Blood Physiology Lecture 3 2024 PDF

Sphinx University Blood Physiology Faculty of Physical Therapy Plasma, Red Blood cells First year Physical Therapy Dr./Rasha Mohammed Ali Lecturer of Medical Physiology, Faculty of Medicine, Assiut University O...

Sphinx University Blood Physiology Faculty of Physical Therapy Plasma, Red Blood cells First year Physical Therapy Dr./Rasha Mohammed Ali Lecturer of Medical Physiology, Faculty of Medicine, Assiut University Objectives To 1. Describe Cellular and non-cellular components of blood. 2. Recognize functions of blood. 3. Describe types of plasma proteins and their different functions. 4. Define Erythropoiesis and recognize sites of RBC formation at different developmental age. 5. Describe regulation of RBC production and erythropoietin hormone secretion in response to hypoxia. 6. Recognize clinical conditions associated with RCBs disorders. 2  Strictly speaking, blood is not a bodily fluid like tears, saliva, and urine. Instead, it is a living connective tissue composed by volume of approximately 45% cellular elements and 55% intercellular fluid.  Blood: is a connective tissue in fluid form. It is considered as the fluid of life because it carries oxygen from lungs to all parts of the body and carbon dioxide from all parts of the body to the lungs. PROPERTIES OF BLOOD 1. Color: Blood is red in color. Arterial blood is Scarlet red because of more O2 and venous blood is purple red because of more CO2. 2. Volume: The average volume of blood in a normal adult is 5 L. In newborn baby it is 450 ml. It increases during growth and reaches 5 L at the time of puberty. In females, it is slightly less and is about 4.5 L. It is about 8% of the body weight in a normal young healthy adult weighing about 70 kg. 3. Reaction and pH: Blood is slightly alkaline and its pH in normal conditions is 7.4. 4. Viscosity: Blood is five times more viscous than water. It is mainly due to red blood cells and plasma protein.  Blood Volume ✓ Average: 5 liter in adult: 45% is packed cells volume (PCV). 55% is plasma volume. Blood Composition 5  Functions of the blood include: 1. Nutrient Function Nutritive substances like glucose, amino acids, lipids and vitamins derived from digested food are absorbed from gastrointestinal tract and carried by blood to different parts of the body for growth and production of energy. 2. Respiratory Function: Transport of respiratory gases is done by the blood. It carries O2 from alveoli of lungs to different tissues and CO2 from tissues to alveoli. 3. Excretory Function: Waste products formed in the tissues during various metabolic activities are removed by blood and carried to the excretory organs like kidney, skin, liver, etc. for excretion. 4. Transport of Hormones and Enzymes Hormones which are secreted by ductless (endocrine) glands.The blood transports these hormones to their target organs/tissues. Blood also transports enzymes. 5. Regulation of Acid-base Balance The plasma proteins and hemoglobin act as buffers and help in regulation of acid-base balance. 6. Regulation of Body Temperature: Because of the high heat conductivity and high specific heat of blood, it is responsible for maintaining the thermoregulatory mechanism in the body. 7. Defensive Function The WBCs in the blood provide the defense mechanism and protect the body from the invading organisms.  Plasma Plasma is a straw-colored clear liquid part of blood. It contains 91 to 92% of water and 8 to 9% of solids. The solids are the organic and inorganic substances. Serum When the blood is collected in a container, it clots because of the conversion of fibrinogen into fibrin. After about 45 minutes, serum oozes out of the clot. It is different from plasma only by the absence of fibrinogen. Fibrinogen is absent in serum because it is converted into fibrin during blood clotting. Thus, the Serum = Plasma – Fibrinogen.  The plasma proteins are: 1. Serum albumin 2. Serum globulin 3. Fibrinogen. Globulin is of three types, Α-globulin, β-globulin and PLASMA γ-globulin. The normal values of the plasma proteins are: PROTEINS Total proteins: 7.3 g/dL (6.4-8.3 g/dL) Serum albumin: 4.7 g/dL Serum globulin: 2.3 g/dL Fibrinogen: 0.3 g/d Albumin/globulin Ratio: The ratio between plasma level of albumin and globulin is called Albumin/Globulin (A/G) ratio. It is an important indicator of some liver and kidney diseases. Normal A/G ratio is 2:1.  