Blood Physical properties

• 8% of body weight

• Heavier than water

• 5x more viscous

• About 38o C

• pH 7.35 - 7.45

• Salty and sticky

Blood Functions

• Transportation– O2 and CO2

– Nutrients

– Waste

• Regulation– pH

– Body temperature

– Fluid volume and osmolarity

Blood Functions

• Protection– Prevention of blood loss

– Prevention of infection

Blood Components

• Plasma

• Formed elements

Plasma

• Water - 90% of plasma volume

• Solutes - 8% of plasma volume– Proteins

» Albumin

» Globulins - alpha , beta and gama

» Clotting proteins

» other

– Non protein nitrogenous waste

– Nutrients (organic)

– Electrolytes

– Respiratory gases

Formed Elements

• Erythrocytes

• Leukocytes

• Platelets

Unusual Features of Formed Elements

• Erythrocytes and platelets are not “true cells”

• Most of formed elements survive in blood stream only a few days

• Most blood cells do not divide

Formation of blood cells

Physical Characteristics of RBCs

• Anucleated and lack most organelles

• Small in size and biconcave

• Flexible

• Mostly a “bag” to carry hemoglobin

Function of RBCs

• Transport of oxygen and carbon dioxide

Erythrocytes disorders• Anemias

– Insufficient number of RBC

» Hemorrhagic

» Hemolytic

» Aplastic

– Decreases in hemoglobin content

» Iron deficiency

» B12 deficiency (pernicicous )

– Abnormal hemoglobin

» Thalassemias

» Sickle cell

• Polycythemia

General Characteristics of Leukocytes

• Diapedesis - the ability of WBCs to exit the circulatory system

• Ameboid motion - The characteristic motion of leukocytes through tissue spaces

• Positive chemotaxis - The motion of WBCs towards certain chemicals released by damaged cells or other leukocytes

WBCs Classification

• Granulocytes– Neutrophyls

– Eosinophils

– basophils

• Agranulocytes– Lymphocytes

» T lymphocytes

» B lymphocytes

– Monocytes

Neutrophils

• Account for about half of all leukocytes and are twice as big as erythrocytes

• Take up both basic (blue) and acidic (red) dyes resulting in lilac color.

• Their nucleus has 3-6 lobes resulting in polymorphonuclear (PMNs) or Polys

• Phagocytic especially bacteria and fungi

• Kill by respiratory burst and defenses

Eosinophyls

• Account for 1- 4% of all leukocytes

• Shaped as a old fashion telephone receiver

• Large coarse granules stained in red brick color

• Most important role fight against invasion of parasitic worms– Reduce allergenic

reactions by phagocytizing allergens

Basophyls

• Rarest of all leukocytes about 0.5% of population

• Have large histamine granules which stain purplish black

• Main role in inflammatory reaction by dilating blood vessels and attacking other leukocytes to the site of inflammation– Mast cells may be tissue

basophils

Lymphocytes• Second most numerous

leukocytes

• Large round deep purple nucleus- classified by size

• Found mainly in lymphoid tissue

– T Lymphocytes- cell mediated immunity

– B Lymphocytes - humoral immunity

Monocytes• Largest of all

leukocytes

• Abundant gray-blue cytoplasm and dark blue-purple kidney shaped nucleus

• Wonder into tissues and become macrophages with prodigal appetites

• Great increase in chronic infections

Leukocyte Disorders

• Excessive production of leukocytes occur in leukemias– Cancer of white blood cells

» Usually single clone lines tend to remain unspecialized mitotic and functionally inoperative

» their sheer number impairs bone marrow function resulting in severe anemia, bleeding problems and inability to mount a defense response against infections

• Leukopenia - low white cell count– usually drug induced, particularly glucocorticoids and anti-

cancer drugs

Platelets (thrombocytes)

• Cytoplasmic fragments megakaryocytes

• Essential for clotting process– Contain, serotonin, Ca+2 , a variety of enzymes, ADP,

PDGF.

• Formation controlled by thrombopoietin

Hemostasis

• Vascular spasms

• Platelet plug formation

• Coagulation

Vascular Spasms• Damage of smooth muscle in

blood vessels causes a reflexive contraction

• Release of chemicals from injured endothelial cells and platelets release vasoactive chemical which cause vasoconstriction

These mechanisms result in reduction in blood loss

• Thought question : Would you rather be injured by blunt or sharp object

Platelet Plug Formation• Platelets adhesion- Sharp edges, release of

sticky chemical such as ADP and exposure of collagen which is under injured epithelia

• Platelets release- Release of chemicals which will attract more platelets and will make them stick

• Platelet aggregation- by sending extensions

• Plug formation- fibrogen gets converted to fibrin forms a mesh which traps formed elements and make a plug

Coagulation

• Phase 1 - A complex substance called prothrombin activator is formed– Two pathways extrinsic and

intrisic» Once factor X is activated

it complexes with tissue thromboplastin PF3 , factor V and calcium ions to form prothrombin activator

• Phase 2 - conversion of prothrombin to thrombin - by the action of prothombin– common pathway

• Phase 3 - conversion of fibronogen to fibrin by the action of thrombin– common pathway

Human Blood Groups

• ABO blood groups

• Rh blood groups