Study Guide: Blood Anatomy & Physiology

Blood Anatomy & Physiology

1. Formed Elements of Blood

The formed elements of blood are the cellular components suspended in plasma. They are essential for various physiological functions.

• Red Blood Cells (Erythrocytes): Transport oxygen and carbon dioxide.

• White Blood Cells (Leukocytes): Defend against infection and disease.

• Platelets (Thrombocytes): Involved in blood clotting.

Example: A blood smear under a microscope reveals erythrocytes as biconcave discs, leukocytes as larger nucleated cells, and platelets as small fragments.

2. Functions of Blood and Physical Characteristics

Blood performs several vital functions and has distinct physical properties.

• Transport: Delivers oxygen, nutrients, hormones, and removes waste products.

• Regulation: Maintains pH, temperature, and fluid balance.

• Protection: Provides immunity and prevents blood loss via clotting.

• Physical Characteristics: Blood is viscous, slightly alkaline (pH ~7.4), and has a temperature of about 38°C.

3. Blood Separation in a Centrifuge

When blood is centrifuged, it separates into distinct layers based on density.

• Plasma: The top layer (~55%), contains water, proteins, and solutes.

• Buffy Coat: Thin middle layer, contains leukocytes and platelets.

• Red Blood Cells: Bottom layer (~45%), contains erythrocytes.

Example: The buffy coat is visible as a thin white layer between plasma and RBCs.

4. Plasma Proteins

Plasma proteins are dissolved proteins in blood plasma, crucial for various functions.

• Albumin: Maintains osmotic pressure and transports substances.

• Globulins: Include antibodies for immune defense.

• Fibrinogen: Essential for blood clotting.

5. Megakaryocytes and Platelets

Megakaryocytes are large bone marrow cells that produce platelets by shedding cytoplasmic fragments.

• Platelets: Small, anucleate cell fragments involved in hemostasis.

6. Blood Cell Lineage

Blood cells originate from hematopoietic stem cells in the bone marrow. Each cell type follows a specific lineage during development.

• Erythrocytes: Derived from erythroid lineage.

• Leukocytes: Derived from myeloid or lymphoid lineages.

• Platelets: Derived from megakaryocyte lineage.

Additional info: Detailed embryonic development is not required for this study guide.

7. Erythrocytes: Characteristics, Hemoglobin Structure, and Function

Erythrocytes are specialized for oxygen transport due to their hemoglobin content.

• Shape: Biconcave disc increases surface area for gas exchange.

• Hemoglobin: Protein that binds oxygen; consists of four polypeptide chains and iron-containing heme groups.

• Function: Transports oxygen from lungs to tissues and carbon dioxide from tissues to lungs.

Equation:

$\text{Hb} + \text{O}_2 \rightarrow \text{HbO}_2$

8. Blood Types: Antigens and Antibodies

Blood types are determined by the presence or absence of specific antigens on erythrocyte surfaces.

• ABO System: Types A, B, AB, and O based on antigen presence.

• Rh Factor: Positive (+) if Rh antigen is present, negative (−) if absent.

• Compatibility: Important for transfusions to prevent immune reactions.

Example: Type O− is the universal donor; AB+ is the universal recipient.

9. Leukocytes (Table 18.7)

Leukocytes are white blood cells involved in immune defense. They are classified as granulocytes or agranulocytes.

Type	Classification	Main Function
Neutrophils	Granulocyte	Phagocytosis of bacteria
Eosinophils	Granulocyte	Combat parasites, modulate allergic responses
Basophils	Granulocyte	Release histamine, mediate inflammation
Lymphocytes	Agranulocyte	Adaptive immunity (B cells, T cells, NK cells)
Monocytes	Agranulocyte	Phagocytosis, become macrophages in tissues

Additional info: Table reconstructed based on standard leukocyte classification.

10. Platelets and Hemostasis

Platelets play a key role in hemostasis, the process that stops bleeding.

• Vascular Spasm: Immediate constriction of damaged blood vessel.

• Platelet Plug Formation: Platelets adhere to exposed collagen and aggregate.

• Coagulation: Cascade of reactions leading to fibrin clot formation.

Equation:

$\text{Prothrombin} \xrightarrow{\text{Thrombin}} \text{Fibrinogen} \rightarrow \text{Fibrin}$

11. Coagulation Pathways

Blood coagulation involves a series of enzymatic reactions resulting in the formation of a stable fibrin clot.

• Intrinsic Pathway: Initiated by damage inside the vessel.

• Extrinsic Pathway: Initiated by external trauma.

• Common Pathway: Both pathways converge to activate thrombin and form fibrin.

Additional info: Detailed steps of the coagulation cascade are not required for this guide.

12. Clot Elimination

After tissue repair, clots are removed through fibrinolysis.

• Plasmin: Enzyme that digests fibrin and dissolves the clot.

13. Age-Related Changes in Blood

Blood composition and function change with age.

• Decreased Hematopoiesis: Reduced production of blood cells.

• Altered Immune Response: Lower efficiency of leukocytes.

• Increased Clotting Risk: Higher risk of thrombosis in elderly.

Example: Older adults may have lower red blood cell counts and increased susceptibility to infections.