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Animal Body Systems in Action: Gas Exchange, Circulation, and Immune…
Animal Body Systems in Action: Gas Exchange, Circulation, and Immune Defense
How do animals obtain exchange w Environment
Circulatory System Types & Evolution
Diffusion
Definition: Passive movement of molecules from high to low concentration
Used by: Simple organisms (e.g., sponges, cnidarians).
Limitation: Inefficient over long distances or in large organisms.
Gastrovascular Cavity
Definition: Central cavity for digestion and circulation.
Examples: Cnidarians, flatworms.
Advantage: Simple, dual-purpose.
Disadvantage: Limited distribution efficiency.
Open Circulatory System
Definition: Hemolymph bathes organs directly; not confined to vessels.
Examples: Arthropods, most mollusks.
Advantage: Low pressure, energy efficient.
Disadvantage: Less control over distribution.
Closed Circulatory System
Definition: Blood confined to vessels; circulates in a loop.
Examples: Annelids, cephalopods, vertebrates.
Advantage: Efficient delivery, high pressure.
Disadvantage: Energetically costly.
Blood Vessels & Flow
Arteries vs Veins
Arteries: Away from heart.
Veins: Toward heart.
All Blood Vessels/ Central lumen lined with endothelium (smooth epithelial layer).
Arterioles
Definition: Small branches of arteries that lead to capillaries.
Function: Regulate blood flow and pressure via vasoconstriction and vasodilation.
Venules
Definition: Small vessels that collect blood from capillaries and lead to veins.
Function: Begin the return of blood to the heart; low pressure.
Vasoconstriction & Vasodilation
Vasoconstriction: Narrowing of vessels → ↑ blood pressure.
Vasodilation: Widening of vessels → ↓ blood pressure.
Fluid Return by the Lymphatic System
Function: Returns leaked plasma (now lymph) to blood.
Mechanism: Muscle contractions, valves.
Failure: Edema, elephantiasis.
Blood Pressure & Capillary Exchange
Measurement: Systolic/Diastolic (e.g., 120/80 mmHg).
Hypertension: Chronic high BP → risk of stroke, heart attack.
Capillaries
Role: Exchange gases, nutrients, waste.
Flow Regulation: Precapillary sphincters, osmotic pressure.
Hemoglobin
Function: Binds O₂ in blood.
Oxygenated: Bright red
Deoxygenated: Dark red
Blood Composition & Function
Plasma
Contents: Water, proteins, nutrients, hormones.
Cellular Components
Erythrocytes (RBCs): Carry oxygen.
Leukocytes (WBCs): Immune defense.
Platelets: Clotting.
Blood Clotting
Mechanism: Platelets + fibrin → clot formation.
Myoglobin
Function: Stores O₂ in muscle cells.
Red vs White Meat
Red Meat: High myoglobin (slow-twitch muscles).
White Meat: Low myoglobin (fast-twitch muscles).
Interstitial Fluid
Definition: Fluid surrounding body cells; site of exchange with blood in capillaries.
Circulatory Pathways
Single Circulation
Definition: Blood passes through heart once per cycle.
Example: Fish (2-chambered heart).
Path: Heart → gills → body → heart.
Double Circulation
Definition: Blood passes through heart twice per cycle.
Examples: Amphibians, reptiles, mammals, birds.
Path: Pulmonary circuit (lungs) + systemic circuit (body).
Evolutionary Variation in Double Circulation
Amphibians: 3 chambers (2 atria, 1 ventricle) – some mixing.
Reptiles: Partial septum – reduced mixing.
Mammals/Birds: 4 chambers – complete separation.
Mammalian Circulation
Pathway: Right atrium → right ventricle → lungs → left atrium → left ventricle → body.
Cardiac Function & Regulation
Cardiac Cycle
Systole: Contraction phase.
Diastole: Relaxation phase.
Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV)
Electrical Conduction
SA Node: Pacemaker.
AV Node: Delays signal.
Bundle Branches & Purkinje Fibers: Spread impulse through ventricles.
Cardiovascular Disease
Heart Attack (Myocardial Infarction)/Cause: Blocked coronary artery.
Stroke/Cause: Blocked or burst brain vessel.
HDL vs LDL
HDL: "Good" cholesterol.
LDL: "Bad" cholesterol.
Respiratory Systems & Gas Exchange
Partial Pressure Gradients
Definition: Gases move from high to low partial pressure.
Importance: Drives O₂ into blood, CO₂ out.
Gills in Aquatic Animals
Mechanism: Countercurrent exchange maximizes O₂ uptake.
Tracheal Systems in Insects
Structure: Air tubes deliver O₂ directly to tissues.
Lungs
Structure: Alveoli for gas exchange.
Surfactant: Reduces surface tension.
Mucus & Cilia: Trap and remove particles.
Lung Volumes
Tidal Volume: Normal breath.
Vital Capacity: Max air exhaled after max inhale.
Residual Volume: Air remaining after full exhale.
Mechanics of Breathing
Negative Pressure Breathing (Humans)
Mechanism: Diaphragm contracts → thoracic volume ↑ → air in.
Positive Pressure Breathing (Frogs)
Mechanism: Air pushed into lungs via buccal cavity.
Bird Breathing
Mechanism: Air sacs → unidirectional flow through lungs.
