Blood Physiology PDF

# BLOOD PHYSIOLOGY (Lecture 1) By Dr. Eman Elbassuoni Professor of Physiology Faculty of Medicine ## Blood - Blood is the vital fluid tissue that circulates inside blood vessels - Represents 8% of body weight, or 5.6 L ### Functions of blood: - **Transport function:** O2, CO2, nutrients, was...

# BLOOD PHYSIOLOGY (Lecture 1) By Dr. Eman Elbassuoni Professor of Physiology Faculty of Medicine ## Blood - Blood is the vital fluid tissue that circulates inside blood vessels - Represents 8% of body weight, or 5.6 L ### Functions of blood: - **Transport function:** O2, CO2, nutrients, waste products, hormones - **Defensive function:** White blood cells and antibodies - **Hemostasis:** Stoppage of bleeding. - **Homeostasis:** Keeping the internal environment (extracellular fluid) of the body constant for optimum function of the cell (PH, osmotic pressure, volume, gases, minerals, temperature, nutrients). ## Composition of Blood | Component | Percentage by Volume | Percentage by Weight | |--------------------------|-----------------------|----------------------| | Whole Blood | 100% | 100% | | Plasma | 55% | 55% | | Forme Elements | 45% | 45% | ### Plasma (55% by weight) - Contains: - **Water:** 91% - **Proteins:** 7% - Albumins (57%) - Globulins (38%) - Fibrinogen (4%) - Prothrombin (1%) - **Other Solutes:** 2% - Ions - Nutrients - Waste products - Gases - Regulatory substances ### Formed Elements (45% by volume) - Contains: - **Leukocytes:** <1% (percentage by number of cells) - Neutrophils (60%-70%) - Lymphocytes (20%-25%) - Monocytes (3%-8%) - Eosinophils (2%-4%) - Basophils (0.5%-1%) - **Platelets:** <1% - **Erythrocytes:** >99% ## Types of Blood Cells: - **Red Blood Cells (Erythrocytes)** - Helps in O2 and CO2 exchange - **White Blood Cells (Leukocytes)** - Fights against infections - Includes: neutrophils, eosinophils, basophils, lymphocytes, and monocytes. - **Platelets (Thrombocytes)** - Helps in blood clotting ## Blood Plasma (55% of the blood) - Yellow clear fluid consisting of: - **Water:** 91% - **Proteins:** 7% - Albumin - Globulin - Fibrinogen - Prothrombin - **Other Substances: ** 2% - Ions (Na+, Ca++, Cl-, and others) - Nutrients - Waste Products - Gases - Regulatory substances (hormones and vitamins) ## Plasma Proteins | Type | Concentration | Function | Site of Formation | |-----------|---------------------------------|---------------------------------------------------------------------------------------------------|--------------------| | Albumin | 4 gm/100 ml plasma (Highest) | - Colloidal osmotic pressure due to its highest concentration. - Transport of some substances. | Liver | | Globulins | 2.5 gm/100 ml plasma | - Defensive function (α, β, γ globulins). - Transport of some substances. | Liver | | Fibrinogen | 0.4 gm/100 ml plasma (Highest) | - Blood clotting. - Plasma viscosity due to its highest MW. | Liver | | Prothrombin | 10 mg/100 ml plasma | - Blood clotting. | Liver | - ** Albumin/Globulin (A/G) Ratio** - This is the ratio between albumin and globulin concentration in blood = 1.2 - 1.7 (Albumin = 1.2-1.7/ Globulin) - **Decreases in:** - Liver disease due to decreased formation of albumin (↓ Albumin / ↓ Globulin) - Kidney disease due to loss of albumin in urine (↓ Albumin / ↓ Globulin) - Infection due to increase globulin concentration (↑ Albumin / ↑↑ Globulin) ## Red Blood Corpuscles (Erythrocytes) - Non-nucleated circular biconcave discs containing the red respiratory pigment (hemoglobin) - Average lifespan of 120 days. - Concentration of hemoglobin in Red Blood Cells is 34%. - Chief ion inside Red Blood Cells is Potassium (K+). - Also contains: - Carbonic anhydrase enzyme - Glucose-6-phosphate dehydrogenase (G-6-PD). ### Red Blood Cells Count: - **In adult males:** 5-6 million per cubic mm ( due to androgen hormone that stimulate its formation & increase male musculature which need more oxygen) - **In adult females:** 4-5 million per cubic mm (due to menstruation) - **In newly born:** 7 million per cubic mm (due to intrauterine oxygen lack & to increase the iron coming from damaged RBCs that can be used for recycling and reformation of new RBCs due to poor iron in the milk.) ### Functions of Red Blood Cells: 1. Hemoglobin carry O₂ to and take CO₂ from tissues. 