In adults, the plasma proteins are synthesized mainly from reticuloendothelial cells of liver and also from spleen, ORIGIN OF bone marrow. PLASMA PROTEINS Gamma globulin is synthesized by B lymphocytes. Functions Of Plasma Proteins 1. Role in the blood Coagulation: Fibrinogen is essential for the coagulation of Blood. 2. Role in Defense Mechanism of Body: The gamma globulins play an important role in the defense mechanism of the body by acting as antibodies. These proteins are also called immunoglobulins. 3. Osmotic pressure of the plasma proteins: It is mainly caused by albumin because of its low molecular weight It is about 28 mm.Hg IT is responsible for fluid exchange between capillaries and interstitial fluids  4. Role in Transport Mechanism: Albumin, alpha globulin and beta globulin are responsible for the transport of the hormones, enzymes, etc. The alpha and beta globulins transport metals in the blood. : 5. Role as Reserve Proteins: During inadequate food intake or inadequate protein intake, the plasma proteins are utilized by the body tissues as the last source of energy. Because of this, the plasma proteins are called the reserve proteins.  6. Role in Regulation of Acid-base Balance: Plasma proteins, particularly the albumin, play an important role in regulating the acid-base balance in the blood. This is because of the virtue of their buffering action. 7. Role in Viscosity of Blood: The plasma proteins provide viscosity to the blood, which is important to maintain the blood pressure. Fibrinogen provides maximum viscosity than the other plasma proteins.  Erythropoiesis: Formation of RBC (erythrocytes) Blood Leucopoiesis: Cells Formation of WBC Formation (leucocytes) Thrombopoiesis: Formation of platelets (thrombocytes) 14  Erythrocytes Red Blood Cells (RBC): Normal Values: 5 million RBCs /UL of blood. Normal adult ranges are : - 5.4 million / L (plus or minus 0.8 million /UL) in an adult male. - 4.8 million /UL (plus or minus 0.6 million /UL)in an adult female. It is higher in infants and lower in growing children and old persons. It is increased in athletes and at high altitudes. Hb = 14-16 g/dl in the blood Male: 16± 2 gram/dl Female: 14± 2 gram/dl  FUNCTIONS OF RBCs: I)Functions of RBCs Membrane: 1) It allows the RBCs to pass through the narrowest capillaries due to its plasticity. 2) The biconcavity of the membrane gives the RBCs a large surface area which helps the exchange of gases (O2 and CO2). 3) It keeps the enzyme carbonic anhydrase inside the RBCs, otherwise it would be lost in urine if it passes into plasma. This enzyme is important for CO2 carriage. 4) It is semipermeable. It is not permeable to K+ , HB., and Na+. So, K +, HB. kept inside, and Na+ outside the RBCs. Meanwhile, It is permeable to H + , Cl and HCO3. This is important for keeping the reaction of the blood constant when CO2 is added by the tissues. 5) The most important function of the membrane is that it keeps HB. inside the RBCs. This is useful because if HB. is free in plasma it: a) May be precipitated in kidney tubules as acid haematin blocking them and inducing anuria (=stoppage of urine formation). b) Would increase the osmotic pressure of plasma proteins 5 times which would prevent tissue fluid formation. c) Is liable to be engulfed and destroyed by the reticuloendothelial cells. d)Would be filtered into Bowman’s capsule in the kidney and lost in urine.  II) Functions of RBCs contents: 1) Haemoglobin (HB.) has the following functions: a) O2 carriage from the lungs to the tissues. b) Co2 carriage from the tissues. c) Buffering system in the blood. 2) Carbonic anhydrase is important in Co2 carriage. 3) Inactivation of histamine by histamines enzyme.  Production of RBC In-utero: Early few weeks of embryo nucleated RBCs are formed in yolk sac. Middle trimester mainly in liver & spleen & lymph nodes. Last months RBCs are formed in bone marrow of all bones ---------------------------------------------------------------------------- After Birth: Bone marrow of both flat bone and long bones continue to produce RBC into adult life At puberty: Shaft of long bone stop to produce RBC while epiphysis (ends 0f long bones) and flat bones continued Life Span:120 days ± 7 days. An erythrocytes exists for approximately 4 months, after which it is removed from the blood and destroyed by macrophages in the spleen, liver, and marrow 20 Regulation of RBC production 21  I- Oxygen Tension (=Pressure): Lowering of O2 tension in arterial blood (hypoxia) stimulates the activity of bone marrow to produce more RBCs e.g. during living at high altitude. O2 lack is the specific stimulus for RBCs regeneration by bone marrow. However, it does not act directly on bone marrow but through the release of erythropoietin hormone. Hypoxia (oxygen deficiency) caused by: High altitude Lung disease II-Kidney: - The juxtaglomerular cells of the kidney respond to hypoxia (O2 lack) as in high altitude by forming a substance called “Renal Erythropoietic Factor” or REF.  