HIST: Blood, Hematopoiesis and Bone Marrow (easy)

Approximately how much blood does an average healthy adult have

roughly 6 L

What are the two broad functions of blood

1. transportation

2. homeostasis

What substances does blood transport

• nutrients

• O2

• CO2

• Hormones

• Components involved in immune responses

What are the homeostatic functions of blood

thermoregulation

clotting

what are the two broad components of blood

plasma + cellular elements

What is plasma

liquid component of blood

Approximately what percentage of plasma is water

90%

What important plasma protein maintains colloid osmotic pressure

Albumin

What is an additional function of albumin

carrier protein

What immune related proteins are found in plasma

immunoglobulins

what plasma protein is particularly important for clot formation

fibrinogen

What happens to fibrinogen during clot formation

fibrinogen → fibrin monomers → cross-linked clot

What other substances can be sound dissolved in plasma

• nutrients

• inorganic salts

• hormones

• dissolved blood gases

What is by far the most abundant formed element on a normal smear

erythrocytes RBCs

What is the major function of erythrocytes

gas exchange/transport (especially transport involving O2 and CO2)

Do mature erythrocytes have a nucleus

NO → anucleate

Does a mature erythrocyte contain typical cellular organelles

NO → mature RBCs lack organelles

What is the characteristic shape of an erythrocyte

biconcave disc

Why does an RBC appear more translucent/pale in its center on a blood smear

because its biconcave shape makes the center thinner, allowing more light to pass through it

What protein is present in extremely high amounts inside RBCs

hemoglobin

what is another name for a platelet

thrombocyte

what is the major function of platelets

control bleeding/ hemostasis

are platelets technically complete cells

NO, they are cytoplasmic fragments derived from megakaryocytes

Do platelets contain any organelles

yes

although they are cytoplasmic fragments rather than complete cells, they contain come organelles and granules

What is the major function of leukocytes

immune defense

What are the 2 broad morphological categories of leukocytes

1. granules

2. agranulocytes

Which cells are granules

neutrophiles

eosinophils

basophils

Which cells are agranulocytes

• lymphocytes

  • B cells

  • T cells

  • NK cells

• Monocytes

Which general nuclear feature can help identify granulocytes

their nuclei are often lobed/segmented

Which characteristic helps identify a lymphocyte histologically

a large nucleus relative to the overall cell size, leaving relatively little visible cytoplasm

What is the key difference between plasma and serum

plasma contains fibrinogen

serum lacks fibrinogen

emphasized concept

How is plasma obtained

blood is collected in the presence of an anticoagulant and then centrifuged

Give 2 examples of anticoagulants

Heparin

sodium citrate

Why does plasma still contain fibrinogen

because anticoagulant prevents normal clotting, so fibrinogen has NOT BEEN CONSUMED in clot formation

How is serum obtained

blood is collected WITHOUT AN ANTICOAGULANT and allowed to clot

Why does serum lack fibrinogen

because fibrinogen has been utilized during the clotting process

After anticoagulated blood is centrifuged, what are the major layers

From bottom to top

• RBCs

• Buffy coat

• Plasma

What is found in the buffy coat

white blood cells + platelets

What is hematopoiesis

the production, differentiation, and maturation of blood cells

From what precursor are RBCs, WBCs, and platelets ultimately derived

hematopoietic stem cells (HSCs)

What three specific maturation processes are discussed within hematopoiesis

• erythropoiesis → RBC development

• leukopoiesis → WBC development

• thrombopoiesis → platelet development

What is erythropoiesis

production and maturation of erythrocytes

What is leukopoiesis

production and maturation and leukocytes

What is thrombopoiesis

production of platelets/ thrombocytes

Where does hematopoiesis

red bone marrow

Where does hematopoiesis initially occur during embryonic fetal development

yolk sac

Which organ becomes the major hematopoietic site after the yolk sac

liver

During which broad fetal period is the liver particularly important for hematopoiesis

second trimester

emphasized in the lecture

What becomes the major hematopoietic site later in fetal development after birth

bone marrow

Give the broad developmental sequence of hematopoietic site later in fetal development and after birth

bone marrow

Give the broad developmental sequence of hematopoietic site

yolk sac → liver → bone marrow

What two major progenitor lineages can arise from hematopoietic stem cells

1. common lymphoid progenitor

2. common myeloid progenitor

What important property do hematopoietic stem cells possess

self-renewal

the can generate differentiated descendants while maintaining the stem-cell population

