• Chronology of Erythropoiesis:
• In vertebrate ontogeny and adult homeostasis, erythropoiesis occurs across multiple anatomical sites:

• Embryonic / Fetal Phase:
  • Mesoblastic phase: Yolk sac blood islands.

• Hepatic phase: (A) Liver serves as the major erythropoietic organ during the second trimester.
• Myeloid / Splenic phase: (B) Spleen actively generates erythrocytes during mid-gestation (and retains extramedullary erythropoietic capacity during severe adult anemia).

• Adult Phase:
  • Bone Marrow (red marrow) is the primary lifelong site of adult erythropoiesis.

• nalysis:
• All three organs (A, B, and C) participate in erythropoiesis across developmental and compensatory stages. Hence, Option 1 is correct.

• Starling's Equation of Microvascular Fluid Movement:

• Factors Promoting Edema:

• Increased capillary hydrostatic pressure ($P_c$) (congestive heart failure, venous obstruction).
• Increased capillary permeability ($K_f$) (inflammation, toxins).
• Obstruction of lymphatic drainage (lymphedema).
• Decreased plasma oncotic pressure ($\pi_c$) (hypoalbuminemia).
  • Effect of Increased Plasma Proteins:

• An increased concentration of plasma proteins elevates intravascular oncotic pressure ($\pi_c$), which reabsorbs fluid from the interstitial space into the vascular bed, thereby preventing edema.
• nalysis:
• (Increased concentration of plasma proteins): Correct (does not cause edema).

• Respiratory Blood Gas Values:
• Systemic Arterial Blood:
• Partial pressure of oxygen ($pO_2$): $\approx 95 - 100\text{ mmHg}$ (oxygen saturation $\approx 98\%$).
• Partial pressure of carbon dioxide ($pCO_2$): $\approx 40\text{ mmHg}$.
• Mixed Venous Blood (Pulmonary Artery / Right Ventricle):
• After delivering oxygen to metabolizing peripheral tissues:
• $pO_2 \approx 40\text{ mmHg}$ (oxygen saturation $\approx 75\%$).
• $pCO_2 \approx 45 - 46\text{ mmHg}$.
• nalysis:
• (40 mmHg): Correct physiological value for venous blood.

Correct option: (1) 40 mmHg