Anatomy & Physiology Exam 1 Study Guide: Blood, Hemostasis, Lymphatic System, and Immunity

Blood and Hemostasis

Composition and Functions of Blood

The blood is a specialized bodily fluid that performs essential functions such as transport, regulation, and protection. It consists of plasma and formed elements (cells and cell fragments).

• Plasma: The liquid component of blood, containing water, proteins (albumin, globulins, fibrinogen), electrolytes, nutrients, and waste products.

• Formed Elements: Includes erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (thrombocytes).

• Albumin: Maintains osmotic pressure and fluid balance.

• Hemostasis: The process of stopping bleeding, involving vascular spasm, platelet plug formation, and coagulation.

Plasma Proteins and Water Homeostasis

Plasma proteins, especially albumin, play a critical role in maintaining blood osmotic pressure and water balance.

• Albumin: Most abundant plasma protein; regulates fluid movement between blood and tissues.

• Globulins: Involved in immune responses and transport.

• Fibrinogen: Essential for blood clotting.

Erythrocytes (Red Blood Cells)

Erythrocytes are responsible for oxygen transport and have a biconcave shape to maximize surface area for gas exchange.

• Structure: Lacks nucleus and organelles; filled with hemoglobin.

• Function: Transports oxygen and carbon dioxide.

• Life Cycle: Produced in bone marrow, circulates for ~120 days, then removed by spleen and liver.

Hemoglobin

Hemoglobin is the oxygen-carrying protein in erythrocytes.

• Structure: Four polypeptide chains, each with a heme group containing iron.

• Function: Binds oxygen in the lungs and releases it in tissues.

Erythropoiesis and Feedback Regulation

Erythropoiesis is the process of red blood cell production, regulated by erythropoietin (EPO) in response to hypoxia.

• Major Cells: Hematopoietic stem cells (HSC), proerythroblast, erythroblast, reticulocyte, erythrocyte.

• Feedback Loop: Low oxygen stimulates EPO release from kidneys, increasing RBC production.

Leukocytes (White Blood Cells)

Leukocytes are immune cells classified as granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).

• Function: Defend against pathogens, remove debris, and mediate immune responses.

• Leukopenia: Low WBC count; Leukemia: Cancer of WBCs.

Platelets and Hemostasis

Platelets are cell fragments essential for blood clotting.

• Activation: Platelets change shape and release granules upon vessel injury.

• Aggregation: Platelets stick together to form a plug.

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

Hemostasis Mechanisms

• Vascular Spasm: Immediate constriction of blood vessels after injury.

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

• Coagulation: Involves intrinsic (contact) and extrinsic (tissue factor) pathways, converging on the common pathway to form fibrin.

Coagulation Pathways

• Intrinsic Pathway: Initiated by damage inside the vessel; involves clotting factors XII, XI, IX, VIII.

• Extrinsic Pathway: Initiated by external trauma; involves tissue factor (factor III) and factor VII.

• Common Pathway: Both pathways activate factor X, leading to conversion of prothrombin to thrombin and fibrinogen to fibrin.

Role of Vitamin K and Calcium

• Vitamin K: Required for synthesis of clotting factors II, VII, IX, X.

• Calcium: Essential cofactor in multiple steps of the coagulation cascade.

Blood Typing and Transfusion

Blood types are determined by the presence of antigens (A, B, AB, O) and Rh factor on RBCs.

• ABO System: Type A (A antigen), Type B (B antigen), Type AB (A and B antigens), Type O (no antigens).

• Rh System: Rh+ (D antigen present), Rh- (D antigen absent).

• Transfusion Reaction: Occurs when incompatible blood is transfused, leading to agglutination and hemolysis.

Blood Type	Antigens Present	Antibodies Present
A	A	Anti-B
B	B	Anti-A
AB	A, B	None
O	None	Anti-A, Anti-B

Additional info: Universal donor: Type O-; Universal recipient: Type AB+

Blood Cell Calculations

• Cell Volume (%): Percentage of WBC and RBC in blood.

