Page 67 - Headlines Histology2024_Neat

• When placed in hypotonic solution (lower concentration than plasma), the
RBCs swell and ruptures. This is called hemolysis.

• In hypertonic solution (higher concentration than plasma), the cell volume
diminishes and the cells become crenated.

• The life span of erythrocytes is about 120 days. Spleen, bone marrow and liver
phagocytes engulf old RBCs. The iron of the hemoglobin is reused in
formation of new cells. The porphyrin portion is used to form bilirubin or bile
pigment.

• The erythrocytes are highly adapted to their function that is the transport of
oxygen and carbon dioxide:

• The plasma membrane is highly selective. It is permeable to water and
electrolytes, but it is impermeable to hemoglobin.

• The elasticity of the plasma membrane allows the erythrocytes to deform
and pass through the smallest capillaries (2-4 ?m in diameter).

• The biconcave shape provides a large surface area relative to cell volume,
which greatly enhances gaseous exchange.

• Before release into the circulation, the nucleus is extruded and by maturity,
all cytoplasmic organelles degenerate which give more space to carry more
hemoglobin.

Reticulocytes

• They are immature RBCs that are released into the peripheral circulation
from the bone marrow. They are slightly large than mature RBCs and when
stained with supravital dyes such as brilliant cresyl blue, blue-stained fine
networks are seen inside their cytoplasm. This is due to ribosomal RNA still
remaining in their cytoplasm. The number of reticulocytes increases in
circulation after blood loss.

II) WHITE BLOOD CELLS (LEUKOCYTES)

• There are five cell types of the WBCs that are subdivided into two main
groups:

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