BIOLOGY FORM 5

LEARNING OUTCOMES1. Explain how the lymphatic system

complements the circulatory system;2. Compare the content of blood,

interstitial fluid & lymph;3. Predict what will happen if interstitial

fluid fails to return to the circulatory system;

4. Conceptualise the relationship between the lymphatic system & circulatory system.

THE LYMPHATIC SYSTEM COMPLEMENT THE CIRCULATORY SYSTEM

• 10% of interstitial fluid drains into the lymphatic capillaries forming lymph.

• Move due to the contraction & relaxation of skeletal muscles backflow is prevented by semilunar valves.

• Lymph in the right lymphatic duct & the thoracic duct flows into the right & left subclavian veins of the BCS, respectively.

COMPARE THE CONTENT OF BLOOD, INTERSTITIAL FLUID

& LYMPH

BLOOD INTERSTITIAL FLUID

LYMPH

SIMILARITIES

• Watery liquid•Transport gases, nutrients &

waste products.

COMPARE THE CONTENT OF BLOOD, INTERSTITIAL FLUID &

LYMPHBLOOD INTERSTITIAL

FLUIDLYMPH

DIFFERENCESInside blood vessel In the intercellular

spacesInside the lymphatic

vessels

More protein than interstitial fluid &

lymph

Less protein than blood & lymph

More protein than interstitial fluid but less

than blood

Oxygenated Oxygenated Deoxygenated

Erythrocytes, leucocytes & platelets

present

Only leucocytes present

Only leucocytes present

Low lipid content Low lipid content High lipid content

If Interstitial Fluid Fails to Return to th Circulatory

System•It accumulates in the organs &

tissues the organs & tissues swell up oedema.

•Interstitial fluid should return to the CS at the same rate as it is produced.

THE RELATIONSHIP BETWEEN LYMPHATIC SYSTEM & BLOOD

CIRCULATORY SYSTEM

• LS & BCS transport interstitial fluid back to the heart.

• The LS joins the BCS when the right lymphatic duct opens into the right subclavian vein & the thoracic duct opens into the left subclavian veins.