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01 Transport System in Mammals

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01 Transport System in Mammals

  1. 1. Transport system in mammals ALBIO9700/2006JK
  2. 2. Arteries, veins and capillaries ALBIO9700/2006JK
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  4. 4.  Arteries: – Transport blood swiftly and at high pressure to the tissues – Walls have 3 layer:  Inner endothelium (lining tissue) – squamous epithelium, layer very smooth and rests on elastic fibres (tunica intima)  Middle layer – smooth muscle, collagen and elastic fibres (tunica media)  Outer layer – elastic fibres and collagen fibres (tunica externa) – Distinctive characteristic: strength – Have the thickest wall – Large amounts of elastic fibres in tunica media allow the wall to stretch – Arteries further from the heart have fewer elastic fibres but more muscle fibres – Elasticity important to ‘even out’ blood flow – Branch into arterioles in tissues having greater proportion of smooth muscle. Muscles contract , narrowing the diameter and reducing blood flow. Helps to control the volume of blood flowing into tissues at different times. ALBIO9700/2006JK
  5. 5.  Veins: – Capillaries join to form venules. These join to form veins. – To return blood to the heart – Pressure has dropped to very low – No need for thick walls, tunica media thinner, fewer elastic fibres and muscle fibres – Muscles squeeze inwards on the veins to raise pressure – To keep blood flowing in right direction, veins contain half-moon valves or semilunar valves ALBIO9700/2006JK
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  8. 8.  Capillaries: – Arterioles continue to branch into capillaries – Takes blood as close as possible to all cells, allowing rapid transfer of substances between cells and blood – Form networks throughout every tissue in body except cornea and cartilage called capillary beds – Small size, thin walls (single layer endothelial cells), tiny gaps – Pressure will have dropped ALBIO9700/2006JK
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