Blood - Human Anatomy and Physiology B. Pharma 1st Semester



At the end of this lecture, student will be able to

    Explain the functions of blood

    Describe the physical characteristics of blood

    List the components of blood

    List the major components of plasma

    Outline blood cell production, function, and destruction

    Describe the structure of red blood cells

• Explain the types and functions of WBC

• Describe the haemostatic mechanism

• Explain the role of platelet in haemostasis


Hemopoietic system

• Blood

• Plasma

• Red blood cells

• White blood cells

• Hemostatic mechanism

Formed Elements in the Blood


• Biconcave discs with a diameter of 7–8 micro m

• 4.8 million/microL in females

• 5.4 million/microL in males

Plasma Membrane

– Strong and flexible

– Allows them to deform without rupturing as they squeeze through narrow capillaries

– Glycolipids in the plasma membrane antigens

• Mature RBCs lack

– Nucleus and other organelles

 – Neither reproduce nor carry on extensive metabolic activities

• The Cytosol

– Contains hemoglobin molecules (each RBC -280 million Hb molecules)

RBC Physiology - Advantages

• No Nucleus

– All their internal space is available for oxygen transport

• Lack Mitochondria

– Generate ATP anaerobically (without oxygen)

• Biconcave disc shape

– Facilitates its function - greater surface area for the diffusion of gas molecules

• Hemoglobin

• Helps in oxygen transport (binding to Iron molecule)

 • Also transports about:

   • 23% of the total carbon dioxide (by binding to aminoacid)

   • Waste products of metabolism

• Plays a role in the regulation of blood flow and blood pressure

Hemoglobin (Hb)

• Consists of a protein called globin (2 Alpha & @ Beta chains)

• A ringlike nonprotein pigment called a heme - bound to each of the four chains

• At the center of each heme ring is an iron ion

• Each Hb is capable of binding four molecules of oxygen

Formation of Blood Cells

RBC Physiology - Role of Hb

RBC Life Cycle


Reticulocytes develop into mature red blood cells within 1 to 2 days after their release from red bone marrow

Negative Feedback Regulation of Erythropoiesis

• Lower oxygen content of air at high altitudes, anemia, and circulatory problems may reduce oxygen delivery to body tissues

• Give a negative feedback

White Blood Cell

• WBCs - Live only a few days

• Lymphocytes - Live for several months or years

• During a period of infection Phagocytic WBCs (Neutrophils and macrophages) live only a few hours

• Classified into granulocytes and agranulocytes

Types of WBC

• Once pathogens enter the body - combat them by phagocytosis or immune responses

• Granular leukocytes and monocytes leave   the   bloodstream   to   fight injury or infection

• They never return to it

• Lymphocytes continually recirculate - From blood to interstitial spaces to lymphatic fluid

• Leukocytosis

– Increase in the number of WBCs above 10,000/L

– Normal, protective response to stress such as invading microbes, strenuous exercise, anesthesia, and surgery

• Leukopenia

– An abnormally low level of white blood cells (below 5000/L)

– Never ďeŶefiĐial and may be caused by radiation, shock, and certain chemotherapeutic agents


• WBCs leave the bloodstream by a process termed emigration

• Formerly called diapedesis


• Microbes and inflaeed tissue Unregistered release different chemicals - attract phagocytes


• Hemostasis - Sequence of responses that stops bleeding

• Hemostatic response must be;

– Quick

– Localized to the region of damage

• Three mechanisms reduce blood loss:

– Vascular spasm

– Platelet plug formation

– Blood clotting (coagulation)

Vascular Spasm

• Arteries or arterioles are damaged

• The circularly arranged smooth muscle contracts immediately

• Reduces blood loss for several Min to Hrs (Meanwhile other haemostatic mechanisms go into operation)

The spasm is probably caused by:

• Damage to the smooth muscle

• Substances released from activated platelets

• By reflexes initiated by pain receptors

Platelet Plug Formation

Platelets store an impressive array of chemicals

• Clotting factors

• Calcium

• Serotonin


• Enzymes that produce TXA2, PG

• FSF - helps to strengthen a blood clot

Membrane Systems

• Take up and store calcium

• Provide channels for release of the granule contents


• Cause proliferation of vascular endothelial cells, vascular smooth ŵusĐle fiďers & fiďroďlasts

• Help repair damaged blood vessel walls

Platelet Adhesion

• Initially, platelets contact and stick to parts of a damaged blood vessel

• To ĐollageŶ fiďers of the connective tissue underlying the damaged endothelial cells

Platelet Release Reaction - Initiation

• Due to adhesion, the platelets become activated

• Extend many projections – enable them to contact and interact with one another

Platelet Release Reaction

• Begin to liberate the contents of their vesicles

• Liberated ADP & TXA2 activates nearby platelets

• Serotonin and TXA2 – vasoconstrictors (sustaining contraction)

Platelet Aggregation

Release of ADP makes other platelets in the area sticky

– This leads to gathering of platelets

– Eventually, the accumulation and attachment of large numbers of platelets form a mass called a platelet plug


• Whole blood can be separated as Liquid and cellular components

• Formed elements – Component buffy coat

• Blood plasma pH - 7.4 the pH level required for normal cellular functioning

• Erythrocytes carry oxygen and Corban dioxide

• Platelets and blood proteins protect the body against blood loss by forming blood clots on damaged vessels     

• White blood cells are classified into granulocytes and agranulocytes

• Hemostasis - Sequence of responses that stops bleeding

• Three mechanisms reduce blood loss

– Vascular spasm

– Platelet plug formation

– Blood clotting (coagulation)                                                                                                           

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