HEME EXAM

What is hematopoiesis?

formation of blood cellular components

What does plasma consist of?

(1) Water [majority]

(2) Proteins

(3) Salts, organic molecules, gases

What are the main cellular components of blood?

(1) Erythrocytes (red blood cells)

(2) Leukocytes (white blood cells)

(3) Platelets

What cells do platelet cells split off from?

Megakaryocytes

What is a hematocrit?

The percentage of total blood volume that is occupied by packed (centrifuged) red blood cells, aka ratio of red blood cells to plasma

What can hemoglobin be used to measure?

The oxygen carrying capacity of red blood cells

What type of cell makes up the majority of leukocytes?

Neutrophils

What can platelet count measure?

The blood’s ability to clot

What does the buffy coat consist of?

Thin layer of white blood cells and platelets

Describe what a hematocrit looks like.

Top layer: Plasma, makes up majority of blood volume

Middle layer: Buffy coat, thinnest layer consisting of white blood cells and platelets.

Bottom layer: Red blood cells, which are denser and settle at the bottom.

What part of the body are red blood cells produced in?

Bone marrow

What is erythropoiesis?

RBC production

What is leukopoiesis?

WBC production

Where are all cellular blood components derived from?

Hematopoietic stem cells

Where are erythrocytes derived from?

erythroblasts

Where are RBCs formed in adults?

Formed in the marrow of:

(1) vertebrae

(2) ribs

(3) sternum

(4) clavicle

(5) pelvic (iliac) crest

(6) proximal epiphyses of long bones

***only looking to maintain population

Where are RBCs formed in children and why?

Mostly the entire body; most bone marrow space is hematopoietically active.

Since children have increased growth requirements, they need an increased amount of oxygen to meet these demands

Sequence the development of red blood cells

(1) Pluripotent stem cell yields an erythroid burst-forming unit

(2) Signaling factors [EPO, IL-3, GM-CSF] stimulate stem cell to form an erythroid colony-forming unit in the marrow

(3) With every division, RBC is slowly maturing overall and nucleus shrinks, eventually disappearing from normal erythrocyte

(4) Hemoglobin and iron are incorporated into slowly maturing RBC, eventually released from marrow through endothelium into circulating blood as a reticulocyte

How long does the maturation process take for RBCs?

1 week

How long does it take for a reticulocyte to lose its nucleus and become an erythrocyte?

Several days

What makes up 90% of the protein content of the erythrocyte?

Hemoglobin (***recall:oxygen carrying molecule)

What is the normal survival time of an erythrocyte?

120 days

What are two things a circulating erythrocyte lacks?

(1) nucleus

(2) ability to divide

What would cellular hypoxia signal in the erythropoietin feedback loop?

negative feedback

decreased O2 = increased EPO = increased RBC production and maturation

***EPO produced by kidney, released in plasma

How is RBC mass kept constant under normal conditions?

EPO makes RBC production = natural RBC loss

What hormone initiates and stimulates the production of RBCs?

Erythropoietin (EPO)

Where is erythropoietin produced and what is the percentage of this production?

kidneys; 90%

What is the mechanism of action of erythropoietin?

prevent apoptosis of erythroid precursor cells and allow their proliferation and subsequent maturation

What is responsible for the oxygen carrying capacity of RBCs?

Hemoglobin

Each iron atom within Hb bind to ___ oxygen molecule. (insert number)

one

What are the components of a hemoglobin molecule?

(1) 4 hemoglobin chains (2 alpha, 2 beta), each centered around…

(2) 1 heme group [4 chains = 4 heme groups total]

What does each heme group within a hemoglobin consist of?

porphyrin ring with an iron atom at the center

Why is iron regulation important for hemoglobin production, RBC production, and oxygen transport?

Iron bonding to oxygen is critical to all three processes

How many iron atoms per hemoglobin?

4

How many oxygen molecules per hemoglobin?

4

What is transferrin?

specific plasma transport protein that

(1) delivers iron to the bone marrow for incorporation into Hb molecule by binding to transferrin receptors on the cell surface

(2) delivers extra iron to body storage sites (ex. liver, marrow, spleen) where it is stored as ferritin

What is the benefit of having fewer transferrin receptors on the surface of cells that do not need iron?

Prevents iron-replete cells from receiving excess iron

All blood cells are formed where?

Bone marrow

What would happen to RBC maturation if EPO decrease?

RBC maturation would also decrease

What percentage of circulating transferrin is saturated with iron?

