Blood Composition & Connective Tissue Types

• Blood is a fluid connective tissue with cells within a matrix

Blood Composition

• Blood is composed of plasma, platelets, leukocytes and erythrocytes
• Plasma accounts for 55% of whole blood volume
• Erythrocytes account for 44% of whole blood volume
• Plasma consists of 92% water, 7% proteins, and 1% of other solutes
• Electrolytes, nutrients, respiratory gases, and waste products constitute the 1% of other solutes in plasma

Classification of Connective Tissue

• Connective tissue is classified into connective tissue proper, supporting connective tissue, and fluid connective tissue
• Connective tissue proper includes loose connective tissue (areolar, adipose, reticular) and dense connective tissue (regular, irregular, elastic)
• Supporting connective tissue includes cartilage (hyaline, fibrocartilage, elastic) and bone (compact, spongy)
• Blood is a fluid connective tissue

Blood Functions

• Blood transports oxygen from the lungs to body cells
• Blood transports carbon dioxide and metabolic waste from cells
• Blood transports nutrients from the digestive system
• Blood transports hormones to target organs
• Blood helps maintain body temperature, normal pH, and fluid volume by regulation
• Leukocytes, platelets, and blood proteins are a part of blood for protection

Blood Plasma

• Blood plasma consist of 92% water, proteins, and solutes
• Serum is plasma without clotting proteins

Blood Plasma Proteins

• The main proteins found in blood plasma are albumin, globulins, fibrinogen, and regulatory proteins
• Albumin prevents water from diffusing out of blood vessels via osmosis and acts as a carrier molecule
• Globulins include antibodies and blood proteins that transport lipids, iron, and copper
• Fibrinogen is essential for blood clotting
• Regulatory proteins include proenzymes and enzymes

Blood Plasma Dissolved Solids

• Blood plasma contains over 100 dissolved solids
• Ions e.g., sodium and chloride
• Nutrients like sugars, amino acids, lipids
• Respiratory gases: oxygen, carbon dioxide, nitrogen
• Vitamins
• Wastes such as carbon dioxide, urea, and ammonia

Formed Elements

• Blood contains three types of formed elements: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets

Erythrocytes

• Erythrocytes lack a nucleus or organelles in humans
• Erythrocytes are bags of hemoglobin bound by a plasma membrane
• Hemoglobin constitutes 97% of an erythrocytes
• Erythrocytes are biconcave, which helps with loading and unloading gases

Erythrocytes Functions

• The primary function of erythrocytes is oxygen transport via hemoglobin
• Hemoglobin binds oxygen easily and reversibly
• Erythrocytes have 250 million hemoglobin molecules
• Each hemoglobin has 4 heme groups, that binds to one oxygen molecule
• 1 erythrocyte binds 1 billion oxygen molecules
• Erythrocytes also transport a small amount of carbon dioxide

Erythrocytes Lifecycle and Destruction

• Erythrocytes lifespan 120 days
• Macrophages in the spleen destroy erythrocytes and recycle their components
• Components are recycled, the others excreted

Blood Types

• Blood types are categorized by ABO and Rh blood groups
• Type A blood has surface antigen A and anti-B antibodies in the plasma
• Type B blood has surface antigen B and anti-A antibodies in the plasma
• Type AB blood has both surface antigens A and B, with neither anti-A nor anti-B antibodies
• Type O blood has neither surface antigen A nor B, containing both anti-A and anti-B antibodies
• Rh-positive blood has surface antigen D on the Erythrocytes
• Rh-negative blood lacks surface antigen D

Erythrocytes Disorders

• Anemias has a low oxygen carrying capacity
• Polycythemia is an abnormal excess of erythrocytes, increasing blood viscosity and the risk of blood clots

Leukocytes

• Leukocytes are complete cells accounting for under 1% of blood cells
• Leukocytes are involved in defense against disease and can leave capillaries to move through tissue
• Granulocytes and Agranulocytes are the two main categories of leukocytes

Granulocytes

• Neutrophils are over 50% of leukocytes, possessing a multilobed nucleus and are drawn to sites of inflammation
• Neutrophils are active phagocytes against bacteria/fungi by engulfing pathogens
• Eosinophils that account for 1-4% of leukocytes and have a bilobed nucleus with large granules
• Eosinophils kill parasitic worms with enzymes in lysosomes
• Basophils are the rarest granulocytes around 0.5%
• Basophils have a large s-shaped nucleus and release histamine

Agranulocytes

• Monocytes are the largest leukocytes with a U-shaped nucleus
• Monocytes act as macrophages of viruses and bacteria
• Lymphocytes, the 2nd most common leukocyte, are about the size of an erythrocyte with spherical/indented nucleus
• Lymphocytes include B and T lymphocytes and are responsible for immunity

Platelets

• Platelets are cell fragments containing chemicals that aid in clotting
• Platelets degenerate in about 10 days
• Platelets form from megakaryocytes

Hemopoiesis

• Hemopoiesis is the formation of blood
• Erythropoiesis is the formation of erythrocytes
• Leukopoiesis is the formation of leukocytes