BS

Blood, Immune, and Lymphatic System Review

Overview: Blood, Immune & Lymphatic Systems (Lab Focus)

  • Lab covers two intertwined topics:
    • Blood (structure, function, clinical tests)
    • Lymphatic / immune anatomy (fluid recovery + defense)
  • Immune “cells doing the action” ≠ Lymphatic “plumbing that drains excess interstitial fluid (≈15 % capillary filtrate not re-absorbed).”
  • Digestive tie-in: lacteals move dietary fats too large for blood capillaries.

Core Functions of Blood

  • Transport
    • Gases: O₂ delivery, CO₂ removal
    • Nutrients (glucose, lipids, amino acids)
    • Waste (e.g.
    • Urea from protein catabolism
    • Nucleic-acid breakdown products)
    • Hormones (endocrine communication highway)
  • Protection
    • Leukocytes + antibodies fight infection
    • Hemostasis (clotting)
  • Regulation
    • Water balance / blood volume
    • Acid-base buffering via [\text{H}^+] modulation

Blood Volume & Basic Composition

  • Typical adult volume: 4–6 L
  • Two broad fractions after centrifugation:
    • Plasma (~55 %) – clear, protein-rich fluid
    • Formed elements (~45 %)
    • Erythrocytes (RBCs)
    • Leukocytes (WBCs)
    • Platelets (thrombocytes)
  • Centrifuge demo:
    • Capillary tube → spin → layers
    • Plasma (top)
    • Buffy coat (thin) = WBCs + platelets
    • Packed RBCs (bottom)
    • % RBC column = Hematocrit
    • Men ≈ 42–52 %
    • Women ≈ 37–48 % (menstrual loss → lower baseline ⇒ dietary iron critical)

Erythrocytes (RBCs)

  • Shape: biconcave discs ("donuts with film")
    • ↑ surface area for rapid gas exchange
  • Anucleate; rely on bone-marrow production
  • Production terminology
    • General: Hematopoiesis
    • RBC specific: Erythropoiesis (stimulated by kidney hormone EPO)
    • Tissue source: Myeloid marrow
  • Hemoglobin (Hb) structure
    • Tetramer = 2 α + 2 β globin chains
    • Each chain holds a heme with Fe²⁺ center ("iron bracket")
    • Requires dietary iron → deficiency ⇒ ↓ Hb ⇒ iron-deficiency anemia
  • Color logic
    • Oxy-Hb (Fe³⁺) = bright red
    • Deoxy-Hb = darker, rusty
    • Talquist paper color scale estimates [Hb] clinically

Leukocytes (WBCs)

  • Production: Leukopoiesis in lymphoid tissue (marrow → maturation elsewhere)
  • Two overarching groups
    • Granulocytes (cytoplasmic granules visible)
    • Neutrophils (≈60 %) – phagocytose bacteria; ↑ in bacterial infections (CBC clue for antibiotics)
    • Eosinophils – attack parasites, modulate allergies
    • Basophils – release histamine (vasodilator) & heparin; ↑ in allergy, diabetes, chickenpox
    • Agranulocytes
    • Lymphocytes (≈30 %; most common agranulocyte) – B cells (antibody makers) & T cells (cell-mediated immunity, thymus matured); destroy viruses, cancer, foreign cells
    • Monocytes – circulate; exit blood → transform to macrophages (tissue phagocytes) during inflammation/viral infection

Platelets (Thrombocytes)

  • Cell fragments from megakaryocyte cytoplasm (no nucleus)
  • Smallest formed element
  • Role in hemostasis
    • Become amoeboid “puzzle pieces”
    • Aggregate → platelet plug
    • Reinforced by fibrin strands → stable clot

Blood Typing & Transfusion Compatibility

ABO Antigens ("flags on flagpoles")

  • Surface glycoproteins = antigens A & B
    • A blood: only A flag
    • B blood: only B flag
    • AB: both (co-dominant genetics)
    • O: none (flagpole empty)
  • Antibodies (Ab) float in plasma like Velcro/magnets
    • Anti-A binds A flag; Anti-B binds B flag
    • Rule: You naturally LACK Ab against your own antigen
  • Agglutination test (lab)
    • Mix drop of blood with Anti-A, Anti-B (and Anti-D)
    • Observe clumping (polka-dot/gritty) vs smooth pool
    • Patterns:
    • Clump only with Anti-A → Type A
    • Clump only with Anti-B → Type B
    • Clump with both → AB
    • Clump with neither → O
  • Genetics & prevalence
    • O the most common (hidden recessive in A/B carriers)
    • AB the rarest

Rh (D) Factor

  • Separate antigen (discovered in Rhesus monkeys)
  • Rh⁺ (≈90 %) – D antigen present
  • Rh⁻ – no D antigen; typically no anti-D Ab unless sensitized
  • Hemolytic Disease of the Newborn (HDN)
    • Rh⁻ mother + Rh⁺ fetus
    • First birth: placental mixing at delivery → mom forms Anti-D Ab
    • Subsequent Rh⁺ pregnancy: maternal Ab cross placenta → fetal anemia (erythroblastosis fetalis)
    • Prevention: RhoGAM injections postpartum (and later pregnancies) neutralize fetal Rh antigen before immune response

