Unit 3 - Blood PART C Flashcards
Hematopoiesis
Production of formed elements (blood cells) from PLURIPOTENT HEMATOPOIETIC STEM CELLS found in bone marrow.
Pluripotent hematopoietic stem cells
- develop into many diff. cell types
- as they specialize, they narrow their possible fates
1st - become UNCOMMITTED STEM CELLS
2nd - then PROGENITOR CELLS that are committed to developing into RBC’s, lymphocytes, other WBC’s, & megakaryocytes (parent cells of platelets)
Bone marrow
a soft tissue that fills the hollow center of bones
Red marrow =
active hematopoiesis (25% of overall production = RBCs, 75% = WBCs)
- contains HEMOGLOBIN - O2 binding protein of RBC’s
Yellow marrow =
adipose cells (fat cells), inactive hematopoiesis
Formed Elements: (3 main cellular elements found in body)
- Erythrocytes (Red Blood Cells or RBCs)
- Leukocytes (White Blood Cells or WBCs)
- Platelets (formed from megakaryocytes).
Erythrocytes (Red Blood Cells or RBCs)
- have LOST their nuclei by the time they enter the bloodstream
- key role in transporting O2 from lungs to tissues, & CO2 from tissues to lungs
Leukocytes (White Blood Cells or WBC’s)
- ONLY functional cells in the circulation
- key role in body’s immune response, defending the body against foreign invaders (parasites, bacteria, & viruses etc.)
- most circulate through the body in the blood, but their work is usually carried out in the tissues rather than in the circulatory system
What are the 5 types of mature Leukocytes (WBC’s)?
a. Lymphocytes
b. Monocytes
c. Neutrophils
d. Eosinophils
e. Basophils
Lymphocytes
produced directly from Pluripotent stem cell.
- produce specific immune responses directed against invaders
- sometimes called IMMUNOCYTES
WBC
Monocytes
- phagocytes; after migrating into tissues, they develop into MACROPHAGES
WBC
Neutrophils
- mobile phagocytes that ingest foreign substances & pathogens
WBC
Eosinophils
- produce toxic compounds directed against invading pathogens
WBC
Basophils
(in tissues = mast cells)
- tissue basophils are also called MAST CELLS
WBC
What develops from the same committed progenitor cell?
Monocytes & Neutrophils
What is collectively known as Phagocytes? Why?
Monocytes, Macrophages (what monocytes dev. into), & Neutrophils
b/c they can engulf & ingest foreign particles such as bacteria (phagocytosis)
What are called granulocytes? Why?
Neutrophils, Eosinophils, & Basophils
- b/c they contain cytoplasmic inclusions that give them a granular appearance
Platelets
formed from megakaryocytes
- also LACK a nucleus
- are CELL FRAGMENTS that have split off a relatively large parent cell known as MEGAKARYOCYTE
- instrumental in COAGULATION - process by which blood clots prevent blood loss in damaged vessels
Hematopoiesis is a…
Specialization of stem cells into specific blood cell types
is regulated by cytokines:
What are cytokines?
- chemical factors
- peptides or proteins released from 1 cell that affect the growth or activity of another cell
What 4 cytokines is Hematopoiesis regulated by?
- Interleukins (e.g. IL-3)
- Erythropoietin (EPO)
- Colony Stimulating Factors (CSFs)
- Thrombopoietin (TPO)
Interleukins EX & FUNCTION
e.g. IL-3 –> numbered names are given to cytokines once their AA sequences have been identified
- variety of functions including stimulation of uncommitted
stem cells to form committed progenitor cells.
(role in immune system)
Where are Interleukins produced & released by?
Produced and released by WBCs to act on other WBCs
Erythropoietin (EPO) FUNCTION
- stimulates erythropoiesis (red blood cell production)
(helps the body maintain HOMEOSTASIS, by stimulating the syn. of RBC’s, EPO puts more hemoglobin into the circulation to carry O2)
(glycoprotein, made on demand & not stored, as classic peptide hormones are)
REGULATES RBC PRODUCTION
Where are Erythropoietin (EPO) produced & released?
produced and released by the KIDNEYS in response to low
oxygen levels (hypoxia). People who are adapted to live at
high altitude have a higher hematocrit as a result.
- helps the body maintain HOMEOSTASIS, by stimulating the syn. of RBC’s, EPO puts more hemoglobin into the circulation to carry O2
Pathway to form a Erythrocyte
Erythroblasts (nucleated) –> Reticulocyte –> Erythrocyte (anucleate)
Colony Stimulating Factors (CSFs) FUNCTION
- stimulate leukopoiesis (white blood cell production (& dev.))
- Responds to need. (e.g. during bacterial infection, CSFs
stimulate production of neutrophils and monocytes.; viral
infections cause increase in proportion of lymphocytes).
REGULATE LEUKOPOIESIS
(named for their ability to stimulate the growth of leukocyte colonies in culture)
(induce both cell division (mitosis) & cell maturation in stem cells (loses ability when leukocyte matures)
What are Colony Stimulating Factors (CSFs) secreted by?
- Secreted by endothelial cells and fibroblasts in bone marrow, and by other leukocytes.
Thrombopoietin (TPO) FUNCTION
- regulates growth and development of megakaryocytes (parent cell of platelets) (and therefore platelet production).
REGULATES PLATELET FORMATION
What are Thrombopoietin (TPO) produced & secreted by?
Produced and secreted by the LIVER
Erythropoietin (EPO) SUMMARY
cytokine involved in hematopoiesis
Site of production: KIDNEY CELLS primarily
Influences growth or differentiation of: RBC’s
Thrombopoietin (TPO) SUMMARY
Cytokine involved in Hematopoiesis
Site of production: LIVER primarily
Influences growth or differentiation of: MEGAKARYOCYTES
Colony Stimulating Factors (CSFs), Interleukins, stem cell factor SUMMARY
Cytokine involved in Hematopoiesis
Site of production: ENDOTHELIUM & FIBROBLASTS of BONE MARROW, LEUKOCYTES
Influences growth or differentiation of: All types of BLOOD CELLS; MOBILIZES hematopoietic stem cells