2. Hemoglobin has buffering action (85% of blood buffering action). 3. Red Blood Cells contain carbonic anhydrase enzyme which is important for CO₂ carriage. 4. The biconcave shape of Red Blood Cells increases the surface area and helps the exchange of gases between Red Blood Cells and tissues. ## Gas Exchange in Humans - Diagram showing a cycle of red blood cells moving through the body to the lungs and back, carrying oxygen and carbon dioxide. ## Erythrocyte Membrane: - Keeps hemoglobin inside, preventing: - Increase in the load on the heart (heart failure). - Hemoglobin increases blood viscosity - Increase in blood volume due to increased plasma colloidal osmotic pressure. - Obstruction of renal tubules (renal failure) - **Contains the specific agglutinogens that determine blood group.** - **Plastic nature** allows Red Blood Cells to compress passing in the narrow capillaries and resume their normal shape on leaving these capillaries without rupture. ## Formation of Red Blood Cells (Erythropoiesis) ### Sites of Red Blood Cell formation: - **In the fetus,** they are formed in the liver and spleen. - **In the last three months of fetal life and after birth,** they are formed in the bone marrow of all bone until adolescent. - **By the age of 20,** they are formed by the bone marrow of the upper parts of the humerus and femur and of membranous bones. - **After the age of 20 years,** they are formed in the bone marrow of membranous bone (skull, vertebra, sternum, and ribs). - Rate of erythropoiesis must be equal to the rate of Red Blood Cell destruction to maintain normal Red Blood Cell count. - After 120 days (average lifespan), Red Blood Cells are engulfed and hemolysed by reticulo-endothelial cells, mainly the spleen. ## Factors affecting erythropoiesis: 1. **Oxygen supply to tissues:** - Hypoxia occurs in: - Hemorrhage (due to Red Blood Cell loss) - High altitude (due to decrease O2 tension around) - Heart failure (blood don't reach tissue properly) - Oxygen lack (hypoxia) releases erythropoietin hormone from (mainly) the kidney, stimulating bone marrow to increase production of Red Blood Cells (↑erythropoiesis rate.) 2. **Diet:** - **Protein:** High biological value containing essential amino acids, essential for formation of globin of hemoglobin. - **Iron:** - Average daily intake of iron is 20 mg. - Most of the diet iron is in the ferric state, poorly absorbed. Ferrous iron is better absorbed. - Ferric iron is reduced to ferrous in the stomach by HCI and Vitamin C (Fe 3+ → Fe 2+) - Intestinal epithelial cells contain Apoferritin protein that combines with the ferrous iron to form ferritin. Iron that is absorbed enters the small intestine (duodenum) in this form (Fe2+ + Apoferritin → Ferritin). - The blood containing transferrin protein carries iron to the bone marrow to form part of Red Blood Cells hemoglobin or to the liver to be stored. - Excessive oxalates, phytic acids, and phosphates in the diet precipitate iron and will decrease its absorption. - **Vitamins:** - **Vitamin B12:** - Extrinsic factor. Important for Red Blood Cell nuclear maturation and cell division. - Responsible for myelination of the nerves and integrity of the digestive system mucosa. - Units with intrinsic factor, secreted by the mucous membrane