30%

What would low serum levels of ferritin be indicative of?

Iron deficiency anemia

Sequence the hemoglobin life cycle.

(1) Fe ingested from diet (body cannot make iron on its own)

(2) Fe absorbed by active transport

(3) Transferrin transports Fe into plasma

(4) Fe used to make Hb as a part of RBC synthesis (Fe → Heme → Hb → RBC synthesis)

(5) RBC lives ~120 days

(6) Spleen destroys old RBCs via phagocytic breakdown

• amino acids from globin chains → amino acid pool

• heme oxygenase → porphyrin heme structure → (a) release Fe (b) form biliverdin

  • (a) iron → iron pool (stored as ferritin)

  • (b) biliverdin → bilirubin → binds to albumin in plasma

(7) Bilirubin and metabolites are excreted in urine (kidneys) and feces

• Liver metabolizes bilirubin and excretes it in bile

What is anemia?

group of diseases characterized by decrease in Hb or RBCs, leading to decreased O2 carrying capacity of blood

What can anemia result from?

• inadequate RBC production

• increased RBC destruction

• blood loss

Iron deficiency limits what kind of production?

hemoglobin

Folate/Vitamin B12 limits what kind of production?

RBC production

What would cause hypoproliferative anemia?

An overall decrease in RBC production

• marrow damage (RBCs are not produced normally)

• iron deficiency (not enough iron to make RBCs)

• decrease stimulation (not enough signaling)

  • renal disease (decreased EPO)

  • inflammation

  • metabolic disease

How can maturation disorders lead to anemia?

Although production normal, RBCs cannot mature

• cytoplasmic defects (interferes with Hb synthesis)

  • Thalassemia (decreased Hb)

  • Iron deficiency

  • Sideroblastic

• Nuclear maturation defect (interferes with DNA synthesis → RBC precursors become large and immature)

  • Folate deficiency

  • Vitamin B12 deficiency

  • Refractory anemia

How can hemorrhage/hemolysis lead to anemia?

Overall, RBCs are lost or destroyed

• blood loss

• intravascular hemolysis (RBCs rupture inside blood units)

• autoimmune disease

• hemoglobinopathy

• metabolic/membrane defect

What is the epidemiology of iron deficiency anemia?

• iron deficiency is the most common nutritional deficiency

• prevalence in young children and women

• due to large normal ranges, iron deficiency may precede the appearance of anemia

What causes iron deficiency anemia?

• reduced iron availability

• increased requirements

  • infants

  • pregnancy

• Blood loss

  • trauma

  • menses (menstruation)

• disruption of iron cycling

  • increased transferrin

  • decreased ferritin

What is absorption’s role in iron deficiency anemia physiology?

• Iron is absorbed in the duodenum and proximal jejunum

• Two sources of iron

  • Heme-Fe (meat/fish): absorbed as ferric (hemin)

  • Non-heme (vegetables): reduced to ferrous Fe by stomach acid → absorbed in duodenum

• Iron deficiency increases absorption 20-30%

What is ferritin’s role in iron deficiency physiology?

• protein that store iron

• plasma concentrations correlate with iron stores in the BM except in renal or liver disease, malignancy, infection or inflammation

• No iron storage

What is the cause of anemia of inflammation

• associated with inflammatory disorders, tissue injury and conditions assoiciated with proinflammatory cytokines

  • developed over days = acute, developed over months/years = chronic

How does the body function with anemia of inflammation?

Multifactoral pathogenesis:

(1) Shortened erythrocyte life span

(2) Inflammatory cytokines release during illness (ex. TNF, IL-1, IL-6, interferon) cause:

• inhibit production or action of EPO → relative resistance to EPO in response to anemia

• Impaired proliferation of erythroid progenitor cells

• Upregulate hepcidin which blocks the release of iron from storage cells resulting in an inadequate delivery of iron to bone marrow (prevents Fe recycling)

What is folic acid deficiency anemia?

• one of the most common vitamin deficiencies in US

• human can’t synthesize enough to meet total daily requirements

Where is folic acid absorbed?

Intestine (duodenum/jejunum)

What foods are rich in folic acid?

• leafy vegetables

• citrus fruits

• fortified grains

General facts about Vitamin B12 deficiency anemia

• risk increases with age

• prevalence unknown

What is Vitamin B12 and its role in the body?

• also known as cobalamin

• essential vitamin

• required to maintain integrity of neurons

What process is folic acid important for?

DNA/RNA synthesis

What foods are poor or rich in Vitamin B12?