Coordination of Circulation & Gas Exchange
Breathing Control
Center: Medulla oblongata.
Trigger: CO₂ levels (not O₂).
Effect on pH: CO₂ → carbonic acid → ↓ pH.
Bicarbonate Buffer: Maintains blood pH.
Bohr Shift
Definition: Lower pH reduces hemoglobin’s affinity for O₂.
The Immune System
Overview of the Immune System
Purpose: Protects the body from pathogens, toxins, and abnormal cells.
Divisions
Innate Immunity
Immediate, non-specific defense.
Adaptive Immunity
Specific, acquired defense with memory
Lymphatic System
Supports immune cell transport and filtration
Innate Immunity
Surface Barriers
Skin: Physical barrier.
Mucous Membranes: Trap pathogens.
Secretions
Lysozyme:
Breaks down bacterial cell walls.
Sebum:
Oily secretion with antimicrobial properties.
Keratin:
Strengthens skin barrier.
Acidic pH:
Inhibits microbial growth.
Internal Defenses
Phagocytosis
engulfing and digesting pathogens
Neutrophils
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Macrophages
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Dendritic Cells
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Kupffer Cells
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More componets
Natural Killer (NK) Cells:
Destroy infected or abnormal cells using perforins.
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Faster than cytotoxic T cells during initial infection.
Mast Cells
Release histamine during allergic and inflammatory responses
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Eosinophils
Target parasites and contribute to allergic responses
Interferons
Proteins that inhibit viral replication.
Complement Proteins (C1–C9)
Enhance immune responses; form membrane attack complexes.
Enhances phagocytosis.
Antimicrobial Peptides and Proteins
Broad-spectrum molecules that inhibit or kill pathogens.
Pyrogens
Cause fever by resetting body temperature
Key Cells
B Cells: Humoral immunity; produce antibodies.
T Cells: Cell-mediated immunity; attack infected cells.
Helper T Cells (CD4⁺): Activate B cells and cytotoxic T cells.
Cytotoxic T Cells (CD8⁺): Kill infected cells using perforins.
Memory B/T Cells: Provide long-term immunity.
Inflammation
Local Inflammatory Response:
Redness, heat, swelling, pain at infection site.
Systemic Inflammation
Widespread immune activation EX Fever (via pyrogens)
Chronic Inflammation
Long-term immune activation; may damage tissues.
Innate Immunity in Digestive Tract
Barriers: Mucus, stomach acid, enzymes.
Cells: Macrophages, dendritic cells in gut-associated lymphoid tissue (GALT).
Lymphatic System
A network of vessels, nodes, and organs that supports immune function.
Main Functions:
Transport of lymph:
Fluid containing immune cells and waste products.
Filtration:
Lymph nodes filter pathogens and debris.
Immune Cell Housing:
Provides sites for lymphocyte activation and proliferation.
Key Structures:
Lymph Nodes:
Filter lymph and trap pathogens.
Spleen:
Filters blood, removes old RBCs, and activates immune responses.
Thymus:.
Site of T cell maturation
Tonsils & Adenoids:
Protect against inhaled or ingested pathogens.
Lymphatic Vessels:
Transport lymph throughout the body.
Adaptive Immunity
Key Features
Specificity: Targets specific antigens.
Memory: Faster response upon re-exposure.
Self-Tolerance: Avoids attacking self.
Clonal Selection: Activation and proliferation of specific lymphocytes.
Antigen Recognition
Antigen: Foreign molecule triggering immune response.
Epitope: Specific part of antigen recognized.
Haptens: Small molecules that become antigenic when bound to proteins.
MHC Complex:
Class I: Presents to cytotoxic T cells.
Class II: Presents to helper T cells.
Antibodies
Bind antigens.
Neutralize pathogens.
Activate complement.
Facilitate phagocytosis.
B Cells (Humoral Immunity)
Development: Bone marrow.
Function: Produce antibodies.
Plasma Cells: Secrete antibodies.
Memory B Cells: Long-term immunity.
T Cells (Cell-Mediated Immunity)
Development: Thymus.
Helper T Cells (CD4⁺):
Activate B cells and cytotoxic T cells.
Secrete cytokines.
Cytotoxic T Cells (CD8⁺
Kill infected cells using perforins.
Respond to antigens presented by MHC I.
Memory T Cells: Provide long-term immunity.
Antigen-Presenting Cells (APCs)
Types: Dendritic cells, macrophages, B cells.
Function: Present antigens to T cells via MHC.
Types of Immunity
Being Immune
Definition: Ability to resist infection due to prior exposure or antibodies.
Disorders & Evasion
Allergies
Cause: Overreaction to harmless antigens (allergens).
Mechanism: Antibodies trigger mast cells → histamine release → symptoms.
Autoimmune Diseases
Cause: Loss of self-tolerance.
Examples: Multiple sclerosis, type 1 diabetes, lupus.
Immunodeficiencies
Inborn: Genetic defects in immune components.
Acquired: HIV/AIDS destroys helper T cells.
Pathogen Evasion
Antigenic Variation: Changing surface proteins.
Latency: Dormant state inside host cells.
Immune Suppression: Direct attack on immune cells.
Active Immunity
Natural: Infection.
Artificial: Vaccination.
Passive Immunity
Natural: Maternal antibodies (placenta, breast milk).
Artificial: Antibody injections (e.g., antivenom).