of the stomach, to form intrinsic factor-Vit B12 complex (Intrinsic factor-Vit B12 → intrinsic factor-Vit B12 complex). - The intrinsic factor protects vitamin B12 from digestion by gastric enzymes and facilitates its absorption in the lower part of the ileum. - Stored in the liver and released slowly as needed by the bone marrow, for new red cell formation. - **Folic Acid:** - Same importance as Vitamin B12. - Important for Red Blood Cell nuclear maturation and cell division. - **Vitamin C:** - Stimulates tissue growth and metabolism in general, including the bone marrow. - **Trace Elements:** - Copper and cobalt act as cofactors for hemoglobin formation. - **Hormones:** - Specific: Erythropoietin hormone - Non-specific: thyroid hormones (↑ metabolism in general) - Male sex hormones (Androgen) increase erythropoietin hormone and hence stimulate erythropoiesis. 3. **Healthy Organs:** - **Bone marrow:** - A healthy bone marrow is essential for normal erythropoiesis (site for formation). - **Liver:** - Important for erythropoiesis as: - Formation of globin of hemoglobin. - Secretes 15% of erythropoietin hormone. - Site of storage of Iron & Vit B12. - **Kidney:** - Secretes 85% of erythropoietin hormone in response to hypoxia, anemia, and androgen hormone. - Patients with renal diseases or failure develop severe anemia because erythropoietin production by the liver cannot compensate for the inability of the kidney to produce the hormone. - **Stomach:** - Gastric HCl is needed to convert ferric iron to ferrous. - Intrinsic factor secreted by gastric mucosa is essential for vitamin B12 absorption. - **Small intestine:** - The site of iron and vitamin B12 absorption. ## Anaemia - Means decreased Red Blood Cell number or their hemoglobin content or both. ## Types and causes of Anemia: ### I. Normochromic Normocytic Anemia: - **Haemolytic anemia** - Occurs due to excessive haemolysis of Red Blood Cells. - Examples: - Incompatible blood transfusion. - Snake venoms. - Sensitivity to drugs. - Infections (types of malaria) - Antibodies against red blood cells. - Increased fragility of Red Blood Cells (spherocytosis, sickle cell anemia and thalassemia.) - **Aplastic anemia** - Due to bone marrow depression. - Examples: - Exposure to radiation (X-rays) - Chemotherapy - Drugs (antibiotics with chloramphenicol) - Destruction of bone marrow (malignant tumors) - **Haemorrhagic anemia** - Due to acute blood loss (haemorrhage) ### II. Microcytic Hypochromic Anemia: - Iron deficiency anemia, either due to: - Deficiency in the diet (commonest cause) - Failure of iron absorption - Absence or removal of acid-producing part of the stomach (congenital achlorohydra, partial gastrectomy) - Excess oxalates, phytic acids, and phosphates in the diet. - Small intestine diseases (upper part) (duodenal ulcers) - Liver disease (site of storage of iron) - Chronic blood loss (bleeding piles and menstruation in females) - **Treatment:** Oral iron or injection (in case of gastric or small intestinal causes) ### III. Macrocytic (Megaloblastic) Anemia: - Occurs due to deficiency of vitamin B12 or folic acid. - **Vitamin B12 Deficiency (Pernicious Anemia)** due to: - Absence of intrinsic factor (from the stomach) - Malabsorption (due to small intestine diseases (lower part)) - Liver disease (site of storage) - Rarely due to lack of vitamin in the diet. - **Treatment:** Vitamin B12 injection for life. - **Folic Acid Deficiency** due to: - Deficiency of folic acid in the diet (especially during pregnancy) - Failure of absorption (due to small intestine diseases) ## Polycythaemia - Means increased number of Red Blood Cells. - It may reach up to 6-8 million/mm3. ## Thank You - A diagram of Red Blood Cells and other blood cells flowing through a blood vessel.