Blood and Tissue Fluid What is blood Blood

Blood and Tissue Fluid

What is blood? Blood is a specialized transport medium that is also considered a special type of connective tissue. An average adult has 4– 6 litres of blood. Blood has a range of functions such as: l transport l defence l thermoregulation l maintaining p. H of body fluids.

The composition of blood

Features of erythrocytes What are the specialized features of an erythrocyte? flattened, biconcave disc shape: ensures large surface area to volume ratio for efficient gas exchange diameter (6– 8 µm) larger than capillary diameter: slows blood flow to enable diffusion of oxygen large amount of haemoglobin: for transporting oxygen no nucleus or organelles: maximises space for haemoglobin, so more oxygen can be transported

1 T I N U Key Ideas Diffusion – the movement of a substance from an area of high concentration to an area of lower concentration. Osmosis – the movement of water from a dilute to a more concentrated solution through a semi -permeable membrane. Water potential?

1 T I N U Water Potential �A measure of the tendency of water molecules to move from one area to another. �Pure water has a water potential of 0 k. Pa. �All other water potentials are negative (i. e. lower values). �The higher the concentration of solute, the more negative the water potential.

1 T I N U Key Ideas Diffusion – the movement of a substance from an area of high concentration to an area of lower concentration. Osmosis – the movement of water from a higher to a lower water potential through a semi-permeable membrane.

Key Terms Osmotic pressure – the ‘physical’ pressure you’d have to apply to stop water moving into a solution by osmosis, i. e. a measure of the likelihood of water moving into/out of a solution. We’re interested in the effect this has on a system.

Key Terms Hydrostatic pressure – the pressure exerted by a fluid at rest, i. e. a measure of the likelihood of water moving into/out of a solution. We’re interested in the effect this has on a system.

Plasma proteins and blood pressure About 8% of blood plasma consists of plasma proteins, of which about half may be albumins. These are a group of small proteins involved in the transport of other substances (e. g. fatty acids, hormones) and which help regulate the osmotic pressure of blood. The balance between the hydrostatic pressure of blood (‘blood pressure’) and the osmotic pressure of blood is important in the formation of tissue fluid. 11 of 33 © Boardworks Ltd 2008

Formation of tissue fluid 12 of 33 © Boardworks Ltd 2008

Lymph Not all tissue fluid returns to the capillaries. The excess drains into the lymphatic system, where it forms lymph. Lymph is a colourless/pale yellow fluid similar to tissue fluid but containing more lipids. lymphatic capillaries The lymphatic system drains into the circulatory system near the vena cavae via the thoracic duct. 13 of 33 © Boardworks Ltd 2008

The lymphatic system is a secondary circulatory system and a major part of the immune system. It consists of: l lymphatic capillaries and vein-like lymph vessels, containing valves l lymph nodes – sac-like organs that trap pathogens and foreign substances, and which contain large numbers of white blood cells l 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

Problems – kwashiorkor • Lack of protein in the diet leads to lower plasma protein concentration • Water potential of blood is higher than normal • More water tends to leave capillaries and less is reabsorbed • Build up of tissue fluid, especially in abdomen. 15 of 33 © Boardworks Ltd 2008

Problems – blockage of the lymph ducts Can lead to lymphedema, elephantiasis or hydrocele. 16 of 33 © Boardworks Ltd 2008

Problems - cancer • Tumour cells multiply out of control • Some may break free from the tumour and travel in the blood/lymphatic system • Can become lodged in other areas • New tumours form - metastasis 17 of 33 © Boardworks Ltd 2008

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