Blood

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Blood consists of plasma, containing dissolved solutes, and a number of different types of cell, each with a specific function. Blood cells are made in the bone marrow.

Leucocytes are white blood cells.

White blood cells are involved in body defence. Fewer leucocytes than red blood cells. 72% are neutrophils (phagocytes), which engulf foreign proteins and pathogens; 24% are lymphocytes which produce antbodies.

Blood Cell

Erythrocytes

Size

7um

Structure

  • Biconcave disk
  • Small and flexible shape
  • No nucleus
  • Packed with red pigment haemoglobin

Function

  • Transports oxygen and carbon dioxide in reversible reactions
  • Has a large surface area over which gases (O2 and CO2) diffuse quickly
  • Can easily change shape and squeeze through capillaries

Blood Cell

Platelets

Structure

  • Small amounts of cytoplasm
  • membrane with no nucleus.

Function

Release blood clotting factors on damage

Lymphocytes:

Blood cell

Neutrophils

Size

9um

Structure

  • Have small granules in cytoplasm
  • Lobed nucleus

Function

Engulf microbes by phagocytosis

Blood Cell

Lymphocytes

Size

5.5um

Structure

  • Very large nucleus
  • Little cytoplasm
  • B lymphoctyes
  • T lymphocytes

Function

  • B lymphocytes produce antibodies
  • T lymphocytes destroy infected cells and have other functions

Blood Cell

Monocytes

Size

13-20um

Structure

  • Large cells
  • Bean shaped nucleus

Function

Become macrophages after 3 days in blood system

Blood cell

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