science

Lymph

Lymph is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lymph rather than just read about it. In short: Lymph (from Latin lympha 'water') is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to be recirculated. At the origin of the fluid-return process, interstitial fluid—the fluid between the cells in all body tissues—enters the lymph capillaries.

Key takeaways

Lymph belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Lymph to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Lymph from memory before moving on to harder problems.

Reference excerpt

Lymph (from Latin lympha 'water') is the fluid that flows through the lymphatic system, a system composed of lymph vessels (channels) and intervening lymph nodes whose function, like the venous system, is to return fluid from the tissues to be recirculated. At the origin of the fluid-return process, interstitial fluid—the fluid between the cells in all body tissues—enters the lymph capillaries. This lymphatic fluid is then transported via progressively larger lymphatic vessels through lymph nodes, where substances are removed by tissue lymphocytes and circulating lymphocytes are added to the fluid, before emptying ultimately into the right or the left subclavian vein, where it mixes with central venous blood. Because it is derived from interstitial fluid, with which blood and surrounding cells continually exchange substances, lymph undergoes continual change in composition. It is generally similar to blood plasma, which is the fluid component of blood. Lymph returns proteins and excess interstitial fluid to the bloodstream. Lymph also transports fats from the digestive system (beginning in the lacteals) to the blood via chylomicrons. Bacteria may enter the lymph channels and be transported to lymph nodes, where the bacteria are destroyed. Metastatic cancer cells can also be transported via lymph.

Etymology The word lymph is derived from the name of the ancient Roman deity of fresh water, Lympha.

Structure

Lymph has a composition similar to that of blood plasma. Lymph that leaves a lymph node is richer in lymphocytes than blood plasma is. The lymph formed in the human digestive system called chyle is rich in triglycerides (fat), and looks milky white because of its lipid content.

Development

Blood supplies nutrients and important metabolites to the cells of a tissue and collects back the waste products they produce, which requires exchange of respective constituents between the blood and tissue cells. This exchange is not direct, but instead occurs through an intermediary called interstitial fluid, which occupies the spaces between cells. As the blood and the surrounding cells continually add and remove substances from the interstitial fluid, its composition continually changes. Water and solutes can pass between the interstitial fluid and blood via diffusion across gaps in capillary walls called intercellular clefts; thus, the blood and interstitial fluid are in dynamic equilibrium with each other. Interstitial fluid forms at the arterial (coming from the heart) end of capillaries because of the higher pressure of blood compared to veins, and most of it returns to its venous ends and venules; the rest (up to 10%) enters the lymph capillaries as lymph. (Prior to entry, this fluid is referred to as the lymph obligatory load, or LOL, as the lymphatic system is effectively "obliged" to return it to the cardiovascular network.) The lymph when formed is a watery clear liquid with the same composition as the interstitial fluid. However, as it flows through the lymph nodes it comes in contact with blood, and tends to accumulate more cells (particularly, lymphocytes) and proteins.

Functions

Components Lymph returns proteins and excess interstitial fluid to the bloodstream. Lymph may pick up bacteria and transport them to lymph nodes, where the bacteria are destroyed. Metastatic cancer cells can also be transported via lymph. Lymph also transports fats from the digestive system (beginning in the lacteals) to the blood via chylomicrons.

Circulation

Tubular vessels transport lymph back to the blood, ultimately replacing the volume lost during the formation of the interstitial fluid. These channels are the lymphatic channels, or simply lymphatics. Unlike the cardiovascular system, the lymphatic system is not closed. In some amphibian and reptilian species, the lymphatic system has central pumps, called lymph hearts, which typically exist in pairs, but humans and other mammals do not have a central lymph pump. Lymph transport is slow and sporadic. Despite low pressure, lymph movement occurs due to peristalsis (propulsion of the lymph due to alternate contraction and relaxation of smooth muscle tissue), valves, and compression during contraction of adjacent skeletal muscle and arterial pulsation. Lymph that enters the lymph vessels from the interstitial spaces usually does not flow backwards along the vessels because of the presence of valves. If excessive hydrostatic pressure develops within the lymph vessels, though, some fluid can leak back into the interstitial spaces and contribute to formation of edema. The flow of lymph in the thoracic duct in an average resting person usually approximates 100ml per hour. Accompanied by another ~25ml per hour in other lymph vessels, the total lymph flow in the body is about 4 to 5 litres per day. This can be elevated several fold while exercising. It is estimated that without lymphatic flow, the average resting person would die within 24 hours.

Clinical significance

Because lymph is interstitial fluid that has been collected by the lymphatic system, diseases arising from primary abnormalities of the lymphatic fluid do not occur. Diseases such as lymphedema occur when the lymphatic ducts are swollen, usually as a result of blockage at the level of lymph nodes. Primary diseases of the lymphatic ducts include benign (lymphangioma) and malignant (lymphangiosarcoma) tumours. Histopathological examination of the lymph system is used as a screening tool for immune system analysis in conjunction with pathological changes in other organ systems and clinical pathology to assess disease status. Although histological assessment of the lymph system does not directly measure immune function, it can be combined with identification of chemical biomarkers to determine underlying changes in the diseased immune system.

As a growth medium In 1907 the zoologist Ross Granville Harrison demonstrated the growth of frog nerve cell processes in a medium of clotted lymph. It is made up of lymph nodes and vessels. In 1913, E. Steinhardt, C. Israeli, and R. A. Lambert grew vaccinia virus in fragments of tissue culture from guinea pig cornea grown in lymph.

References

External links Media related to Lymph fluid at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Lymph

Start with the simplest possible case. Write down what Lymph claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lymph before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lymph ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lymph

In research: Lymph appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Lymph in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Lymph is common in secondary-school and first-year university syllabi. It links to neighbouring topics Body fluids, Lymph fluid, Lymphatic system, so understanding it makes those chapters shorter.
In everyday life: Look for Lymph outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Lymph in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Lymph means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Lymph out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lymph in simple terms?

Why does Lymph matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lymph?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lymph.