Signal Transduction Pathways: Basic Hematology

Comprehensive practice questions covering blood composition, plasma proteins, cellular elements (RBCs, WBCs, Platelets), hematopoiesis regulators, ABO/Rh blood typing, and the stages of hemostasis.

What are the two primary components of blood and their approximate percentages of whole blood volume?

Blood consists of Plasma ($~55\%$) and Cellular Elements ($~45\%$).

In an average adult, what is the typical volume of blood moving within the circulatory system?

$5$ or $6\,L$

What is the weight-based composition of blood plasma?

$92\%$ water, $7\%$ proteins (Albumins, Globulins, Fibrinogen, and Regulatory proteins), and $1\%$ other solutes (electrolytes, nutrients, gases, and waste).

What are the normal reference ranges for Erythrocytes (RBCs), Leukocytes (WBCs), and Platelets per cubic mm?

Erythrocytes: $4.2-6.2 \text{ million}$; Leukocytes: $4.5-11 \text{ thousand}$; Platelets: $150-400 \text{ thousand}$.

Which plasma protein is primarily responsible for maintaining oncotic pressure and acting as a carrier protein?

Albumin

Describe the synthesis and function of the different types of Globulins.

$\alpha$ & $\beta$-globulins are synthesized in the liver and handle transport (e.g., transferrin); $\gamma$-globulins are produced by plasma cells and function as antibodies for immune defense.

What is the clinical consequence of low albumin levels in the plasma?

Edema, caused by the loss of oncotic pressure.

Define Hemoglobin and its primary function.

A tetrameric protein in RBCs composed of $4$ globin chains and $4$ heme groups; it transports $O_2$ (binding one molecule per heme) and $CO_2$.

What are the normal Hematocrit (Hct) values for males and females?

Males: $~40-50\%$; Females: $~35-45\%$.

According to the 'Rule of Three', how are RBC count, Hemoglobin, and Hematocrit related?

$\text{Hemoglobin} = \text{RBC} \times 3$ and $\text{Hematocrit} = \text{Hemoglobin} \times 3$.

What is the typical lifespan of an Erythrocyte and why is its shape significant?

The lifespan is $~120\,\text{days}$; its biconcave shape increases surface area for efficient gas exchange and allows flexibility through capillaries.

What is the function and clinical relevance of Neutrophils (PMNs)?

They are early responders that phagocytize bacteria; they represent $50-70\%$ of WBCs and increase in number during bacterial infections.

Which white blood cell types are expected to increase during viral infections?

Lymphocytes ($20-40\%$ of WBCs).

What clinical condition is associated with an increase in Eosinophils ($1-4\%$ of WBCs)?

Parasitic infections and allergies.

Which immature leukocyte is not normally seen in blood but is associated with acute myelogenous leukemia and Auer rods?

Myeloblasts

Where does hematopoiesis occur in adults?

In the red bone marrow, mostly located in the axial skeleton.

What hormone stimulates RBC production, where is it produced, and what triggers its release?

Erythropoietin (EPO); it is produced by the kidneys in response to tissue hypoxia.

Which growth factor promotes platelet formation and where is its source?

Thrombopoietin (TPO), produced by the liver and kidney.

Explain the inheritance and antibody presence in the ABO blood group system.

A and B alleles are codominant, while O is recessive. Individuals possess antibodies against the antigens they lack (e.g., Type O has anti-A and anti-B antibodies).

Under what specific conditions does Hemolytic Disease of the Fetus and Newborn (HDFN) occur?

When an $Rh^-$ mother is pregnant with an $Rh^+$ fetus, leading to the formation of maternal anti-D IgG that can cross the placenta in future $Rh^+$ pregnancies.

What are the four major steps of Hemostasis?

1. Vascular spasm, 2. Platelet plug formation (aggregation), 3. Coagulation (clotting cascade), 4. Fibrinolysis (breakdown of the clot).

During primary hemostasis, how do platelets adhere to exposed collagen?

Via von Willebrand factor and glycoprotein $Ib/IX/V$.

At which factor do the intrinsic and extrinsic coagulation pathways converge to begin the common pathway?

Factor $X$

Which clotting factors are Vitamin-K dependent?

Factors $II$, $VII$, $IX$, and $X$.

Describe the process of Fibrinolysis.

Plasminogen is converted to Plasmin via $tPA$; Plasmin then degrades the fibrin mesh to dissolve the clot.