Transfusion rules summary

  • Universal donor = O⁻ (no A, B, or D flags)
  • Universal recipient = AB⁺ (already has A, B, D; makes no corresponding antibodies)

Selected Blood Pathologies

  • Polycythemia (↑ RBC count)
    • Primary: marrow cancer
    • Secondary: dehydration, emphysema, high altitude
    • Dangers: ↑ viscosity → embolism, stroke, heart failure
  • Anemia (↓ RBC or Hb)
    • Causes: nutrition (Fe, B₁₂), kidney failure (↓ EPO), hemorrhage
    • Symptoms: hypoxia, fatigue, pallor, tachycardia (thin blood)
  • Sickle Cell Disease
    • African/Caribbean genetic trait (Hb mutation)
    • Deoxygenated Hb polymerizes → RBC "crescent" shape
    • Capillary blockage, pain, organ damage
    • Heterozygote advantage vs malaria Plasmodium
  • WBC disorders
    • Leukopenia (< 5 000 µL) – infection risk (e.g., chemo, AIDS)
    • Leukocytosis (> 10 000 µL) – infection, allergy, stress
    • Leukemia – cancer of WBC line; massive counts (~100 000 µL) but nonfunctional → infection & anemia common

Lymphatic System – Structure & Flow

  • Three major roles: fluid return, lipid absorption, immune surveillance ("secondary circulatory system")
  • Lymph = recovered interstitial fluid
  • Vessels: begin as blind lymphatic capillaries → converge through lymph nodes → large trunks → ducts → venous angle
  • Key vessels/landmarks
    • Cisterna chyli – dilated sac in abdomen receiving lumbar & intestinal trunks
    • Thoracic duct (left) – drains cisterna chyli + left head/neck + left arm → left subclavian vein
    • Right lymphatic duct – drains right head/neck + right arm → right subclavian vein
  • Clinical correlate: nodes swell (palpable) during local infection; MD palpates cervical/submandibular chains for ENT illnesses

Lymphoid Organs & Tissues

  • Bone marrow – B cell maturation; hematopoiesis
  • Thymus – anterior mediastinum; huge in infants → involutes; T cell education ("self-tolerance")
  • Spleen – LUQ; filters aged/damaged RBCs, platelet reservoir
  • Tonsils (5 total)
    • 1 Pharyngeal (adenoid)
    • 2 Palatine
    • 2 Lingual
  • Peyer’s patches – ileum; guard intestinal lumen
  • Lymph nodes – clusters along vessels; reticular mesh + macrophages

Laboratory / Practical Procedures & Safety

  • Capillary tube & centrifuge
    • Seal with clay, spin → measure hematocrit using ruler card
    • Buffy coat often microscopic
  • Finger-stick blood typing kit (Carolina card)
    • Prep card wells labeled Anti-A, Anti-B, Anti-D
    • Add drop of distilled water, then fresh blood from spring-loaded lancet
    • Stir with separate applicators to prevent cross-contamination
    • Observe for agglutination patterns (solid vs speckled)
    • Submit liability waiver; watch demo video (Dr Kaiser)
    • If unable to self-stick, must still interpret photos/diagrams on quiz (identify where clumping occurred)
  • Visible Body modules supplement content; may mention liver/kidney roles (context from future lectures: hepatic portal nutrient processing; renal blood-pressure regulation)
  • Safety/ethics:
    • Use alcohol swab & bandage; dispose lancet properly
    • Do not perform test while fasting/queasy

Inter-Lecture Connections

  • Circulation lecture: 15 % capillary filtrate reclaimed by lymphatics
  • Endocrine lecture: kidneys secrete EPO → erythropoiesis
  • Reproduction lecture: placental blood mixing & Rh incompatibility
  • Immunology lecture: B vs T lymphocytes, antibody mechanism
  • Respiratory lecture: high altitude hypoxia → secondary polycythemia

Equations / Numbers to Remember

  • Plasma pH buffering concept: \text{pH} = -\log_{10}[\text{H}^+]
  • Hematocrit normal ranges: \text{Male} \approx 0.45-0.52, \text{Female} \approx 0.37-0.48
  • WBC counts
    • Normal: 5\times10^3\; \text{to}\; 10\times10^3\; \text{cells/µL}
    • Leukocytosis: >10\times10^3\; \text{cells/µL}
    • Leukemia: \sim100\times10^3\; \text{cells/µL (nonfunctional)}

Practical & Ethical Implications

  • Correct matching of antigens/antibodies critical to avoid transfusion reactions (agglutination → renal failure/death)
  • O⁻ supplies in blood banks prioritized (universal donor)
  • RhoGAM prophylaxis saves Rh⁺ second pregnancies from HDN
  • Antihistamines (e.g., Benadryl) counter basophil histamine in allergic reactions
  • Awareness of iron intake especially in menstruating females to prevent anemia