Poor - vegetables

Rich - Meat

What are the three histopathological classifications of anemia?

• macrocytic (RBCs are larger in size)

• normocytic (RBCs are normal in size, but lack in numbers)

• microcytic (RBCs are smaller in size)

What conditions would fall under macrocytic anemia?

• vitamin B12 deficiency

• folic acid deficiency

What conditions would fall under normocytic anemia?

• recent blood loss

• chronic disease (hemolysis → RBC die before 120 days)

• increase blood volume (plasma dilutes RBCs)

• Anemia of renal failure

  • Kidney failure → decrease EPO → decrease stimulation of bone marrow → decrease RBC production → anemia

• Mixed anemia (Iron deficiency anemia + folic acid or Vitamin B12)

What conditions would fall under microcytic anemia?

• deficiency in Hb synthesis

• Iron deficiency

• Sickle cell

• Thalassemia (decrease Hb production)

What are hemolytic anemias?

• group of rare or drug-induced blood disorders

• they occur when the body destroys RBCs more rapidly than when it produced them

• Characterized by premature destruction of RBCs by autoantibody

• Diagnosed via Direct/Indirect Coombs Test

Explain a Direct Coombs Test

(1) Take blood from anemic patient

(2) Incubate RBCs with antihuman antibodies (Coombs reagent)

(3) RBC agglutinate → antihuman antibodies form links between RBCs by binding to the human antibodies on the RBCs (positive test result)

Explain an Indirect Coombs Test

(1) Take patients serum

(2) The patients blood sample is added into a tube with their serum

(3) The patient’s Ig’s that target the blood cells will form antigen antibody complexes

(4) Coombs reagent recognizes the human antibodies → connects antibodies sitting on different RBCs

How does WHO define anemia in men and women

Men: Hb<13 g/dL

Women: Hb<12 g/dL

What happens to MCV levels in macrocytic anemia?

MCV increases

What happens to MCV levels in microlytic anemia?

MCV decreases

What happens to MCV levels in normocytic anemia?

levels stay the same

What are the most common areas to address in anemia clinically?

• vitamin b12 deficiency

• folic acid deficiency

• iron deficiency

• anemia inflammation

Signs and symptoms of anemia are related to?

• Decreased Hb: classic signs and symptoms 

• Anemia itself: anemia-specific 

• Disorder causing the anemia

Hb level at which anemia signs and symptoms develop depends on?

• Onset: acute vs chronic onset 

• Age 

• Cardiovascular/pulmonary status

Classic signs and symptoms of anemia?

• Fatigue

• Dizziness 

• Weakness

• Decreased tolerance to exercise 

• Dyspnea 

• Headache 

• Chest pain

• Palpitations 

• Tachycardia

• Pallor/pale mucus membranes

• Ischemia

How is RBC measured in a complete blood count (CBC)

Actual count of RBC per unit of blood

Why is RBC count not used to determine anemia?

Indirectly estimate of the Hb content of the blood

Why is hemoglobin measured in a complete blood count? What may cause it to decrease?

provides an accurate estimate of the oxygen-carrying capacity of the RBC, can be used to determine anemia

can decrease because of (1) low number of RBC, (2) low amount of Hb per RBC

What range in men and women would indicate a low hematocrit?

Men: <41%

Women: <36%

Describe the hematocrit in a Complete Blood Count and what low levels may indicate.

• percentage of the RBCs to the total volume of blood

• Approximately 3x the Hb value

• Low Hct indicate: (1) Reduction in either number or size of RBC, (2) Increased plasma volume → pregnancy, kidney disease, heart failure

What does a Mean Cell Volume (MCV) count?

Average RBC size

What does a Mean Cell Hemoglobin (MCH) count?

Hb amount in an RBC

What would low MCH indicate?

(1) Microcytosis: small cell → low Hb

(2) Hypochromia: normocytic cell with low Hb

Describe MCHC. What does the Mean Cell Hemoglobin Concentration (MCHC) measure?

Concentration of Hb per volume of cells

MCHC = Hb/Hct x100

independent of RBC size

What does low MCHC indicate?

ALWAYS indicates Hypochromia → pale RBCs

What range indicates normal Hb count in men and women?

• Male: 13-17 g/dL

• Female: 12-15 g/dL

What is a normal range for MCV?

80-96 fL

What is a normal range for MCHC?

32-25%

What does Red blood cell distribution width (RDW) measure in a Complete Blood Count?

Measures anisocytosis: