Page 215 - Atlas of Histology with Functional Correlations

SECTION 1 Blood

Unique form of connective tissue in which cells are suspended in circulating

fluid
Consists of cells erythrocytes, leukocytes, and cell fragments platelets
suspended in plasma
Blood cells have limited life span and are continually replaced in the red
bone marrow

SITES OF HEMATOPOIESIS

Depend on the stage of development of the organism
In embryo, the initial hematopoietic site is the yolk sac
Later in development, liver, spleen, lymph nodes, and bone marrow form

blood
In adults, red marrow is limited to the skull, sternum, vertebrae, and pelvic
bones
Long bones become filled with fat, yellow marrow, and lose hematopoietic
functions

HEMATOPOIESIS

Common pluripotential stem cell forms pluripotential myeloid and lymphoid
stem cells
Myeloid stem cells give rise to erythrocytes, eosinophils, neutrophils,
basophils, monocytes, and megakaryocytes

Lymphoid stem cells give rise to B lymphocytes, T lymphocytes, and natural
killer cells
B lymphocytes mature in bone marrow; T lymphocytes mature in the thymus
gland

B lymphocytes and T lymphocytes have separate development paths
B and T lymphocytes reside in peripheral lymphoid tissue, lymph nodes, and
spleen

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