Blood Blood is a mixture of cellular components suspended in plasma:

1. Erythrocytes (RBCs). 2. Leukocytes (WBCs).3. Thrombocytes (platelets).4. Plasma.

Transport1.Blood gases O2 and CO2 2.Nutrients 3.Metabolic wastes to disposal sites (kidney and sweats)4.Hormones to target tissues/organs

Blood Functions

1. Body temperature2. The pH of body fluids3. Regulation of water balance

Regulates

1. Prevent blood loss (blood clotting).2. Foreign bodies, toxins and microorganism by white blood

cells through phagocytosis and formation of antibodies.

RBCs: blood viscosity

Wh

ole

blo

od

8%

of b

od

y

weig

ht

Plasma55%

Cells45%

Water 91.5 %

Plasma protein 7%

Other solutes 1.5%

Albumin 54%Globulin 38% Fibrinogen 7%

Other 1%

enzymes & HormonesNutrient

Electrolytes &Gases Wastes

RBCs 4.5-6 million/mm3

Platelets150,000-400,000/mm3

WBCs 4000 -11000/mm3

Neutrophils 60-70%

Lymphocytes 20-25%

Monocytes 4-8%

Eosinophils 2-4 %

Basophils 0-1%

Physical Characteristics of Blood

• Blood volume: approximately 8% of body weight

• Viscosity: 4 - 5 time of water

• pH: 7.4 (arterial blood) and 7.36 (venous blood)

• Osmolarity (concentration of solutes in plasma): 300 mOsm/liter

• Salinity (NaCl concentration): 0.85%

• Temperature: 37C

Red Blood Corpuscles (RBCs)

Shape: Non nucleated biconcave

discs.Average diameter: (7.8 µm = micron).Thickness: Periphery (2.5 µm). Center (1 µm).

RBCS

Average size: (90 µm3) = Normocytes. = Macrocytes = Microcytes.

Average count: 5 million/mm3

- in adult females (4.5 – 5 million/mm3). - in adult males (5 – 5.5 million/mm3). - in new borne (6 – 8 million/mm3). = Polycythaemia. = Anaemia.

Average life span: 120 days.

Structure of RBCsCytoplasm enclosed by cell membrane

Cytoplasm

Hb in each cell: 30 pg = Normochromic Electrolytes (K+ & HCO3). Enzymes (carbonic anhydrase & G-6-PD).

Functions of RBCs RBCs:1. Blood viscosity → peripheral resistance → diastolic Bp

Hb:1. Respiratory function: Transport O2 from the lungs to the

tissues & CO2 from tissue to lungs to be expired.

2. Important Buffer.

Haemoglobin (Hb)

Haemoglobin (Hb) Structure of Hb molecule:• 4 Fe++ atoms and 4 globin chains.• Each Hb molecule carry up to 4 O2 molecules.

Hb content averages 15 gm%

Respiratory function of HB O2 – Hb combination:• Loose • Reversible • Gradual • Oxygenation (not oxidation).

Erythropoiesis = Haematopoiesis(RBCs formation)

Site: Yolk sac (in early weeks of embryonic life). Extramedullary (liver, spleen and lymph nodes) middle

trimester. Medullary (from last trimester).

Regulation of Hematopoiesis

N.B. Hypoxia is the most effective stimulus for Erythropoiesis

Fate of RBCs

Fate of RBCs

- RBCs have a life span of 120 days

- Old RBCs become fragile & less flexible.

- Old RBCs ruptured when pass through small capillaries

Fate of RBCs

Fate of RBCs Old RBCs(fragile & hemolyzed)

Hbengulfed by RES

HaemGlobin

reused in Hb synthesis

Fe++ stored as ferritinreused in Hb synthesis

Biliverdin reduced - Bilirubinreleased into circulation

In the liver Bilirubin is conjugated with gluoronide

and excreted in bile

In intestine Bilirubin is converted - Stercobilinogenexcreted in stools )brown(

Absorbed Stercobilinogenmostly reexcreted in bile

Small amount converted- Urobilinogen excreted in urine

- RBCs have a lifespan of 120 days

- Old RBCs become fragile & less flexible.

- Old RBCs ruptured when pass through small capillaries

- The released Hb engulfed by Macrophages of reticulo-endothelial system )RES(

Haematocrit

Separation of Components

Plasma = Less Dense

Hematocrit“Packed Cells”More Dense

Platelets / WBC’s

Anemia: decreased oxygen-carrying capacity of blood due to reduction of RBCs (No., or size) or Hb content or both.

