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Chapters 42 & 43 – Circulation and Immunity - Coggle Diagram
Chapters 42 & 43 – Circulation and Immunity
Diffusion and Circulatory Needs
→ effective only over short distances
→ larger, complex animals need circulatory systems
Types of Circulatory Systems:
Open circulatory system → hemolymph bathes organs directly (arthropods, mollusks)
Closed circulatory system → blood confined to vessels (vertebrates, annelids, cephalopods)
Advantages of Closed System:
higher pressure → faster, more directed transport
Vertebrate Circulatory Systems
Basic components:
Heart (muscular pump)
Blood vessels (arteries, capillaries, veins)
Blood
Heart Structure & Circuits
Fish → 2-chambered heart → single circulation
Amphibians & reptiles → 3-chambered heart → double circulation (partial separation)
Mammals & birds → 4-chambered heart → double circulation (complete separation)
Double Circulation:
Pulmonary circuit → right side → lungs → left side
Systemic circuit → left side → body → right side
Human Heart
Right atrium → right ventricle → pulmonary arteries → lungs
Pulmonary veins → left atrium → left ventricle → aorta → body
Valves prevent backflow: atrioventricular (AV) & semilunar valves
Cardiac Cycle:
Systole → contraction
Diastole → relaxation
→ creates heartbeat
Pacemaker (SA node):
→ sets rhythm
→ regulated by autonomic nervous system & hormones
Blood Vessels
Arteries → carry blood away from heart
Veins → return blood to heart
Capillaries → site of exchange
thin walls (endothelium + basal lamina)
exchange via diffusion, pressure gradients
Blood Pressure:
→ highest in arteries
→ drops in capillaries
→ lowest in veins (aided by valves & skeletal muscles)
Blood Composition
Plasma → water, ions, proteins, nutrients, wastes
Cellular elements:
→ Platelets → clotting
→ Leukocytes (WBCs) → immune defense
→ Erythrocytes (RBCs) → carry O₂ (hemoglobin)
Clotting process:
→ platelet plug + fibrin clot formation (cascade of clotting factors)
Gas Exchange
→ uptake of O₂ and release of CO₂
→ occurs by diffusion across moist membranes
Respiratory Surfaces:
skin, gills, tracheae, lungs
Ventilation:
movement of air/water over respiratory surface
increases gas exchange efficiency
Countercurrent exchange (fish gills)
blood and water flow opposite directions → maintains O₂ gradient
Mammalian Respiratory System
Air pathway:
→ nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli
Alveoli:
→ site of gas exchange
→ surrounded by capillaries
→ gases diffuse via partial pressure gradients
Breathing control:
→ medulla oblongata monitors CO₂ → adjusts breathing rate
O₂ Transport:
→ hemoglobin binds O₂ cooperatively
→ affected by pH (Bohr shift: ↓pH = ↓affinity for O₂)
CO₂ Transport:
→ dissolved in plasma, bound to hemoglobin, or as bicarbonate ions (HCO₃⁻)
Immunity
Innate Immunity
Barrier defenses:
→ skin, mucous membranes, secretions (lysozyme, pH)
Internal defenses:
→ phagocytic cells (macrophages, neutrophils)
→ natural killer (NK) cells → destroy infected/cancerous cells
→ antimicrobial peptides → disrupt pathogen membranes
→ inflammatory response → histamine increases blood flow/permeability
Inflammation:
→ redness, heat, swelling, pain
→ cytokines recruit immune cells
Adaptive Immunity
Key traits:
→ specificity, diversity, self-tolerance, memory
Lymphocytes:
B cells (mature in bone marrow) → humoral immunity
T cells (mature in thymus) → cell-mediated immunity
Antigens → foreign molecules recognized by receptors
B Cell Function (Humoral Response)
Antigen recognition → receptor binds specific epitope
Activation → helper T cell + cytokines stimulate proliferation
Clonal selection → forms:
→ Plasma cells → secrete antibodies
→ Memory B cells → long-term immunity
Antibodies (Immunoglobulins):
→ neutralize pathogens
→ opsonization (mark for phagocytosis)
→ activate complement system
T Cell Function (Cell-Mediated Response)
Recognize antigens bound to MHC molecules on host cells
Cytotoxic T cells → kill infected cells by releasing perforin/granzymes
Helper T cells → activate B cells, cytotoxic T cells, macrophages
MHC classes:
Class I → all nucleated cells → recognized by cytotoxic T cells
Class II → antigen-presenting cells → recognized by helper T cells
Immune Memory
Primary response → first exposure, slower
Secondary response → faster, stronger (due to memory cells)
Vaccination
→ exposes immune system to harmless antigens → builds memory
Immune System Regulation
Self-tolerance:
→ lymphocytes tested for self-reactivity → eliminated if harmful
Disorders:
Autoimmune diseases → immune system attacks self (e.g., lupus, Type I diabetes)
Immunodeficiency → weakened immune response (e.g., HIV)
Allergies → hypersensitive response to harmless antigens (histamine release)
Integration: Circulation <--> Immunity
Blood carries immune cells & antibodies throughout body
Lymphatic system → returns interstitial fluid → transports immune cells
Immune cells rely on circulation for surveillance and rapid deployment