Human Physiology Blood Quiz

Blood Composition and Volume

• Blood is a fluid connective tissue, thick and homogeneous
• It comprises 55% plasma and 45% formed elements
• Plasma, the liquid portion, is about 90% water
• Plasma proteins, including albumin, fibrinogen, and globulins, contribute to osmotic balance, blood clotting, and defense
• Dissolved substances transported by blood include nutrients, waste products, respiratory gases, hormones, electrolytes, and salts

Formed Elements

• Formed elements (45%) are cells and cell fragments
• Erythrocytes (red blood cells): 4-6 million per mm³; transport oxygen and carbon dioxide
• Leukocytes (white blood cells): 4,800-10,800 per mm³; essential for defense and immunity
• Platelets (thrombocytes): 250,000-400,000 per mm³; crucial for blood clotting

Physical Characteristics of Blood

• Sticky and opaque (not clear) with a metallic taste
• Color: scarlet (oxygen-rich) to dull red (carbon dioxide-rich)
• Heavier than water, about five times thicker
• Slightly alkaline; pH (7.35–7.45)
• Temperature: slightly higher than body temperature (38°C)
• Approximately 8% of body weight
• Volume: 5–6 liters in healthy adults

Hematopoiesis

• Hematopoiesis: the process of blood cell formation
• Occurs in red bone marrow or myeloid tissue
• In adults, found in axial skeleton, pectoral and pelvic girdles, and proximal epiphyses of the humerus and femur
• Stimulated by hormones (colony-stimulating factors and interleukins)
• All formed elements originate from a stem cell, the hemocytoblast, in bone marrow

Erythrocytes (RBCs)

• Anucleate; unable to synthesize proteins, grow, or divide
• Mature RBCs are sacs of hemoglobin molecules
• As they age they become rigid and fragment in 100-120 days
• Eliminated by phagocytes in spleen, liver, and other tissues
• Reticulocytes are immature RBCs with some ER
• Production regulated by erythropoietin, a hormone primarily produced by the kidneys
• Normal values: 12-18 g/100ml of blood in males and 12-16 g/100ml of blood in women

Hemoglobin

• Hemoglobin is a protein in red blood cells that carries oxygen
• It contains iron, and its major function is transporting oxygen and a small amount of carbon dioxide
• Each RBC contains millions of hemoglobin molecules

Sickle Cell Anemia (SCA)

• Genetic disorder
• Caused by a change in a single amino acid within hemoglobin
• Resulting in abnormal hemoglobin
• Abnormal hemoglobin in RBCs causes them to become spiky and sharp

Polycythemia

• Excessive increase in the number of erythrocytes
• Can result from bone marrow cancer or a physiological response to high altitude

Leukocytes (WBCs)

• Contain a nucleus and usual organelles
• Function in defending the body against bacteria, viruses, parasites, and tumor cells
• Divided into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes)

Platelets

• Fragments of megakaryocytes
• Crucial for the clotting process
• Normal count is approximately 150,000–400,000 per mm³

Hemostasis

• Process of stopping bleeding
• Involves three main mechanisms: vascular spasm, platelet plug formation, and coagulation (blood clotting)

Blood Typing & Transfusion

• ABO blood groups (A, B, AB, O) and Rh factor (positive or negative) are crucial for compatibility in transfusions
• Blood typing, using antibodies, identifies blood antigens
• Cross-matching tests compatibility between donor and recipient blood for safe transfusions
• Rh incompatibility can cause hemolytic disease of the newborn. -RhoGAM is an immune serum to prevent sensitization in Rh− mothers carrying Rh+ babies