Lymph, Tissue Fluid and the Lymphatic Organs

Challenges to clear

• Match every card to what it does.
• Connect lymph to what it actually is — tissue fluid that has gone somewhere.

The task

Blood is not the only fluid that circulates. Match each part of the lymphatic story to what it does.

What this lesson covers

• Tissue fluid — Plasma and leukocytes that have leaked out through capillary walls (It bathes the cells directly. Every cell takes its oxygen and nutrients from this fluid and returns carbon dioxide and wastes into it.)
• Lymph — Tissue fluid once it has entered the lymph vessels (Some tissue fluid is reabsorbed straight into the blood, but most drains into lymph vessels and takes a new name. The three fluids are stages of one another.)
• Cells found in lymph — Leukocytes only, mostly lymphocytes (No red cells and no platelets ever enter the lymph vessels, which is why lymph is colourless rather than red.)
• Composition of lymph by weight — 94 per cent water and 6 per cent solids (The solids are proteins, fats, carbohydrates, enzymes and antibodies — the antibodies are why lymph counts as a defence fluid.)
• What makes lymph flow along its vessels — Contraction of the surrounding muscles (There is no pump for lymph as the heart is for blood, so movement itself drives it. This is one more benefit of physical exercise.)
• Lacteals in the intestinal villi — Absorb fats from the intestine (Fats bypass the blood capillaries of the villi and travel by the lymphatics instead. This is the absorption function of lymph.)
• Lymph nodes — Localise an infection and stop it spreading through the body (They trap bacteria coming from the tissues. The painful swelling in the groin or armpit after a boil on a limb is a node doing its job — a protective sign, not a bad one.)
• Tonsils — Lymph glands on the sides of the neck (They guard the entrance to the throat, one of the commonest routes for germs to enter the body.)
• The spleen — The largest lymphatic organ, lying in the abdomen behind the stomach (About the size of a clenched fist and reddish brown, it sits above the left kidney. It acts as a blood reservoir, releasing stored blood in a haemorrhage or in carbon monoxide poisoning.)
• The spleen in an embryo — Produces red blood cells (In an adult the spleen destroys worn-out red cells instead, sharing that job with the liver. The same organ builds them before birth and breaks them down after it.)

Hint

Lymph flows one way only — tissues to blood, never back — and empties into the large veins close to where they enter the right auricle. Learn the four functions as nutritive, drainage, absorption and defence, and remember the two lymphatic organs named by the syllabus are the spleen and the tonsils.