Blood

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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