The Hematopoietic System

Hematopoiesis

development or maturation of red blood cells, white blood cells, and platelets from blood stem cells

Hematocrit

percent of RBC in a blood sample

Erythrocytes

Red Blood Cells

Stem Cells

relatively undifferentiated cells that retain the ability to divide throughout life to provide progenitor cells that can differentiate into specialized cells

units of biological organization, responsible for the development and regeneration of tissue and organ systems

clonogenic

Clonogenic

the ability to expand from a single cell

Key Features of Stem Cells

1. self-renewing capacity

2. proliferation (expansion)

3. differentiation (lineage commitment)

What Are the Two Subsets of Stem Cells?

1. long term stem cells

2. short term stem cells

How Many Times Can Long-Term Stem Cells Renew?

Infinite

How Many Times Can Short-Term Stem Cells Renew?

Non-infinite

Short-Term Stem Cells

give rise to self renewing stem cells and non-self renewing oligo-lineage progenitors, which in turn give rise to progeny that are more restricted in their differentiating potential, and finally to functionally mature cells

How Are Stem Cells Identified?

by their surface markers

Ex: hematopoietic stems cells (HSCs) are identified based on CD34

Totipotent Stem Cell

these cells have unlimited capability, and have the ability to form extra-embryonic membranes and tissues, the embryo itself, and all post-embryonic tissues and organs

Ex: an embryo

Pluripotent Stem Cell

these cells are capable of giving rise to most, but not all, tissues of an organism

Ex: inner mass cells

Multipotent Stem Cell

these cells are committed to give rise to cells that have a specific function

Ex: blood stem cells

Telomeres

a terminal section of a chromosome which has a specialized structure and which is involved in chromosomal replication and stability

Role of Bone Marrow

provides the necessary structural and chemical cues to drive stem cell differentiation and proliferation

Where is Bone Marrow Found?

in tubular, flat, and long bones

What Does Bone Marrow Consist of?

a connective tissue framework called stroma

Yellow Pulp

major marrow constituent in long tubular bones and is comprised of aggregated fat cells

Red Pulp

major source of hematopoietic stem cells

found in flat bones in adults

What Happens to Red Pulp Through Aging?

red pulp in the long bones decreases and eventually basically disappears

What Are the 2 Major Lineages of Hematopoietic Stem Cells?

1. Myeloid Progenitor Cells

2. Lymphoid Progenitor Cells

What Cells Come from the Lymphoid Progenitor Cells?

1. T lymphocytes

2. B lymphocytes

3. Natural Killer Cells

What Cells Come From Myeloid Progenitor Cells?

1. eosinophils

2. basophils

3. neutrophils

4. reticulocytes (erythrocytes, i.e. RBCs)

5. megakaryocytes (thrombocytes, i.e. platelets)

6. monocytes (become macrophages and dendritic cells)

What Cells Are Leukocytes?

1. T lymphocytes

2. B lymphocytes

3. Natural Killer Cells

4. Eosinophils

5. Basophils

6. Neutrophils

7. Monocytes (become macrophages and dendritic cells)

Epotein

mimics the actions of erythropoietin (drives production of RBCs)

Filgrastim

mimics the actions of colony granulocyte stimulating factors (C-GSF) (drives production of neutrophils)