• It is a symptom rather than a disease itself• Signs/symptoms include fatigue, pallor, shortness of

breath

Hypoxia: deficiency in either delivery or utilization of oxygen at the tissue level, which can lead to changes in function, metabolism and even structure of the body.

Shock: is inadequate tissues perfusion and is considered a transition between homeostasis and death.

1. PolycythemiaIs the increased No.of red cells more than 6.5 million/mm3

A. Primary – neoplastic = polycythemia vera Myeloproliferative neoplasmB. Secondary - increased erythropoietin stimulation

Physiological ( high altitude, pregnancy) Pathological (heart disease, lung diseases)

Is the decrease of RBCs (No., Size) or Hb content or both than normal

→ decrease of O2 carrying capacity of blood. This may be due to: 1. Defect of bone marrow function (hypoplastic or a plastic anemia).2. Lack of the blood forming element (nutritional anemia).3. Blood loss in hemorrhage (hemorrhagic anemia).4. Destruction of RBCs in the circulation (hemolytic anemia).

2. Anemia

Disorders of RBCs Count

Disturbance of RBCs number /or sizePolycythemia

abnormally high hematocrit (too many RBCs in circulation).

Anemia abnormally low haematocrite (too low

RBCs No./ or size

Physiological Pathological

High altitudeNewborn

Lung diseases

Heart failure

:

Nutritional,

Aplastic, renal,

hemorrhagic,

Hemolytic

White Blood Cells (Leukocytes)

• Are the mobile units of the body’s protective system. • WBCs are called “white” blood cells because they lack hemoglobin

and are colorless.• They are nucleated and larger in size than RBCsWBCs Functions

1. Destruction of invading microorganisms (bacteria and viruses) by phagocytosis

2. Forming antibodies and sensitized lymphocytes and destroy or inactivate the invader

3. Identification and destruction of cancer cells4. Phagocytosis of tissue debris including dead and injured cells

Types of WBC’sGranulocytesAgranulocytes

WBCs life span in the circulation is about 5 days

The normal WBCs count is 4000 - 11000 / mm3

WBCs abnormalities• Leukopenia is a condition characterized by a decreased number

of white cells in the blood, lower than 4000 which is usually due to:• Viral disease such as measles and infectious hepatitis.• Some bacterial infections such as typhoid fever, brucellosis,

and typhus fever.• Certain drugs such as radio therapy and chemotherapy and

some antibiotics.

Leukocytosis is a condition characterized by an elevated number of white cells in the blood, above 11,000-30000 is usually due to an increase in one of the five types of white blood cells and is given the name of the cell that shows the primary increase.

• Bacterial infection such as appendicitis, tonsillitis, ulcers and urinary tract infection

Leukemia. • Elevation of leukocytes above 30000/µl

3. Platelets (Thrombocytes)

Cell fragments bound to megakaryocytes.

Platelets Number disturbance

• Average platelets No.: 150,000 - 400,000/mm3

• Thrombocytosis > 400,000/mm3

• Thrombocytopenia < 150,000/mm3

• Platelets life span: 7 to 10 days

Haemostasis or blood clotting

Extrinsic way Intrinsic way

Haemostasis 1. Vascular contraction (spasm of injured blood vessel).

2. Formation of platelet plug (temporary haemostatic plug).

3. Formation of blood clot (definitive haemostatic plug).

Mechanism of blood clotting

Functions of platelets

A. Platelets are mainly concerned with haemostasis by

1. Formation of platelet plug.

2. Release of serotonin & thromboxane A2 )strong V.C.(.

3. Induction of clot retraction.

4. Stabilization of blood clot by )factor XIII(.

5. Repair of damaged vessel wall by releasing )PDGF(.

B. Platelets have a slight phagocytic functions.

Clotting Time - Slide Method (Intrinsic)•The surface of the glass tube initiates the clotting process. This test is sensitive to the factors involved in the intrinsic pathway

•The expected range for clotting time is 4-4-10 min.10 min.is a crude test of hemostasis.

Bleeding time It is a blood test that looks at how fast small blood vessels in the skin close to stop bleeding

Purpose•To assess overall hemostatic function (platelet response to injury and functional capacity of vasoconstriction). • To detect congenital and acquired platelet function disorders. Patient preparation 

•Normal = 3-5 min