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Blood composition

There are two main components of blood: cells, or

Blood cells

Composed of three main cell types: erythrocytes, leucocytes & platelets.

Erythrocyte.png

Erythrocytes

  • Most numerous cells (5.5x10'^12^'/L).
  • No mitochondria
  • No nucleus
  • Lifespan 120 days
  • Contains haemoglobin, with four subunits with a polypeptide globin chain and an iron containing haem group. Adult haemoglobin has two alpha and two beta chains.
  • Binds reversibly to four O2 molecules.

Leukocytes

Check out the immune pages for more on these... 4-10x10'^9^'/L (20x10'^9^'/L in newborn)

Lymphocyte.png

Lymphocytes

  • Agranulocyte, which means that they have clear cytoplasm under a H&E stain.
  • Made from lymphoblasts
  • Two types: B and T cells.
  • Make antibodies (immunoglobulins)
  • Allows immunological memory (for vaccines etc)
Monocyte.png

Monocytes

  • Found in blood and bone marrow, are the precursors of macrophages, which are found in connective tissue and ingest foreign bacteria.
  • After formation in marrow they circulate for around 72 hours before entering tissues.
Neutrophil.png

Neutrophils

  • A granulocyte - meaning the cells go grainy under a H&E stain.
  • Life span 10 hours
  • Phagocytose bacteria
  • Secrete cytokines and chemotaxins
  • Important in the inflammatory response.
  • Made from myeloblasts in bone marrow
Eosinophil.png

Eosinophils

  • Granulocyte
  • Ingest foreign particles.
  • Cover surfaces within the body.
  • Involved in allergic responses
Basophil.png

Basophils

  • Granulocyte
  • Contain histamine (causes vasodilation, contraction of smooth muscle, mediates inflammation) and heparin (anticoagulant).
  • Ingests foreign particles.

Platelets

  • 140-400x10'^9^'/L
  • Small, vesicle like structures.
  • Formed from megakaryocytes in the bone marrow.
  • Contain dense granules and receptors from ADP and collagen.
  • Lifespan of 4 days.

Blood Fluid

Plasma, mainly composed of water, blood proteins and inorganic electrolytes

Plasma proteins

Albumin

  • Determines oncotic pressure (the pressure difference between the blood and the lymph/ tissue fluid).
  • Lack of albumin results in oedema, liver disease and nephritic syndrome.

Immunoglobins

  • Also known as antibodies, these are produced by plasma cells, which are differentiated B lymphocytes.
  • IgG
  • IgA
  • IgM
  • IgE (GAME)
  • Produced in response to non-self antigens.

Others

  • Coagulation factors - fibrinogen, prothrombin and plasminogen.
  • Carrier proteins and hormones

Inorganic electrolytes

  • Ca2+
  • Na+
  • K+
  • Mg2+
  • Cl-
  • CO32-
  • PO43-
  • Fe2+/3+