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Identifying blood vessels 1 of 33 © Boardworks Ltd 2008 Module 3 Exchange and transport 8.3 Blood, tissue and lymph Starter – Osmosis recap Quick Recap First! Osmosis is the diffusion of water through a partially permeable 1) In which direction will osmosis occur in these cells? membrane 2) Between which cells will the net movement of water be the greatest? Explain why. 3) Which has the higher water potential, the solution of water in the soil or the root hair cell? Explain your answer. Answers 1) From C to B to A. 2) Between C and B, because there is a greater water potential gradient between these cells. 3) The water in the soil. It has the greater amount of water in the solution. Learning Objectives Success Criteria • Define the terms tissue fluid, blood and lymph (Grade E - D) • To understand how tissue fluid is formed and the • Describe how tissue fluid is differences between blood, formed from plasma tissue fluid and lymph (Grade C –B) • Explain the difference between blood, tissue fluid & lymph (Grade B – A) The composition of blood What are the main components of blood? What are their functions? 6 of 33 © Boardworks Ltd 2008 Blood • Describe the main functions of blood (4 marks) Transport oxygen (1) carbon dioxide (1) to and from respiring cells respectively; transport of digested food from the intestine to cells (1): transport of nitrogenous wastes from tissues to excretory organs (1); transport of : hormones (1); platelets (for clotting) (1) and antibodies (1);immune response (1); maintaining constant body temperature (1) and pH (1) Tissue Fluid and its formation • What is it? – A watery liquid containing glucose, amino acids, salts, fatty acids and oxygen. Can contain some white blood cells eg neutrophils. • It supplies the materials to cells and receives carbon dioxide and waste substances from the cells for removal. • Formed by blood plasma, provides a constant environment for the cells it surrounds. • Similar to blood – but no rbc or platelets How does it get to the tissues? • When blood flows into the capillaries, water and other substances are exchanged between the blood and tissue fluid. • Two forces affect this exchange: – Hydrostatic pressure: caused by pumping action of heart – forces water out through capillary walls into tissue fluid – Water Potential: Due to large protein molecules in plasma, attracts water back into blood vessels from tissue fluid Lymphatic system Some tissue fluid remains in tissues It is carried away by lymphatic system Network of vessels around body Drains contents back to heart Lymphatic system Movement through vessels caused by Hydrostatic pressure of fluid in tissue Contraction of body muscles squeezing the lymph vessels tissues arteriole venule capillary artery vein Formation of tissue fluid Tissue fluid movement Arterial End Hydrostatic pressure forcing water out is greater force than water potential forcing water back in NET movement = into tissues Venous End Water Potential gradient attracting water into vessel is greater force than hydrostatic pressure forcing water out into tissues. NET movement = into vessel tissues arteriole venule capillary artery vein Lymph Formation • Not all tissue fluid returns to capillaries, some is drained into the lymphatic system. • Lymph has less oxygen and nutrients than tissue fluid more carbon dioxide more fatty material absorbed from the intestines. presence of lymphocytes produced in lymph nodes 13 of 33 lymphatic capillaries © Boardworks Ltd 2008 The lymphatic system The lymphatic system is a secondary circulatory system and a major part of the immune system. It consists of: lymphatic capillaries and vein-like lymph vessels, containing valves lymph nodes – sac-like organs that trap pathogens and foreign substances, and which contain large numbers of white blood cells lymphatic tissue in the spleen, thymus and tonsils – these also contain large amounts of white blood cells and are involved in their development. 14 of 33 © Boardworks Ltd 2008 Task 1 •Describe how tissue fluid is formed from plasma (Grade C –B) • Complete worksheet describing how tissue fluid is formed • Extension – Albumin is a protein found in the blood. Hypoalbuminemia is a condition where the level of albumin in the blood is vey low. It causes an increase in tissue fluid, which can lead to swelling. Explain how hypoalbuminemia causes an increase in tissue fluid. • Water potential of the capillary ids higher because there is less albumin in the blood. This means less water is absorbed by osmosis back into the capillary at the vein end of the capillary bed, which leads to an increase in tissue fluid. Task 2 • In pairs complete the table comparing blood, tissue fluid and lymph. • Homework – exam question Blood Red Blood cells White blood cells Platelets Proteins Water Dissolved solutes Oxygen Carbon dioxide Tissue fluid Lymph Comments Plenary • Give one difference between blood and tissue fluid • Give one difference between tissue fluid and lymph •Explain the difference between blood, tissue fluid & lymph (Grade B – A)