Module 2 – Exchange and Transport Lesson 9

Title: Tissue fluid Lesson objectives: 1.Can I distinguish between blood, tissue fluid and lymph? Grade B 2.Can I describe how tissue fluid is formed? Grade C Starter: Card sort activity…

Blood… Name the four components of blood. Plasma Erythrocytes Leucocytes Platelets In plasma, but what else do we find in the plasma? Structure of red blood cells and white blood cells….

Erythrocytes…. Very small – diameter is about 7ųm Biconcave disc No organelles Transports O 2 and CO 2

Leucocytes Nucleus – different shapes (phagocytes and lymphocytes) Larger than RBC Spherical or irregular shaped

Platelets Cell fragments formed from cytoplasm of larger cells Blood clotting

Tissue Fluid…. Transports oxygen and nutrients from the blood to the cells, carries carbon dioxide and wastes back to the blood. Similar to blood but no cells or plasma proteins.

Under high pressure due to contraction of heart – hydrostatic pressure

How does tissue fluid return? Blood and tissue fluid contain solutes = negative water potential Water potential of tissue fluid is less negative than blood so water moves back into the blood by OSMOSIS, down the gradient.

Lymph… Not all the tissue fluid is returned to the capillaries – drained into the lymphatic system. Vessels starts in tissues and drains excess fluid containing the same solutes, into larger vessels which rejoin the blood system. Lymphocytes – produced in the nodes and filter bacteria out, digesting them…

Lymph fluid has less oxygen and nutrients. It will contain more carbon dioxide and wastes plus more fatty material (intestines) but has the same solutes as tissue fluid.

Plenary…. Draw up a table to compare blood, tissue fluid and lymph using these headings: Types of cells Location Direction of flow (and cause of flow)