Blood Physiology Overview

Blood Physiology

• Blood is 55% plasma and 45% blood cells
• Red blood cells (RBCs) are not true cells, lacking nuclei
• Structure of RBCs: Biconcave discs, circular, non-nucleated
• RBCs are responsible for oxygen (O2) transport
• RBCs assist in carbon dioxide (CO2) transport via carbonic anhydrase enzyme
• RBCs lack mitochondria, using anaerobic glycolysis for energy
• RBC lifespan around 120 days
• Erythrocyte count: Males: 5.0-5.5 million/mm³, Females: 4.5-5.0 million/mm³; Newborn: increased; Child and old age: decreased; Persons living at high altitude: increased
• Haemoglobin (Hb):iron-containing red pigment in RBCs
• Hb structure: heme and polypeptides
• Hb value: Adults males 14-18 g/dL, Adults females 12-16 g/dL; Newborn 18 g/dL; Children 12 g/dL
• Blood viscosity: RBCs contribute to blood viscosity maintaining arterial blood pressure.
• Functions of RBC membranes: large surface area for gas diffusion, flexible for capillaries, preventing Hb loss in urine.

Erythropoiesis

• The process of RBC production
• Sites: Red bone marrow (all bones), yolk sac (early embryonic life), liver and spleen (middle trimester)

Factors Affecting Erythropoiesis

• Diet: Proteins, vitamins, minerals are crucial for RBC production
• Tissue Oxygenation: Hypoxia (low oxygen) increases EPO secretion (90% from kidneys, 10% from liver) EPO transfers stem cells, accelerates development of mature RBCs
• Healthy Organs: Liver stores iron and vitamin B12, creates globin part of Hb and contributes 10% to EPO secretion, healthy bone marrow allows RBC formation, healthy tissues are conducive to RBC production.

Hormones

• Thyroid hormones, androgens, glucocorticoids influence erythropoiesis

Anemia:

• Reduced capacity of blood to carry oxygen due to Hb deficiency
• types of anemia: Blood loss anemia (acute and chronic), Aplastic anemia, Megaloblastic anemia, Hemolytic anemia

Blood Loss Anemia

• Acute: Caused by rapid blood loss, leading to normocytic normochromic anemia (normal shape, size, and hemoglobin content)
• Chronic: Results from slow, ongoing blood loss, often from ulcers or other sources resulting in microcytic hypochromic anemia (small size and low hemoglobin content)

Aplastic Anemia

• Bone marrow destruction by factors such as radiation, tumors, or anticancer drugs.

Megaloblastic Anemia

• Due to deficiency of vitamin B12, folic acid, or intrinsic factor from stomach mucosa

Hemolytic Anemia

• Excessive RBC destruction due to abnormalities, like sickle cell anemia or thalassemia, or incompatible blood transfusion.

Polycythemia

• Increased number of red blood cells, potentially reaching 6-8 million/mm³

Explore the essential functions and characteristics of blood, focusing on red blood cells and their role in oxygen and carbon dioxide transport. This quiz covers the structure, lifespan, and composition of erythrocytes, along with key physiological parameters like hemoglobin levels. Test your understanding of blood physiology and its significance in the human body.