What mature cells arise from the common lymphoid progenitor

• B lymphocytes

• T lymphocytes

• Natural Killer NK cells

Does an erythrocyte come from the lymphoid lineage

No → myeloid lineage

Does a platelet come from the lymphoid lineage

no → myeloid lineage

What major cell types arise from the common myeloid progenitor

• erythrocytes

• platelets

• granulocytes

• monocytes

• dendritic cells

Which lineage produces erythrocytes

myeloid

which lineage produces megakaryocytes and therefore platelets

myeloid

which lineage produces neutrophils, eosinophils, and basophils

myeloid

Which lineage produces monocytes

myeloid

myeloid vs lymphoid

Lymphoid

• B cells + T cells + NK cells

Myeloid

• RBCs + platelets + granulocytes + monocytes + dendritic cells

Why is the biconcave shape of the RBC advantageous

it facilitates efficient gas exchange and contributes to the cells ability to deform

why must erythrocytes be highly deformable

they need to pass through very small capillaries

What structure helps maintain RBC shape

plasma membrane + cytoskeletal elements

Where does postnatal erythropoiesis occur

bone marrow

What major hormone drives erythrocyte formation

erythropoietin (EPO)

What other growth factor is associated with early erythroid development

Interleukin - 3 (IL-3)

What lineage does an HSC enter to ultimately become an erythrocyte

common myeloid progenitor

What biopotential progenitor can give rise to either erythrocytes or megakaryocytes

megakaryocyte-erythroid progenitor (MEP)

Why is the megakaryocyte-erythroid progenitor considered bipotential

it can develop toward either

• erythroid cells

• megakaryocytes/platelets

In the presence of erythropoietin, the megakaryocyte-erythroid [progenitor moves toward what lineage

erythroid lineage

What committed erythroid precursor follows this pathway

erythroid colony forming unit

What major changes occur as erythroid

• cell size DECREASES

• nucleus becomes increasingly more CONDENSED

• hemoglobin INCREASES

• cytoplasm becomes increasingly EOSINOPHILIC

• nucleus is ultimately LOST

Why does erythroid cytoplasm become progressively more eosinophilic/pink during maturation

increasing accumulation of hemoglobin

What happens to the nucleus during erythrocyte maturation

it becomes increasingly condensed and eventually extruded/lost

What is the first immature erythroid cell that normally leaves the bone marrow

Reticulocyte

Does a reticulocyte have a nucleus

NO → the nucleus has already been lost

What distinguishes a reticulocyte from a fully mature erythrocyte

a reticulocyte still contains some residual intracellular material, particularly ribosomal RNA, whereas the mature RBC has lost essentially all organelles

What happens to the reticulocyte after it enters circulation

it completes maturation into an erythrocyte

Why is the reticulocyte count clinically useful

it gives information about how actively the bone marrow is producing RBCs

What does an increased reticulocyte count generally suggest

increased bone marrow erythropoietic activity

A patient is anemic but has an appropriately HIGH reticulocyte count. What does this suggest about the bone marrow

the marrow is responding by increasing RBC production

A patient is anemic with an inappropriately LOW reticulocyte response. What general problem should you consider

insufficient RBC production/ bone marrow response

What does erythropoietin stimulate

erythrocyte formation and release

Which cells have many erythripooietin receptors

erythroid progenitor cells

What important survival effect does EPO have on early erythroid progenitors

anti-apoptotic effect

it promotes survival rather than allowing these precursor cells to undergo apoptosis

conceptually, what happens when the body needs more RBCs

increased EPO signaling → increased survival/ proliferation of erythroid precursors → increased RBC production

What determines ABO blood type?

The surface antigens present on RBCs.

What RBC surface antigen does type A blood have?

A antigen

What antibody is present in the plasma of a person with type A blood?

Anti-B antibody

What surface antigen does type B blood have?

B antigen

What antibody does type B blood have in plasma?

Anti-A antibody

What RBC antigens are present in type AB blood?

A + B antigens

What anti-A or anti-B antibodies are normally present in type AB plasma?

neither

What A/B surface antigens are present on type O RBCs?

Neither A nor B

What ABO antibodies are present in type O plasma?

Anti-A + Anti-B

Why is ABO incompatibility dangerous?

Recipient antibodies can recognize donor RBC surface antigens and:

Attack/agglutinate the transfused RBCs.

For packed RBC transfusion, why can type O RBCs be broadly compatible from an ABO perspective

type O RBCs lack A and B surface antigens

so recipient anti-A or anti-B antibodies do not have those antigens to attack.

Why is type AB often considered broadly compatible as an RBC recipient from an ABO standpoint?

AB plasma contains neither anti-A nor anti-B antibodies.