• Normal Hematocrit (Ht) Ranges: Males: ~40-54%; Females: ~36-48%

• Normal % WBC Value: ~1%

Lymphatic System

Functions of the Lymphatic System

The lymphatic system maintains fluid balance, absorbs dietary fats, and supports immune functions.

• Regulation of Interstitial Fluid: Returns excess fluid from tissues to the bloodstream.

• Absorption of Dietary Fats: Lacteals in the small intestine absorb fats.

• Immune Functions: Houses and transports immune cells.

Organization of the Lymphatic System

• Lymphatic Vessels: Network of capillaries and larger vessels transporting lymph.

• Lymphatic Trunks: Drain lymph from specific body regions (lumbar, intestinal, bronchomediastinal, subclavian, jugular).

• Thoracic Duct: Drains lymph from most of the body into the left subclavian vein.

• Right Lymphatic Duct: Drains right upper body into right subclavian vein.

Lymph Formation and Circulation

Lymph is formed from interstitial fluid collected by lymphatic capillaries and returned to the bloodstream.

• Mechanism: Capillary filtration, entry into lymphatic capillaries, transport through vessels, filtration in lymph nodes, return to blood.

• Pathway: Interstitial fluid → lymphatic capillaries → lymphatic vessels → lymph nodes → lymphatic trunks → ducts → subclavian veins.

Lymphatic Organs and Their Functions

• Lymph Nodes: Encapsulated clusters filtering lymph and trapping pathogens; site of lymphocyte interaction.

• Spleen: Filters blood, removes pathogens and old erythrocytes.

• Thymus: Site of T cell maturation.

• MALT (Mucosa-Associated Lymphoid Tissue): Protects mucosal surfaces in gastrointestinal and respiratory tracts.

Immunity

Innate vs. Adaptive Immunity

The immune system protects the body from pathogens through innate (nonspecific) and adaptive (specific) mechanisms.

• Innate Immunity: Immediate, nonspecific defense; includes physical barriers, phagocytic cells, antimicrobial proteins, and inflammation. No immunological memory.

• Adaptive Immunity: Specific response to antigens; involves B cells (antibody-mediated) and T cells (cell-mediated). Has immunological memory for faster secondary responses.

Antibody-Mediated vs. Cell-Mediated Immunity

• Antibody-Mediated (Humoral) Immunity: B cells produce antibodies that bind and neutralize antigens.

• Cell-Mediated Immunity: T cells recognize and destroy infected or abnormal cells.

Type	Main Cells	Function
Antibody-Mediated	B cells	Produce antibodies, neutralize pathogens
Cell-Mediated	T cells	Destroy infected/cancerous cells, regulate immune response

Primary vs. Secondary Immune Response

• Primary Response: First exposure to antigen; slower, less robust.

• Secondary Response: Subsequent exposure; faster and stronger due to memory cells.

Other Key Immune Concepts

• Phagocytic Cells: Neutrophils and macrophages engulf pathogens.

• Complement Proteins: Enhance phagocytosis and inflammation.

• Cytokines: Chemical messengers regulating immune responses.

• Hypersensitivity Disorders: Excessive or inappropriate immune responses (e.g., allergies, autoimmune diseases).

Key Calculations and Values

• Cell Volume (%): $\text{Cell Volume} = \frac{\text{Number of Cells}}{\text{Total Blood Volume}} \times 100$

• Hematocrit (Ht): $\text{Hematocrit} = \frac{\text{Volume of RBCs}}{\text{Total Blood Volume}} \times 100$

• Normal Ranges: Hematocrit: Males 40-54%, Females 36-48%; WBC: ~1% of blood volume

Summary Table: Blood Types and Transfusion Compatibility

Recipient Blood Type	Compatible Donor Types
A	A, O
B	B, O
AB	A, B, AB, O (universal recipient)
O	O (universal donor)

Additional info: For Rh compatibility, Rh- individuals should not receive Rh+ blood.