Erythropoietin: Glycoprotein. 90% from renal cortex 10% liver. Stimulate the growth of early stem cells. Does not affect maturation process. Conditions like: High altitude Heart failure Lung Disease Result in High erythropoietin levels and polycythemia 23  Regulation of RBC production, Continued,,,,, III- Food Factors: i.Proteins: proteins of high biological value (=containing all essential amino acids),are more effective in erythropoiesis ii.Iron (Fe): Forms a part of HB. of the RBCs. Iron deficiency anaemia, which is characterized by the formation of small RBCs (=microcytic) with content HB. (=hypochromic) iii.Copper (Cu) and Cobalt (Co): These elements act as catalysts for Hb. synthesis but do not form a part of Hb molecule. iv- Vitamins: folic acid and vitamin B12 are specific in RBCs regeneration. They are called “Maturation Factors”.  Regulation of RBC production, Continued,,,,,  IV- Hormones: erythropoietin hormone, Thyroxine. and testosterone.  V- Liver: Healthy liver is essential for normal erythropoiesis because it helps in the manufacture of globin of HB. and stores Fe, Cu and vitamin B12.  VI- Bone Marrow: It is the only site in adults for normal erythropoiesis.  GIT lumen Iron absorption Enterocyte Capillaries CYTB: cytochrome B DMT1: divalent metal transporter-1 HT: Heme transporter FPN: Ferroportin 1 HP: Hephaestin  Vitamin B12 Vitamin B12 of food (Extrinsic factor) exists in a combined form with proteins. In the stomach, an enzyme-like substance is secreted by gastric mucosa in the fundus region. This substance is named the “Intrinsic factor” and its function is to help absorption of vitamin B12 from the intestine (lower part of the ileum). Deficiency of B12 in the body leads to “Pernicious Anaemia”.  THE ANAEMIAS Definition: These are conditions characterized by a decrease in the number of RBCs or their HB. content or both. Aetiological Classification of anaemias: 1)Anaemias due to excessive destruction of RBCs:(=Haemolytic Anaemias) by: a) Chemicals: as in lead poisoning. b) Disease : as in malaria. c) Increased fragility of RBCs: Spherocytosis, thalassemia, sickle cell anaemia. 2) Anaemias due to excessive loss of RBCs: (= Post hemorrhage Anaemias): a) Acute : as in rapid hemorrhage. b) Chronic : as in piles (chronic hemorrhage). 3) Anaemias due to defective formation of RBCs: a) Nutritional : e.g. in Fe, Cu or protein deficiency. b) Pernicious : e.g. in vitamin B12 deficiency. c) Aplastic : e.g. in destruction of bone marrow by X-rays. Blood Indices  Morphological (Wintrobe’s) Classification of Anaemia MCV< 80 fL MCV= (80-100) fL MCV > 100 fL Iron Deficiency Anaemia It is due to: 1- Decreased dietary intake 2- Malabsorption 3- Increase demands: pregnancy 4- Prolonged loss of blood (=chronic Haemorrhage) as in piles Decreased Fe in the body leads to the formation of RBCs that are smaller than normal (=Microcytic) and contain less amount of HB. (=Hypochromic). Treatment: Give ferrous salts by mouth. In severe cases or decreased absorption, give iron by injection. Pernicious Anaemia Lack of Intrinsic Factor secretion leads to lack of absorption of Vit.B.12 from the intestine. 1- RBCs: they are nucleated, bigger in size (= Macrocytic) and contain more Hb. (= Hyperchromic). 2- C.N.S.: Degenerative lesions occur in spinal cord and in peripheral nerves. 3- Stomach: Atrophy occurs in gastric mucosa and failure of intrinsic factor secretion. Treatment of Pernicious Anaemia: Injections of vitamin B12. Polycythemia Increased number of RBCs, (6-8 million per mm3). Types and Causes: 1. Physiological Polycythemia: In case of prolonged exposure to low O2 tension, e.g., at high altitudes for several weeks. 2. Polycythemia Vera: The bone marrow forms excessive numbers of RBCs for an unknown cause.