THE PHYSIOLOGY OF BLOOD

Size: px

Start display at page:

Download "THE PHYSIOLOGY OF BLOOD"

Brian Simmons
6 years ago
Views:

1 2 THE PHYSIOLOGY OF BLOOD

2 Objectives 1. ERYTHROCYTES 2. ERYTHROCYTE AGGLUTINOGENES, 3. PLASMA AGGLUTININS 4. TRANSFUSION 5. Practical tasks ERYTHROCYTE COUNT BLOOD GROUPING RH FACTOR CROSSMATCHING TEST

3 BLOOD COMPOSITION: PLASMA BLOOD CORPUSCULES: RED BLOOD CELLS ERYTHROCYTES WHITE BLOOD CELLS LEUKOCYTES PLATELLETS THROMBOCYTES FUNCTION: TRANSPORT NUTRIENTS, WARMTH, GASSES PROTECTION- BLOOD LOSS, ILLNESS,

4 ERYTHROCYTES - RBC Function: transport of oxygen in the blood. Shape: biconcaved discs. (This shape increases the surface area-to-volume ratio of the cell, thus increasing the efficiency of diffusion of oxygen and carbon dioxide) Fexible plasma membrane (This feature allows erythrocytes to squeeze through capillaries) No nucleus, no other organelles in the mature Erythrocyte (to have more room for hemoglobin carries oxygen) Limited life span of about 120 days. The removal of old and dying erythrocytes is carried out by the spleen. NORMOCYTE

ERYTHROPOESIS The process of Ery formation (tibia, femur ribs, sternum, vertebra) The kidney monitors the level of oxygen in the blood. Erythropoetin is secreted in decreased oxygenation.

5 ERYTHROPOESIS The process of Ery formation (tibia, femur ribs, sternum, vertebra) The kidney monitors the level of oxygen in the blood. Erythropoetin is secreted in decreased oxygenation. (90% kidneys, 10% liver) All cells are exposed to erythropoetin, but only red bone marrow cells, respond to the hormone. Erythropoetin stimulates the production of erythrocytes in the bone marrow. Erythropoetin induces the differentiation of the erythropoetic cells As the erythrocyte population increases, The oxygen carrying capacity of the blood increases, kidney responds by slowing the secretion of erythropoetin. This negative feedback loop ensures that the size of the erythrocyte population remains relatively constant and that the oxygen carrying capacity of the blood is always sufficient to meet the needs of the body.

6 ERYTHROPOESIS STEM CELL 1% in blood Takes 1-2 days To mature

7 NORMOCYTE Most of the erythrocytes are of normal size and shape: Diameter: 7.5 micrometers Width: 1.9 micrometers Volume: 83 cubic micrometers Those are called NORMOCYTES Erythrocytes having in diameter less than 7 micrometers are called MICROCYTES Erythrocytes having in diameter more than 8.5 micrometers are called MACROCYTES In normal blood there is a distribution of erythrocytes of different size some 10 % of them are less than 6, some 5 % are more than 8.5 WE CALL THIS DISTRIBUTION PHYSIOLOGICAL ANISOCYTOSIS Normal erythrocyte count: For women: 4, per Liter of blood ( per Liter) For men: 5, per Liter of blood ( per Liter) ANEMIA, POLYCYTEMIA

8 ANEMIA Causes of Anemia characterized by either low hemoglobin, low hematocrit, or both. The causes of anemia include: Dietary deficiencies of iron, vitamin B12 or folic acid. Hemorrhage Hemolysis Bone marrow failure Kidney disease Dietary deficiencies Iron is required for the production and function of hemoglobin. In the absence of adequate iron, hemoglobin production slows down. Low hemoglobin can lower the hematocrit. Vitamin B12 and Folic Acid are required for DNA synthesis prior to cell division. In the absence of these nutrients production of erythrocytes is reduced. The hematocrit is low and many erythrocytes are huge, fragile cells called macroblasts. B12 deficiency can be caused by a lack of intrinsic factor, this is called pernicious anemia. Intrinsic factor, which is produced in the stomach, is required for efficient absorption of B12 out of the small intestine and into the blood.

9 SYMPTOMS OF ANEMIA Fatigue - particularly with exercise. Oxygen is required to metabolize fuel molecules (sugars, fats and proteins) to obtain energy. A person with a low hematocrit cannot carry enough oxygen in the blood to meet their energy demands. Increased heart rate. The body increases heart rate to compensate for the low oxygen carrying capacity of the blood. If more blood is moved faster through the tissue then tissues get more oxygen per unit time hyperkinetic circulation. Shortness of breath faster breathing - tachypnea This is a compensation for the poor delivery of oxygen to the tissues. Low blood pressure. The viscosity of the blood drops as the hematocrit decreases. A decrease in blood viscosity directly lowers total peripheral resistance (TPA) to the flow of blood, thus lowering mean arterial blood pressure (MAP). Pale Skin. Hemoglobin is bright red when oxygenated and less red when deoxygenated. Because the redness of skin is due to the redness of blood, the skin of an anemic person is less red than the average person.

10 BLOOD TYPING Blood groups A,B,AB,O (according of the presence of antigens) Antigens - agglutinogens Antibodies / agglutinins FENOTYPE vs GENOTYPE

11 BLOOD TYPE DISTRIBUTION According to race: in percentage A B O AB WHITE Yellow Red 3 97 Black

12 BLOOD TYPING COMPATIBLE BLOOD NO AGGLUTINATION INCOMPATIBLE BLOOD AGGLUTINATION AND HEMOLYSIS (IMMUNOLOGICAL HEMOLYSIS)

Mother develops antibodies 2nd pregnancy mother s antibodies

13 Erythroblastosis fetalis in Rh incompatibility 1st pregnancy Rh+ Ery of a child pass to mother s blood. Mother develops antibodies 2nd pregnancy mother s antibodies Hemolyse the child s Rh+ Ery Causing anemia that leads to Fetal erythroblastosis production of unmatured Ery

14 HEMOLYTIC NEWBORN DISEASE 1. Anemia 2. Fetal erythroblastosis

Lec.2 Medical Physiology Blood Physiology Z.H.Kamil

Lec.2 Medical Physiology Blood Physiology Z.H.Kamil Destruction of Red Blood Cells When red blood cells are delivered from the bone marrow into the circulatory system, they normally circulate an average of 120 days before being destroyed. Even though mature