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Blood and blood vessels This demo contains only a sample of the full content Blood Blood, a specialised transport and defensive tissue, is composed of cells and watery plasma. 10ml Plasma (55% of blood total 5ml White blood cells (Leucocytes) Red Blood cells (Erythrocytes) Plasma supernatant composed of: Water, solutes, waste substances, proteins. Cellular components 40% of total blood volume: Erythrocytes (red blood cells) and Leucocytes (white blood cells). Erythrocytes Erythrocytes (red blood cells) = Biconcave discs 6-8mm Elastic membrane reduces damage in high pressure blood flow. 2mm Lack of nucleus and organelles allows packing space for haemoglobin. Haemoglobin binds with oxygen (and carbon dioxide) and is important for oxygen transport in the body. Very small thus providing a large (total) exchange surface. Small size allows cells to come into close and intimate contact with exchanging tissues. Leucocytes • Leucocytes (white blood cells) are defensive, protecting the body from invading pathogens. • The blood contains two types of leucocytes. Granulocytes - cytoplasmic granules and lobed nuclei. Agranulocytes - no cytoplasmic granules and smooth nuclei. Neutrophils - Phagocytosis Phagocytosis is a non-specific immune response: a general defence against all infective particles. 3 stages: • Ingestion • Intracellular digestion • Release of products of digestion 1. Bacteria become attached to the neutrophil. 2. The neutrophil engulfs the bacteria. 3. Bacteria are enclosed in a vacuole. Lysosomes fuse with the vacuole and release digestive enzymes that destroy the bacteria. Antibody Actions • • Antibodies protect against pathogens by: Agglutination sticking them together, preventing dispersal. antibody antigen pathogen A different antibody will be made for this antigen • Lysis (bursting), causing death of pathogen and host cell. antibodies Foreign particle (pathogen) Bursting host cell containing pathogens Leucocytes summary Leucocytes Basophils Granulocyte Agranulocyte (granules lobed nuclei) (no granules smooth nuclei) Neutrophils • Migrate through capillary walls to infections • Phagocytic Eosinophils Lymphocytes Monocytes (round nucleus) •Produce antibodies •Phagocytic (bean-shaped nucleus) •Phagocytic Cell Functions What do these cells do? Cell Function Plasma cell Produce antibodies Neutrophil Migrate through capillary wall to site of infection Monocyte Phagocytosis Red blood cell Carry oxygen Artery Structure Lumen Elastic tissue Endothelium thin lining Elastic tissue and smooth muscle Diameter: 4mm to 25mm (aorta) Connective tissue (collagen & elastic tissue) Arteries and Muscle Elastic tissues absorb the high pressure, expand and ‘smooth’ large pressure changes Arteries mass transport blood away from the heart Elastic tissue Elastic tissue Elastic and muscle tissue Elastic and muscle tissue • • • Thick muscular walls contain the high blood pressure. Smooth muscle fibres contract rhythmically on the blood, exerting pressure. • • As pressure falls the artery recoils releasing energy. Elastic tissue ensures a continuous blood pressure. The pulse remains as evidence of the surge in blood pressure produced by ventricular contraction. Capillary Structure Capillaries are smaller in diameter than the cells they supply, allowing close and intimate contact. Endothelium – thin lining Lumen (Hole) Basement membrane Diameter: 8mm Fenestration • • • The endothelium, supported on the basement membrane, is one cell thick allowing easy exchange across the capillary. Fenestrations or gaps between endothelial cells increase the rate of exchange with the tissues. Very low blood pressure at the capillary produces low velocity blood flow. Vein Structure Lumen (Hole) Elastic tissue Endothelium – thin lining Elastic and muscle tissue Connective tissue Diameter: Up to 2.5cm (vena cavae) Veins Connective tissue Small amount elastic and smooth muscle tissue Endothelium Basement membrane valve • Veins carry blood at low pressure and velocity. • Venous walls do not require the thickness and strength of arteries to contain high blood pressure. Veins • • Pressure differences within the venous system are low. One-way valves ensure blood flows only towards the heart after leaving the capillaries. Veins • Muscles pushing on veins increase localised pressure and push blood, producing flow. • Valves ensure flow is one way.