Introduction to Blood Flashcards
What are the possible progenitors of the hematopoietic stem cell?
hemangioblast - differentiates into smooth muscle, angioblasts, and HSCs (previous thought)
hemogenic endothelium - rise adn generate multilineage hematopoietic stem cells in the yolk sac, aorta- gonad-mesonephros region and the placenta (recent thought)
these cells arise in the yolk sac and migrate to sites of definitive hematopoiesis
When and where does hematopoiesis begin?
shortly after implantation with the production of primitive red cells in the blood islands of the yolk sac
What is the primary site for hematopoiesis from weeks 6 to 22?
liver
What is the main site of hematopoiesis after 22 weeks?
bone marrow
cells that colonize the bone marrow
first are the myeloid cells followed by the erythroid cells
the first cells to reside in the marrow are not hematopoietic stem cells but are committed progenitor cells with the hematopoietic stem cells establishing residence later
most active marrow sites of hematopoeisis
vertebral column, femur, pelvis, fibula/tibia and humerus
marrow produces red cells that are anucleated in contrast to the earlier sites of hematopoeisis
osteoblastic niche
quiescent hematopoietic cells with adult HSCs
vascular niche
contains stress and reconstitution hematopoetic cells
myeloid/granulocytic precursors
identified by the presence of primary granules (myeloperoxidase positive)
specific secondary granules in the more mature cells
secondary granules become more numerous in the cytoplasm with successive rounds of division and maturation
erythoid cells
located primarily in “islands” in the interstitial area of the marrow
these cells develop progressively “pinker cytoplasm due to increased levels of hemoglobin
they also develop smaller and smaller nuclei with more condensed chromatin as they mature
polychromatophilic red cells
the early circulating red cells that are a bit more “blue” and larger
megakaryocytes
large cells with multilobated nuclei
these cells undergo endomitosis
cytoplasm fragments off to become platelets
approximately 1000 platelets are generated per megakaryocytes
lymphocytes
develop from hematopoietic stem cells
in contrast to the erythroid, myeloid andgranulocytic cells they are defined immunologically rather than by morphology and cytochemistry
central or primary organs
where antigen independent differentiation of lymphocytes into naive or virgin cells occurs
these cells can interact with antigen
peripheral or secondary organs
where naive cells interact with antigen and differentiate into proliferating cells and mature into antigen specific effector cells (lymph nodes, spleen mucosa)
plasma
what remains in the blood after the cells have been removed
accounts for approximately 50-55% of the blood and contains proteins/amino acids, electrolytes needed for cellular function as well as proteins and glycoproteins
also contains glucose and hormones
>90% water by volume
three broad classes of proteins in plasma
carrier proteins, immunoproteins, and coagulation proteins
main functions of carrier proteins
bind molecules in plasma to decrease nonspecific diffusion into the tissue and/or nonspecific interaction with blood and tissue cells
allow for more specific uptake by cells of specific molecules
diminish toxic effect of certain substances and helps excrete them through localization
maintain the proper pH of the system
examples of carrier proteins
albumin
lipoproteins
transferrin
transcobalamins
haptoglobin
hemopexin
alpha-1-antiprotease and alpha-2-macroglobulin
ceruloplasmin
albumin
main plasma protein
accounts for 2/3 of the plasma protein mass
major source of osmotic pressure
carries a veriety of substances such as bile pigments, free fatty acids, and bilirubin
lipoproteins
transport of cholesterol, triglycerides, and phospholipids
transferrin
transport of iron
transcobalamins
transport of cobalamins
haptoglobin
binds hemoglobin following red cell destruction
hemopexin
binds free heme from denatured hemoglobin
alpha-1-antiprotease and alpha-2-macroglobulin
bind and neutralize proteolytic enzymes released from destroying tissues and phagocytic leukocytes for clearance by macrophages
ceruloplasmin
binds copper and detoxifies oxygen-derived free radicals released during inflammation
immunoproteins
proteins active in defense and participate with cells in this endeavor
includes immunoglobulins and complement proteins
coagulation proteins
proteins that maintain the integrity of the vascular system
cells and plasma constituents work together to maintain the body’s vasculature
coagulation factor function is dependent on calcium
includes coagulation factors and fibrinolytic factors
serum
blood that has had the cells and clot removed
erythrocytes
carry oxygen through hemoglobin
vary in size (ansiocytosis) or shape (poikilocytosis)
circulate in the blood for about 120 days
leukocytes
consist of neutrophils, eosinophils, lymphocytes, and monocytes
platelets are also included in this group
neutrophils
monst abundant white cell
multilobated and called polymorphonuclear cells
important for ingesting and killing bacteria
present in peripheral blood for only a few hours
eosinophils
have a bilobed nucleus and large, chunky, eosinophilic secondary granules in the cytoplasm
important in the defense against parasites and in controlling allergic insults
maturation promoted by IL3 and IL5
basophils
contain large blod/purple granules in the cytoplasm
account for 1% or so of the leukocytes
granules are sulfated or carboxylated acidic proteins such as heparin
release histamine when properly stimulated
monocytes
large cells with blue-gray cytoplasm
kidney-shaped or folded nuclei
spend less than a day in the circulation
migrate to tissues where they transform into macrophages\
important for ingesting mycobacteria, fungi, and macromolecules
remove senescent red cells form the pleen
lymphocytes
round small cells with scant cytoplasm
involved in immune response
platelets
cellular components of the coagulation system
coagulation and aggregation form platelet plugs
participate in the inflammatory response
circulate in the blood for 9-10 days
progression of hematopoiesis throughout development
yolk-sac
aorta-gonad mesonephros (AGM)
placenta
fetal liver
bone marrow
stages and characteristics of hematopoiesis
HSC - morphologically unrecognizable, self-renewal and multilineage mautration, express CD34
progenitor cell - morphologically unrecognizable, may lack self-renewal, irreversible lineage commitment
blast cell - recognizable, mitotically active, IHC and cytochemical features of lineage
intermeidate cell - continuum of maturation, progressive loss of mitotic capability, additional lineage specific characteristics
mature cell
