Biology Unit 1, Module 2: Blood, Tissue Fluid and Lymph

What does the blood consist of?

The blood contains: - erythrocytes (red blood cells) - leucocytes (white blood cells) - platelets - plasma, which contains several substances (including oxygen, carbon dioxide, salts, glucose, fatty acids, amino acids, hormones and plasma proteins)

Outline how tissue fluid is formed.

The formation of tissue fluid: - arteries branch into arterioles and then capillaries, which then branch back into veins using venules (artery-arteriole-capillary-venule-vein) - the ends of these contained capillaries are at high pressure due to the contraction of the heart muscle (hydrostatic pressure), and this causes the blood fluid to leave the capillaries through gaps in their walls - the fluid pushed through these gaps does not contain red or white blood cells, platelets or plasma proteins as these are too big to fit through, and is known as the tissue fluid - when this fluid leaves, it surrounds the body cells, so allowing exchange of oxygen and nutrients by diffusion and facilitated diffusion (oxygen and nutrients enter the cells, carbon dioxide and other waste products leave the cells)

Outline how the tissue fluid is able to return to the blood.

The tissue fluid: - has its own hydrostatic pressure for pushing it back to the capillaries - contain solutes, but the blood contains more solutes, making its water potential lower than that of the tissue fluid, so water tends to move by osmosis from the tissue fluid to the blood down the water potential gradient - at the venous end of the capillary, the blood has lost its hydrostatic pressure, so the combined effect of the hydrostatic pressure of the tissue fluid, and the osmotic force of the plasma proteins, is enough to move the fluid back into the capillaries, along with carbon dioxide and other waste products

a) What is the lymphatic system? b) How is lymph similar to the tissue fluid? c) How is lymph different from the tissue fluid?

a) The lymphatic system: - is a series of vessels similar to capillaries - these start in the tissues and drain the excess fluid into larger vessels, which eventually rejoin in the chest cavity b) Lymph is similar to the tissue fluid because: - they contain the same solutes c) Lymph is different from the tissue fluid because: - it contains less oxygen and nutrients, as these have been absorbed - it contains more carbon dioxide and waste products, as these have been released from the body cells - it contains more fatty material that has been absorbed from the intestines - it contains lymphocytes, which engulf and destroy bacteria from the lymph (which has been filtered by the lymph nodes, swellings in the lymphatic system), and are a part of the immune system

a) What does tissue fluid consist of? b) What is its role?

a) Tissue fluid is similar to blood, but does not contain many of the cells or the plasma b) It transports oxygen and nutrients from the blood to the cells, and carbon dioxide or waste products from the cells to the blood

Compare the content of i) blood, ii) tissue fluid and iii) lymph according to: a) cells b) proteins c) fats d) glucose e) amino acids f) oxygen g) carbon dioxide

a) i) blood contains: - erythrocytes - leucocytes - platelets ii) tissue fluid contains: - some phagocytic white blood cells iii) lymph contains: -lymphocytes b) i) blood contains: - hormones - plasma proteins ii) tissue fluid contains none iii) lymph contains some proteins c) i) blood contains some fats transported as lipoproteins ii) tissue fluid contains none iii) lymph contains more fat than the blood, as it has been absorbed from the intestine d) i) blood contains 80-120mg of glucose per 100cm cubed ii) tissue fluid contains less glucose than the blood iii) lymph contains less glucose than the blood e) i) blood contains more oxygen than the tissue fluid and lymph ii) tissue fluid contains less oxygen than the blood iii) lymph contains less oxygen than the blood f) i) blood contains little carbon dioxide ii) tissue fluid contains more carbon dioxide than the blood iii) lymph contains more carbon dioxide than the blood