29 topics with concise summaries: definitions, key facts, and classroom questions.
This section is dedicated to blood as the body's vital integrating system. Here we cover the basic constants: from circulating blood volume (CBV), hematocrit, and viscosity to the complex cascade of hematopoiesis. You will study plasma composition, the life cycle and functions of erythrocytes, all types of leukocytes and platelets, as well as gas transport mechanisms involving hemoglobin.
Special attention is paid to homeostasis maintenance. The section details vascular-platelet and coagulation hemostasis, clotting factors, the function of anticoagulants, clot retraction, and fibrinolysis. A separate block covers the operation of buffer systems and the physiological regulation of acid-base balance (ABB).
What is most frequently asked in class? Traditionally, stumbling blocks on exams include the cascades of coagulation hemostasis, compensatory mechanisms in hypovolemia, and pH regulation. Instructors will also demand a flawless understanding of the ABO and Rh blood group systems—without this knowledge, blood transfusion is impossible in real clinical practice.
The system includes three parts: blood proper (circulating and pooled fractions), hematopoietic and hemoclasic organs, and the neurohumoral regulatory apparatus.
Is adipose tissue included in the blood volume calculation?
No, adipose tissue mass is not taken into account when calculating the proper blood volume. The 6–8% calculation is based only on active or "lean" body mass.
How does plasma differ from intercellular (interstitial) fluid?
In terms of electrolyte chemical composition, they are very similar (sodium, chlorides, and bicarbonates predominate in both media). The main difference is that there is significantly more protein in the vascular bed (about 70 g/L).
What is the difference between osmolarity and osmolality?
Osmolarity is calculated per unit volume of solution (liter), while osmolality is calculated per mass of solvent (kilogram of water).
Which blood elements make the main contribution to the hematocrit value?
Hematocrit is 99% determined by erythrocytes, as they constitute the absolute majority among all formed elements.
Why might you experience mild dizziness when standing up abruptly?
This is the effect of orthostasis. Upon transitioning to a vertical position, part of the blood is briefly pooled in the veins of the lower extremities and abdominal cavity due to gravity. CBV temporarily drops, reducing blood flow to the brain until baroreceptors are activated.
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