PREPARED BY : EN. MUHD FAZLI DOLLAH

1. BIOLOGY FORM 5 1.4 LYMPHATIC SYSTEM PREPARED BY : EN. MUHD FAZLI DOLLAH

2. LYMPHATIC SYSTEM

3. LEARNING OUTCOMES • Describe the formation of interstitial fluid • State the composition of interstitial fluid • State the importance of interstitial fluid • Describe the fate of interstitial fluid • Describe the structure of the lymphatic system

4. THE LYMPHATIC SYSTEM • Part of the circulatory system & immune system. • A closed system consist of a network of lymphatic vessels, ducts & nodes. • No pump, the fluid (lymph) id squeeze along the lymphatic vessels by pressure associated with movements of skeletal muscles, intestinal movements & breathing. • Thymus & spleen are important organs of lymphatic system.

7. FORMATION OF INTERSTITIAL FLUID • Blood flows from arteries  capillaries, there is a higher hydrostatic pressure at the arterial end of the capillaries

9. LYMPHATIC FLUID • Oxygenated blood @ arterial end of the capillaries  high pressure  force water & dissolved substances out  capillary wall  interstitial spaces (spaces between cells)  interstitial fluid/ tissue fluid/ extracellular fluid. • Erythrocytes & plasma protein are too large to pass through  remain in the capillary.

10. COMPOSITION OF INTERSTITIAL FLUID • Contains water + dissolved oxygen + amino acids + glucose + fatty acids + glycerol + vitamins + minerals + hormones. • An adult has ~11 litres of interstitial fluid providing the cells of the body with nutrients & a means of waste removal. • At the venous end of the capillary  90% absorbs by blood consists of water, minerals & waste products. • The rest  passes back into the BCS as lymph via the LYMPHATIC SYSTEM.

11. The Importance of Interstitial Fluid • Carries dissolved substances (O2, amino acids, glucose, fatty acids, glycerol, vitamins, minerals & hormones) to cells for exchange. • Carries waste products (CO2, urea, etc.) into BCS.

12. THE FATE OF INTERSTITIAL FLUID • 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.

15. THE STRUCTURE OF THE LYMPHATIC SYSTEM • Starts from the minute blind-ended tubes including lacteals (in the ileum) & lymphatic capillaries in other tissues. • Lymphatic capillaries  form larger lymphatic vessels  lymphatics. • Semilunar valves are present along the lymphatics. • Lymphatics from all parts of the body  two large ducts  the right lymphatic duct, the thoracic duct.

16. THE STRUCTURE OF THE LYMPHATIC SYSTEM • Situated at intervals along the lymphatics are the oval-shaped structures  lymph nodes (neck, armpits & groin). • Lymphocytes are found in the lymph nodes  produce antibodies & play an important role in the body’s immune system. • Phagocytes in the lymph nodes help to remove bacteria.

18. to be continued...