidase, an intensely green antibacterial protein.

Lymph draining the small intestine after a fatty meal takes on which appearance because of the fat it carries?

Milky white lymph owes its look to triglycerides picked up from digested food. Elsewhere in the body, lymph forms as a clear, watery liquid.

Which enzyme in tears and nasal mucus did Alexander Fleming name in 1922, before he discovered penicillin?

Lysozyme got its name because it could lyse, or dissolve, bacteria. Fleming first spotted the effect in mucus from the nose, and the enzyme also turns up in saliva and human milk.

Lady Mary Wortley Montagu championed smallpox inoculation in Britain after seeing it practised in which empire?

Ottoman practice convinced her so fully that she had her son inoculated at the embassy there, then her daughter back in England during the 1721 epidemic.

David Vetter, a Texas boy born without a working defence against germs, spent nearly all of his life inside what?

A plastic bubble was his home from the moment he was born in 1971. Six years later NASA built him a spacesuit so he could walk outside it, though he wore it only six times.

Burkitt lymphoma is named after an Irish surgeon who first described it in 1958 while working on which continent?

Africa's equatorial belt is where the childhood form of the tumour is commonest, in the same regions where malaria is endemic.

Drug names ending in '-mab', such as the breast cancer medicine trastuzumab, mark a drug as which kind of molecule?

Monoclonal antibody names all took that ending from about 1990 until 2021, with the syllables before it coding for the drug's target.

Surgical removal of the thymus can treat which autoimmune disease, known for drooping eyelids and double vision?

Myasthenia gravis patients sometimes have a tumour of the thymus, and removing the gland can ease the muscle weakness even when no tumour is found.

In the HLA system used to match organ donors and recipients, what does the letter L stand for?

Leukocyte is another name for a white blood cell. The HLA genes sit together on chromosome 6 and code for proteins on the surface of the body's cells.

Kupffer cells, also known as stellate macrophages, line the blood-filled sinusoids of which organ?

Liver Kupffer cells form the largest population of tissue-resident macrophages anywhere in the body.

Which antibody class is the only one that can cross the placenta to protect a baby before birth?

IgG is also the most common antibody in the bloodstream, making up roughly 75% of those found in human serum.

Which term for a community's indirect protection through vaccination was first used in 1894 about well-fed hogs?

Herd immunity started as a veterinary phrase. It is vulnerable to free riders, who skip vaccination and rely on everyone else being protected.

Which cells of the outer skin, able to migrate to lymph nodes, were discovered by a 21-year-old German medical student?

Langerhans cells take their name from Paul Langerhans, who found them while still a student. They are not to be confused with the islets in the pancreas that also bear his name.

Which proteins, first described in 1957 by Isaacs and Lindenmann, do virus-infected cells release to shield others?

Interferons are named for their power to interfere with viral replication, an effect the pair first saw in chicken embryo membranes exposed to flu virus.

Which discoverer of the dendritic cell died three days before the announcement of his 2011 Nobel Prize?

Ralph Steinman's prize was allowed to stand, although Nobels are not awarded posthumously, because the committee had chosen him in good faith without knowing he had died.

Podoconiosis, a disease of the leg's lymphatic vessels, comes from years of walking barefoot on soil formed from what?

Volcanic rock breaks down into an irritant red clay whose particles get through the skin of the feet and collect in the lymph vessels. Rwanda has banned going barefoot in public to help prevent it.

The transplant drug rapamycin is named after the native name of which remote Pacific spot, where it was first found?

Easter Island is Rapa Nui to its people, and the drug comes from a soil bacterium collected there. It is especially useful in preventing the rejection of kidney transplants.

Quinsy, an abscess famous for causing a muffled 'hot potato voice', forms behind which lymphoid organ?

Tonsil infections that go untreated, or are only partly treated, are the usual cause, and the pus gathers in the space behind the gland.