Introduction to Blood

Question 1

What are the possible progenitors of the hematopoietic stem cell?

Answer 1

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

Question 2

When and where does hematopoiesis begin?

Answer 2

shortly after implantation with the production of primitive red cells in the blood islands of the yolk sac

Question 3

What is the primary site for hematopoiesis from weeks 6 to 22?

Answer 3

liver

Question 4

What is the main site of hematopoiesis after 22 weeks?

Answer 4

bone marrow

Question 5

cells that colonize the bone marrow

Answer 5

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

Question 6

most active marrow sites of hematopoeisis

Answer 6

vertebral column, femur, pelvis, fibula/tibia and humerus

marrow produces red cells that are anucleated in contrast to the earlier sites of hematopoeisis

Question 7

osteoblastic niche

Answer 7

quiescent hematopoietic cells with adult HSCs

Question 8

vascular niche

Answer 8

contains stress and reconstitution hematopoetic cells

Question 9

myeloid/granulocytic precursors

Answer 9

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

Question 10

erythoid cells

Answer 10

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

Question 11

polychromatophilic red cells

Answer 11

the early circulating red cells that are a bit more “blue” and larger

Question 12

megakaryocytes

Answer 12

large cells with multilobated nuclei

these cells undergo endomitosis

cytoplasm fragments off to become platelets

approximately 1000 platelets are generated per megakaryocytes

Question 13

lymphocytes

Answer 13

develop from hematopoietic stem cells

in contrast to the erythroid, myeloid andgranulocytic cells they are defined immunologically rather than by morphology and cytochemistry

Question 14

central or primary organs

Answer 14

where antigen independent differentiation of lymphocytes into naive or virgin cells occurs

these cells can interact with antigen

Question 15

peripheral or secondary organs

Answer 15

where naive cells interact with antigen and differentiate into proliferating cells and mature into antigen specific effector cells (lymph nodes, spleen mucosa)

Question 16

plasma

Answer 16

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

Question 17

three broad classes of proteins in plasma

Answer 17

carrier proteins, immunoproteins, and coagulation proteins

Question 18

main functions of carrier proteins

Answer 18

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

Question 19

examples of carrier proteins

Answer 19

albumin

lipoproteins

transferrin

transcobalamins

haptoglobin

hemopexin

alpha-1-antiprotease and alpha-2-macroglobulin

ceruloplasmin

Question 20

albumin

Answer 20

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

Question 21

lipoproteins

Answer 21

transport of cholesterol, triglycerides, and phospholipids

Question 22

transferrin

Answer 22

transport of iron

Question 23

transcobalamins

Answer 23

transport of cobalamins

Question 24

haptoglobin

Answer 24

binds hemoglobin following red cell destruction

Question 25

hemopexin

Answer 25

binds free heme from denatured hemoglobin

Question 26

alpha-1-antiprotease and alpha-2-macroglobulin

Answer 26

bind and neutralize proteolytic enzymes released from destroying tissues and phagocytic leukocytes for clearance by macrophages

Question 27

ceruloplasmin

Answer 27

binds copper and detoxifies oxygen-derived free radicals released during inflammation

Question 28

immunoproteins

Answer 28

proteins active in defense and participate with cells in this endeavor

includes immunoglobulins and complement proteins

Question 29

coagulation proteins

Answer 29

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

Question 30

serum

Answer 30

blood that has had the cells and clot removed

Question 31

erythrocytes

Answer 31

carry oxygen through hemoglobin

vary in size (ansiocytosis) or shape (poikilocytosis)

circulate in the blood for about 120 days

Question 32

leukocytes

Answer 32

consist of neutrophils, eosinophils, lymphocytes, and monocytes

platelets are also included in this group

Question 33

neutrophils

Answer 33

monst abundant white cell

multilobated and called polymorphonuclear cells

important for ingesting and killing bacteria

present in peripheral blood for only a few hours

Question 34

eosinophils

Answer 34

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

Question 35

basophils

Answer 35

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

Question 36

monocytes

Answer 36

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

Question 37

lymphocytes

Answer 37

round small cells with scant cytoplasm

involved in immune response

Question 38

platelets

Answer 38

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

Question 39

progression of hematopoiesis throughout development

Answer 39

yolk-sac

aorta-gonad mesonephros (AGM)

placenta

fetal liver

bone marrow

Question 40

stages and characteristics of hematopoiesis

Answer 40

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