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

Blood

Objectives

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

Content

Hemopoietic system

• Blood

• Plasma

• Red blood cells

• White blood cells

• Hemostatic mechanism

Formed Elements in the Blood

RBC

• 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

Erythropoiesis

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

Emigration

• WBCs leave the bloodstream by a process termed emigration

• Formerly called diapedesis

Chemotaxis

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

Hemostasis

• 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

• ADP & ATP

• 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

PDGF

• 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

Summary

• 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)