Blood Composition and Functions

Study Notes

Blood is a sticky red fluid that circulates in a closed system
It has a volume of 5.5 liters and a pH of 7.4
It is composed of plasma and formed elements
- Plasma is the liquid portion of blood
- Formed elements include red blood cells, white blood cells, and platelets

Blood is important for transporting substances, regulating body conditions, and protecting the body
It transports gases, nutrients, waste products, hormones, electrolytes, and more
It regulates pH, osmotic pressure, and body temperature
It provides protection and immunity
It facilitates clot formation

Plasma is the liquid portion of blood
It is composed of 91% water, 7-8% proteins, and 1% electrolytes, glucose, gases, and other substances
Plasma proteins include albumin, globulins, fibrinogen, lipoproteins, and prothrombin

Blood cells are called formed elements
Red blood cells (erythrocytes) make up 95% of formed elements
White blood cells (leukocytes) make up 5% of formed elements
Platelets (thrombocytes) are also formed elements
Leukocytes can be further categorized into granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes)

Blood cells are studied using smears or films
Smears are prepared by spreading a drop of blood on a slide, drying, and fixing with alcohol
The smears are then stained with Giemsa, Wright's, or Leishman's stains to visualize cell nuclei and cytoplasmic granules
Bone marrow samples are obtained from the iliac crest and stained with Hematoxylin & Eosin (H&E)

Blood smears and bone marrow sections help visualize the structure and characteristics of blood cells under a microscope

Red blood cells do not have nuclei or organelles
They contain normal adult hemoglobin (HbA)
They are flexible to accommodate small capillaries
They are surrounded by a cell membrane composed of phospholipids, cholesterol, glycolipids, proteins, and carbohydrates
The erythrocyte membrane contains a protein called spectrin

RBCs are responsible for transporting oxygen and carbon dioxide for gas exchange

Hematocrit is a clinical test that measures the volume of packed red blood cells in a blood sample
It is determined by centrifuging a heparinized blood sample
The hematocrit value is represented by the basal layer of packed red blood cells after centrifugation
The normal hematocrit range is 40-50% for males and 35-45% for females

Anemia is a condition characterized by decreased numbers or size of erythrocytes, or reduced hemoglobin content in the blood
Erythrocytosis and polycythemia involve an increased number of erythrocytes
Macrocytes are erythrocytes with diameters greater than 9 micrometers, often caused by folic acid or vitamin B12 deficiency
Microcytes have diameters less than 6 micrometers and are commonly associated with iron deficiency
Aplastic Anemia is characterized by bone marrow failure
Hemolytic Anemia is caused by inherited genetic alterations in RBCs or autoimmune conditions
Reticulocytosis is an increase in the number of reticulocytes in blood due to rapid blood loss, normally 0.5-1.5%
Poikilocytosis involves an increase in the number of distorted RBCs